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Biomedical subjects

M Petrou

Publications and source records attributed to M Petrou.

At least 55 records · Page 3Linked to original sources
PubMed1994

Evaluation of unstented aortic homografts for the treatment of prosthetic aortic valve endocarditis.

BACKGROUND: Prosthetic aortic valve endocarditis is a serious complication that carries a high morbidity and mortality. Aortic homografts have been used in this setting, but long-term results are not available. METHODS AND RESULTS: Over a 23-year period, 48 patients presented with infected aortic valve substitutes: 28 homografts, 15 mechanical, and 5 xenografts. Nineteen patients had emergency surgery, and the mean interval between the first and second operation was 5.9 years (range, 1 month to 22 years). In 28 patients, the preoperative New York Heart Association (NYHA) class was III or IV. Active endocarditis was present in 39 patients, and the microorganisms grown were Staphylococcus epidermidis (n = 13), Staphylococcus aureus (n = 6), Streptococcus viridans (n = 6), Streptococcus faecalis (n = 4), Candida albicans (n = 5), and Gram-negative spp (n = 2). Aortic root abscesses were found in 28 (58%) patients, and transesophageal echocardiography was 95% accurate in their localization. All patients received homograft aortic valves, 19 as root replacement and 29 using the freehand technique. There were four (8.3%) early deaths; poor left ventricular function and concomitant procedure were identified as risk factors. At a mean follow-up of 4 years (range, 2 months to 19 years) 95% of the patients were in NYHA class I or II without significant aortic regurgitation. The actuarial survival at 5 years was 97% (confidence limit, 84% to 100%), and freedom from endocarditis at 10 years was 97% (confidence limit, 84% to 100%). Multivariate analysis did not identify risk factors for these late events. CONCLUSIONS: Homograft aortic valves offer good early and long-term results in patients with infected aortic valve substitutes.

Actuarial Analysis↗
PubMed1994

The use of unstented homograft valves for aortic valve reoperations. Review of a twenty-three-year experience.

Unstented homograft valves offer several theoretical advantages when used for patients who have had previous operations on the aortic valve. Between January 1970 and February 1993, 177 patients received unstented homograft valves after previous aortic valve operations. One hundred thirty-four patients had previous aortic valve replacement in the form of homografts (101 patients), mechanical prostheses (24 patients), and bioprostheses (9 patients), and 43 had previous valve repair. The indication for reoperation was deterioration of a noninfected valve (124 patients), infective endocarditis (40 patients), and failure of a noninfected mechanical valve (12 patients). Fresh homograft valves were implanted in 60 patients, homografts preserved in antibiotics were used in 111 patients, and 6 patients received cryopreserved valves. Aortic valve and root replacement was performed in 60 patients, and in 117 the homograft was inserted freehand in the subcoronary position. The early mortality was 5.1%. The actuarial survival at 10 years was 71%. Multivariate analysis demonstrated that patients with previous homograft replacement have a better long-term survival than patients who had previous mechanical valves (p = 0.017). The freedom from valve-related death and reoperation was 70% at 10 years. Fresh homografts faired better than antibiotic-sterilized homografts (p = 0.007). None of the patients had recurrence of endocarditis at 6 months, although 1 patient died of uncontrolled infection despite valve replacement. The freedom from recurrent endocarditis was 88% at 10 years. We conclude that unstented aortic homografts provide good early and long-term results for aortic valve reoperations, particularly in patients with previous homograft replacement. Recurrent endocarditis is uncommon even in patients operated on for prosthetic valve infections.

Adolescent↗
PubMed1993

Variation of short tandem repeats within and between populations.

Using the polymerase chain reaction (PCR) the frequency distributions of three short tandem repeats (STR) were investigated in five populations: North European, Cypriot, Pakistani, Gujarati and Vietnamese. Each STR is situated within an intron; the markers are in the genes for human coagulation factor XIII (4bp repeat), lipoprotein lipase (4bp repeat) and CD4 (5bp repeat). Population data were generated for each STR and allele frequencies calculated. A calculation of the level of population substructuring for the three systems was also made. The lipoprotein lipase STR data showed no evidence for population substructuring, but there was a significant level of substructuring in the other two systems. This initial pilot study demonstrates the need to validate each marker used for DNA profiling in different human populations, and that some markers (such as LPL) can be used with confidence in widely differing ethnic groups, while others (such as CD4 and F13A) may be of value in distinguishing sub-groups.

