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T M Cox

Publications and source records attributed to T M Cox.

At least 37 records · Page 2Linked to original sources
PubMed2000

Widespread expression of tartrate-resistant acid phosphatase (Acp 5) in the mouse embryo.

Tartrate-resistant acid phosphatase (TRAP, Acp 5) is considered to be a marker of the osteoclast and studies using 'knockout' mice have demonstrated that TRAP is critical for normal development of the skeleton. To investigate the distribution of TRAP in the mammalian embryo, cryostat sections of 18 d murine fetuses were examined by in situ hybridisation, immunohistochemistry and histochemical reactions in situ. Abundant expression of TRAP mRNA was observed in the skin and epithelial surfaces of the tongue, oropharynx and gastrointestinal tract including the colon, as well as the thymus, ossifying skeleton and dental papillae. TRAP protein was identified at the same sites, but the level of expression in the different tissues did not always correlate with apparent enzyme activity. The findings indicate that abundant TRAP expression is not confined to osteoclasts in bone, but occurs in diverse tissues harbouring cells of bone marrow origin, including dendritic cells and other cells belonging to the osteoclast/macrophage lineage.

Acid Phosphatase↗
PubMed2000

Massive hepatic fibrosis in Gaucher's disease: clinico-pathological and radiological features.

Hepatomegaly is frequent in patients with type 1 Gaucher's disease and is associated with infiltration of the liver with pathological macrophages. Most patients suffer no significant clinical consequences, but a few develop portal hypertension which may progress to parenchymal liver failure. We describe four patients with Gaucher's disease who have developed portal hypertension. We have reviewed their clinical histories and all available histological and radiological material. All had severe Gaucher's disease with multi-organ involvement, and had undergone splenectomy in childhood. Histologically, this advanced liver disease was characterized by a picture of extreme and advanced confluent fibrosis occupying the central region of the liver. This massive fibrosis is associated with characteristic radiological appearances. The liver histology in these cases is highly unusual and virtually unknown in other conditions. Our studies indicate that without specific treatment the liver disease is progressive and rapidly fatal. However, institution of enzyme replacement therapy with imiglucerase may have beneficial effects even when the condition is far advanced.

Adolescent↗
PubMed2000

Localization of iron transport and regulatory proteins in human cells.

The recent discovery of HFE, the MHC-Class-I-like gene mutated in up to 90% of patients with hereditary haemochromatosis, and the gene encoding the Nramp2/divalent metal transporter-1 (DMT-1) implicated in ferrous iron transport holds promise for a greater understanding of human iron metabolism. Since the HFE protein can be crystallized as a ternary complex with the transferrin receptor and iron-saturated transferrin, and DMT-1 expression is up-regulated in hereditary haemochromatosis, these proteins are likely to interact in a common pathway for human iron homeostasis. To investigate the cellular interactions between the cognate proteins encoded by these genes, we generated a panel of rabbit and avian antisera from human HFE and DMT-1 derived peptides. The antibodies were characterized by ELISA reactions and Western immunoblotting. Immunohistochemical staining showed that DMT-1 protein localized to the brush border of human duodenum where it is predicted to serve as the principal transporter of ferrous iron from the intestinal lumen. In the human cell lines, Caco-2 (small intestinal phenotype upon differentiation) and K562 (erythroleukaemic) HFE, in the presence of iron-saturated transferrin, co-localized with transferrin receptors in an early endosome compartment using confocal immunofluorescence microscopy. This interaction may be critical in small-intestinal crypt cells which express HFE, where it may function to modulate their intrinsic iron status thereby programming iron absorption by DMT-1 in the mature enterocyte. In undifferentiated Caco-2 cells, DMT-1 localized to a discrete late endosome compartment distinct from that occupied by HFE where, in addition to brush-border iron uptake, it may function to regulate the availability of iron delivery to intracellular iron pools. Disruption of the HFE gene as a result of mutations associated with hereditary haemochromatosis may thus impair homeostatic mechanisms controlling iron absorption within the small-intestine epithelium by a direct interaction with transferrin receptors and by subsequent alteration of DMT-1 expression. Identification of the molecular interactions of HFE with DMT-1 and other key components of the iron transport pathway has implications for a mechanistic understanding of the pathophysiology of human iron storage diseases as well as the regulation of normal iron balance.

