Neuropathological observations in maple syrup urine disease: branched-chain ketoaciduria

In Vivo Intracerebral Administration of α-Ketoisocaproic Acid to Neonate Rats Disrupts Brain Redox Homeostasis and Promotes Neuronal Death, Glial Reactivity, and Myelination Injury

Maple syrup urine disease (MSUD) is caused by severe deficiency of branched-chain α-keto acid dehydrogenase complex activity, resulting in tissue accumulation of branched-chain α-keto acids and amino acids, particularly α-ketoisocaproic acid (KIC) and leucine. Affected patients regularly manifest with acute episodes of encephalopathy including seizures, coma, and potentially fatal brain edema during the newborn period. The present work investigated the ex vivo effects of a single intracerebroventricular injection of KIC to neonate rats on redox homeostasis and neurochemical markers of neuronal viability (neuronal nuclear protein (NeuN)), astrogliosis (glial fibrillary acidic protein (GFAP)), and myelination (myelin basic protein (MBP) and 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNPase)) in the cerebral cortex and striatum. KIC significantly disturbed redox homeostasis in these brain structures 6 h after injection, as observed by increased 2',7'-dichlorofluorescein oxidation (reactive oxygen species generation), malondialdehyde levels (lipid oxidative damage), and carbonyl formation (protein oxidative damage), besides impairing the antioxidant defenses (diminished levels of reduced glutathione and altered glutathione peroxidase, glutathione reductase, and superoxide dismutase activities) in both cerebral structures. Noteworthy, the antioxidants N-acetylcysteine and melatonin attenuated or normalized most of the KIC-induced effects on redox homeostasis. Furthermore, a reduction of NeuN, MBP, and CNPase, and an increase of GFAP levels were observed at postnatal day 15, suggesting neuronal loss, myelination injury, and astrocyte reactivity, respectively. Our data indicate that disruption of redox homeostasis, associated with neural damage caused by acute intracerebral accumulation of KIC in the neonatal period may contribute to the neuropathology characteristic of MSUD patients.

A Gain-of-Function Mutation on BCKDK Gene and Its Possible Pathogenic Role in Branched-Chain Amino Acid Metabolism

BCKDK is an important key regulator of branched-chain ketoacid dehydrogenase complex activity by phosphorylating and so inactivating branched-chain ketoacid dehydrogenases, the rate-limiting enzyme of the branched-chain amino acid metabolism. We identified, by whole exome-sequencing analysis, the p.His162Gln variant of the BCKDK gene in a neonate, picked up by newborn screening, with a biochemical phenotype of a mild form of maple syrup urine disease (MSUD). The same biochemical and genetic picture was present in the father. Computational analysis of the mutation was performed to better understand its role. Extensive atomistic molecular dynamics simulations showed that the described mutation leads to a conformational change of the BCKDK protein, which reduces the effect of inhibitory binding bound to the protein itself, resulting in its increased activity with subsequent inactivation of BCKDC and increased plasmatic branched-chain amino acid levels. Our study describes the first evidence of the involvement of the BCKDK gene in a mild form of MSUD. Although further data are needed to elucidate the clinical relevance of the phenotype caused by this variant, awareness of this regulatory activation of BCKDK is very important, especially in newborn screening data interpretation.

Brain Branched-Chain Amino Acids in Maple Syrup Urine Disease: Implications for Neurological Disorders

Maple syrup urine disease (MSUD) is an autosomal recessive disorder caused by decreased activity of the branched-chain α-ketoacid dehydrogenase complex (BCKDC), which catalyzes the irreversible catabolism of branched-chain amino acids (BCAAs). Current management of this BCAA dyshomeostasis consists of dietary restriction of BCAAs and liver transplantation, which aims to partially restore functional BCKDC activity in the periphery. These treatments improve the circulating levels of BCAAs and significantly increase survival rates in MSUD patients. However, significant cognitive and psychiatric morbidities remain. Specifically, patients are at a higher lifetime risk for cognitive impairments, mood and anxiety disorders (depression, anxiety, and panic disorder), and attention deficit disorder. Recent literature suggests that the neurological sequelae may be due to the brain-specific roles of BCAAs. This review will focus on the derangements of BCAAs observed in the brain of MSUD patients and will explore the potential mechanisms driving neurologic dysfunction. Finally, we will discuss recent evidence that implicates the relevance of BCAA metabolism in other neurological disorders. An understanding of the role of BCAAs in the central nervous system may facilitate future identification of novel therapeutic approaches in MSUD and a broad range of neurological disorders.