Alleles↗
PubMed1993

Bronchoscopic diathermy resection and stent insertion: a cost effective treatment for tracheobronchial obstruction.

BACKGROUND: Major airways obstruction is a distressing cause of morbidity and mortality. For disease that is extensive and recurrent, there is a need for a safe and cost effective technique for palliation. METHODS: The results of 29 patients with tracheobronchial obstruction (24 malignant and five benign) treated by diathermy resection alone or in combination with endobronchial stenting have been reviewed. RESULTS: The major site of obstruction was the trachea in 14, main carina in seven, right main bronchus in six, and left main bronchus in two patients. Fifteen had received other forms of treatment beforehand including external radiotherapy, endoscopic dilatation, and laser resection (Nd:YAG). Five patients required two or more treatment sessions for symptom recurrence. Ten patients also received additional treatment with a stent (nine) or insertion of gold grains (one). There were no intraoperative deaths or complications and the average length of stay was five days (range 2-14). Twenty eight patients reported immediate symptomatic relief, and objective improvement in the results of lung function tests was seen in eight patients whose condition was less acute and where preoperative lung function tests could be undertaken (average improvement in FEV1 of 53.1% and in FVC of 20.6%). CONCLUSIONS: Bronchoscopic diathermy resection is an effective and safe method for relieving the symptoms of tracheobronchial obstruction at appreciably less cost than laser resection.

Adult↗
PubMed1992

Alpha thalassaemia hydrops fetalis in the UK: the importance of screening pregnant women of Chinese, other South East Asian and Mediterranean extraction for alpha thalassaemia trait.

OBJECTIVE: Alpha zero (alpha 0 or alpha-1) thalassaemia is an important genetic risk for women originating from Hong Kong, Singapore, Vietnam, Thailand, the Philippines or South China. Cypriots are also at risk. Carriers of alpha zero thalassaemia trait can be detected by routine haemoglobinopathy screening. When a couple are both carriers, in each pregnancy there is a 25% risk that the fetus will have alpha thalassaemia hydrops fetalis; this is fatal for the fetus and carries serious obstetric and psychological risks for the mother. Most informed couples at risk request prenatal diagnosis and selective abortion. This study investigates the effectiveness of screening, counselling and prenatal diagnosis for alpha thalassaemia hydrops fetalis in the UK. DESIGN: Retrospective analysis of the notes. SUBJECTS: 18 couples attending University College Hospital London for prenatal diagnosis of alpha thalassaemia hydrops fetalis since 1982. RESULTS: The study shows underdiagnosis of both alpha zero thalassaemia trait and alpha thalassaemia hydrops fetalis leading to avoidable stillbirths and complications in pregnancy. CONCLUSION: We recommend early screening for alpha zero thalassaemia trait for all women of Southeast Asian or eastern Mediterranean origin and the offer of prenatal diagnosis when indicated. The diagnosis of alpha thalassaemia hydrops fetalis should be considered in women of the relevant ethnic origin who have a stillbirth, neonatal death, abnormal ultrasound findings at fetal anomaly scanning (especially a large placenta), or who develop pre-eclampsia.

Abortion, Spontaneous↗
PubMed1992

Factors affecting the uptake of prenatal diagnosis for sickle cell disease.

Between 1979 and 1990, 170 couples at risk of having children with sickle cell disease, resident in the UK and with a continuing pregnancy, were referred for counselling at the University College Hospital Perinatal Centre. Approximately 50% of the couples, including those where one partner actually had sickle cell disease, requested prenatal diagnosis. This was requested in 82% of pregnancies when the mother was seen in the first trimester of pregnancy and in 49% when she was seen in the second trimester. More than 90% of referred couples who already had an affected child requested prenatal diagnosis. The type of sickle cell disease involved and ethnic group also influenced choice. These results show the importance of detecting and counselling couples at risk before pregnancy whenever possible.

