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Biomedical subjects

M Iriarte

Publications and source records attributed to M Iriarte.

At least 37 records · Page 2Linked to original sources
PubMed1995

The fliA gene encoding sigma 28 in Yersinia enterocolitica.

Yersinia enterocolitica is an enterobacterium responsible for gastrointestinal syndromes. Its pathogenicity depends on the presence of the 70-kb pYV plasmid, which directs Yop secretion. The Yop secretion machinery, consisting of the YscA-U and LcrD proteins, presents some structural similarity with the flagellum assembly machinery characterized in other bacteria. Flagellum assembly requires sigma 28, an alternative sigma factor. The region upstream of the lcrD gene resembles promoters recognized by sigma 28, suggesting that the similarity between Yop secretion and flagellum assembly could extend to their regulation. The chromosome of Y. enterocolitica also contains pathogenicity determinants such as myfA, which encodes the Myf antigen subunit. The promoter region of myfA also resembles promoters recognized by sigma 28. In an attempt to clarify the role of sigma 28 in the expression of lcrD, myfA, and flagellar genes, we cloned, sequenced, and mutagenized the fliA gene encoding the sigma 28 homolog in Y. enterocolitica. As is the case in other bacteria, fliA was required for motility. However, it was involved neither in fibrilla synthesis nor in Yop secretion. The fliA mutant allowed us to monitor the role of motility in pathogenesis. At least in the mouse model, motility seemed not to be required for Y. enterocolitica pathogenesis.

Animals↗
PubMed1993

Congestive heart failure from left ventricular diastolic dysfunction in systemic hypertension.

Previous studies have pointed out that congestive heart failure (CHF) with normal ejection fraction presents a uniform clinical profile that is indistinguishable from heart failure with low ejection fraction. Thirty-six patients with systemic hypertension who had recently experienced CHF with normal ejection fraction (> or = 50%) and no clinical history of ischemic cardiomyopathy were studied. The patients were divided into 2 groups according to degree of echocardiographic hypertrophy: group A (19 patients) with a ventricular mass/volume ratio > 1.8, and group B (17 patients) with a ratio < 1.8. Group A patients had a higher ejection fraction (67 +/- 6 vs 57 +/- 3%, p < 0.01), smaller ventricular diameters and a lower thallium-201 positive rate at peak stress (10 vs 70% in group B, p < 0.001), with 8 of 10 showing severe coronary stenosis. Clinically, group A had a more frequent audible fourth sound (79 vs 17%, p < 0.001), a low incidence of audible third sound (5 vs 55%, p < 0.001) and a cardiothoracic ratio < or = 0.5 (63 vs 17%, p < 0.01). The degree of radionuclide-detected resting diastolic dysfunction and exercise intolerance was similar in both groups. In conclusion, CHF with normal ejection fraction in hypertensive patients presents 2 different profiles: one characterized by severe hypertrophy and the other by a high rate of myocardial regional ischemia. Therapy should be aimed at pathophysiologic regression of the hypertrophy in the first case, and at improvement of the ischemia in the second.

Aged↗
PubMed1993

Usefulness of exercise testing performed with vasodilators for predicting the severity of myocardial ischaemia during daily activities and treatment.

Fifty patients (aged 53 +/- 7 years) with confirmed coronary disease performed two stress tests (baseline and following treatment with vasodilators) and were divided into two groups: (A) fixed ischaemic threshold (n = 27), and (B) variable ischaemic threshold (n = 23). All patients underwent 24-h baseline Holter monitoring and monitoring following treatment with nifedipine, placebo, propranolol and nifedipine + propranolol. In Group A, 92% of ischaemic episodes occurred at heart rates similar to those found during exercise testing. In Group B, the heart rate was lower in 66%. In Group A, positive stress testing before the first 3 min of exercise, or at < 140 beat,min-1 with ST segment depressions > or = 0.02 mV, correlated with higher Holter indexes. In Group A, propranolol reduced both the number of episodes and total ischaemia time. In Group B, the best effects were achieved with nifedipine and combined treatment. Our results further emphasize the contrasts between patients with angina and fixed and variable ischaemic thresholds and suggest that therapy tailored to the physiopathology may be most efficacious.

Activities of Daily Living↗
PubMed1993

The Myf fibrillae of Yersinia enterocolitica.

The Myf antigen produced by Yersinia enterocolitica appeared as a proteic polymer composed of 21 kDa subunits. By transposon mutagenesis we isolated Myf-defective mutants. Those allowed us to clone and sequence a 4.4 kb chromosomal locus involved in Myf production. This region was found to contain three genes that we called myfA, myfB and myfC. Genes myfB and myfC encode an assembly machine related to those involved in the synthesis of many fimbriae: MyfB, the putative chaperone, possesses the consensus residues of the PapD family and myfC encodes a putative outer-membrane protein. MyfA, the major subunit, was found to be 44% identical to the pH 6 antigen of Y. pestis. Myf is thus the Y. enterocolitica counterpart of this antigen, but it is by far not so well conserved as the other virulence determinants such as the Yops, suggesting that Myf and pH 6 antigen do not necessarily play the same role in Y. enterocolitica and Y. pestis. The study of the prevalence of myfA in various species of Yersinia revealed that, like the yst enterotoxin gene, its presence is restricted to the pathogenic serotypes of Y. enterocolitica. By immunogold labelling, Myf appeared as a layer of extracellular material extending locally 2 microns from the bacterial surface, indicative of a fibrillar structure.

Amino Acid Sequence↗
PubMed1993

Functional and organic components of diastolic dysfunction in hypertensive heart disease: therapeutic implications.

