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Triosephosphate isomerase is the fifth enzyme in glycolysis and its canonical function is the reversible isomerization of glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. Within the last decade multiple other functions, that may not necessarily always involve catalysis, have been described. These include variations in the degree of its expression in many types of cancer and participation in the regulation of the cell cycle. Triosephosphate isomerase may function as an auto-antigen and in the evasion of the immune response, as a factor of virulence of some organisms, and also as an important allergen, mainly in a variety of seafoods. It is an important factor to consider in the cryopreservation of semen and seems to play a major role in some aspects of the development of Alzheimer's disease. It also seems to be responsible for neurodegenerative alterations in a few cases of human triosephosphate isomerase deficiency. Thus, triosephosphate isomerase is an excellent example of a moonlighting protein., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Whole body cytosolic phosphoenolpyruvate carboxykinase knockout (PEPCK-C KO) mice die early after birth with profound hypoglycemia therefore masking the role of PEPCK-C in adult, non-gluconeogenic tissues where it is expressed. To investigate whether PEPCK-C deletion in the liver was critically responsible for the hypoglycemic phenotype, we reexpress this enzyme in the liver of PEPCK-C KO pups by early postnatal administration of PEPCK-C-expressing adenovirus. This maneuver was sufficient to partially rescue hypoglycemia and allow the pups to survive and identifies the liver as a critical organ, and hypoglycemia as the critical pathomechanism, leading to early postnatal death in the whole-body PEPCK-C knockout mice. Pathology assessment of survivors also suggest a possible role for PEPCK-C in lung maturation and muscle metabolism.

Camelids develop a number of disturbances related to energy metabolism. Some are similar to disorders seen in other species, but most relate to camelids' unusual characteristics of poor glucose tolerance, partial insulin resistance, and low concentrations of circulating insulin. Camelids are especially prone to abnormalities related to stimuli that inhibit insulin release or activity, or that promote activities normally antagonized by insulin. These include stimuli that mobilize glycogen or fat stores, or inhibit glucose uptake or intravascular glycolysis. These stimuli are generally more important than negative energy balance in triggering these disorders. Treatment must concentrate on the hormonal aspects, and not just provision of energy. Treatments related to hormonal aspects include those to decrease catecholamine release and to provide exogenous insulin until the camelid is again able to maintain appropriate energy substrate homeostasis.

Glycogen storage diseases or glycogenoses are inherited diseases caused by abnormalities of enzymes that regulate the synthesis or degradation of glycogen. Deleterious mutations in many genes of the glyco(geno)lytic or the glycogenesis pathways can potentially cause a glycogenosis, and currently mutations in fourteen different genes are known to cause animal or human glycogenoses, resulting in myopathies and/or hepatic disorders. The genetic bases of two forms of glycogenosis are currently known in horses. A fatal neonatal polysystemic type IV glycogenosis, inherited recessively in affected Quarter Horse foals, is due to a mutation in the glycogen branching enzyme gene (GBE1). A second type of glycogenosis, termed polysaccharide storage myopathy (PSSM), is observed in adult Quarter Horses and other breeds. A severe form of PSSM also occurs in draught horses. A mutation in the skeletal muscle glycogen synthase gene (GYS1) was recently reported to be highly associated with PSSM in Quarter Horses and Belgian draught horses. This GYS1 point mutation appears to cause a gain-of-function of the enzyme and to result in the accumulation of a glycogen-like, less-branched polysaccharide in skeletal muscle. It is inherited as a dominant trait. The aim of this work was to test for possible associations between genetic polymorphisms in four candidate genes of the glycogen pathway or the GYS1 mutation in Cob Normand draught horses diagnosed with PSSM by muscle biopsy.