Evaluation of plasma biomarkers of inflammation in patients with maple syrup urine disease

Maple syrup urine disease (MSUD) is an autosomal recessive inherited disorder that affects branched-chain amino acid (BCAA) catabolism and is associated with acute and chronic brain dysfunction. Recent studies have shown that inflammation may be involved in the neuropathology of MSUD. However, these studies have mainly focused on single or small subsets of proteins or molecules. Here we performed a case-control study, including 12 treated-MSUD patients, in order to investigate the plasmatic biomarkers of inflammation, to help to establish a possible relationship between these biomarkers and the disease. Our results showed that MSUD patients in treatment with restricted protein diets have high levels of pro-inflammatory cytokines [IFN-γ, TNF-α, IL-1β and IL-6] and cell adhesion molecules [sICAM-1 and sVCAM-1] compared to the control group. However, no significant alterations were found in the levels of IL-2, IL-4, IL-5, IL-7, IL-8, and IL-10 between healthy controls and MSUD patients. Moreover, we found a positive correlation between number of metabolic crisis and IL-1β levels and sICAM-1 in MSUD patients. In conclusion, our findings in plasma of patients with MSUD suggest that inflammation may play an important role in the pathogenesis of MSUD, although this process is not directly associated with BCAA blood levels. Overall, data reported here are consistent with the working hypothesis that inflammation may be involved in the pathophysiological mechanism underlying the brain damage observed in MSUD patients.

Structural white matter changes in adolescents and young adults with maple syrup urine disease

OBJECTIVE

To get insight into the nature of magnetic resonance (MR) white matter abnormalities of patients with classic maple syrup urine disease (MSUD) under diet control.

METHODS

Ten patients with classic MSUD and one with a severe MSUD variant (mean age 21.5 ± 5.1 years) on diet and 11 age and sex-matched healthy subjects were enrolled. Apart from standard MR sequences, diffusion weighted images (DWI), diffusion tensor images (DTI), and magnetization transfer images (MT) were obtained and comparatively analyzed for apparent diffusion coefficient (ADC), tensor fractional anisotropy (FA) and MT maps in 11 regions of interest (ROI) within the white matter.

RESULTS

In MSUD patients DWI, DTI and FA showed distinct signal changes in the cerebral hemispheres, the dorsal limb of internal capsule, the brain stem and the central cerebellum. Signal intensity was increased in DWI with a reduced ADC and decreased values for FA. MT did not reveal differences between patients and control subjects.

CONCLUSION

Signal abnormalities in the white matter of adolescents and young adults under diet control may be interpreted as consequence of structural alterations like dysmyelination. The reduced ADC and FA in the white matter with preserved MT indicate a reduction in fiber tracks.

Interrupting the mechanisms of brain injury in a model of maple syrup urine disease encephalopathy

Maple syrup urine disease (MSUD) was first recognized as an inherited lethal encephalopathy beginning in the first week of life and associated with an unusual odor in the urine of affected children. It was later confirmed as a deficiency of branched-chain keto acid dehydrogenase (BCKDH), which is the second step in branched-chain amino acid (BCAA) breakdown. MSUD is characterized by BCAA and branched-chain keto acid (BCKA) accumulation. BCAAs are essential amino acids and powerful metabolic signals with severe consequences of both deprivation and accumulation. Treatment requires life-long dietary restriction and monitoring of BCAAs. However, despite excellent compliance, children commonly suffer metabolic decompensation during intercurrent illness resulting in life-threatening cerebral edema and dysmyelination. The mechanisms underlying brain injury have been poorly understood. Recent studies using newly developed mouse models of both classic and intermediate MSUD have yielded insight into the consequences of rapid BCAA accumulation. Additionally, these models have been used to test preliminary treatments aimed at competing with blood-brain barrier transport of BCAA using norleucine. Assessment of biochemical changes with and without treatment suggests different roles for BCAA and BCKA in the mechanism of brain injury.

