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T M Cox

Publications and source records attributed to T M Cox.

At least 55 records · Page 3Linked to original sources
PubMed1997

Erythropoietic protoporphyria.

Partial deficiency of the last enzyme of haem biosynthesis, ferrochelatase, leads to a distinct syndrome of photosensitivity caused by overproduction of protoporphyrin by erythropoietic tissue. Erythropoietic protoporphyria has an indeterminate pattern of inheritance and may be complicated by fulminating liver disease. The recent development of simple assays for ferrochelatase activity and cloning of the human ferrochelatase gene promises to shed light on the transmission of this disorder and may allow clinical expression of disease to be predicted. This review surveys the pathological features, genetics and treatment of porphyria.

Humans↗
PubMed1997

The tau protein in human cerebrospinal fluid in Alzheimer's disease consists of proteolytically derived fragments.

Previous studies have shown that the levels of the microtubule-associated protein tau in the CSF of patients with Alzheimer's disease (AD) are elevated compared with age-matched controls. In spite of these findings, the nature of tau in CSF has not been well documented. In the present study, tau was immunoprecipitated from CSF of patients with AD or acute stroke, as well as normal elderly controls, followed by immunoblot analysis. In all cases, CSF tau consisted primarily of a band migrating at 26-28 kDa. In AD and stroke patients, several smaller tau fragments were also detected. No intact tau was detected in any of the CSF samples examined. Further immunoprecipitation studies showed that the majority of the tau fragments contained the amino terminus of the molecule. Treatment of CSF tau with alkaline phosphatase did not alter the electrophoretic properties of the fragments. These studies clearly demonstrate that CSF tau is truncated rather than intact.

Alzheimer Disease↗
PubMed1997

Pro-inflammatory cytokines and the pathogenesis of Gaucher's disease: increased release of interleukin-6 and interleukin-10.

Gaucher's disease is characterized by hepatosplenomegaly, bone-marrow infiltration, osteonecrosis and bone thinning, associated with the presence of pathological macrophages that contain undegraded glycosphingolipids. To investigate the possible role of cytokines in the systemic and local manifestations of established Gaucher's disease, interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), tumour necrosis factor-alpha (TNF alpha) and interleukin-10 (IL-10) were measured in freshly-separated serum. Samples from eight male and 14 female patients with type 1 Gaucher's disease were compared with sera from 22 healthy age- and sex-matched controls. Concentrations of IL-6 and IL-10 were significantly elevated in sera from patients with Gaucher's disease (11.9 +/- 1.8 (SEM) pg/ml and 5.4 +/- 0.5 (SEM) pg/ml, respectively) compared with those of controls (4.1 +/- 0.9 (SEM) and 0.8 +/- 0.3 (SEM) pg/ml, p < 0.0001). No significant differences in concentrations of TNF alpha or IL-1 beta were identified. IL-6 has been implicated in the development of localized osteolysis in multiple myeloma and in the development of post-menopausal osteoporosis. High concentrations of IL-6 in the serum of patients with Gaucher's disease may thus reflect the development of the bone lesions commonly associated with this disorder. Since IL-6 and IL-10 are important regulators of lymphocyte growth and differentiation, and IL-6 concentrations were significantly raised in patients with oligo- or polyclonal increases in serum immunoglobulins, enhanced release of these cytokines from pathological macrophages provides a pathological link between Gaucher's disease and associated lympho-proliferative disorders.

Adult↗
PubMed1997

Homozygosity for the predominant Cys282Tyr mutation and absence of disease expression in hereditary haemochromatosis.

A candidate gene for hereditary haemochromatosis, HLA-H, has recently been presented. Two missense mutations in the HLA-H gene sequence are predicted to account for nearly 90% of all cases of the disease. The aim of this study was to correlate the presence of these missense mutations with the expressivity of the disease, as assessed by standard biochemical evaluation of serum iron parameters. Detection of the known mutations in haemochromatosis, Cys282Tyr and His63Asp, was undertaken in a large pedigree showing variable expression of the disease in successive generations. In three sibs with overt disease (one male, two female, aged 50 to 53 years), homozygosity for the predominant G to A transition (Cys282Tyr) in HLA-H was detected. However, homozygosity for this mutation was also detected in an asymptomatic male sib, aged 50, harbouring an identical genotype. The finding of an asymptomatic homozygous Cys282Tyr subject, haplo-identical to affected sibs, indicates that clinical expression of symptomatic disease is variable, even in middle aged Cys282Tyr homozygotes. This has profound implications for the future use of genetic screening for haemochromatosis.

Adult↗
PubMed1997

Translational control of erythroid delta-aminolevulinate synthase in immature human erythroid cells by heme.