The major structural and functional determinants of impaired left ventricular diastolic function in the hypertensive patient are reviewed, together with the indices normally used to detect this failure. The alteration of functional determinants can be quickly modified, while structural determinants are modified only over the long term. Drug therapy first affects the functional determinants, bringing about their attenuation and initiating the modification of the structural factors, thus accounting for the improvement in diastolic function over the long term.

Cardiomegaly↗
PubMed1993

Segmentary coronary reserve in hypertensive patients with echocardiographic left ventricular hypertrophy, gamma-graphic ischaemia and normal coronary angiography.

Stress thallium scintigraphies are frequently positive in patients with systemic hypertension (SHT), especially in the presence of left ventricular hypertrophy (LVH). In order to determine whether positive thallium perfusion scans in patients with LVH secondary to SHT and normal coronary angiographies are due to segmentary reduction of coronary reserve (CR), we have studied 10 out of 60 consecutive cases of SHT with echocardiographic LVH, using intracoronary Doppler. We compared coronary blood flow velocity at rest and post-papaverine (PP), and CR in at least two major coronary vessels, always including the one corresponding to the ischaemic segment. In the vessel with the least CR at rest, a new determination of CR was made under intracoronary nitroglycerin. A group of five normal patients acted as controls. The mean CR of the controls and patients, respectively, was 6.2 +/- 1.4 vs 2.7 +/- 0.9 (P < 0.001). In patients with positive thallium perfusion scans, the coronary arteries corresponding to the ischaemic segments had less CR (2.5 +/- 0.6) than arteries from non-ischaemic segments (3.4 +/- 1, P < 0.05). These differences were greater when the ischaemia was anterior. There was no correlation either between CR and left ventricular mass (r = 0.23) or rest coronary blood flow velocity (r = 0.07). Only one patient exhibited functional behaviour indicating reduced CR; this rose from 1.9 to 7.5 after nitroglycerin 300 micrograms. In conclusion, CR determined by intracoronary Doppler and papaverine shows segmentary differences both in normal patients and in patients with LVH and normal coronary angiograms. This could be the cause of segmental ischaemia detected by means of radionuclide stress tests.

Aged↗
PubMed1993

Prognostic significance of ventricular arrhythmias in the presence of pathological left ventricular hypertrophy.

It is well known that pathological left ventricular hypertrophy, either primary or secondary to cardiac overload, is associated with a high incidence of ventricular arrhythmias and sudden death, and that asymptomatic ventricular arrhythmias seem to be related to a high incidence of sudden death in patients with hypertrophic cardiomyopathy and ischaemic heart disease. However, this association has not been prospectively evaluated in patients with hypertensive LVH, where other factors, such as myocardial ischaemia, can play an important role. More studies are needed in this respect before establishing therapeutic implications.

Arrhythmias, Cardiac↗
PubMed1993

Classification of hypertensive cardiomyopathy.

A clinical pathophysiological classification of hypertensive cardiomyopathy has been established on the basis of the degree to which the heart is affected by chronic, systemic arterial hypertension: Degree I: Asymptomatic patients without left ventricular hypertrophy but with left ventricular diastolic dysfunction according to Doppler mitral inversion relation (E/A < 0.9) or to gamma scintigraphy (peak filling rate reduction < or = 2.7 EDC.s-1. These patients are classified as Group 1. Degree II: Asymptomatic or mildly symptomatic patients (New York Heart Association class I) with echocardiographic left ventricular hypertrophy; classified as Group IIA or IIB according to whether weight-adjusted maximal oxygen uptake is normal or below normal, respectively. Degree III: The basic characteristic is the presence of congestive heart failure with normal ejection fraction (EF > or = 50%). Two subsets can be distinguished on the basis of degree of hypertrophy: Group IIIA, with a mass/volume index > 1.8, and IIIB with a mass/volume index < 1.8. The differences between the two are as follows: patients classified as IIIA had a lower rate of regional ischaemia, a higher ejection fraction, a more frequently audible fourth sound, rarely a third sound and a cardiothoracic ratio < 0.5; IIIB patients had a higher prevalence of regional ischaemia (thallium-positive), a frequently audible third sound and a cardiothoracic ratio > 0.5. Degree IV: This category is characterized by the presence of depressed contractility, which could cause heart failure, by an ejection fraction < 50% and an increase in ventricular volumes. Echocardiography shows increased distance between mitral point E and the septum.

Adult↗
PubMed1992

[Isolation of Yersinia enterocolitica 0:8 in Spain].

BACKGROUND: We presented three cases of enterocolitis due to Yersinia enterocolitica 0:8. METHODS: We use common isolation media, pathogenicity markers and plasmid analysis. RESULTS: The study of genetic and biochemical characteristics of the strains showed that they belonged to 1B biotype, 0:8 serotype, and that they not carry the virulence plasmid. However, they have pathogenicity markers that were considered typical of highly virulent strains. SUMMARY: This are the first isolations of this particular serotype in Spain and they showed, as it happens in other European countries, the spread of serotype 0:8 around the world.

Acute Disease↗
PubMed1989

[Diagnosis of pulmonary hypertension by means of continuous, pulsed and color Doppler, and its correlation with hemodynamics].

We have performed a study on 28 patients (20 with valve disease and eight with Eisenmenger syndrome) to evaluate the degree of pulmonary hypertension by means of continuous, pulsed and color Doppler, comparing these results with those obtained at cardiac catheterisation. Invasive systolic pulmonary pressure corresponded excellently with the transtricuspid gradient determined by continuous Doppler (r = 0.97). The study by pulsed Doppler of pulmonary artery flow enabled us to establish a good correlation between total pulmonary resistance with the quotient time to peak flow/ejection time and time to peak flow (r = 0.87 and r = -0.81), and between systolic pulmonary pressure and the time to peak flow (r = -0.80). Color Doppler enabled us to easily establish the presence of tricuspid and pulmonary regurgitation.

Adult↗