Animals↗
PubMed2000

Osteoclastic tartrate-resistant acid phosphatase (Acp 5): its localization to dendritic cells and diverse murine tissues.

Tartrate-resistant acid phosphatase (TRAP) is a histochemical marker of the osteoclast. It is also characteristic of monohistiocytes, particularly alveolar macrophages, and is associated with diverse pathological conditions, including hairy cell leukemia and AIDS encephalopathy. To study the biology of this enzyme, we investigated its expression and activity in mouse tissues. Confocal fluorescence studies showed that TRAP is localized to the lysosomal compartment of macrophages. In adult mice, high activities of the enzyme were demonstrated in bone, spleen, liver, thymus, and colon, with lower amounts in lung, stomach, skin, brain, and kidney. Trace amounts were detected in testis, muscle, and heart. Expression of TRAP mRNA was investigated in tissue sections by in situ hybridization and protein expression was monitored by histochemical staining or immunohistochemically. TRAP is widely expressed in many tissues, where it is associated with cells principally originating from the bone marrow, including those of osteoclast/macrophage lineage. The cellular distribution of TRAP mRNA and enzyme antigen in the tissues corresponds closely to that of cells staining with an antibody directed to the CD80 (B7) antigen. Therefore, to confirm its putative localization in dendritic cells, isolated bone marrow dendritic cells were matured in culture. These co-stained strongly for TRAP protein and the CD80 antigen. These studies demonstrate that TRAP is a lysosomal enzyme that is found in diverse murine tissues, where it is expressed in dendritic cells as well as osteoclasts and macrophages, as previously shown. (J Histochem Cytochem 48:219-227, 2000)

Acid Phosphatase↗
PubMed1999

Alteration of substrate specificity by a naturally-occurring aldolase B mutation (Ala337-->Val) in fructose intolerance.

A molecular analysis of human aldolase B genes in two newborn infants and a 4-year-old child with hereditary fructose intolerance, the offspring of a consanguineous union, has identified the novel mutation Ala337-->Val in homozygous form. This mutation was also detected independently in two other affected individuals who were compound heterozygotes for the prevalent aldolase B allele, Ala149-->Pro, indicating that the mutation causes aldolase B deficiency. To test for the effect of the mutation, catalytically active wild-type human aldolase B and the Val337 variant enzyme were expressed in Escherichia coli. The specific activities of the wild-type recombinant enzyme were 4.8 units/mg and 4.5 units/mg towards fructose 1,6-bisphosphate (FBP) and fructose 1-phosphate (F-1-P) as substrates with Michaelis constants of 4 microM and 2.4 mM respectively. The specific activities of purified tetrameric Val337 aldolase B, which affects an invariant residue in the C-terminal region, were 4.2 units/mg and 2.6 units/mg towards FBP and F-1-P as substrates respectively; the corresponding Michaelis constants were 22 microM and 24 mM. The FBP-to-F-1-P substrate activity ratios were 0.98 and 1.63 for wild-type and Val337 variant enzymes respectively. The Val337 mutant aldolase had an increased susceptibility to proteolytic cleavage in E. coli and rapidly lost activity on storage. Comparative CD determinations showed that the Val337 protein had a distinct thermal denaturation profile with markedly decreased enthalpy, indicating that the mutant protein is partly unfolded. The undegraded mutant had preferentially decreased affinity and activity towards its specific F-1-P substrate and maintained appreciable activity towards FBP. In contrast, fluorescence studies of the mutant showed an increased binding affinity for products of the aldolase reaction, indicating a role for the C-terminus in mediating product release. These findings in a rare but widespread naturally occurring mutant implicate the C-terminus in the activity of human aldolase B towards its specific substrates and demonstrate its role in maintaining the overall stability of the enzyme tetramer.