Heme formation in immature erythroid cells is subject to end-product negative feedback control. Although studies with immature erythroid cells obtained from animals have shown that increased intracellular hemin inhibits the acquisition of iron from transferrin, our experiments with human reticulocytes indicate that feedback inhibition of heme biosynthesis is primarily regulated at one or more steps that lead to formation of the first committed precursor, delta-aminolevulinate (ALA). To identify the site of control of heme biosynthesis in the human erythron further, region-specific antibodies to human erythroid delta-ALA synthase (e-ALA synthase) were used to immunoprecipitate newly-synthesised enzyme from human reticulocytes after biosynthetic labelling. Low concentrations of exogenous hemin (30-35 microM) inhibited the biosynthetic labelling of mature erythroid ALA synthase that was detected by exon 4 peptide-specific antibodies and antibodies raised against the entire recombinant human erythroid ALA synthase molecule. Pulse-chase experiments after biosynthetic labelling indicated no differences in the effect of hemin on the turnover of the radiolabelled enzyme and hemin did not influence the distribution of precursor froms of the ALA synthase molecule. Parallel experiments using antibodies directed against human H-chain ferritin confirmed the specificity of the effects of hemin on translation of the e-ALA synthase mRNA. At the concentrations of hemin used to inhibit heme formation from 14C-glycine, no significant effects on the rate of overall protein synthesis were observed. We conclude that heme regulates synthesis of the first committed precursor of the porphyrin biosynthetic pathway in immature human erythroid cells by effects on the synthesis of the e-ALA synthase molecule. Although the mechanism of hemin action is unknown, it is apparently independent of 5'-iron-response elements and influences the translational activity of erythroid ALA synthase mRNA.

5-Aminolevulinate Synthetase↗
PubMed1996

Therapeutic delivery of proteins to macrophages: implications for treatment of Gaucher's disease.

BACKGROUND: The primary defect in Gaucher's disease, a lysosomal disorder affecting macrophages, is in the activity of glucocerebrosidase. Treatment with exogenous enzyme (modified to increase its affinity for macrophage glycoprotein receptors) aims to restore this activity. However, the fate of the exogenous enzyme in vivo is unknown. We used radiolabelled enzyme to assess macrophage receptor activity for mannosylated ligands in vivo. METHODS: We examined the uptake and tissue distribution of radiolabelled enzyme molecules by gamma scintigraphy after bolus injection of iodine-123-labelled recombinant or placental enzyme (imiglucerase and alglucerase, respectively) in eight patients with type 1 Gaucher's disease, and in one healthy individual. The metabolism of the tracer enzyme was followed by scintigraphy and by analysis of blood, urine, and faeces. RESULTS: The tracer enzyme was rapidly cleared from blood (half-life 4.7 min [SD 1.0]). Concomitantly, there was avid uptake by the liver (about 30% of the injected dose), the spleen (about 15%), and the bone marrow. 40-55% of the tracer was cleared rapidly from the viscera (half-life 1-2 h) and 45-60% was cleared slowly (half-life 34-42 h). The half-life in the bone marrow was 14.1 h. Infusion of alglucerase at dose of 5 U/kg bodyweight normalised acid beta-glucosidase activity of splenic Gaucher's cells in vivo. When the enzyme was administered at a seven-fold higher dose (35 U/kg over 1 h), the receptor-mediated uptake in vivo was saturated, as shown by the increase in blood-clearance half-life of tracer enzyme from 4.5 min to 12 min. INTERPRETATION: Avid and saturable uptake of modified glucocerebrosidase was found, which indicates high-affinity targeting to the macrophage system in vivo. The rate of enzyme turnover suggests a rational basis for use of this therapy in treatment of Gaucher's disease.

Adult↗
PubMed1996

Neonatal screening for hereditary fructose intolerance: frequency of the most common mutant aldolase B allele (A149P) in the British population.

Hereditary fructose intolerance (HFI) causes severe and sometimes fatal metabolic disturbances in infants and children but responds to dietary treatment. To determine the practicability of screening newborn infants for HFI, we have investigated the frequency of the most common and widespread mutant allele of aldolase B, A149P, in the neonatal population. The polymerase chain reaction was used to amplify aldolase B exon 5 genomic sequences in DNA present in dried blood specimens preserved on Guthrie cards. The A149P mutation was identified by discriminatory hybridisation to allele specific oligonucleotides and confirmed independently by digestion with the restriction endonuclease BsaHI. Twenty-seven A149P heterozygotes were identified by the molecular analysis of aldolase B genes in blood samples obtained from a random cohort of 2050 subjects born in 1994 and 1995, 1.32 +/- 0.49% (95% confidence level). Although no A149P homozygotes were identified, the data allow the frequency of 1 in 23,000 homozygotes for this allele to be predicted. Our findings have implications for establishing an interventional mass screening programme to identify newborn infants with HFI in the UK.

Alleles↗
PubMed1996

Mice lacking tartrate-resistant acid phosphatase (Acp 5) have disrupted endochondral ossification and mild osteopetrosis.