Muscle samples were obtained at necropsy from 225 horses and ponies 1 year of age or older. Samples were processed in routine manner and were stained with hematoxylin and eosin and with periodic acid-Schiff for glycogen. Sections were examined for abnormal glycogen content and amylase-resistant complex polysaccharide and for chronic myopathic change (excessive fiber size variation, increase in number of internal nuclei). A total of 101 horses and ponies with lesions of polysaccharide storage myopathy were identified. Age of affected horses ranged from one to 30 years, with a mean of 14.7 years. Mean age of nonaffected horses was 12 years. Incidence of polysaccharide storage myopathy varied depending on breed; Thoroughbreds had the lowest (27%) and draft-related horses had the highest (86%) incidence. Chronic myopathic changes were more severe in polysaccharide storage myopathy-affected horses than in nonaffected horses. Results of this study indicate that polysaccharide storage myopathy is a common disorder of many breeds of horses and ponies.

This study was designed to investigate whether horses with clinical signs of back pain due to suspected soft tissue injuries were affected by polysaccharide storage myopathy (PSSM). Diagnosis of PSSM in muscle biopsies obtained from the M. longissimus lumborum of 5 showjumpers and 4 dressage horses with a history of back pain is reported. M. longissimus lumborum biopsies of these horses were characterised histopathologically and in 3/9 cases also by electron microscopy. Observations were compared with M. gluteus biopsies of the same horses, and with M. gluteus biopsies obtained from 6 Standardbreds with recurrent exertional rhabdomyolysis and from 6 healthy trotters. M. longissimus biopsies from horses with back pain showed pathognomonic signs of PSSM, i.e. high glycogen and/or abnormal complex amylase-resistant polysaccharide deposits. Similar features were found in M. gluteus biopsies of the same horses. Sections of horses with rhabdomyolysis had increased PAS stain when compared with healthy horses, but did not show amylase-resistant material. Qualitative observations were corroborated by quantitative histochemistry (optical densities) of sections stained with PAS and amylase PAS. This study demonstrated the presence of PSSM in the M. longissimus of showjumpers and dressage horses with back pain and indicates that epaxial muscle biopsy is an option in diagnosing back problems in horses when clinical examination and imaging techniques do not provide a precise diagnosis.

Skeletal muscle samples from 38 draft horse-related animals 1-23 years of age were evaluated for evidence of aggregates of glycogen and complex polysaccharide characteristic of equine polysaccharide storage myopathy (EPSSM). Cardiac muscle from 12 of these horses was also examined. Antemortem serum levels of creatine kinase (CK) and aspartate aminotransferase (AST) from 9 horses with EPSSM and 5 horses without EPSSM were compared. Skeletal muscle from 17 horses contained inclusions of periodic acid-Schiff (PAS)-positive, amylase-resistant complex polysaccharide. Similar inclusions were also present in the cardiac muscle of 1 horse. A vacuolar myopathy with aggregates of PAS-positive, amylase-sensitive glycogen was seen in 8 other horses, and these findings are also considered diagnostic for EPSSM. Antemortem serum activities of CK and AST were often higher in EPSSM horses than in horses without EPSSM. Using the presence of amylase-resistant complex polysaccharide as the criterion for diagnosis of EPSSM, the incidence in this population was 45%. Inclusion of horses with aggregates of glycogen but no amylase-resistant complex polysaccharide as representative of the range of pathologic findings in horses with EPSSM resulted in a 66% incidence in this population.

Polysaccharide storage myopathy is an equine neuromuscular disorder characterized by accumulation of glycogen-related polysaccharide inclusions within skeletal muscle fibers. The pathologic criteria for diagnosis of this disorder are somewhat controversial; however, periodic acid-Schiff-positive, amylase-resistant inclusions are considered pathognomonic. Although these inclusions are most often found in affected horses related to the Quarter Horse, draft horse, and Warmblood breeds, this report describes these characteristic inclusions in muscle of five horses from nonrelated breeds (two Morgans, one Arabian, one Arabian x Thoroughbred, and one Standardbred) and two Welsh cross ponies. Affected horses had histories of recurrent exertional rhabdomyolysis, and one developed progressive weakness leading to increased recumbency. The affected ponies were part of an unrelated research project and had no apparent clinical signs.