Amino Acid Substitution↗
PubMed1999

Metachromatic leucodystrophy: a newly identified mutation in arylsulphatase A, D281Y, found as a compound heterozygote with I179L in an adult onset case.

The majority of mutations identified in patients with Metachromatic leucodystrophy are unique to individual families. We report here a new mutation in the arylsulphatase A gene (D281Y) identified in a patient with late-onset Metachromatic leucodystrophy. This mutation was inherited in cis with the common pseudo-deficiency allele and in trans with the previously described I179S (250100.0008) mutation which complicated the enzymatic diagnosis of this condition. Sequence comparison shows D281 to be highly conserved amongst the arylsulphatases. The clinical features of this patient which are predominantly of a slowly progressive psychiatric and intellectual deterioration rather than rapid neurological impairment are typical of I179S compound heterozygotes.

Adult↗
PubMed1999

Mice deficient in the urea-cycle enzyme, carbamoyl phosphate synthetase I, die during the early neonatal period from hyperammonemia.

Ammonia liberated during amino acid catabolism in mammals is highly neurotoxic and is detoxified by the five enzymes of the urea cycle that are expressed within the liver. Inborn errors of each of the urea cycle enzymes occur in humans. Carbamoyl phosphate synthetase I (CPSase I; EC 6.3.4.16) is located within the inner mitochondrial matrix and catalyzes the initial rate-limiting step of the urea cycle. Unless treated, complete deficiency of CPSase I, a rare autosomal recessive disease, causes death in newborn infants. Survivors are often mentally retarded and suffer frequent hyperammonemic crises during intercurrent illness or other catabolic stresses. Biochemically, CPSase I deficiency is characterized by high levels of blood ammonia, glutamine, and alanine, with low or absent citrulline and arginine levels. As a first step toward the development of gene therapy directed to the hepatocyte, we have generated a CPSase I-deficient mouse by gene targeting. Mice with homozygous disruption of CPSase I (CPSase [-/-] mice) die within 36 hours of birth with overwhelming hyperammonemia, and without significant liver pathology. This animal is a good model of human CPSase I deficiency.

Amino Acid Sequence↗
PubMed1999

Inherited disorders of iron storage and transport.

Diverse hereditary disorders associated with iron accumulation cause widespread organ damage. New insights into cellular pathways of iron transport have emerged from the identification of molecules implicated in heritable defects of iron metabolism. Unravelling the genetic basis of rare variants of haemochromatosis should provide vital functional information to further our mechanistic understanding of iron homeostasis.

Adult↗
PubMed1999

Juvenile hemochromatosis locus maps to chromosome 1q.

Juvenile hemochromatosis (JH) is an autosomal recessive disorder that leads to severe iron loading in the 2d to 3d decade of life. Affected members in families with JH do not show linkage to chromosome 6p and do not have mutations in the HFE gene that lead to the common hereditary hemochromatosis. In this study we performed a genomewide search to map the JH locus in nine families: six consanguineous and three with multiple affected patients. This strategy allowed us to identify the JH locus on the long arm of chromosome 1. A maximum LOD score of 5.75 at a recombination fraction of 0 was detected with marker D1S498, and a LOD score of 5. 16 at a recombination fraction of 0 was detected for marker D1S2344. Homozygosity mapping in consanguineous families defined the limits of the candidate region in an approximately 4-cM interval between markers D1S442 and D1S2347. Analysis of genes mapped in this interval excluded obvious candidates. The JH locus does not correspond to the chromosomal localization of any known gene involved in iron metabolism. These findings provide a means to recognize, at an early age, patients in affected families. They also provide a starting point for the identification of the affected gene by positional cloning.

