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Biomedical subjects

M Layton

Publications and source records attributed to M Layton.

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

Metabolic correction of triose phosphate isomerase deficiency in vitro by complementation.

Inherited deficiency of triose phosphate isomerase (TPI), the enzyme that catalyses the interconversion of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate, is characterised by an accumulation of intracellular DHAP and markedly reduced enzyme activity in cells and tissues, resulting in progressive, usually fatal neuromuscular dysfunction. Since specific enzyme replacement for TPI deficiency is not currently available, the secretion and recapture of the missing enzyme was investigated in a co-culture model comprising K562 human erythroleukaemia cells and lymphoblastoid cells taken from a TPI deficient patient. A sevenfold reduction in intracellular DHAP with concomitant increase in intracellular TPI activity from 7.25 +/- 0.1 to 197.2 +/- 10 units/mg protein was achieved for co-cultured lymphoblastoid cells. These novel results confirm the existence of a transport mechanism which permits transfer of active TPI from K562 cells to deficient cells, and may have important implications for developing different therapeutic approaches for TPI deficiency and other metabolic disorders of glycolysis.

Cell Line, Transformed↗
PubMed1997

Leukemia inhibitory factor (LIF) binding protein attenuates the phlogistic and abolishes the chondral effects of LIF in goat joints.

OBJECTIVE: To investigate the ability of murine leukemia inhibitory factor (LIF) binding protein (mLBP) to attenuate the effects of recombinant human LIF (rhLIF) in goat radiocarpal joints in vivo. METHODS: Endotoxin-free saline (1 ml) containing either 0.5 or 1 microg of rhLIF was injected into the left and right radiocarpal joints of male angora goats. One hour later the right radiocarpal joints were injected with either 1 or 5 microg of naturally occurring mLBP in 1 ml saline, while the left radiocarpal joints (controls) received 1 ml saline vehicle alone. Goat joints were examined for clinical features of inflammation and synovial fluid (SF) was aspirated on Day 0 (before injection) and Days 2 and 6 postinjection. Leukocyte counts and concentrations of keratan sulfate were determined in the SF. Proteoglycan synthesis and proteoglycan content of cartilage was determined ex vivo in cartilage explants obtained at Day 6. RESULTS: Preliminary time course studies in vitro showed that mLBP had to be added to cartilage explant cultures within 1 h of rhLIF for effective antagonism to occur. In joints injected with either 0.5 or 1 microg rhLIF significant increases in swelling, effusion volume, leukocyte counts, and SF keratan sulfate concentrations were observed relative to controls. Statistically significant depressions of ex vivo proteoglycan synthesis and in proteoglycan content of articular cartilage were also observed relative to controls. In joints injected with 1 microg rhLIF followed by 1 microg mLBP, statistically significant improvement was only observed in the rate of ex vivo cartilage proteoglycan synthesis. The observed rate did not differ significantly from that obtained in joints treated with vehicle alone. In contrast, in joints injected with 0.5 microg rhLIF followed by 5 microg mLBP, statistically significant improvement was observed in all variables. Treatment with 5 microg mLBP effectively negated the effects of rhLIF on joint swelling, effusion volume, leukocyte infiltration, and cartilage proteoglycan catabolism. CONCLUSION: Murine LBP has the ability to attenuate the phlogistic effects of rhLIF in radiocarpal joints of goats and also abolishes the stimulatory effect of rhLIF on cartilage proteoglycan catabolism and depression of ex vivo proteoglycan synthesis. These antiinflammatory and chondral effects suggest that a humanized derivative of mLBP could be a clinically useful antagonist for LIF in inflammatory diseases.

Animals↗
PubMed1996

Severe perinatal thrombosis in double and triple heterozygous offspring of a family segregating two independent protein S mutations and a protein C mutation.

