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M Walters

Publications and source records attributed to M Walters.

At least 37 records · Page 2Linked to original sources
PubMed1998

Pancreatic exocrine and endocrine function after pancreatectomy for persistent hyperinsulinaemic hypoglycaemia of infancy.

AIM: To evaluate long term detailed pancreatic endocrine and exocrine function in children with persistent hyperinsulinaemic hypoglycaemia of infancy (PHHI) after 85-95% pancreatectomy. METHODS: Six children with PHHI between 0.9 and 12.7 years after pancreatic resection underwent clinical and investigative follow up at 1.0 to 14.9 years of age. One child with PHHI who had not had pancreatectomy was also assessed. Standard endocrine assessment, pancreatic magnetic resonance imaging (MRI), and detailed direct and indirect tests of exocrine pancreatic function were performed. RESULTS: Pancreozymin-secretin stimulation test results were normal in only one child, borderline in two, and deficient in four, one of whom requires daily pancreatic enzyme supplements. Pancreolauryl tests performed in three children were borderline in two and abnormal in the other. Only one child had low faecal chymotrypsin values. One child developed insulin dependent diabetes at 9 years and two children at 1.0 and 13.3 years require diazoxide to maintain normoglycaemia. MRI showed no major regrowth of the pancreatic remnant after resection (n = 5). CONCLUSIONS: Clinical evidence of endocrine or exocrine dysfunction has developed in only two patients to date, but detailed pancreatic function testing suggests subclinical deficiency in all but one of our patients with PHHI. Although 95% pancreatectomy results in postoperative control of blood glucose, subclinical pancreatic insufficiency is present on long term follow up and development of diabetes mellitus and exocrine failure remain ongoing risks.

Child↗
PubMed1998

Mutation analysis of the MEN1 gene in multiple endocrine neoplasia type 1, familial acromegaly and familial isolated hyperparathyroidism.

Multiple endocrine neoplasia type 1 (MEN 1) is an autosomal dominant disease characterized by neoplasia of the parathyroid glands, the endocrine pancreas, and the anterior pituitary gland. In addition, families with isolated endocrine neoplasia, notably familial isolated hyperparathyroidism (FIHP) and familial acromegaly, have also been reported. However, whether these families constitute MEN 1 variants or separate entities remains speculative as the genetic bases for these diseases are unclear. The gene for MEN 1 has recently been cloned and characterized. Using single strand conformation analysis (SSCA) and sequencing, we performed mutation analysis in: a) a total of 55 MEN 1 families from 7 countries, b) 13 isolated MEN 1 cases without family history of the disease, c) 8 acromegaly families, and d) 4 FIHP families. Mutations were identified in 27 MEN 1 families and 9 isolated cases. The 22 different mutations spread across most of the 9 translated exons and included frameshift (11), nonsense (6), splice (2), missense mutations (2), and in-frame deletions (1). Among the 19 Finnish MEN 1 probands, a 1466del12 mutation was identified in 6 families with identical 11q13 haplotypes and in 2 isolated cases indicating a common founder. One frameshift mutation caused by 359del4 (GTCT) was found in 1 isolated case and 4 kindreds of different origin and haplotypes; this mutation therefore represents a common "warm" spot in the MEN1 gene. By analyzing the DNA of the parents of an isolated case one mutation was confirmed to be de novo. No mutation was found in any of the acromegaly and small FIHP families, suggesting that genetic defects other than the MEN1 gene might be involved and that additional such families need to be analyzed.

Acromegaly↗
PubMed1997

c-Jun inhibits NF-E2 transcriptional activity in association with p18/maf in Friend erythroleukemia cells.

We have reported previously that antisense c-jun overcomes a block of Friend erythroleukemia cells to differentiation suggesting that the factor c-Jun may be an important negative regulator of erythroid differentiation. The recently described erythroid transcription factor NF-E2 plays an important role in the regulation of the transcription of globin genes and recognizes a sequence containing an AP-1 site. NF-E2 is a complex of two bZip proteins, p45 and p18/Maf. In order to determine whether c-Jun can interact with NF-E2/AP-1 sites to regulate transcriptional activation from them, we have compared the activity of AP-1 and NF-E2 in transient transcriptional assays, in erythroid and nonerythroid cells in the presence of c-jun sense and antisense expression vectors. In non-erythroid cells, c-Jun activates and NF-E2p18 inhibits both AP-1 and NF-E2 activities, suggesting that NF-E2/AP-1 sites function as AP-1 binding sites in these cells. In contrast, NF-E2p18 is a positive regulator of NF-E2 activity in erythroid cells. c-Jun alone is also a positive regulator of NF-E2 activity in erythroid cells but in association with NF-E2p18 inhibits this activity. Moreover antisense c-jun increases endogenous NF-E2 activity in erythroid cells. These results suggest that c-Jun could act as a repressor of NF-E2 transcriptional activity by forming inactive c-Jun/NF-E2p18 heterocomplexes which interfer with the transcription of globin genes in Friend erythroleukemia cells.