Two Belgian geldings, 4 and 14 years old, respectively, with muscle atrophy, weakness, and abnormal gait characteristic of severe advanced shivers were examined clinically and on necropsy. Neurologic examination revealed no evidence of ataxia, and the clinical diagnosis was neuromuscular weakness and shivers. Necropsies of both horses, including examination of pituitary, brain, spinal cord, spinal roots and ganglia, and peripheral nerves, revealed no gross or histologic abnormalities. Examination of multiple skeletal muscle specimens revealed chronic myopathic changes and periodic acid-Schiff positive, amylase-resistant inclusions within muscle fibers, characteristic of equine polysaccharide storage myopathy. It is suggested that underlying metabolic myopathy may be the cause of muscle weakness and cramping in horses with shivers.

Ganglioside analysis and quantitative Golgi studies of the cerebral cortex of cats with ganglioside and nonganglioside lysosomal storage diseases reveal a correlation between the amount of accumulated GM2 ganglioside and the extent of ectopic dendrite growth on cortical pyramidal neurons. This correlation was not observed with any of the other gangliosides assayed for, including GM1 ganglioside. These results suggest a specific role for GM2 ganglioside in the initiation of ectopic neurites on pyramidal cells in vivo and are consistent with the developing hypothesis that different gangliosides have specific roles in different cell types dependent upon the receptor or other effector molecules with which they may interact.

Prospective and retrospective genetic studies were performed on sheep with a recently described inherited lysosomal storage disease that involves a profound deficiency of beta-galactosidase and an associated deficiency of alpha-neuraminidase. Retrospective studies of the flock of sheep in which four affected lambs were born indicated little inbreeding but the presence of a common ram in both the maternal and paternal sides of the pedigrees. When unrelated rams were used in the flock in subsequent years, no affected lambs were born. The affected lambs' parents were phenotypically normal, so the disease was investigated as a putative autosomal recessive condition in prospective breedings of related sheep over two breeding seasons. For the third breeding season, heterozygous ewes were superovulated and bred to a heterozygous ram, and the resultant embryos were transferred to recipient ewes. Later in the same breeding season, the heterozygous ewes were re-bred naturally to the heterozygous ram. Lambs were identified as affected by the development of signs of ataxia, levels of beta-galactosidase that were less than 7% of the levels in controls by spectrofluorometric assay, or the histopathologic demonstration of vacuolization of neurons. Heterozygous sheep were identified by the production of affected offspring and/or by levels of beta-galactosidase in fibroblast cultures that were approximately 50% of control levels. The phenotypic ratio of affected sheep to normal sheep and the genotypic ratio of affected to heterozygous to normal sheep were consistent, by chi-square analysis, with an autosomal recessive trait. It was concluded that this ovine lysosomal storage disease is an autosomal recessive disease.

Studies using the Golgi method were performed on neocortical and cerebellar tissues from a 9-month-old cat with a history of progressive neurological deterioration and a subsequently demonstrated deficiency of the lysosomal enzyme alpha-D-mannosidase in both neural and non-neural tissues. Many cortical pyramidal neurons demonstrated morphological alterations involving formation of abnormal enlargements (meganeurites) at the axon hillock-initial segment area, abnormal sprouting of neurites (secondary neurites) in this same region, and various types of dendritic changes, such as formation of focal enlargements, thinning, and spine loss. Many nonpyramidal neurons also were abnormal but displaced only dendritic changes similar to those seen in pyramidal neurons. Cerebellar Purkinje cells displayed dendritic systems marked by focal swellings and often demonstrated one or more enlargements within axons (axonal spheroids) at some distance from otherwise normal-appearing cell bodies. Feline mannosidosis appears to be another of the lysosomal storage diseases in which highly specialized morphological changes accompany storage of unmetabolized substrate and contribute to the pathogenesis of the disease process.

