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Biomedical subjects

C McMahon

Publications and source records attributed to C McMahon.

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

Liver biopsy in Irish hepatitis C-infected patients with inherited bleeding disorders.

The majority of patients receiving plasma-derived clotting factor concentrates between 1970s and the mid-1980s are now hepatitis C positive. The progression of hepatitis C is extremely variable and there is frequently a poor correlation among liver biochemistry, viral load and the stage of liver disease. Liver biopsy remains the only definitive way of staging fibrosis and grading necroinflammatory activity. Concerns have been expressed about the safety of the procedure; however, with modern regimes for the correction of coagulopathy in patients with inherited bleeding disorders, normal haemostasis may be maintained during the peribiopsy period. We performed 21 liver biopsies between 1984 and 1997 on patients with factor VIII (FVIII) or IX (FIX) deficiency and von Willebrand's Disease (VWD). Four had concomitant human immunodeficiency virus (HIV) infection, five were thrombocytopenic and one had a prolonged prothrombin time (PT). Haemostasis was achieved using an intermittent bolus of factor concentrate or continuous infusion regimens. One patient with VWD received Desmopressin (DDAVP). There were no bleeding episodes associated with biopsy. We suggest that liver biopsy is a safe procedure in patients with inherited bleeding disorders when the coagulopathy is fully corrected. It is the only definitive method of staging the extent of fibrosis associated with hepatitis C infection, and it is this that defines prognosis.

Adult↗
PubMed2000

Central venous access devices in children with congenital coagulation disorders: complications and long-term outcome.

Reliable venous access is essential to facilitate the administration of prophylactic factor concentrate or blood products in children with congenital coagulation disorders and immune tolerance therapy (ITT) regimens in those who develop high responding inhibitors. Poor venous access is even more problematic in very young children, the vast majority of whom will require the insertion of central venous access devices (CVADs). Previous studies have suggested that infection rates are low and that there are few long-term complications associated with CVAD usage. We have reviewed 86 CVADs that have been inserted, since 1988, in 58 children with congenital bleeding disorders, aged 6 d to 16.5 years, attending Great Ormond Street Hospital, London, and the National Children's Hospital, Dublin. The devices have remained in situ for 2 weeks to 92 months (median 22.5 months). Early (0-2 weeks) complications of CVAD insertion included nine bleeding episodes, one extravasation of factor concentrate, three allergic reactions to factor concentrate and five catheter infections. Overall, CVAD infection was the commonest problem encountered, with 52 devices (60%) becoming infected. Twenty-seven CVADs (31%) required removal. Infection rates in children without inhibitors (29/68) were 1/20 patient-months or 1. 6 infections/1000 patient-days, but infection rates for those with inhibitors were 1/8.5 patient-months or 4.3/1000 patient-days. Staphylococcus epidermidis was the predominant organism (25/52) isolated. Blockage of CVAD (four) and catheter disconnection (four) were the most frequently occurring non-infectious long-term complications. Skin erosion of the port was also seen in three children, in one child at 20 months, in one at 29 months and in one at 34 months after insertion. This study demonstrates a high CVAD infection rate and highlights the long-term complications of CVAD usage.

Adolescent↗
PubMed2000

Regulation of the functional interaction between cyclin D1 and the estrogen receptor.

We report that the functional interaction between cyclin D1 and the estrogen receptor (ER) is regulated by a signal transduction pathway involving the second messenger, cyclic AMP (cAMP). The cell-permeable cAMP analogue 8-bromo-cAMP caused a concentration-dependent enhancement of cyclin D1-ER complex formation, as judged both by coimmunoprecipitation and mammalian two-hybrid analysis. This effect was paralleled by increases in ligand-independent ER-mediated transcription from an estrogen response element containing reporter construct. These effects of 8-bromo-cAMP were antagonized by a specific protein kinase A (PKA) inhibitor, indicating that the signaling pathway involved was PKA dependent. Further, we show that culture of MCF-7 cells on a cellular substratum of murine preadipocytes also enhanced the functional interaction between cyclin D1 and ER in a PKA-dependent manner. These findings demonstrate a collaboration between cAMP signaling and cyclin D1 in the ligand-independent activation of ER-mediated transcription in mammary epithelial cells and show that the functional associations of cyclin D1 are regulated as a function of cellular context.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2000

Flicker-photometric electroretinogram estimates of L:M cone photoreceptor ratio in men with photopigment spectra derived from genetics.