3T3 Cells↗
PubMed1997

Ganglion.

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Humans↗
PubMed1996

The influence of surface slope on human gait characteristics: a study of urban pedestrians walking on an inclined surface.

Human locomotion on inclined surfaces has been little studied. This work investigated uphill and downhill walking of urban pedestrians on slopes of up to 9 degrees. During a 3-month period, the gait characteristics of 1200 female and 1200 male pedestrians were recorded as they traversed a ramp of naturally varying slope at Sydney's Circular Quay. Walking speed, cadence and step length were determined for each subject, and average population gait parameters, for each ramp angle, were also calculated. The most significant finding was that the pedestrians' step length was decreased during ramp descent. Since theoretical analysis concludes that a reduction in step length produces a reduction in the friction demand, a shortening of the stride length is probably a means of counteracting the higher friction demand that would otherwise be required at heel strike during downhill walking.

Adolescent↗
PubMed1996

Predictive diagnosis of multiple endocrine neoplasia (MEN 1) in four Australian kindreds.

BACKGROUND: Multiple endocrine neoplasia type 1 (MEN 1) is a tumour predisposition syndrome that usually manifests in the first four decades of life. It has an autosomal dominant mode of inheritance which means that any new member of a MEN1 kindred has roughly a 50% chance of developing the disorder during their lifetime. The localisation of the MEN1 gene to a small region of chromosome band 11q13 has led to the development of DNA-based predictive diagnosis for this disease. AIMS: To establish a polymerase chain reaction (PCR)-based system, using simple tandem repeat polymorphisms (STRPs), to predict gene carriers in four Australian MEN 1 kindreds. METHODS: Six STRP markers flanking the MEN1 region of chromosome band 11q13 were used to screen individuals for a common haplotype in order to determine carrier status. RESULTS: The accuracy of prediction was calculated to be > 95% in informative individuals. CONCLUSIONS: DNA-based presymptomatic detection of affected members of MEN 1 kindreds could facilitate their care and reduce the inconvenience and expense of repeated testing of unaffected members. However, due to occasional recombination events or uninformativeness of markers in certain individuals, carrier status cannot always be predicted.

Adult↗
PubMed1996

Erythroid AP-1/NF-E2 elements vary in their response to NF-E2.

AP-1/NF-E2 motifs found in erythroid transcription control elements are associated with powerful transcription activation and thought to be regulated by the erythroid transcription factor NF-E2. We have studied AP-1/NF-E2 motifs from three different erythroid control elements (5'HS2 of the human beta-globin locus control region [LCR], the porphobilinogen deaminase [PBGD] promoter, and the mouse Band 3 promoter). We find that these AP-1/NF-E2 elements differ both in their ability to bind NF-E2 and their activity in transient assays. Each of the elements is bound by AP-1, but only the 5'HS2 and PBGD sites are bound by NF-E2. We examined the activity of these sites in minimal promoter constructs in transient assays. In erythroid cells, activity of duplicated NF-E2 motifs is positively correlated with binding by NF-E2; however, the Band 3 element not bound by NF-E2 is also active in some contexts. In HeLa cells, all sites were active and duplicated sites were most active. In F9 mouse teratocarcinoma cells, which express neither NF-E2 nor AP-1, the elements' activity parallels that in erythroid cells. While these finding are consistent with other evidence that NF-E2 is an important regulator of erythroid transcription, they suggest that some sites that resemble NF-E2 elements are actually regulated by other factors; we speculate that other tissue-specific and/or generally expressed factors may act on these sites.

Animals↗
PubMed1995

Exclusion of the 13-kDa rapamycin binding protein gene (FKBP2) as a candidate gene for multiple endocrine neoplasia type 1.