Adolescent↗
PubMed1998

Haemochromatosis: an inherited metal and toxicity syndrome.

A newly-identified major histocompatibility Class I-like gene, HFE (originally HLA-H) located approximately 3.5 Mb telomeric to the Class I cluster on chromosome 6p 21.3 harbours mutations in haemochromatosis. Two of these, Cys282Tyr (C282Y) and His63Asp (H63D, a minor determinant) have diagnostic utility as approximately 90% of adults are homozygous or compound heterozygotes for these alleles. The pathophysiological role of HFE is unclear: it is expressed as a surface molecule on many cells and the C282Y mutation disrupts interactions with beta 2-microglobulin, thus preventing surface expression. Lately, there has been experimental evidence that HFE protein interacts with the transferrin-receptor, affecting receptor turnover or its affinity for ligand.

Animals↗
PubMed1998

Protoporphyria.

Human protoporphyria results from mutations in the ferrochelatase gene. Heritable deficiency of ferrochelatase causes overproduction of protoporphyrin IX, principally in the erythron. Photosensitivity is a universal feature of protoporphyria but hepatic clearance of the hydrophobic protoporphyrin molecule with excretion in bile may lead to precipitation within biliary pathways. Thus cholestatic injury and protoporphyrin gallstones occur. Minor hepatic abnormalities are frequent, but at least 30 patients have been reported with a progressive liver disease that requires transplantation. Fulminant hepatic disease appears to be recessively inherited in some pedigrees. Hazards of liver transplantation include tissue photolysis, hemolysis, and an unexplained neurological syndrome, but most of the 15 patients reported after transplantation have survived for several months to > 6 years. Aspects of protoporphyria, its pathogenesis and contemporary therapeutic strategies are considered, with emphasis on hepatic sequelae.

Animals↗
PubMed1998

Hereditary juvenile haemochromatosis: a genetically heterogeneous life-threatening iron-storage disease.

Juvenile haemochromatosis is a rare inborn error of iron metabolism with clinical manifestations before 30 years of age. Unlike adult haemochromatosis which principally affects men, juvenile haemochromatosis affects the sexes equally; it causes early endocrine failure, dilated cardiomyopathy and joint disease. We report four patients (two of each sex) from three pedigrees affected by juvenile haemochromatosis with a mean onset at 22 years (range 14-30). All had endocrine deficiency with postpubertal gonadal failure secondary to pituitary disease; two suffered near-fatal cardiomyopathy with heart failure. Mean time to diagnosis from the first clinical signs of disease was 9.8 years (range 0.5-20) but general health and parameters of iron storage responded favourably to iron-depletion therapy. A 24-year-old man listed for heart transplantation because of cardiomyopathy [left ventricular (LV) ejection fraction 16%] responded to intravenous iron chelation with desferrioxamine combined with phlebotomy (ejection fraction 31%). A 27-year-old woman with subacute biventricular heart failure refractory to medication required orthotopic cardiac transplantation before the diagnosis was established (LV ejection fraction 25%). Genetic studies showed that these two patients with cardiomyopathy from unrelated families were heterozygous for the HFE 845G-->A (C282Y) mutation and wild-type at the H63D locus: complete sequencing of the intron-exon boundaries and entire coding sequence of the HFE gene failed to identify additional lesions. Two siblings in a pedigree without cardiomyopathy were wild-type at the HFE C282Y locus; although the brother harboured a single copy of the 187C-->G (H63D) allele, segregation analysis showed that in neither sibling was the iron-storage disease linked to MHC Class I markers on chromosome 6p. Juvenile haemochromatosis is thus a genetically heterogenous disorder distinct from the common adult variant.

Adolescent↗
PubMed1998

Hereditary fructose intolerance.