Molecular genetic and phenotypic analyses were performed in a highly unusual case of combined protein S and protein C deficiency manifesting in a family in which a child had died perinatally from renal vein thrombosis. Antenatal diagnosis in a second pregnancy was initially performed by indirect restriction fragment length polymorphism (RFLP) tracking using a neutral dimorphism within the PROS gene and served to exclude severe protein S deficiency. Am umbilical vein blood sample at 22 weeks gestation showed isolated protein C deficiency. This pregnancy proceeded to a full-term delivery without thrombotic complications. Molecular genetic analysis of the PROC and PROS gene segregating in the family then yielded one PROC gene lesion in the father and two PROS gene lesions, one in each parent. These lesions were shown to segregate with the respective deficiency states through the family pedigree. Analysis of DNA from paraffin-embedded liver tissue taken from the deceased child showed the presence of both PROS mutations, as well as the PROC mutation. Genotypic analysis of the second child showed a PROC mutation, but neither PROS mutation consistent with its possession of normal protein S levels and a low/borderline protein C level. Antenatal diagnosis was then performed in a third pregnancy by direct mutation detection. However, although the fetus carried only the paternal PROS and PROC gene lesions, the child developed renal thrombosis in utero. It may be that a further genetic lesion at a third locus still remains to be defined. Alternatively, the intrauterine development of thrombosis in this infant could have been caused, at least in part by a transplacental thrombotic stimulus arising in the protein S-deficient maternal circulation. This analysis may, therefore, serve as a warning against extrapolating too readily from genotype to phenotype in families with a complex thrombotic disorder.

Female↗
PubMed1996

Neuroimaging Findings in Anxiety Disorders.

Individuals with severe anxiety have long sought a physical basis for their symptoms. There is increasing evidence to suggest brain abnormalities as the primary mechanism responsible for pathological anxiety, particularly panic disorder. However, older-generation brain imaging techniques, capable of assessing brain structure, have not identified consistent anatomical differences or structural abnormalities by which to explain the symptoms. In this regard, the development of modern functional imaging techniques that can specifically assess regional brain blood flow, metabolic status, or chemical composition are beginning to elucidate underlying brain mechanisms which may be responsible for "state" or situational-specific anxiety and "trait" or pathological anxiety. The intent of this article is to provide a review of neuroimaging studies undertaken to investigate state anxiety or specific anxiety disorders. The focus of this article is on studies that have used newer brain imaging techniques capable of assessing brain functionality, such as single photon emission computerized tomography, positron emission tomography, or magnetic resonance spectroscopy (MRS), in relationship to specific anxiety disorders. We have undertaken studies of panic disorder using MRS to investigate acute panic precipitated by physiological or chemical challanges, such as intravenous sodium lactate infusion, while measuring brain metabolic responses. These studies are presented in detail as a model of how these newer functional imaging modalities can be applied as a tool to begin to unravel the underlying pathophysiological processes responsible for production of panic. It is anticipated that future application of these newer functional imaging techniques will allow both the determination of a brain mechanism(s) responsible for pathological anxiety and advance our understanding of mechanisms responsible for effective treatments.

Journal Article↗
PubMed1995

Mosquito-transmitted malaria in New York City, 1993.

In August, 1993, 3 cases of Plasmodium falciparum malaria in people without recent travel histories or bloodborne exposure were reported in New York City. An epidemiological investigation confirmed the absence of risk factors for acquisition of malaria in two cases. The third case could not be definitively classified as locally acquired malaria because the patient had travelled to Thailand two years before malaria was diagnosed. The 3 individuals lived in separate houses in the same neighbourhood of Queens, New York and had onset of illness within a day of each other. The investigation consisted of patient interviews, active case finding, reviewing recent New York flight and shipping arrivals, and an entomological survey for anopheline mosquitoes and breeding sites. No other cases were identified. The 3 patients lived several miles from air and sea ports and prevailing winds would have carried any mosquitoes at those sites away from the patient's homes. By the time of the environmental investigation (September, 1993), the area was dry and neither adult nor larval anophelines were found. However, weather conditions at the probable time of infection (July, 1993) were very different. Malaria was probably transmitted to these 2 patients by local anopheline mosquitoes that had fed on infected human hosts. Mosquito-control measures were not implemented because there was no evidence of ongoing transmission. The occurrence of mosquito-transmitted malaria in New York City demonstrates the potential for reintroduction of malaria transmission into areas that are no longer endemic and emphasises the need for continued surveillance and prompt investigations, if cases without risk factors are reported.

Adult↗
PubMed1995

Induced tolerance and chimaerism in human fetuses using coelocentesis: a medical opportunity to avert genetic disease?