The MEN1 gene is considered to be a tumour suppressor gene and has been localised to a 1-Mb region of 11q13.1. In this study, we report the physical localisation of the 13-kDa FK506 and rapamycin binding protein gene (FKBP2) to the cosmid marker D11S750, which is located inside the MEN1 region of non-recombination. The product of this gene is involved in signal transduction and is thus a candidate cell growth regulator or tumour suppressor gene. Northern studies have revealed that FKBP2 is expressed in those tissues predisposed to hyperplasia in MEN1; however, single-strand conformation polymorphism analysis and direct sequencing of DNAs from affected members of MEN1 kindreds and sporadic tumour DNAs have been performed and no mutations have been found. These studies exclude FKBP2 as a candidate gene for MEN1.

Base Sequence↗
PubMed1995

The effect of cadmium on the formation and properties of hydroxyapatite in vitro and its relation to cadmium toxicity in the skeletal system.

In order to understand the biological action of cadmium (Cd) in inducing bone pathologies, the effect of Cd on the formation, structure, and properties of hydroxyapatite (HA) in vitro was investigated using three biologically relevant test systems: (1) direct precipitation of HA with no precursor phase; (2) transformation of amorphous calcium phosphate (ACP) to crystalline HA; and (3) growth of HA seed crystals. Cd-containing HA was prepared by transforming ACP to HA in the presence of Cd at a pH of 10; Cd/Ca ratios of 0.05, 0.10, and 0.20 were obtained. Infrared and x-ray diffraction analyses were performed on the Cd-HA samples, and measurements were made of Cd adsorption on HA and of the dissolution characteristics of Cd-containing HA. Cd incorporation in HA introduced little strain in the lattice but resulted in a decreasing C-axis spacing and a corresponding crystal size decrease in the C-axis direction. Cd incorporation had a nominal effect on HA dissolution. Cd had an inhibitory effect on HA formation kinetics in all three test systems. Infrared spectroscopy of Cd-HA showed a complex series of small changes in the spectra as a function of Cd concentration resulting from some distortion in the crystal perfection and symmetry. The interference of Cd with mineralization can be partially explained by its inhibitory effect on HA nucleation and growth in addition to any cellular involvement. Furthermore, Cd probably has little effect on bone mineral dissolution. Our results explain the Cd incorporation reported in bone.

Adsorption↗
PubMed1994

Incidence of familial melanoma and MLM2 gene.

The overall incidence of melanoma is increasing world wide. We investigated whether there has been an increase in familial melanoma by studying age at onset among different birth cohorts in 18 melanoma kindreds linked to a predisposition gene (MLM2) on chromosome 9. The cumulative incidence of melanoma was 21-fold higher (95% CI 5.2-84.6) among subjects born after 1959 than in those born before 1900. The expected age of onset of the group born after 1959 was 24 years earlier (21.0 vs 45.0 years). These data support the notion that phenotypic penetrance of the MLM2 gene is increasing, presumably as a result of the interaction of sunlight exposure and mutation at this locus.

Adolescent↗
PubMed1994

Airborne environmental endotoxin: a cross-validation of sampling and analysis techniques.

A standard method for measurement of airborne environmental endotoxin was developed and field tested in a fiberglass insulation-manufacturing facility. This method involved sampling with a capillary-pore membrane filter, extraction in buffer using a sonication bath, and analysis by the kinetic-Limulus assay with resistant-parallel-line estimation (KLARE). Cross-validation of the extraction and assay method was performed by comparison with methanolysis of samples followed by 3-hydroxy fatty acid (3-OHFA) analysis by gas chromatography-mass spectrometry. Direct methanolysis of filter samples and methanolysis of buffer extracts of the filters yielded similar 3-OHFA content (P = 0.72); the average difference was 2.1%. Analysis of buffer extracts for endotoxin content by the KLARE method and by gas chromatography-mass spectrometry for 3-OHFA content produced similar results (P = 0.23); the average difference was 0.88%. The source of endotoxin was gram-negative bacteria growing in recycled washwater used to clean the insulation-manufacturing equipment. The endotoxin and bacteria become airborne during spray cleaning operations. The types of 3-OHFAs in bacteria cultured from the washwater, present in the washwater and in the air, were similar. Virtually all of the bacteria cultured from air and water were gram negative composed mostly of two species, Deleya aesta and Acinetobacter johnsonii. Airborne countable bacteria correlated well with endotoxin (r2 = 0.64). Replicate sampling showed that results with the standard sampling, extraction, and Limulus assay by the KLARE method were highly reproducible (95% confidence interval for endotoxin measurement +/- 0.28 log10). These results demonstrate the accuracy, precision, and sensitivity of the standard procedure proposed for airborne environmental endotoxin.

