Biomedical subjects
Publications and source records attributed to J McDonagh.
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OBJECTIVE: To assess the wide-field multifocal electroretinogram (WF-mfERG) for assessment of retinal function in vigabatrin-treated patients. METHODS: Thirty-two adults who had taken vigabatrin for at least 3 years for localization-related epilepsy underwent WF-mfERG, ERG, logMar visual acuity and color vision evaluation, Humphrey visual field analysis (static perimetry), and funduscopy. The group was matched with a cohort of patients who had never received vigabatrin. Results were compared with a normative data set (120 drug-free controls) with respect to potential bilateral abnormalities in response timing. RESULTS: There were no significant differences between groups in visual acuity or color vision testing. Of the vigabatrin patients, 19 (59%) had bilateral visual field defects compared to none of the controls. Using WF-mfERG, all patients on vigabatrin with visual field defects showed abnormalities (100% sensitivity) and only 2 of the 13 patients without a field defect showed retinal abnormalities (86% specificity). CONCLUSIONS: WF-mfERG may be useful for detecting retinal pathology in patients taking vigabatrin. The majority of previous reports based on subjective testing may have underestimated the prevalence of peripheral retinal toxicity related to the drug.
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Medical education has traditionally been focused on the understanding of pathophysiology and treatment of disease. While there is an increasing level of attention focused on the doctor- patient relationship and the social aspects of medicine, there remains a relative lack of educational efforts regarding the care of individuals who are dying. This paper addresses the cultural context of medical school with respect to end-of-life care and proposes the role of physicians in caring for dying patients. In addition we report initial efforts at the University of Vermont College of Medicine to construct a preclinical course for medical students about end-of-life issues. As part of these efforts we sought to assess the attitudes of entering medical students towards end-of-life care. Review of the data suggests that the majority (66-98%, depending on measure used) of new medical students possess sophisticated attitudes regarding the care of dying individuals. Our conclusion is that medical education should seek to nurture these sophisticated attitudes and supply the basic tools of palliative care in order to improve the quality of experience for individuals who are dying.
Fibrinogen participates in important cellular physiological processes, such as cell adhesion and blood clotting. Although the primary and secondary structures of fibrinogen are known, its tertiary structure is yet to be determined. In attempts to understand the tertiary structure of this important hydrated cellular and plasma membrane protein, the present study using atomic force microscopy was carried out. The techniques presented in this manuscript may also be applicable to enhance the imaging of live cells as well as their subcellular components. The authors have imaged fibrinogen by Tapping Mode atomic force microscopy in fluid. Purified human fibrinogen, together with 15-nm colloidal gold particles serving as an internal calibration standard, were adhered to a poly-L-lysine substrate on freshly cleaved mica. Atomic force microscopy images were obtained using oxide-sharpened silicon nitride probes, either unaltered or with an electron beam deposited extended tip. Although various structures were observed, the predominant forms consisted of a bi- or trinodular slightly curved linear shape. Approximately 300 of these structures were observed with six different tips (1 unaltered and 5 electron beam deposited) and their lengths and heights were analyzed. The mean length of the fibrinogen molecules was 65.8 nm and the mean height was 3.4 nm. The quantitative measurements were little influenced by the shape of the tip, whereas the sharper electron beam deposited tips seemed to produce qualitatively superior images.
Plasma factor XIIIa (A*2) is a regulator in balancing the opposing coagulation and fibrinolytic processes. Its enzymatic activity is to catalyze epsilon-(gamma-glutamyl)lysyl bonds between certain substrate molecules to link them by strong bonds. The primary physiological substrates are crosslinks between the gamma and alpha chains of fibrin that produce gamma-gamma-dimer and alpha-polymer, between alpha 2-plasmin inhibitor (alpha 2-PI) and alpha chains of fibrin, and between fibronectin and fibrin. We have characterized a unique factor XIII antibody that is specific for the middle 54-kDa section of A*2. It does not react with the zymogen (A2) or the inactive intermediate (A'2), and it does not inhibit the active center, as do most patient antibodies to factor XIII. This antibody inhibits the formation of A*2-fibrin complexes. Because of this specificity, the antibody was used to study other substrate interactions. It inhibited formation of fibronectin-factor XIIIa complexes, similarly to fibrin, and there was very little crosslinking of fibronectin to a fibrin clot. However, the amount of alpha 2-PI crosslinked to a fibrin clot was normal. It was concluded that this antibody interferes with exosite binding of fibrin and fibronectin interferes with exosite binding of fibrin and fibronectin in a similar way, while at least one critical exosite binding domain for alpha 2-PI is different from those of the other two substrates. Furthermore, with this antibody, it was shown that both alpha 2-PI-alpha chain crosslinking and alpha-polymer formation are necessary to normalize the rate of fibrinolysis.