Coelocentesis offers a new opportunity for gaining access to the coelomic cavity of human embryos from 28 days post-fertilization (42 days menstrual age). With this technique, cells can be extracted from the cavity for the genetic typing of embryos in early pregnancy. Coelocentesis may also offer a unique opportunity of inducing tolerance to foreign grafts and chimaerism in these human embryos by replacing donor cells into the coelomic cavity. This cavity appears to be closely associated with the fetal haemopoietic system. The optimal age to inject stem cells designed to produce chimaerism may be at 5-6 weeks embryonic age, and these grafted cells may induce tolerance later in gestation. Two successive coelocenteses would be needed, the first to extract fetal cells to type the fetus, and a second within a few days to inject the donor cells into the coelomic cavity. Alternatively, non-invasive methods of diagnosis such as lower uterine pole extramembranous sampling of fetal trophoblast, or the extraction of fetal cells from maternal blood, could be combined with coelocentesis. If tolerance and chimaerism can be established, repeated tissue grafts could be carried out during fetal life and after birth, so that disorders caused by single or multiple gene defects in the haemopoietic system and other organs may be corrected.

Chimera↗
PubMed1995

Detection of sickle gene by coelocentesis in early pregnancy: a new approach to prenatal diagnosis of single gene disorders.

Coelomic fluid, placental tissue and maternal blood were collected at 7-10 weeks gestation from each of 58 women undergoing elective termination of pregnancy for psychological indications. In all samples, a 364 bp fragment of the human beta-globin gene spanning positions -23 to 341 was amplified. The restriction endonuclease Ddel was used to detect the sickle mutation which abolishes its restriction site. beta-Globin DNA was successfully amplified from all samples. In 53 cases a normal maternal beta-globin genotype was detected. In three out of five cases, where the maternal haemoglobin phenotype was HbAS, heterozygosity for the sickle mutation was demonstrated on analysis of coelomic fluid. In the remaining two cases a normal beta-globin genotype was observed. Three further coelomic fluid samples were found to be heterozygous for the sickle mutation. In these instances the maternal haemoglobin phenotype was normal, indicating paternal transmission of the sickle gene. The results of the present study have established that the diagnosis of sickle cell anaemia, and potentially other human single gene disorders, is feasible by coelocentesis.

Amniocentesis↗
PubMed1995

Paroxysmal nocturnal haemoglobinuria and Budd-Chiari syndrome.

An 11 year old boy developed pancytopenia, haemolysis, and Budd-Chiari syndrome. The venous thrombosis extended to involve other intra-abdominal vessels before paroxysmal nocturnal haemoglobinuria was recognised as the underlying haematological abnormality. Earlier diagnosis would have made curative bone marrow transplantation a possibility.

Bone Marrow Transplantation↗
PubMed1992

The osmotic/calcium stress theory of brain damage: are free radicals involved?

This overview presents data showing that glucose use increases and that excitatory amino acids (i.e., glutamate, aspartate), taurine and ascorbate increase in the extracellular fluid during seizures. During the cellular hyperactive state taurine appears to serve as an osmoregulator and ascorbate may serve as either an antioxidant or as a pro-oxidant. Finally, a unifying hypothesis is given for seizure-induced brain damage. This unifying hypothesis states that during seizures there is a release of excitatory amino acids which act on glutamatergic receptors, increasing neuronal activity and thereby increasing glucose use. This hyperactivity of cells causes an influx of calcium (i.e., calcium stress) and water movements (i.e., osmotic stress) into the cells that culminate in brain damage mediated by reactive oxygen species.

Amino Acids↗
PubMed1992

Fetal and maternal erythropoietin levels in normal pregnancy.

In a cross-sectional study of 120 pregnancies undergoing cordocentesis for prenatal diagnosis (n = 90) or elective caesarean section (n = 30), the umbilical cord and maternal venous plasma erythropoietin (Epo) concentrations were measured. Fetal Epo levels increased from a mean of 4 mU/ml at 16 weeks to 13 mU/ml at 40 weeks' gestation. There were no significant associations between fetal plasma Epo concentration and fetal blood gases, haemoglobin concentration, oxygen content or erythroblast count. The maternal plasma Epo concentration (mean = 14 mU/ml, range 1-77 mU/ml) did not change with gestation but was significantly higher than levels in non-pregnant females (mean = 6.6 mU/ml, range 1-25 mU/ml).

Erythroblasts↗
PubMed1990

Leukemia characterized by multiple sub-clones with unbalanced translocations involving different telomeric segments: case report and review of the literature.

A 68-year-old man presented with t(4;11)(q21;q23), B-lineage acute lymphoblastic leukemia (ALL) which was negative for C-ALL antigen and TdT. Clonal evolution to five different, but related karyotypes, in which chromosomal material distal either to 1q11 or 1q21 was translocated to the terminal regions of 4q-, 11q, 16q, and 19p resulted in partial or total trisomy of 1q. The patient, having achieved a short remission, died 14 weeks after diagnosis. Five reports of jumping translocations in hematological malignancies, four with B-lineage malignancy, are reviewed. One (four cases) or both (one case) of the same 1q breakpoints were consistently found and 11q and 16q were repeatedly involved. Such cases, having multiple subclones with trisomy 1q, may form a distinct subgroup of ALL.