Anemia, Sickle Cell↗
PubMed1990

The antibody repertoire of early human B cells. I. High frequency of autoreactivity and polyreactivity.

Cord blood and fetal liver B cells were immortalized using Epstein-Barr virus, and IgM antibodies from the resulting lines and clones were examined for their binding to a variety of auto-antigens and micro-organisms by ELISA and fluorescence assays. Auto-antigens tested included Fc of IgG, ssDNA and dsDNA, cardiolipin, histones 1-4, collagens type I and II, thyroglobulin, cytoskeletal components, and a tissue section screen. Of 71 cell lines tested, all but 19 showed some autoreactivity. All 32 fetal liver lines reacted to some self-antigens. In cord blood clones, 16 out of 26 bound to auto-antigens. Many of the clones reacted with more than one auto-antigen and were 'polyreactive'. Some of the cord blood clones bound to extracts of micro-organisms, showing specificity for both endogenous and exogenous antigens. The high frequency of CD5+ B cells in the cord blood (greater than 50%) and fetal liver (greater than 70%) argues for many of these clones being derived from this subset. Therefore, our data support the concept that many 'early' B cells produce polyreactive IgM which can bind to a variety of different auto-antigens and micro-organisms. These IgM antibodies are similar to those described by others as 'natural antibodies'.

Antibody Specificity↗
PubMed1989

Excitatory transmitter amino acid-containing neurons in the rat visual cortex: a light and electron microscopic immunocytochemical study.

The distribution and morphology of neurons labelled with antisera to glutamate or aspartate were examined, at the light and electron microscope levels, in the rat visual cortex. Using widely accepted light microscopic features as well as well-established nuclear, cytoplasmic, and synaptic criteria, we noted that glutamate-immunoreactive neurons were pyramidal cells distributed in layers II-VI, with an increased concentration in layers II and III. Aspartate immunoreactivity was localized chiefly to pyramidal neurons in layers II-VI. However, approximately 10% of immunolabeled cells were nonpyramidal neurons scattered throughout the cortex. Cell-body measurements revealed that, for both groups of neurons, layer V contained the largest labelled neurons, whereas layers IV and VI contained the smallest. Furthermore, in every layer, aspartate-stained neurons were larger than glutamate-positive cells. Finally, glutamate- and aspartate-labelled axon terminals formed asymmetrical synapses, which are presumably excitatory in nature, primarily with dendritic spines. These findings, together with recent detailed studies of the projections of glutamate- and aspartate-labelled cortical neurons, may provide essential background information for studies aimed to elucidate the function(s) of excitatory amino acids in the cortex and their role in pathological conditions.

Animals↗
PubMed1988

Changes in circulating alphafetoprotein and human chorionic gonadotrophin following chorionic villus sampling.

Chorionic villus sampling (CVS) is rapidly becoming established as a routine procedure for first-trimester fetal diagnosis. The technique can result in fetomaternal haemorrhage and this might sensitize Rhesus-negative mothers and on occasion lead to spontaneous abortion. Serial sampling indicates that there is a rapid rise in alphafetoprotein (AFP) levels following CVS; however, this is not reflected by raised levels at 16-18 weeks and does not influence the subsequent pregnancy outcome. Unlike AFP, alterations in hCG levels are small and variable. Anti-D prophylaxis for non-sensitized Rhesus negative mothers should be given after CVS and the procedure may be contra-indicated in patients who are already sensitized.

Chorionic Gonadotropin↗
PubMed1988

Chorionic villus sampling in a high-risk population--4 years' experience.

Between August 1982 and July 1986 a total of 163 pregnancies in 136 patients with a high genetic risk have had prenatal diagnosis by chorionic villus sampling. Villi were not obtained in five pregnancies (two of which subsequently miscarried), and 11 fetal losses followed successful sampling (four in pregnancies in which the fetus was shown to be affected). The rate of fetal loss fell with increasing experience of the team. Three sets of twins were all sampled successfully.

Abortion, Spontaneous↗
PubMed1987

Two unusual cases of first trimester prenatal diagnosis of cystic fibrosis using DNA probes.