Mutation of zebrafish dihydrolipoamide branched-chain transacylase E2 results in motor dysfunction and models maple syrup urine disease

Analysis of zebrafish mutants that demonstrate abnormal locomotive behavior can elucidate the molecular requirements for neural network function and provide new models of human disease. Here, we show that zebrafish quetschkommode (que) mutant larvae exhibit a progressive locomotor defect that culminates in unusual nose-to-tail compressions and an inability to swim. Correspondingly, extracellular peripheral nerve recordings show that que mutants demonstrate abnormal locomotor output to the axial muscles used for swimming. Using positional cloning and candidate gene analysis, we reveal that a point mutation disrupts the gene encoding dihydrolipoamide branched-chain transacylase E2 (Dbt), a component of a mitochondrial enzyme complex, to generate the que phenotype. In humans, mutation of the DBT gene causes maple syrup urine disease (MSUD), a disorder of branched-chain amino acid metabolism that can result in mental retardation, severe dystonia, profound neurological damage and death. que mutants harbor abnormal amino acid levels, similar to MSUD patients and consistent with an error in branched-chain amino acid metabolism. que mutants also contain markedly reduced levels of the neurotransmitter glutamate within the brain and spinal cord, which probably contributes to their abnormal spinal cord locomotor output and aberrant motility behavior, a trait that probably represents severe dystonia in larval zebrafish. Taken together, these data illustrate how defects in branched-chain amino acid metabolism can disrupt nervous system development and/or function, and establish zebrafish que mutants as a model to better understand MSUD.

Animal models of maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited aminoacidopathy resulting from dysfunction of the branched-chain keto acid dehydrogenase (BCKDH) complex. This disease is currently treated primarily by dietary restriction of branched-chain amino acids (BCAAs). However, dietary compliance is often challenging. Conversely, liver transplantation significantly improves outcomes, but donor organs are scarce and there are high costs and potential risks associated with this invasive procedure. Therefore, improved treatment options for MSUD are needed. Development of novel treatments could be facilitated by animal models that accurately mimic the human disease. Animal models provide a useful system in which to explore disease mechanisms and new preclinical therapies. Here we review MSUD and currently available animal models and their corresponding relevance to the human disorder. Using animal models to gain a more complete understanding of the pathophysiology behind the human disease may lead to new or improved therapies to treat or potentially cure the disorder.

Dual mechanism of brain injury and novel treatment strategy in maple syrup urine disease

Maple syrup urine disease (MSUD) is an inherited disorder of branched-chain amino acid metabolism presenting with life-threatening cerebral oedema and dysmyelination in affected individuals. Treatment requires life-long dietary restriction and monitoring of branched-chain amino acids to avoid brain injury. Despite careful management, children commonly suffer metabolic decompensation in the context of catabolic stress associated with non-specific illness. The mechanisms underlying this decompensation and brain injury are poorly understood. Using recently developed mouse models of classic and intermediate maple syrup urine disease, we assessed biochemical, behavioural and neuropathological changes that occurred during encephalopathy in these mice. Here, we show that rapid brain leucine accumulation displaces other essential amino acids resulting in neurotransmitter depletion and disruption of normal brain growth and development. A novel approach of administering norleucine to heterozygous mothers of classic maple syrup urine disease pups reduced branched-chain amino acid accumulation in milk as well as blood and brain of these pups to enhance survival. Similarly, norleucine substantially delayed encephalopathy in intermediate maple syrup urine disease mice placed on a high protein diet that mimics the catabolic stress shown to cause encephalopathy in human maple syrup urine disease. Current findings suggest two converging mechanisms of brain injury in maple syrup urine disease including: (i) neurotransmitter deficiencies and growth restriction associated with branched-chain amino acid accumulation and (ii) energy deprivation through Krebs cycle disruption associated with branched-chain ketoacid accumulation. Both classic and intermediate models appear to be useful to study the mechanism of brain injury and potential treatment strategies for maple syrup urine disease. Norleucine should be further tested as a potential treatment to prevent encephalopathy in children with maple syrup urine disease during catabolic stress.

Cytoskeleton as a potential target in the neuropathology of maple syrup urine disease: insight from animal studies

In this short review we provide evidence that the branched-chain keto acids accumulating in the neurometabolic disorder maple syrup urine disease disturb rat cerebral cytoskeleton in a developmentally regulated manner. Alterations of protein phosphorylation leading to brain cytoskeletal misregulation and neural cell death caused by these metabolites are associated with energy deprivation, oxidative stress and excitotoxicity that may ultimately disrupt normal cell function and viability.