Factor XIIIa belongs to a family of ubiquitous transglutaminases, which catalyze formation of covalent bonds between the epsilon-amino group of specific lysines and the gamma-carboxyl group of glutamines. Factor XIII is synthesized as a zymogen and after activation, it participates in both the coagulation and fibrinolytic mechanisms. Most transglutaminases are intracellular, but factor XIII is both intracellular and extracellular. the biosynthesis of extracellular (plasma) factor XIII, with the structure of a noncovalent heterotetramer, A2B2, is complex. Here, evidence is presented from PCR analysis and Northern blotting that mRNAs for both A and B subunits are present in the liver. The distribution of mRNA, specific for factor XIII subunits, in various human tissues was also analyzed. Among the tissues examined, the only signal for B subunit was found in the liver. For subunit A, the signal was observed in placenta, liver, kidney, lung, skeletal muscle and heart with varying intensities; in brain or pancreas there was no signal. With an immunoperoxidase method, factor XIII A subunit was identified in the PLC/PRF/5 cell line. By ELISA and reverse immunoblotting, with antibodies specific for the A-B complex, it was also shown that these cells produce and secrete factor XIII. From all of these results, we conclude that the liver is a source of plasma factor XIII, and that the complex A2B2 is secreted from these cells.
The addition of 2 mM sodium butyrate to monolayers enhances differentiation of Ishikawa endometrial cells. Cells from this cell line have been shown to enlarge and lift off the dish into dome structures over a period of 24-48 h in response to a factor in fetal bovine serum (FBS) [Fleming, 1995 J Cell Biochem in press]. When butyrate is added to monolayers, together with FBS, three- to fourfold higher numbers of differentiated structures, domes and predomes, can be counted. It had previously been shown [Holinka et al., 1986b] that estradiol induces heat stable placental alkaline phosphatase in Ishikawa cells. The addition of butyrate, on the other hand, results in a significant increase in levels of a heat labile alkaline phosphatase isozyme. The heat labile isozyme is also increased to some extent in cells stimulated to differentiate in response to FBS in the absence of butyrate. Differential inhibition by homoarginine and phenylalanine indicates that butyrate is inducing the liver-bone kidney isozyme that is found in endometrial glands in vivo.
We have studied anti-Proteus antibodies (APA), isolation of Proteus, and their relation to various measures of RA disease activity. Seventy RA patients with a CRP > 10 mg/l had higher APA titres than 17 RA patients with CRP < or = 10 mg/l (P = 0.006), and 36 non-RA controls (P = 0.003). However, in a cross-sectional study of the RA group, there was no correlation between APA and a number of clinical and laboratory measures of disease activity, including the CRP and Stoke RA activity index. A longitudinal study showed no correlation between changes in these measures of disease activity and change in APA titre. We were unable to isolate Proteus in the urine or faeces of RA patients more frequently than controls, and the isolation of Proteus did not correlate with serum APA titres. Urinary APA was present in equal frequencies in RA and non-RA patients. NSAIDs, DMARDs and steroids did not appear to influence APA titres in the RA group. These results suggest that APA may act as an acute phase protein, distinct from CRP, but not correlating with RA disease activity in its broadest context. The fact that the antibody we are measuring binds to Proteus may be irrelevant, and the study does not support a role for Proteus in RA.
We performed high resolution computed tomography (HRCT) on the lungs of 20 patients with RA and clinical and radiological evidence of interstitial lung disease (ILD). A case control group of patients with RA but without evidence of ILD were similarly studied and all patients underwent detailed pulmonary function testing. Clinical findings, drug therapy, smoking status, the presence/absence of SS and disease activity were also assessed. HRCT showed a range of abnormalities among patients thought to have ILD. Interstitial fibrosis was confirmed in 16 but was frequently associated with emphysema. Ground glass opacification was present in seven, while basal honey-combing was also evident in seven patients. Both these features were present in two patients with ILD. Bronchiectasis was identified in six patients and was the predominant finding in two patients previously thought to have ILD. Among the control patients, HRCT was normal in only five. Clinically unsuspected ILD was present in four patients, while a further four had bronchiectasis. Pleural disease was identified in seven controls. Pulmonary function tests were generally poor predictors of HRCT findings, although a reduced residual volume (RV) [> 1 S.D.] was 83% specific for the presence of ILD and a raised RV [> 1 S.D.] was 64% specific for emphysema. Smoking did not correlate with the presence of either ILD or emphysema and there were no correlations between disease activity and HRCT findings. RA patients with evidence of ILD have abnormalities on HRCT which cannot be confidently predicted on any other non-invasive test.(ABSTRACT TRUNCATED AT 250 WORDS)