Aged↗
PubMed1990

The murine situs inversus viscerum (iv) gene responsible for visceral asymmetry is linked tightly to the Igh-C cluster on chromosome 12.

The iv gene controls left-right determination during murine organogenesis. To map this gene, we analyzed backcross progeny produced by mating (C57BL/6J X MEV/Ty)F1-iv/+heterozygotes to C57BL/6J-iv homozygotes. Hybridization of a murine ecotropic virus probe and several homeotic box gene probes coupled with analysis of dominant visible markers enabled us to exclude the iv locus from much of the mouse genome. Spurred by a recent report that mapped the iv gene to mouse chromosome 12 which was not excluded by our previous work, we used the polymerase chain reaction on our larger cohort to determine that the iv gene is indeed linked tightly to the Igh-C locus on this chromosome: we observed 0/156 recombinants between the iv and Igh-C loci. Combining data from the two studies demonstrates that the murine iv gene is close (1/201 recombinants) to the Igh-C cluster on chromosome 12.

Animals↗
PubMed1989

Clonal analysis of myelodysplastic syndromes: evidence of multipotent stem cell origin.

Restriction fragment length polymorphisms (RFLPs) of the X-chromosome genes hypoxanthine phosphoribosyl transferase (HPRT) and phosphoglycerate kinase (PGK) were studied in 34 female patients with primary myelodysplastic syndromes (MDS). Twelve patients (35%) were heterozygous at the HPRT or PGK loci for BamHI or BglI RFLPs, respectively. In eight patients showing PGK polymorphisms, clonality was determined by X-chromosome inactivation analysis. These included patients from different morphologic subtypes: four with refractory anemia (RA), two with RA and ring sideroblasts (RARS), one patient with RA with excess of blasts (RAEB), and one with chronic myelomonocytic leukemia (CMML). A monoclonal pattern of X-chromosome inactivation was observed in seven cases. In a further case characterized by bone marrow hypoplasia, peripheral blood (PB) leukocytes were polyclonal in origin. Following low-dose cytarabine therapy, reversion to polyclonal hematopoiesis was observed in a case of RAEB indicating the presence of residual normal hematopoietic stem cells with the capacity for marrow reconstitution. The clonal relation of lymphoid and granulocyte/monocyte lineages was studied directly in two cases of CMML exhibiting somatic mutations of N-ras or Ki-ras oncogenes. By selective oligonucleotide hybridization to ras gene sequences amplified in vitro by the polymerase chain reaction, a mutated ras allele was demonstrated in PB granulocytes, monocytes, and B and T lymphocytes of both patients. We conclude that MDS arise from a multipotent hematopoietic stem cell with the potential for myeloid and lymphoid differentiation.

Adult↗
PubMed1988

Mutation of Ki-ras and N-ras oncogenes in myelodysplastic syndromes.

Somatic mutation of the N-ras oncogene occurs frequently in de novo acute myeloid leukemia (AML). By virtue of their relation to AML, myelodysplastic syndromes (MDS) provide an in vivo model of human leukemogenesis. By using a strategy for analysis of gene mutation based on in vitro amplification of target sequences by the polymerase chain reaction (PCR) and selective oligonucleotide hybridization we analyzed the mutational status of codons 12, 13, and 61 of Ha-ras, K-ras, and N-ras in peripheral blood (PB) and/or bone marrow (BM) in 34 cases of primary MDS. Mutations at codon 12 of Ki-ras or N-ras were detected in three cases (9%): one of six cases of refractory anemia with excess blasts (RAEB) and two of nine cases of chronic myelomonocytic leukemia (CMML). The nucleotide substitution differed in each. In all cases the mutant allele was detectable in PB cells. A sustained hematologic remission was achieved after low-dose cytarabine therapy in the case of RAEB. Neither case of CMML exhibited signs of disease progression during follow-up at 7 and 12 months. In contrast, four of 31 patients without the ras mutation underwent transformation to AML within 12 months of genetic analysis. We conclude that ras mutations in MDS are heterogeneous and may develop at an early stage during the evolution of MDS. Their detection in PB cells illustrates the potential utility of ras mutation as a clonal marker in myeloid malignancy.

Genes, ras↗