Mature osteoclasts specifically express the purple, band 5 isozyme (Acp 5) of tartrate-resistant acid phosphatase, a binuclear metalloenzyme that can generate reactive oxygen species. The function of Acp 5 was investigated by targeted disruption of the gene in mice. Animals homozygous for the null Acp 5 allele had progressive foreshortening and deformity of the long bones and axial skeleton but apparently normal tooth eruption and skull plate development, indicating a rôle for Acp 5 in endochondral ossification. Histomorphometry and mineralization density analysis of backscattered electron imaging revealed widened and disorganized epiphyseal growth plates with delayed mineralization of cartilage in 6- to 8-week-old mutant mice. The membrane bones of the skull showed increased density at all ages examined, indicating defective osteoclastic bone turnover. Increased mineralization density was observed in the long bones of older animals which showed modelling deformities at their extremities: heterozygotes and homozygous Acp 5 mutant mice had tissue that was more mineralized and occupied a greater proportion of the bone in all regions. Thus the findings reflect a mild osteopetrosis due to an intrinsic defect of osteoclastic modelling activity that was confirmed in the resorption pit assay in vitro. We conclude that this bifunctional metalloprotein of the osteoclast is required for normal mineralization of cartilage in developing bones; it also maintains integrity and turnover of the adult skeleton by a critical contribution to bone matrix resorption.

Acid Phosphatase↗
PubMed1995

Anti-interleukin-4 treatment diminishes secretion of Th2 cytokines and inhibits hepatic fibrosis in murine schistosomiasis japonica.

Anti-interleukin-4 (IL-4) treatment of Schistosoma japonicum-infected mice markedly inhibited in vitro secretion of the Th2 cytokines IL-4 and IL-5 from antigen-stimulated spleen cells, but enhanced the secretion of the Th1 cytokine IFN-gamma. IL-2 secretion was unaffected. Hepatic fibrosis was markedly diminished in anti-IL-4-treated-mice at ten weeks of infection while granulomas around S. japonicum eggs in the livers were slightly-to-moderately increased in size. The number of eggs per worm pair in the tissues and feces did not differ significantly in treated and untreated mice. These findings suggest that Th2 cytokine responses are important in the genesis of schistosomal hepatic fibrosis.

Animals↗
PubMed1995

Generation and characterization of monoclonal antibodies to human type-5 tartrate-resistant acid phosphatase: development of a specific immunoassay of the isoenzyme in serum.

We have characterized four monoclonal antibodies (mAbs) to the purple ("tartrate-resistant," band 5) acid phosphatase of the human osteoclast (TRAP) and used these to develop a specific serum immunoassay. All four mAbs are of high affinity (Ka = 1-5 x 10(8) L/mol) with a very fast Kassoc (0.2-2.0 x 10(5) L mol-1 s-1) and a moderate Kdissoc (1-3 x 10(-3) s). Two of the mAbs were selected to develop a time-resolved fluorescence immunoassay to measure serum concentrations of TRAP. The mean serum immunoreactive TRAP in a group of healthy premenopausal women and men was 3.7 +/- 1.8 micrograms/L (mean +/- SD) and 3.5 +/- 1.6 micrograms/L, respectively. Significantly higher concentrations of TRAP were found in postmenopausal women (6.3 +/- 2.3 micrograms/L) and in eight patients with Gaucher disease (19.3 +/- 4.7 micrograms/L). Further studies are required to investigate the value of serum TRAP as a marker of bone resorption.

Acid Phosphatase↗
PubMed1995

Autosomal recessive erythropoietic protoporphyria: a syndrome of severe photosensitivity and liver failure.

Erythropoietic protoporphyria is caused by inherited deficiency of the haem synthetic enzyme ferrochelatase, and is characterized by lifelong photosensitivity. About 5% of patients also develop rapidly progressive liver failure. Inheritance is considered to be autosomal dominant, with transmission of a single ferrochelatase defect from one parent. We describe a family in which two siblings with protoporphyria suffered from severe photosensitivity and developed hepatic failure requiring liver transplantation. Their asymptomatic parents were heterozygous for distinct ferrochelatase gene mutations (exon 10 donor site a(+3)-->g and 1088T-->G). Both mutations disrupt splicing of the transcript and cause partial deficiency of ferrochelatase. The affected offspring were compound heterozygotes for these mutations. These patients suffered from an autosomal recessive form of protoporphyria characterized by severe photosensitivity and cholestatic liver disease in adolescence. We postulate that hepatic failure in erythropoietic protoporphyria may in some cases represent an autosomal recessive type of ferrochelatase deficiency distinct from the purely dermatological disorder. Studies of disease inheritance in families affected by protoporphyria may help identify those predisposed to develop severe liver complications, a distinction not currently possible.

Adolescent↗