Mannosidosis of Angus calves is an inherited lethal disease associated with a deficiency of the lysosomal enzyme alpha=mannosidase. It is characterised by vacuolation of neurons, macrophages, fixed reticuloendothelial cells, exocrine epithelial cells and to a lesser extent a wide variety of other cells. Vacuoles are shown to be membrane-bound vesicles and are considered to be secondary lysosomes in which are stored mannose-containing oligosaccharides that result from incomplete degradation of glycoproteins. Such glycoproteins may enter the lysomal system by heterophagy, autophagy or crinophagy. The presence in the pancreas of zymogen granules in storage vesicles indicates that incomplete degradation of secretory granules might help explain the widespread vacuolation of other exocrine cells. It is suggested that such granules may enter the lysosomal system by crinophagy.

Histopathologic, ultrastructural and Golgi impregnation studies disclosed lesions characteristic of a neuronal lysosomal storage disease in related sheep with onset of neurologic signs at 4-6 months. Biochemical and enzymatic evaluation disclosed storage of GM1 ganglioside, asialo-GM1, and neutral long chain oligosaccharides in brain, urinary excretion of neutral long chain oligosaccharides, and deficiencies of lysosomal beta-galactosidase and alpha-neuraminidase. Retrospective and limited prospective genetic studies suggested autosomal recessive inheritance. A gene-dosage effect on beta-galactosidase levels was documented in fibroblasts from putative heterozygous sheep. Fibroblasts from affected sheep did not have increased beta-galactosidase activity after incubation with the protease inhibitor, leupeptin. In some aspects this disease is similar to GM1 gangliosidosis, but is unique in that a genetic defect in lysosomal beta-galactosidase may cause the deficiency of lysosomal alpha-neuraminidase.

Preincubation of EDTA plasma with 4mM ZnCl2 restores acidic alpha mannosidase activity, previously inhibited as a result of chelation of Zn++ by EDTA. This allows estimation of acidic alpha mannosidase activity in EDTA plasma samples, followed by granulocyte tests on those samples with low activities.

A marked deficiency of alpha-L-fucosidase and the accumulation of fucose-containing glycoasparagines were found in the brains of two English Springer spaniels suffering from a progressive nervous disorder. Both forms of alpha-L-fucosidase in normal brain, which are separable by ion-exchange chromatography, are absent from the affected animals. The storage products were characterized by t.l.c., gel filtration, g.l.c. and fast-atom-bombardment mass spectrometry. The postulated structures of the main components are: (formula; see text) The enzymic defect and nature of storage products justify designation of this disorder as canine fucosidosis.

Mannosidosis, an inherited lysosomal storage disease, was diagnosed in two purebred Angus calves in the United States. Calf 1 was 5 months old and calf 2 was 7 months old when they were necropsied. Both calves had a history of progressive incoordination and ataxia. Gross postmortem findings included moderate hydrocephalus. Histologic examination revealed intracytoplasmic vacuolation of neurons throughout spinal cord and brain as well as in exocrine pancreatic cells, reticuloendothelial cells of the liver, and medullary sinusoids of lymph nodes. Biochemical study of 61 blood samples from the first calf's herd revealed bimodal distribution of enzyme activity for mannosidase. Two populations could be distinguished in that herd, those with normal mannosidase activity and those heterozygous for the disease.

Beta-mannosidosis, an inherited defect of glycoprotein catabolism associated with deficiency of tissue beta-mannosidase and accumulation of Man(beta 1-4)GlcNAc and Man(beta 1-4)GlcNAc(beta 1-4)GlcNAc, appeared in four of 13 offspring of a single pair of clinically normal, related Nubian goats. Neurological examinations revealed that all four affected goats were unable to rise or walk. All had facial dysmorphism, dome-shaped skulls, small palpebral fissures, carpal contractures, hyperextension of the pastern joints, proximal muscle atrophy, intermittent ocular oscillations resembling pendular nystagmus, marked intention tremor, and deafness. With intensive care, three affected kids were hand-reared and then killed at 1, 7, and 21 days of age. Macroscopically, there were paucity of myelin in the cerebral and cerebellar hemispheres and ventricular dilatation. Microscopically, the extent and distribution of cytoplasmic vacuolation, myelin paucity, axonal spheroids, and filamentous expansions were evaluated in the cerebrum, cerebellum, brainstem, spinal cord, and peripheral nerves of the four affected kids and two age-matched, clinically normal kids. Widespread cytoplasmic vacuolation correlated with the previously reported accumulation of oligosaccharides in the brain and kidney and the deficiency of tissue beta-mannosidase. beta-Mannosidosis, not yet identified in man or other species, is characterized by distinctive neonatal clinical, pathological and biochemical features which differentiate it from the alpha-mannosidosis and other inherited diseases of glycoprotein catabolism.