Relative proportions of long-wavelength-sensitive (L) to middle-wavelength-sensitive (M) cones were estimated by use of the flicker-photometric electroretinogram (ERG). It has been demonstrated that a major source of error in estimates of cone proportions from spectral luminosity functions is the known variation in the lambda(max) of the photopigments [Vision Res. 38, 1961 (1998)]. To correct for these errors, estimates of cone proportions were derived by use of individualized L-cone spectral sensitivity curves deduced from photopigment gene sequences from each subject. For some individuals this correction made a large difference in the estimated cone proportions compared with the value obtained when a fixed standard L cone was assumed. The largest discrepancy occurred in a man estimated to have 62% L cones (L:M ratio 1.6:1) when a standard L pigment was assumed but a value of 80% L cones (L:M ratio 4:1) when his individualized L-cone spectrum was used. From repeated measurements made with the ERG, it was determined that individual estimates of the relative L-to-M cone contributions, expressed as %L cones, are usually reliable within approximately 2%. The average L:M ratio for 15 male subjects was estimated at 2:1 (67% L cones). Previously, a large range of individual variability was reported for L:M ratios obtained from photometry. An unresolved issue concerns how much of the range might be attributed to error. Here efforts have been taken to markedly reduce measurement error. Nonetheless, a large range of individual differences persists. Estimated L:M ratios for individuals ranged from 0.6:1 to 12:1 (40% L to 92% L).

Adolescent↗
PubMed1999

The ankyrin repeat-containing adaptor protein Tvl-1 is a novel substrate and regulator of Raf-1.

Tvl-1 is a 269-amino acid ankyrin repeat protein expressed primarily in thymus, lung, and testes that was identified by screening a murine T-cell two-hybrid cDNA library for proteins that associate with the serine-threonine kinase Raf-1. The interaction of Tvl-1 with Raf-1 was confirmed by co-immunoprecipitation of the two proteins from COS-1 cells transiently transfected with Tvl-1 and Raf-1 expression constructs as well as by co-immunoprecipitation of the endogenous proteins from CV-1 and NB2 cells. Tvl-1 interacts with Raf-1 via its carboxyl-terminal ankyrin repeat domain. The same domain also mediates Tvl-1 homodimerization. Tvl-1 was detected by immunofluorescence in both the cytoplasm and the nucleus suggesting that in addition to Raf-1 it may also interact with nuclear proteins. Activated Raf-1 phosphorylates Tvl-1 both in vitro and in vivo. In baculovirus-infected Sf9 insect cells, Tvl-1 potentiates the activation of Raf-1 by Src and Ras while in COS-1 cells it potentiates the activation of Raf-1 by EGF. These data suggest that Tvl-1 is both a target as well as a regulator of Raf-1. The human homologue of Tvl-1 maps to chromosome 19p12, upstream of MEF2B with the two genes in a head to head arrangement.

Adaptor Proteins, Signal Transducing↗
PubMed1999

P/CAF associates with cyclin D1 and potentiates its activation of the estrogen receptor.