Hereditary fructose intolerance (HFI, OMIM 22960), caused by catalytic deficiency of aldolase B (fructose-1,6-bisphosphate aldolase, EC 4.1.2.13), is a recessively inherited condition in which affected homozygotes develop hypoglycaemic and severe abdominal symptoms after taking foods containing fructose and cognate sugars. Continued ingestion of noxious sugars leads to hepatic and renal injury and growth retardation; parenteral administration of fructose or sorbitol may be fatal. Direct detection of a few mutations in the human aldolase B gene on chromosome 9q facilitates the genetic diagnosis of HFI in many symptomatic patients. The severity of the disease phenotype appears to be independent of the nature of the aldolase B gene mutations so far identified. It appears that hitherto there has been little, if any, selection against mutant aldolase B alleles in the population: in the UK, approximately 1.3% of neonates harbour one copy of the prevalent A149P disease allele. The ascendance of sugar as a major dietary nutrient, especially in western societies, may account for the increasing recognition of HFI as a nutritional disease and has shown the prevalence of mutant aldolase B genes in the general population. The severity of clinical expression correlates well with the immediate nutritional environment, age, culture, and eating habits of affected subjects. Here we review the biochemical, genetic, and molecular basis of human aldolase B deficiency in HFI, a disorder which responds to dietary therapy and in which the principal manifestations of disease are thus preventable.

Animals↗
PubMed1997

Transglutaminase activity is increased in Alzheimer's disease brain.

Transglutaminase is a calcium-activated enzyme that crosslinks substrate proteins into insoluble, often filamentous aggregates resistant to proteases. Because the neurofibrillary tangles in Alzheimer's disease have similar characteristics, and because tau protein, the major component of these tangles is an excellent substrate of transglutaminase in vitro, transglutaminase activity and levels were measured in control and Alzheimer's disease brain. Frozen prefrontal cortex and cerebellum samples from Alzheimer's disease and control cases matched for age and postmortem interval were used in the analyses. Total transglutaminase activity was significantly higher in the Alzheimer's disease prefrontal cortex compared to control. In addition the levels of tissue transglutaminase, as determined by quantitative immunoblotting, were elevated approximately 3-fold in Alzheimer's disease prefrontal cortex compared to control. To our knowledge, this is the first demonstration that transglutaminase is increased in Alzheimer's disease brain. There were no significant differences in transglutaminase activity or levels in the cerebellum between control and Alzheimer's disease cases. Because the elevation of transglutaminase in the Alzheimer's disease samples occurred in the prefrontal cortex, where neurofibrillary pathology is usually abundant, and not in the cerebellum, which is usually spared in Alzheimer's disease, it can be suggested that transglutaminase could be a contributing factor in neurofibrillary tangle formation.

Aged↗
PubMed1997

Gaucher's disease: clinical features and natural history.

Gaucher's disease is an inherited disorder characterized by pathological storage of glycolipid in mononuclear phagocytes: it is a multi-system disease associated with striking variation in its clinical manifestations, severity and course. Although molecular analysis of the glucocerebrosidase gene in patients with Gaucher's disease has permitted broad correlations between genotype and phenotype to be made, with few exceptions genetic variation at this locus does not allow confident prediction of clinical phenotype or prognosis. Partial deficiency of glucocerebrosidase is associated principally with parenchymal disease of the liver, spleen, bone marrow and, in severe cases, the lung, in non-neuronopathic, Type 1, Gaucher's disease: here storage material in macrophages originates from turnover of exogenous glycolipids. Severe deficiency of glucocerebrosidase caused by disabling mutations is additionally associated with neurological manifestations that in part reflect a failure to degrade endogenous neuronal glycosphingolipids, the so-called neuronopathic, Type 2 and Type 3 disease categories. Here we describe the clinical features, complications and natural history principally of Type 1 Gaucher's disease: emphasis is placed on emerging pulmonary, osseous and other manifestations of obscure pathogenesis that respond poorly to enzyme-replacement therapy.

Gaucher Disease↗