Evidence is presented for the biochemical diagnosis of the first case of feline mannosidosis. A marked deficiency of acidic alpha-D-mannosidase in the brain, kidney and liver and excessive excretion of mannose-rich oligosaccharides in the urine were found in a kitten suffering from a nervous disorder. Residual acidic alpha-D-mannosidase, ranging from 2 to 5.5% of the normal activity, was observed in the tissues of the affected kitten. It has similar kinetic and physicochemical properties to the normal activity. The amount of mannose in the urine of the affected kitten was 19-fold greater than in a comparable control, and the molar ratio of mannose to N-acetylglucosamine was approx. 6 : 1. High concentrations of neutral oligosaccharides were detected in the urine. The predominant oligosaccharide appeared to be a hexasaccharide. The biochemical features of bovine, feline and human mannosidosis are compared, and it is concluded that feline mannosidosis may be a useful animal model for studying the human disease.

alpha-Mannosidase and beta-N-acetylglucosaminidase activities were found to differ between lymphocytes and granulocytes isolated from bovine blood. Activities of both enzymes in granulocyte preparations were found to be related to the eosinophil content of the preparations. A procedure is described that allows definition of the mannosidosis genotype of adult cattle by giving consideration to the influence of eosinophil content of granulocyte preparations upon the activity of alpha-mannosidase relative to that of beta-N-acetylglucosaminidase.

Carriers of an inborn error of lysosomal catabolism can be recognized, as they have enzyme levels approximately half those of normal individuals. Of the various tissues readily available for assay, plasma and leukocytes and, in some situations, tears are preferred. Although mixed leukocytes have proved satisfactory in Tay-Sachs screening programs, purified preparations of granulocytes or lymphocytes will allow better discrimination in most situations. Enzymes are assayed relative to some other reference parameter which must be a constant or highly correlated with test enzyme activity. In the two mass screening programs in operation, beta-hexosaminidase A and alpha-mannosidase have both been assayed relative to total beta-hexosaminidase activity. Carrier detection is particularly important in X-linked diseases. The techniques used mostly involve hair roots or fibroblasts and depend on random inactivation of the X chromosome. In the mucolipidoses II and III, in which there are a number of deficient enzymes in cells, carriers may be identified on the basis of the ratio of beta-hexosaminidase I1 and I2 to total hexosaminidase.

Lectin histochemistry is a useful technique to identify and to localize in cells and tissues the terminal carbohydrate moieties of glycoproteins and glycolipids. The specific diagnosis of some glycoprotein storage diseases was accomplished using lectin staining patterns, and such methods of diagnosis have been attempted for some glycolipid storage diseases. This technique was applied to formalin-fixed paraffin-embedded and frozen neural, hepatic, and renal tissues of sheep with an inherited lysosomal storage disease with deficiencies of beta-galactosidase and alpha-neuraminidase. The cytoplasm of central nervous system neurons of affected sheep in paraffin-embedded sections stained with peanut agglutinin (PNA), Ricinus communis agglutinin-I (RCA-I), Dolichos biflorus agglutinin (DBA), and soybean agglutinin (SBA). The cytoplasm of neurons in frozen sections of these tissues stained with PNA, RCA-I, wheat germ agglutinin (WGA), and Ulex europaeus agglutinin-I (UEA-I). The cytoplasm of frozen and paraffin-embedded sections of liver and kidney of affected sheep stained with PNA, whereas paraffin-embedded sections also stained with RCA-I. These results suggest the stored material in this disease has terminal saccharide moieties consisting of beta-galactose, N-acetylneuraminic acid, and N-acetylgalactosamine. Paraffin processing altered lectin staining patterns. Although the staining pattern in this glycolipid storage disease was complex, lectin histochemistry may prove to be a useful technique for the characterization of storage products and for the diagnosis of lysosomal storage diseases.