Maple Syrup Urine Disease

We present conventional magnetic resonance (MR) imaging with diffusion-weighted and diffusion-tensor imaging findings in a 10-day-old neonate with maple syrup urine disease (MSUD). On conventional MR imaging, signal abnormalities were noted in the affected white matter of cerebellum, dorsal brainstem, thalami, posterior limbs of internal capsules, and the corona radiata. These regions showed marked hyperintensity on diffusion-weighted images with decreased apparent diffusion coefficient values (average 68% reduction). Diffusion-tensor imaging showed decreased anisotropy (average 57% reduction) in the corresponding areas. Both diffusion-weighted and diffusion-tensor imaging are valuable in the diagnosis and understanding of the pathogenesis of MSUD, with findings that suggest cytotoxic edema and damaged oligodendro-axonal units within the affected white matter.

Synaptosomal transport of branched chain amino acids in young, adult and aged rat brain cortex

Uptake of branched chain amino acids (BCAA, leucine and isoleucine) was studied in synaptosomes prepared from the cerebral cortex of rats of 1, 3 and 24 months of age. In addition to the conventional low affinity sodium independent transport system, a high affinity sodium dependent stereospecific transport system for the transport of BCAA was identified in synaptosomes prepared from the cerebral cortex of the above three age groups. There was an overall decrease in Km and Vmax of both high and low affinity transport systems for leucine and isoleucine in the cortical synaptosomes of 24-month-old rats when compared with younger age groups. This study indicates that the non-neurotransmitter essential amino acids are transported by high and low affinity transport systems and these systems undergo age-dependent alterations. These changes might be due to the altered synthesis of these transporter proteins and/or synthesis of transporters with altered conformation and/or changes in the physical properties (fluidity) of the membrane. The decrease in the transport of BCAA is on a par with the decrease in the overall metabolism of BCAA in brain. As food consumption decreases in the older age groups of animals, the availability of essential amino acids to the tissues might also be lowered. Under such conditions, it is suggested that the observed increase in the affinity (decreased Km) of the carrier might be helpful in the supply of essential amino acids.

Maple syrup urine disease: clinical, EEG, and plasma amino acid correlations with a theoretical mechanism of acute neurotoxicity

Classical Maple Syrup Urine Disease (MSUD) is a disease of infancy which is an inherited disorder of metabolism of branched-chain amino acids (BCAA). The BCAA are normally transaminated to branched-chain keto acids (BCKA). However, the enzyme required to metabolize the BCKA is deficient, resulting in elevation of both, the BCAA and the BCKA. One of the BCAA (isoleucine) produces a metabolite that causes the urine to smell like maple syrup. The elevations of the BCAA and BCKA are associated with an acute, critical neurotoxic condition often prior to the age of two weeks. The clinical state, the electroencephalogram-(EEG), and plasma BCAA levels were evaluated in 26 patients with classical and variant MSUD. Patients were seen from the time of diagnosis, often within a week after birth, and some were followed clinically for more than 20 years while on specific diet therapy. They were monitored by plasma BCAA (leucine, isoleucine and valine) levels and a total of 101 EEGs were performed during different phases of their illness. During periods of acute metabolic decompensation, there were marked clinical symptoms of neurotoxicity including opisthotonos, seizures, and coma with elevated BCAA plasma levels. The EEGs revealed spikes, polyspikes, spike-wave complexes, triphasic waves, severe slowing and bursts of periodic suppression. Occasionally paradoxical EEG arousal was noted while the patient was lethargic. During asymptomatic periods when the plasma BCAA were at low or normal levels, EEG abnormalities occurred in patients with and without residual neurological deficit. These observations included rolandic sharp waves (comb-like rhythm) which were observed in 7 of 15 patients less than two months of age. Additionally, paroxysmal spike and spike-wave response to photic stimuli were observed in 9 of 17 patients. Loading tests were performed on three patients. Clinical and EEG changes were most marked after leucine. Less dramatic EEG changes also occurred with the other two BCAA loads but without clinical manifestations. Elevation of the appropriate BCAA plasma level occurred after each load. These studies and a review of the literature suggest that one component of the pathophysiological mechanism for the acute neurotoxic effects in this disorder is related to a defect in glutamate, glutamine and gamma-aminobutyric acid (GABA) production. The BCAAs are transaminated to BCKAs. Further metabolism of the BCKAs are blocked because of enzyme deficiency required for decarboxylation.(ABSTRACT TRUNCATED AT 400 WORDS)