There are now several DNA probes which localize the cystic fibrosis mutation (CF) to chromosome 7q2.2-q3.1. The most tightly linked probes, pJ3.11 and met, are useful for first trimester prenatal diagnosis for many families provided that there is at least one living child affected by CF (Farrall et al., 1986). We describe here two families seeking prenatal diagnosis for CF which present unusual counselling problems. The first is an extended family in which there is no living affected member with CF; the second, a consanguinous marriage at risk both for cystic fibrosis and beta-thalassaemia. In both cases first trimester chorionic villus sampling and DNA haplotype analysis predicted that the fetus is a carrier for CF, and in the doubly affected family a carrier for beta-thalassaemia as well. Both pregnancies resulted in live births and subsequent immunoreactive trypsin estimations were both in the normal range.

Chorionic Villi↗
PubMed1986

First-trimester fetal diagnosis for haemoglobinopathies: report on 200 cases.

First-trimester prenatal diagnosis by DNA analysis was found to be possible in 224 (80%) of 281 families at risk of having a child with beta-thalassaemia major. 200 prenatal diagnoses, mainly for beta-thalassaemia or sickle-cell anaemia, were made by means of chorionic villus sampling and fetal DNA analysis. The overall fetal loss rate was 6.7%, the majority being in the first half of the programme. There was one misdiagnosis. Prenatal diagnosis was also carried out successfully for both pairs of twins in two pregnancies. Comparison of these results with 53 prenatal diagnoses made with DNA prepared from amniotic fluid suggests that the first-trimester procedure is more reliable. If further experience confirms that chorionic villus sampling has an acceptably low risk for both mother and fetus it will largely replace other methods for prenatal diagnosis of the haemoglobin disorders and other single-gene conditions.

Amniotic Fluid↗
PubMed1986

Iron chelation using subcutaneous infusions of diethylene triamine penta-acetic acid (DTPA).

The iron chelating ability and potential toxicity of subcutaneous infusions of the calcium and zinc salts of diethylene triamine penta-acetic acid (DTPA) have been assessed in metabolic balance studies in 2 iron-loaded thalassaemic patients. Infusions of calcium DTPA were locally well tolerated and the drug was as effective as desferrioxamine in mobilising iron. However, daily infusions in the 1st patient also produced symptomatic zinc depletion which could not be controlled by simultaneous oral zinc supplements. Zinc DTPA proved ineffective as an iron chelator, but zinc balance could be maintained in the 2nd patient by combining intermittent (every 4 d) use of calcium DTPA with oral zinc supplements. Combined studies with desferrioxamine and calcium DTPA showed the drugs to have additive effects, probably as a result of the chelation of iron from different body sites.

Administration, Oral↗
PubMed1986

Meiotic recombination between two polymorphic restriction sites within the beta globin gene cluster.

Analysis of beta globin gene haplotypes for prenatal diagnosis of beta thalassaemia has revealed a recombination event within the beta globin gene cluster. Both a change in the AvaII polymorphic site within the beta globin gene and a change in the phenotype of the beta globin gene were observed. Paternity was established by the pedigree analysis of hypervariable 'minisatellite' DNA polymorphisms and the most probable explanation of the recombination event is a crossover between the psi beta globin gene and the beta globin gene. The data provide direct evidence in support of a DNA region 3' to the beta globin gene with a recombination frequency much higher than expected, and have important implications for the prenatal diagnosis of beta thalassaemia by linked restriction fragment length polymorphisms.

Alleles↗
PubMed1985

Diagnostic fetal blood sampling for the haemoglobinopathies--10-year experience.

The development of methods for fetal blood sampling in the second trimester of pregnancy offers the possibility of fetal diagnosis for couples at risk for having children with a haemoglobinopathy. We review the evolution of 10 years' experience of fetal blood sampling for 681 patients. The obstetric risk associated with the procedure has fallen from an initial 15% (in the first 87 pregnancies) to about 3%, in parallel with increased experience, improved ultrasound control, identification of the causes of complications and implementation of simple steps to avert them.

Diseases in Twins↗