Biomedical subjects
Publications and source records attributed to E Lucas.
Heart rate variation at the respiratory frequency was examined in young adult and aged cats during waking and quiet sleep. Respiratory sinus arrhythmia was found to be significantly enhanced during quiet sleep compared with waking in both groups of cats. Aged cats exhibited respiratory sinus arrhythmia comparable to that of young adult cats during both waking and quiet sleep.
Despite the similarities in their mechanism of action, the structural requirements for selective interaction with angiotensin-converting enzyme or enkephalinase are different. Inhibitory potency of a series of new mercaptoalkanoyl amino acids were determined on pure angiotensin-converting enzyme (EC 3.4.15.1) from porcine plasma and on neutral metalloendopeptidase (EC 3.4.24.11) purified from rat brain. This latter enzyme, first designated as enkephalinase, seems to be synaptically involved in the degradation of enkephalins. All tested compounds, whose design was based on the classical active-site model of metallopeptidases, are reversible and competitive inhibitors of both enzymes. Owing to the remarkable similarity in the general topology of metallopeptidases, the differences in optimal binding requirements to enkephalinase and angiotensin-converting enzyme were interpreted from crystallographic studies on related enzymes such as thermolysin and carboxypeptidase A. The large size of the S'1 subsite of enkephalinase allows efficient binding (Ki approximately equal to 2-30 nM) of aromatic and bulky hydrophobic residues such as a cyclohexyl ring. In contrast, a methyl group in position P'1 favors inhibitory potency against angiotensin-converting enzyme while a cyclohexyl ring leads to a complete loss of activity. This feature could mean that optimal binding of the Zn atom present in the catalytic site is a more stringent requirement in angiotensin-converting enzyme than in enkephalinase. An increase in the size of the P'2 component of thiol inhibitors potentiates the affinity for angiotensin-converting enzyme without a significant change on enkephalinase. Finally, methylation of the ultimate amide bond of inhibitors produces a 30-fold decrease in potency towards enkephalinase but does not affect the binding of angiotensin-converting enzyme. These findings allow a rational design of selective inhibitors of enkephalinase, an essential prerequisite for their possible clinical use as new analgesic and psycho-active agents.
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In 130 posterior fossa operations 6 cases of progressive distension of the operation site have been recorded and documented. The possible causes of this complication and the surgical management are discussed. Isotope studies after injection of Ytterbium 169DTPA into the underlying cyst have shown abnormal patterns in CSF circulation and absorption. All the cases have resolved after ventriculo-peritoneal shunts.
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OBJECTIVE: To emphasize the importance of chest X-Rays in the diagnosis of Scimitar Syndrome. This anomaly is usually characterized by the presence of anomalous venous drainage of the right lung to the inferior vena cava, abnormal bronchial segmentation, and alterations of pulmonary artery and right lung vascularization.METHODS: The authors report a case of Scimitar Syndrome in an 8 year-old-child, discussing its diagnostic methods and surgical treatment.RESULTS: The child presented good outcome after surgical therapy, with an uneventful follow-up.CONCLUSION: The Scimitar Syndrome is a rare anomaly, which may present few clinical manifestations. The chest X-Ray is a very relevant tool in the screening of this disease, since it discloses a persisting right paracardiac image, as a result of abnormal right pulmonary venous drainage to inferior vena cava ("Scimitar sign").
OBJECTIVE: Children s chest X-ray calcification images can be related to pulmonary, mediastinal and rarely cardiac parenchymatous pathology. This report describes cases of cardio thoracic calcifications. We emphasize the importance of chest X-ray to track thoracic calcifications. In spite of the fact that it is rare, the cardiac etiology must be considered due to the possibility of surgical treatment.METHODS: Regarding the period from 1988 to 1997 the authors reviewed the chest X-rays of 2108 patients. In 3 of them thoracic calcifications of cardiac etiology were observed.RESULTS: Of these three patients, two were 7 years old and the third was 3 years old. Case 1 presented a calcification in the right atrium topography caused by a heart tumor of Fibroma type. In case 2 the calcification was in the pulmonary trunk, presenting as a calcified aneurysm of the ductus arteriosus. In case 3 the child had pulmonary stenosis and the chest X-ray showed a calcified image on the left cardiac boards caused by a thrombo in the right ventricle wall.CONCLUSION: The authors emphasize the importance of chest X-ray in the diagnosis of thoracic calcifications, and comment that in spite of the being rare, the cardiac causes should be considered due to the possibility of surgical treatment.
Systematic 24-h automatic physiologic monitoring has obvious merits, even without rhythmometry. It can lead more readily to the recognition of odd-hour blood pressure elevation (e.g., of 'evening' or 'morning' hypertension). Such a condition can constitute an initial diagnosis or it may be found under treatment that may seem to be satisfactory if its effects are assessed only on the basis of a conventional check at a casual, possibly 'wrong' time. The mere inspection of a 24-h record, however, does not necessarily allow one to make objective quantitative global statements as to a change in pattern, e.g., after a given intervention. This paper illustrates how by rhythmometry, some of the uncertainties of a subjective interpretation of a record may be removed by practitioners of medicine, as well as basic scientists interested in mechanisms of blood pressure variability. This is possible since a large part of blood pressure variability can be accounted for by its circadian periodic behavior. We herein present a methodology for data collection and analysis that allows the objective quantification of blood pressure rhythm parameters in health and disease and the derivation of reference standards for such parameters. The chronobiologic approach thus makes it possible to define 'hypertension' objectively, and to distinguish between 'mesor-' and 'amplitude-hypertension', i.e., between an elevation in overall mean and one in the predictable extent of variability. Moreover, chronobiology has shown that mesor-hypertension may be preceded by an elevation in circadian amplitude only (amplitude-hypertension). Parameter tests readily allow the assessment, in relation to an objective reference standard, of these conditions, with a defined probability. Similarly, response to drug or non-drug therapy can be established and a given intervention optimized by timing treatment. Using chronobiologic tools in cardiovascular research provides new insights into possible mechanisms underlying mesor- and amplitude-hypertension. The teaching of the chronobiology of blood pressure and autorhythmometry in schools has been proven to be feasible and has been recommended as a step toward self-help for health care.
We report the case of a patient with Henoch-Schönlein Purpura related to a treatment with cefuroxime and diclofenac who presented important systemic manifestations including a glomerulonephritis with IgA mesangial deposits. Skin testing with beta lactam antibiotics and diclofenac were negative in immediate and late reaction as well as RAST test to penicillins G and V. No cautious administration of drugs was done because of the illness severity. Although a reaction to diclofenac could not be excluded we thought that the more probably implicated drug was cefuroxime because the patient referred a purpuric rash after the intake of cephradine for a mastitis, ten years ago.