Myelination in the developing human brain: biochemical correlates

To delineate the biochemical sequences of myelination in the human brain, we analyzed the protein and lipid composition of white matter in 18 baseline cases ranging in age from midgestation through infancy, the critical period in human myelination when the most rapid changes occur. Three adult cases were used as indices of maturity, and 4 cases with major disorders of CNS myelination (maple syrup urine disease, severe periventricular leukomalacia, idiopathic central hypomyelination, and metachromatic leukodystrophy) were analyzed. Brain samples were obtained < or = 24 hours after death. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high performance thin-layer chromatography were used to separate and identify proteins and polar and neutral lipids in an average of 10 sites/brain; computer-based densitometry was used to quantify polar lipids. Biochemical sequences, as manifested by the appearance of the myelin-associated lipids and myelin-specific proteins, closely followed previously described anatomic sequences both temporally and by region, and were identical in all sites sampled: sphingomyelin was followed simultaneously by cerebrosides, MBP, PLP, and nonhydroxy-sulfatide, followed by hydroxy-sulfatide. The onset and tempo of the expression of individual constituents, however, were quite variable among sites, suggesting a wide differential in vulnerable periods to insult in biochemically-specific pathways in early life. Cholesterol ester was transiently elevated during late gestation and early infancy, prior to and around the time of the appearance of cerebrosides, sulfatides, PLP, and MBP. Distinctive lipid and protein abnormalities were detected in idiopathic central hypomyelination and metachromatic leukodystrophy. This study underscores the feasibility of the combined biochemical approaches in pediatric brains and provides guidelines for the assessment of disorders of myelination in early human life.

Is demyelination a feature of maple syrup urine disease?

To determine whether disturbance of myelination is a pathophysiologic feature in patients with treated maple syrup urine disease (MSUD), neurophysiologic studies were performed in 10 MSUD patients ages 4-16 years. Afferent and efferent pathways were studied by visual evoked potentials, somatosensory evoked potentials, motor evoked potentials, stance-stabilizing reflexes, and peripheral nerve conduction velocity. Magnetic resonance imaging was used to detect possible cerebral white matter abnormalities. Visual evoked potentials were normal in all patients. There was only slight prolongation of central afferent and efferent conduction times and the long latency component of the stance-stabilizing reflexes. Peripheral nerve conduction studies revealed reduced sensory nerve conduction velocity in 3 patients. The neurophysiologic findings were not consistently correlated to the neurologic outcome of the patients. Magnetic resonance imaging did not reveal major abnormalities and demonstrated bilateral periventricular high intensity periventricular signals on T2-weighted images in 4 of 10 patients. It is concluded that dysmyelination is not a major pathophysiologic feature in patients with MSUD.

Computed tomography in maple syrup urine disease

Maple Syrup Urine Disease (MSUD) is an inherited metabolic disorder characterized by a severe, usually lethal, neonatal course in the early stages with pseudotumor cerebri and pathologically documented increased cerebral water content. CT and MRI studies in MSUD are few and the data are overlapping. This study reports CT features before and after dietary treatment in three patients; two with classical MSUD and one with an intermediate variant of MSUD. At diagnosis, CT consistently showed evidence of abnormally high lucidity involving not only white matter, but also areas of grey matter, particularly the pallidum. Furthermore, these CT changes are present both in the acute phase of classical MSUD and in an intermediate variant of the disease. The observed abnormalities evolve favorably under dietary treatment, simultaneously with clinical and neurological improvement. It is concluded that the observed CT changes indicate a diagnosis of MSUD and are relevant findings in the neuroradiologic differential diagnosis in acutely ill newborns, in which a metabolic disease may be not immediately suspected.

Abnormal dendritic development in maple syrup urine disease

The neuropathology of a 6-year-old boy with maple syrup urine disease revealed spongy appearance of the white matter and marked edema of the brainstem. Golgi studies demonstrated aberrant orientation of neurons together with abnormalities of dendrites and dendritic spines. Similar changes were observed in a patient with dihydropteridine reductase deficiency. Disorders of amino acid metabolism may be associated with alterations in the terminal stages of neuronal migration and maturation.

Non-ketotic hyperglycinaemia: clinical and biochemical aspects

Non-ketotic hyperglycinaemia is an autosomal recessive disorder of glycine metabolism characterized by elevated concentrations of glycine in plasma, urine and cerebrospinal fluid. The fundamental defect was found to lie in the glycine cleavage system. It is of significance that the major pathway for the catabolism of glycine was elucidated through the studies of hyperglycinaemia. The present knowledge about non-ketotic hyperglycinaemia is described in clinical and biochemical aspects.