Cyclin D1 is overexpressed in a significant percentage of human breast cancers, particularly in those that also express the estrogen receptor (ER). We and others have demonstrated previously that experimentally overexpressed cyclin D1 can associate with the ER and stimulate its transcriptional functions in the absence of estrogen. This effect is separable from the established function of cyclin D1 as a regulator of cyclin-dependent kinases. Here, we demonstrate that cyclin D1 can also interact with the histone acetyltransferase, p300/CREB-binding protein-associated protein (P/CAF), thereby facilitating an association between P/CAF and the ER. Ectopic expression of P/CAF potentiates cyclin D1-stimulated ER activity in a dose-dependent manner. This effect is largely dependent on the acetyltransferase activity of P/CAF. These results suggest that cyclin D1 may trigger the activation of the ER through the recruitment of P/CAF, by providing histone acetyltransferase activity and, potentially, links to additional P/CAF-associated transcriptional coactivators.

Acetyltransferases↗
PubMed1999

Unexplained aplastic anaemia, immunodeficiency, and cerebellar hypoplasia (Hoyeraal-Hreidarsson syndrome) due to mutations in the dyskeratosis congenita gene, DKC1.

Hoyeraal-Hreidarsson (HH) syndrome is a multisystem disorder affecting boys characterized by aplastic anaemia (AA), immunodeficiency, microcephaly, cerebellar-hypoplasia and growth retardation. Its pathogenesis is unknown. X-linked dyskeratosis congenita (DC) is an inherited bone-marrow-failure syndrome characterized by skin pigmentation, nail dystrophy and leucoplakia which usually develop towards the end of the first decade of life. AA occurs in >90% of cases of DC. We speculated that mutations in the gene responsible for X-linked DC (DKC1) may account for the HH syndrome, due to the phenotypic similarities between the disease in respect of AA and gender bias. We therefore analysed the DKC1 gene in two HH families. In one family a nucleotide change at position 361(A --> G) in exon 5 was found in both affected brothers; in the other family a nucleotide change at position 146(C --> T) in exon 3 was found in the affected boys. The finding of these two novel missense DKC1 mutations demonstrates that HH is a severe variant of DC. They also show that mutations in DKC1 can give rise to a very wide clinical spectrum of manifestations. Boys with unexplained AA or immunodeficiency should be tested for mutations in DKC1 even though they may lack diagnostic features of DC.

Amino Acid Substitution↗
PubMed1999

The retinoblastoma protein is linked to the activation of Ras.

The inner membrane-bound protein Ras integrates various extracellular signals that are subsequently communicated from the cytoplasm to the nucleus via the Raf/MEK/MAPK cascade. Here we show that the retinoblastoma protein pRb, previously reported to be a nuclear target of this pathway, can in turn influence the activation state of Ras. Rb-deficient fibroblasts display elevated levels (up to 30-fold) of activated Ras during G(1). Expression of wild-type pRb or a number of pRb mutants defective in E2F regulation reverses this effect. We provide evidence that the mid-G(1) activation of Ras in Rb-deficient cells, which occurs at the level of guanine nucleotide binding, differs from that of epidermal growth factor-induced stimulation of Ras, being dependent on protein synthesis. The aberrant levels of Ras activity associated with loss of pRb may be responsible for the differentiation defects in Rb-deficient cells, because suppression of Ras activity in Rb(-/-) fibroblasts restores the transactivation function of MyoD and the expression of a late marker of skeletal muscle differentiation. These data suggest that nuclear-cytoplasmic communication between pRb and Ras is bidirectional.

Alleles↗
PubMed1998

Changes in somatotropic axis response and body composition during growth hormone administration in progressive cachectic parasitism.