OBJECTIVE: To determine if there is evidence for genetic anticipation in rheumatoid arthritis (RA) by analysing the possibility that parental disease status and age at proband conception influence the age of onset and disease severity of the proband. METHOD: RA outpatients were identified and data were also taken from Newcastle multicase RA pedigrees. Comparisons of age of onset and parental age at proband conception were made for pedigrees grouped according to the disease status of the parents. Correlation coefficients and linear regression models were calculated for the age of RA onset in the probands. Measures of disease severity were compared in RA mother-proband pairs. RESULTS: The results were similar in both the outpatient (n = 153) and multicase pedigree (n = 15) samples. Significant results were confined to pedigrees in which the mother had RA (20 of the outpatient probands and seven of the multicase group). Probands in these sibships had a younger age of RA onset than their affected mothers (38.3 years (95% confidence interval (CI) 33.8 to 42.8) versus 53.7 (47.3 to 60.0) (p = 0.002) in the outpatient sample; 32.4 years (25.3 to 39.6) versus 43.4 years (29.0 to 57.9) (p = 0.1) in the multicase pedigrees). In the maternal RA group, both the maternal and paternal age at proband conception showed significant negative correlations (r = -0.65, p = 0.002 and r = -0.60, p = 0.005, respectively in the outpatient sample) and linear regression coefficients with age of proband disease onset. In seven affected mother-proband pairs, the probands had a tendency to more severe disease, despite shorter disease duration and younger age. CONCLUSIONS: This preliminary analysis has suggested that within pedigrees in which the mother has RA, the features of genetic anticipation and observations consistent with premutation models may prevail.
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Electron microscopic and physical-chemical properties of one- and two-chain tissue plasminogen activator (t-PA) were studied. The molecular weight of one-chain t-PA obtained by both sedimentation equilibrium and SDS-PAGE was estimated to be about 65,000, while both chains in the reduced two-chain form were in the range of 35,000-40,000. Sedimentation coefficients were identical for both forms of t-PA (S(0)20,w = 4.12). The two forms of t-PA were indistinguishable by electron microscopic analysis, which confirmed the sedimentation results, and showed that they were ellipsoidal and relatively compact. The major and minor axes were approx. 13 nm and approx. 10 nm and f/f0 was 1.36. The individual domains of t-PA are relatively small and are folded within the molecule, so that the overall appearance is globular.
A 63-year-old man was evaluated for a lifelong history of bleeding commencing with frequent epistaxis as a child; all previous routine coagulation parameters were within the normal range. The patient's hemorrhagic disorder is characterized predominantly by delayed bleeding at surgical sites. In the resting state, there was no clinical or laboratory evidence of excessive fibrin(ogen)olysis. Bleeding was not caused by disseminated intravascular coagulation, factor XIII deficiency, alpha 2-antiplasmin deficiency, or dysfibrinogenemia. It was found that the patient was deficient in plasma PAI-1 antigen and activity but with approximately half normal antigen and normal activity of platelet PAI-1. The low concentration of plasma PAI-1 was insufficient to neutralize circulating t-PA, resulting in high t-PA activity with normal antigen and causing the hyperfibrinolytic activity observed. Studies on seven family members of the proband indicated autosomal inheritance of plasma PAI-1 deficiency. Studies on this patient emphasize a clear correlation between decreased plasma PAI-1 activity and hyperfibrinolytic bleeding and also emphasize the unique role of plasma PAI-1 in the balance between the coagulation and fibrinolytic mechanisms.
Gly-Pro-Arg-Pro (GPRP) is a potent inhibitor of fibrin polymerization. It also causes a concentration-dependent inhibition of the activation of plasminogen by t-PA when soluble desAABB-fibrinogen (fibrin II) or fibrinogen are used as promoters of t-PA. Fibrinogen has a much weaker promoter activity than does fibrin II. Experiments were undertaken to explain the mechanism of action of GPRP on plasminogen activation. Kinetic data indicated that when GPRP was present in the assay system, the fibrin(ogen)-GPRP complex was ineffective as a t-PA promoter. Only the free forms of fibrin II or fibrinogen were promoters of t-PA. GPRP specifically eluted t-PA, which was previously bound to a fibrin-Sepharose column, and also inhibited t-PA binding to fibrin-Sepharose in a concentration-dependent manner. These experiments were compared to those with other tetrapeptides: GHRP, GPGG, and GRGD. Only GHRP, which is known to bind more weakly to fibrin(ogen) than GPRP, had any effect. These results suggest that the GPRP binding site on the fibrin(ogen) molecule is important for t-PA activation and is a binding site for t-PA in the initial interaction between t-PA and fibrin. We propose that at or near the GPRP binding site on fibrin there is an initial binding site for t-PA. We hypothesize that kringle 1, which contains the sequence G128RRP, may be involved in the initial binding of t-PA to fibrin.
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