Aerosols↗
PubMed1993

Neural aromatase activity in a marsupial, the gray short-tailed opossum (Monodelphis domestica): ontogeny during postnatal development and androgen regulation in adulthood.

Neural aromatase activity (AA) was measured in gray short-tailed opossums (Monodelphis domestica) on the day of birth and at selected ages through adulthood. In adulthood, regulation by testicular androgens was examined. In mixed-sex samples of whole brain, AA was present at birth and increased until postnatal day (PD) 16. In hypothalamus-preoptic area (HPOA), significantly higher levels of AA were seen in animals on PD 16 than on PD 30 and PD 30 animals had higher levels of AA than all older ages including adults. Significant sex differences in HPOA AA with male levels higher, were seen only on PD 16 and in adulthood. While lower overall than in HPOA, AA was present also in cerebral cortex (CX). In CX, AA was higher on PDs 16 and 30 than at older ages. Significant sex differences in CX AA were observed only in adulthood. One week following castration in adulthood, AA dropped significantly in CX but not in HPOA. These findings are compared with those obtained from other marsupial and eutherian mammals with reference to the possible significance of AA in sexual differentiation of the gray opossum brain.

Androgens↗
PubMed1993

Cytogenetic survey of Apert syndrome. Reevaluation of a translocation (2;9)(p11.2;q34.2) in a patient suggests the breakpoints are not related to the disorder.

The association of Apert syndrome with a translocation (2p-;Cq+) was previously reported in this journal. On reexamination using high-resolution chromosome banding, results showed both the patient and her unaffected father carry the balanced translocation (2;9)(p11.2;q34.2). This finding suggests the rearrangement is unlikely to be the cause of her disorder. Other chromosomal anomalies and genes known to be located at or near these breakpoints and a cytogenetic survey of patients with Apert syndrome are reviewed.

Acrocephalosyndactylia↗
PubMed1992

Functional erythroid promoters created by interaction of the transcription factor GATA-1 with CACCC and AP-1/NFE-2 elements.

We have investigated interactions between the erythroid transcription factor GATA-1 and factors binding two cis-acting elements commonly linked to GATA sites in erythroid control elements. GATA-1 is present at all stages of erythroid differentiation, is necessary for erythropoiesis, and binds sites in all erythroid control elements. However, minimal promoters containing GATA-1 sites are inactive when tested in erythroid cells. Based on this observation, two erythroid cis elements, here termed CACCC and AP-1/NFE-2, were linked to GATA sites in minimal promoters. None of the elements linked only to a TATA box created an active promoter, but GATA sites linked to either CACCC or AP-1/NFE-2 elements formed strong erythroid promoters. A mutation of T to C at position -175 in the gamma-globin promoter GATA site, associated with hereditary persistence of fetal hemoglobin (HPFH), increased expression of these promoters in both fetal and adult cells. A construct bearing the beta-globin CACCC element was more active in adult and less active in fetal erythroid cells, when compared with the gamma-globin CACCC element. These studies suggest that erythroid control elements are formed by the interactions of at least three transcription factors, none of which functions alone.

Animals↗
PubMed1991

Characterization of a DNA binding activity in DNAse I hypersensitive site 4 of the human globin locus control region.

A portion of the beta-globin Locus Control Region (LCR), which included DNAse I hypersensitive site 4 (HS4), was analyzed for its interactions with nuclear extracts and its contribution to LCR activity in a functional assay. In gel retardation assays, a short fragment from HS4 formed complexes with nuclear extracts from both erythroid and nonerythroid cells, and a core protected sequence 5'GACTGGC3' was revealed by DNAse I protection and methylation interference studies. This sequence resembles the binding sites of CCAAT-family members. Purified CP-2 but not CP-1 was shown to bind this HS4 sequence in a gel shift reaction, suggesting that the HS4 binding activity shares some sequence specificity with the CCAAT-factor family. Utilizing a transient expression assay in murine erythroleukemia cells, steady-state RNA levels were measured from pairs of LCR constructs linked to distinguishable beta-globin reporter genes. A short DNA fragment from HS4 which included the binding site for this novel binding activity accounted for most of the contribution to high level expression made by the entire HS4 region.

Animals↗