Plasma and leucocytes from six springer spaniels with clinical signs of fucosidosis had low activities of alpha-L-fucosidase. Fucosidase activities in plasma and leucocytes from parents of springers with fucosidosis were approximately half those in non-springer dogs. Examination of pedigree information in relation to classifications based upon plasma and leucocyte assays provided convincing evidence that fucosidosis is inherited in an autosomal recessive manner and that it is possible to detect heterozygotes using plasma and leucocyte assays.

Central nervous system (CNS) morphological changes were delineated in goats affected with beta-mannosidosis to determine the extent and distribution of lesions associated with this inherited glycoprotein metabolic perturbation. Coronal sections of one cerebral hemisphere, sagittal sections of one cerebellar hemisphere, and transverse sections of the brain stem of 4- and 16-week-old affected and control goats were analyzed. Lysosomal storage vacuoles, probably representing storage of uncleaved oligosaccharides, were present to various extents in different cell types, with variation in the size of vacuoles. Axonal spheroids were present throughout the white matter, but were most numerous in the rostal thalamic peduncle and brachium of the inferior colliculus. Mineralization occurred only in the globus pallidus and cerebellum. Unlike related storage disorders, severe deficiency of myelin occurred throughout the brain, with regional variation in the extent of myelin deficits. White matter of the corpus callosum, anterior commissure, alveus, fornix, fimbria, and medullary pyramids showed the most severe myelin paucity. Reduction in the number of oligodendroglia and vacuolation of remaining oligodendroglia occurred throughout the white matter. In general, later myelinating tracts showed the most severe myelin deficiency, suggesting that the time of myelination may be a major factor in determining the severity of myelin paucity in beta-mannosidosis.

A rapidly fatal neurovisceral storage disease was discovered in both male and female offspring of clinically normal Nubian goats. Microscopic examination of fixed tissues revealed extensive demyelination and ubiquitous distribution of lysosomal storage vacuoles containing dispersed floccular material and membranous fragments. Urine was found to contain elevated levels of both mannose and N-acetylglucosamine, suggestive of an oligosaccharide storage disease. Brain was found to contain 2.2 mumol/g of a trisaccharide Man(beta 1-4)GlcNAc(beta 1-4)GlcNAc; (Jones, M. Z., and Laine, R. A. (1980) Fed. Proc. 39, 2521 and Jones, M. Z., and Laine, R. A. (1981) J. Biol. Chem. 256, 5181-5184). A profound deficiency of beta-D-mannosidase activity was found in a number of tissues from affected goats; obligate heterozygotes showed a partial enzyme deficiency. Other lysosomal hydrolase activities were normal or elevated over normal, including alpha-D-mannosidase, confirming that this was a hitherto undescribed inborn error of glycoprotein catabolism.

Antiserum was raised in a rabbit against bovine kidney acidic alpha-mannosidase that had been purified 570-fold by affinity chromatography on concanavalin A--Sepharose and Sepharose 4B-xi-aminohexanoylmannosylamine. The antiserum precipitated the acidic but not the neutral alpha-mannosidase in normal calf tissues. Human acidic alpha-mannosidase cross-reacted partially with the antiserum, emphasizing the close structural resemblance between the enzyme in the two species. The residual acidic alpha-mannosidase in the tissues of a calf with mannosidosis was also precipitated by the antiserum, the same volume of antiserum being required to precipitate a unit of alpha-mannosidase activity from the normal and pathological tissues. The concentration of cross-reacting material detected by antibody-consumption experiments in the organs of the calf with mannosidosis appeared to be proportional to the concentration of the residual acidic alpha-mannosidase. It is suggested that the residual acidic alpha-mannosidase in mannosidosis accounts for the cross-reacting material detected and that it is unlikely that enzymically inactive but cross-reacting material is present. The residual acidic alpha-mannosidase could be a decreased concentration of the normal gene product or an altered enzyme with a decreased specific enzymic activity and a correspondingly decreased antigenicity.