Ultrastructural findings in maple syrup urine disease in Poll Hereford calves

Ultrastructural findings in the nervous systems of two Poll Hereford calves affected with maple syrup urine disease or branched chain ketoacid decarboxylase deficiency are described. The calves were affected within 2 days of birth with a severe generalised central nervous system (CNS) disorder characterised by dullness and weakness, progressing to recumbency and opisthotonus. The urine had an odour of burnt sugar. Analysis of plasma and cerebrospinal fluid demonstrated significantly elevated levels of the branched chain amino acids leucine, isoleucine and valine. Status spongiosus affecting mainly the white matter was recorded at microscopic examination of the CNS, with ultrastructural examination confirming the presence of intramyelinic vacuole formation, suggesting myelin oedema.

Phenylketonuria in Indian children

Three untreated phenylketonuric Indian children aged respectively 3 1/2 years, 1 1/2 years and 1 year showed rapid neurological deterioration. Plasma, cerebrospinal fluid and urine phenylalanine concentrations were significantly raised and the phenylalanine-tyrosine ratio was high. Analysis of a biopsy of the right frontal lobe of the brain in one case showed the myeline lipids--cerebroside and sulphatide--to be decreased. The total cerebroside in white matter was low. Light microscopy showed marked pallor of the white matter of the brain and extensive spongy degeneration. Ultrastructurally these spongy vesicles are located between the lamellae of the myelin sheath.

Spongy degeneration of the central nervous system (van Bogaert-Bertrand type?) in a newborn infant. A light and electron microscopic study

Autopsy findings on a 5 day old infant with hypotonia from birth showed extensive spongy changes of the myelinating tracts within the cerebrum, cerebellum and brain stem. The spongy changes, similar to Van Bogaert-Bertrand disease, resulted from intramyelinic edema. However, unlike the typical forms of this disease, swollen astrocytes with abnormal mitochondria were not found. The relationship of this case to typical forms of Van Bogaert-Bertrand disease is discussed. This case may represent a very early form of Van Bogaert-Bertrand disease or a new pathological entity.

Neuropathological considerations in cerebro-hepato-renal syndrome (Zellweger's syndrome)

The nervous system in patients with cerebro-hepato-renal syndrome appeared to be affected at various tissue levels. There was evidence of a migrational disorder manifested by polymicrogyria and lack of normal neuronal maturation. There was dysmyelination of the white matter associated with accumulation of neutral fat in astrocytes. Within the peripheral nerves, masses of tangled neurofilaments producing dystrophic axons were demonstrated by electron microscopy. These findings could be explained on the basis of a genetic metabolic defect, one that involved particularly the amino acids. The defect may have interfered with the normal intercellular reaction during embryogenesis resulting in the malformation of multiple organs. The same metabolic abnormality could have caused the hepatic damage and disturbance in normal myelination during the neonatal period.

Infantile spongy degeneration of the central nervous system associated with glycogen storage and markedly fatty liver

The clinical, biochemical, and pathological features of an unusual expression of infantile spongy degeneration of the central white matter are presented with emphasis on neuropathological observations. The topographical distribution of the spongy change along with the observed defect in myelination were such as to suggest an arrest in development of the white matter in late foetal life. Of additional interest, in the present case, is the observed deposition of glycogen in the brain, heart, and liver along with a markedly fatty liver. Our findings are compared with those in other cases of so-called spongy degeneration, as well as with certain of the aminoacidurias and, as a consequence, we wish to suggest that the basic pathogenetic factor probably lies in a disturbance of the biochemical energy supply system rather than in a disorder of myelin lipid metabolism per se.

Hereditary neuraxial edema in Hereford calves

Twelve newborn Hereford calves from 8 herds showed extensor spasms upon stimulation and inability to rise. Neuraxial lesions consisted of widespread vacuolation interpreted as edema and seen chiefly in terminal portions of myelinated bundles and in gray substance containing heavily myelinated fibers. Genetic analysis of 2 of these herds indicated an autosomal recessive pattern of transmission tracing back to a single bull. The identity of the disease in all herds suggested that it had the same hereditary basis in all of them.

Spongy degeneration in the white matter of the central nervous system in the newborn: pathological findings in three infants, one with hyperglycinaemia

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