A multistage protozoan parasitic disease was used as a cachexia model to study the effects of daily administration of bovine growth hormone (GH) on endocrine and body composition changes of young calves from the onset of the acute phase response (APR). Male calves averaging 127.5 +/- 2.0 kg body weight were assigned to control, ad libitum fed, noninfected (C); ad libitum fed, infected (250,000 oocysts Sarcocystis cruzi, per os, I); noninfected, pair-fed (PF) to matched I-treatment calves and these respective same treatments in calves injected daily with GH (USDA-bGH-B1), 12.5 mg/calf/day, im) designated as CGH, IGH and PFGH. GH injections were initiated on Day 20 postinfection (PI), 3 to 4 d before the onset of clinical signs of APR, and continued to Day 56 PI, at which time animals were euthanized for tissue collections. Abrupt increases in rectal temperature commensurate with up to 70% reduction in voluntary feed intake were observed in I and IGH beginning 23-25 d PI. For the trial period between Days 20 and 56 PI, average daily carcass protein gains were 123, 52, 109, 124, 48, and 67 g/d and average daily carcass fat gains were 85, 11, 43, 71, -23, and 29 g/d for C, I, PF, CGH, IGH, and PFGH, respectively. Effects of GH were significant for fat accretion and plasma urea depression. Rectus femoris was highly refractory to catabolic effects of infection while psoas major was significantly catabolized during infection. Plasma concentrations of insulin-like growth factor-I (IGF-I) increased significantly in all GH-treated calves between Day 20 and 23 PI. Plasma IGF-I declined well below Day 20 values in all infected calves from the onset of the APR through the end of the study. The decrease in plasma IGF-I concentrations in I and IG was highly correlated with the magnitude of the fever response. Hepatic mRNA for GH receptor and IGF-I was decreased in infected calves. Hepatic microsomal membrane binding of 125I-GH did not differ between groups. The data suggest that effects of GH and parasitism on tissue metabolism during disease may vary among different specific tissue pools. The data demonstrate that daily GH administration in young calves does not prevent lean tissue losses and may accelerate fat depletion associated with cachectic parasitism. Furthermore, the onset of APR overrode the capacity for GH to maintain elevated plasma concentrations of IGF-I, an effect not readily explained through changes of GH-receptor binding.

Acute-Phase Reaction↗
PubMed1998

Successful use of protease inhibitors in HIV-infected haemophilia patients.

The haemophilias are a group of inherited haemostatic disorders that require regular clotting factor replacement therapy in the severe and moderately severe subgroups. Prior to the introduction of adequate viral inactivation methods in 1985, haemophilia patients were at exceptionally high risk of contracting blood-borne viruses from factor concentrates as each batch was derived from the plasma of thousands of donors. As a result, approximately 60% of these patients were infected with HIV between 1979 and 1985, and HIV infection now contributes significantly to the morbidity and mortality seen in this group. Protease inhibitors (PIs) have been shown to significantly log reduce viral loads and increase CD4 cell counts in HIV-infected individuals. Recently, there has been concern about their use in HIV-infected haemophilia patients following increased bleeding episodes in some patients during PI therapy. We prospectively studied the effect of PI therapy in 20 HIV-infected haemophilia patients at our centre over a 6-month period. The mean increase in CD4 cell count was 70 x 10(6)/l and the mean log decrease in viral load was 1.59 over the study period. Gastrointestinal side-effects (nausea and vomiting in five, diarrhoea in two) were the most frequent and resulted in discontinuation of the medication in two patients. Factor concentrate usage for the group on and off study was similar. One severe FVIII patient reported a single episode of an unusual bleed which responded promptly to FVIII concentrate infusion. The significant clinical and laboratory benefits in terms of HIV disease and the paucity of added bleeding complications suggest that PI therapy should not be withheld from HIV-infected haemophilics. Further prospective studies evaluating the efficacy and possible haemostatic complications related to these promising inhibitors of the HIV protease are needed.

AIDS-Related Opportunistic Infections↗
PubMed1998

Infants conceived using in-vitro fertilization do not over-utilize health care resources after the neonatal period.