Analysis of the neutral urinary oligosaccharides in bovine, feline and human mannosidosis by thin-layer and gel-permeation chromatography has shown that the patterns of stored oligosaccharides in the three species are different. In bovine and feline mannosidosis the most abundant urinary oligosaccharide is also the most abundant in the tissues of each species. The predominant oligosaccharides were purified by a combination of gel-filtration, ion-exchange and thin-layer chromatography and shown to contain only mannose and N-acetylglucosamine by g.l.c. and g.l.c.--mass spectrometry. The probable composition and size of each oligosaccharide were predicted from its chromatographic properties, sugar composition and the known structure of asparagine-linked oligosaccharides. The bovine and feline oligosaccharides belonged to a homologous series of general composition Mann (GlcNAc)2, whereas the human oligosaccharides belong to a different series, MannGlcNAc. These structures suggest that lysosomal endohexosaminidase is not present in bovine and feline tissues. The predominant feline storage product, Man3(GlcNAc)2, was the expected storage product from the catabolism of complex asparagine-linked glycans. In contrast, the predominant bovine oligosaccharide, Man2(GlcNAc)2, probably lacks one of the alpha-linked mannose residues in the core region. A similar situation occurs in human mannosidosis. It is predicted that in these species either that the residual mutant alpha-D-mannosidase retains activity towards one of the core alpha-linked mannose residues or that another form of lysosomal alpha-D-mannosidase that is unaffected in these disorders occurs. It is concluded that the differences in storage products are due to differences in the catabolic pathways of glycoproteins among the species.

Recovery of alpha-mannosidase, beta-N-acetylglucosaminidase and arylsulphatase activity from granulocytes is increased by inclusion of 154 mM sodium chloride, in place of 1 mM zinc chloride, in aqueous Triton X-100 used to extract the cells. Calculation of the ratio of alpha-mannosidase to beta-N-acetylglucosaminidase and to arylsulphatase permits diagnosis of the mannosidosis genotype without recourse to examination of smears of the granulocyte preparations.

Mannosidosis, an inherited and lethal lysosomal storage disease of Aberdeen Angus cattle, was diagnosed on a farm in north-east Scotland. Two affected calves were examined in detail. Both were poorly grown and ataxic, though the intention tremor and aggression considered characteristic of the disease were not recorded. Histological examination revealed typical vacuolation of nerve cells, fixed macrophages and epithelial cells of the viscera. Deficiency of the enzyme alpha mannosidase was demonstrated. The epidemiology of the disorder in Scotland is considered and control methods indicated.

The clinical symptoms, gross and histopathological, as well as the ultrastructural appearance of a condition in cross-bred Aberdeen Angus calves resembling the inherited lysosomal storage disease, alpha-mannosidosis, are reported. The neurones and perithelial cells in the brain and the reticuloendothelial cells in the lymph nodes and spleen were extensively vacuolated. The vacuoles were filled with a sparse, flocculated to granular material within which membranous structures were frequently seen. No specific substance could be identified within the vacuoles, either histochemically or ultrastructurally. Besides the vacuolation, cystic tubular structures were seen in the kidneys. The lining epithelial cells of the thyroid follicles were vacuolated while some of the follicles contained no colloid.

The finding of zymogen granules within lysosomal storage vesicles in pancreatic exocrine tissue in bovine mannosidosis may explain the widespread vacuolation of exocrine cells in this disease. It is uncertain if they enter the lysosomal system by the process of crinophagy but if so it would indicate that this regulatory mechanism could operate in normal exocrine tissue as well.

Enzyme replacement therapy was studied in a chimeric mannosidosis calf which had received a natural transplacental transplant of normal lymphocytes from its co-twin. There was considerable reduction in the pathology of certain organs and in the amount of storage oligosaccharides, but the clinical course of this neurologic disease was not significantly altered. It was postulated that if this disease had been purely visceral the transplant would have been relatively effective.