Health outcomes during the first year for 95 infants born following in-vitro fertilization (IVF) were compared with those of 79 naturally conceived controls whose mothers were of identical parity and similar age. Primigravid women were enrolled prospectively at 30 weeks gestation, perinatal and neonatal data were collected during pregnancy and following birth, and details of health care resource use were obtained from mothers at 4 and 12 months. Median (range) number of medical problems during the first year tended to be less for IVF infants, 4 (0-41) versus 5 (0-12) (P = 0.07), whilst total number of visits to health care workers was similar for IVF and control infants, 19 (2-47) versus 19 (1-47). IVF infants were more likely to have an excessive number of visits to Early Childhood Health Care Centres [odds ratio (OR; 95% confidence interval, CI) = 2.44 (1.11-5.56)], but less likely to have an excessive number of visits to general medical practitioners [OR = 0.45 (0.22-0.93)] and other health care workers [OR = 0.48 (0.23-0.99)]. These data provide some degree of reassurance about medium-term health outcomes for children conceived using IVF. Although they are more likely to utilize the resources of neonatal intensive care units, IVF infants do not appear to have an increased number of medical problems or to over-utilize health care resources during the remainder of their first year of life.

Adult↗
PubMed1997

B-cell-negative severe combined immunodeficiency associated with a common gamma chain mutation.

Severe combined immunodeficiency (SCID) is caused by a variety of underlying defects. Approximately 40% of cases are thought to be of the X-linked type (SCIDX1), which is phenotypically characterised by the absence, or very low numbers, of T cells, but normal or even high B cell numbers. The gene responsible for SCIDX1 is that coding for the common gamma chain (gamma c), a component of multiple cytokine receptors. Mutations in this gene have been demonstrated in a large number of boys affected by typical SCIDX1. We describe a sporadic case of a boy who had SCID with absent B cells and absent T cells, but in whom a mutation in the gamma c gene has been demonstrated. In the absence of a typical X-linked pedigree, the phenotype in this boy suggested an autosomal recessive form of SCID and the family would usually have been counselled accordingly. This family raises the question of the true frequency of SCIDX1 amongst sporadic male cases of SCID and highlights the need to screen these boys for gamma chain mutations.

Antigens, CD↗
PubMed1997

Immediate and short-term effects of benzalkonium chloride on the human nasal mucosa in vivo.

The in vivo effects of benzalkonium chloride, which is a preservative in most nasal sprays and drops, have been investigated in normal human volunteers. Saccharin clearance time was slightly prolonged 10 min after 0.02% benzalkonium chloride was applied, compared to that following 0.9% saline (n = 27, P = 0.04, Wilcoxon test). Sixty-five normal volunteers were randomly assigned to receive saline, fluticasone propionate aqueous nasal spray or placebo (which contained all the ingredients of fluticasone aqueous spray incl. 0.02% benzalkonium chloride, minus the fluticasone propionate) for 2 weeks, two puffs twice a day on a double-blind basis. Symptom scores, acoustic rhinometry, saccharin clearance time and ciliary beat frequency were measured immediately prior to this study and again at 2 weeks. Fifty-eight individuals completed the study with > 80% compliance. There was no significant difference between the three groups in any of the variables tested. Benzalkonium chloride causes slight prolongation of mucociliary clearance shortly after application but has no detectable effect on nasal mucosal function after 2 weeks regular use.

Adult↗
PubMed1996

Le Nez du Vin--a quick test of olfaction.

There is a need for a quick and inexpensive smell identification test. A six odour multiple choice smell test derived from Le Nez du Vin, a winetaster's kit, is described. One hundred and thirty-two subjects assessed a mean of 5.28 +/- 1.18 odours correctly. There was a significant difference between those who considered themselves to have a normal sense of smell (n = 91), mean score 5.52 +/- 0.76, and those who thought themselves hyposmic (n = 41), mean score 4.76 +/- 1.68. (P < 0.001). No significant differences could be detected between the scores of smokers and non-smokers, nor those of males and females. Twenty-one patients performed both the Nez du Vin and University of Pennsylvania Smell Identification Test (UPSIT) in random order. Results of the two tests showed good correlation (r = 0.79, P < 0.001).

Adolescent↗
PubMed1995

Managed care in Iowa. A difficult transition.

On March 1, Medco Behavioral Care began managing mental health services for Iowa's Title 19 population. The state says Medco can improve access and save money, but many providers and other patient advocates have grave concerns about Iowa's first major experience with managed care.

Humans↗