Biomedical subjects
Publications and source records attributed to I Maurer.
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Conventional biologic and mechanical prostheses have important limitations with regard to their hemodynamic characteristics and long-term durability. We evaluated the hemodynamic function of a stentless porcine aortic prosthesis in 10 patients by invasive pressure measurements and angiography with videodensitometry 8 +/- 4 days after operation, as well as by Doppler echocardiography 35 +/- 15 months after valve replacement. The early postoperative invasive study revealed a mean gradient of 8 +/- 6 mm Hg across the prosthesis, no regurgitation in eight patients, and mild regurgitation, defined as less than 20% regurgitant fraction, in the remaining two patients. The late postoperative Doppler echocardiographic study revealed a mean gradient across the aortic prosthesis of 6 +/- 3 mm Hg, mean Doppler-derived valve orifice area of 1.8 +/- 0.6 cm2, and color Doppler flow velocity mapping suggested no regurgitation in eight patients and mild regurgitation in two patients corresponding to early postoperative angiography. None of the 10 patients received anticoagulation therapy. The clinical course of all patients was without incident. This stentless aortic bioprosthesis may offer hemodynamic advantage; however, further studies are needed to allow comparison with conventional mechanical and biologic prostheses.
A case of mitral valve reconstruction with replacement of the chordae tendineae by polytetrafluoroethylene (PTFE) sutures is described in a 52-year-old man. 21 days after operation mitral valve insufficiency due to rupture of a natural chorda led to reoperation with mitral valve replacement. The cardiac valve tissue was examined both macroscopically and microscopically. It showed a proliferation of fibroblasts. However, there was no endothelial cell layer detectable. To the best of our knowledge our case is the first report of the histological changes in human cardiac valvular tissue after implantation of PTFE sutures.
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We describe a simple, reproducible technique of achieving more normal left ventricular function after mitral valve replacement. Polytetrafluoroethylene (PTFE) sutures are used as chordae tendineae to restore the integrity between the mechanical valve and papillary muscles and thus the left ventricular wall.
The anatomy of valsalva's sinus is such that it decreases the mechanical stress on the leaflets of the aortic valve. Artificial stents impair the hemodynamic performance of an aortic bioprosthesis and lead to unphysiological functional stresses and may also shorten their durability. Therefore a semi-supported xenograft was developed which can be attached with an one-suture row in subcoronary position. This facilitates surgery considerably. Moreover, the commissures can be attached directly to the patient's aortic wall. The semi-supported valve was successfully implanted in a 69 years old patient with a combined aortic valve lesion. Postoperative invasive investigations, including angiography and videodensitometry, showed a normal performance of the valve and a normal anatomy of the aortic root.
Vasopressin binding sites could be clearly demonstrated in the cochlea. Membrane staining was mainly limited to the apical and ciliar membranes of the cochlear and vestibular hair cells, and hence to membranes in which adenylate cyclase activity could not be demonstrated. In addition to V2-vasopressin receptors that mediate hormonal signals by adenylate cyclase activation and cAMP release, in V1-vasopressin-receptors extracellular vasopressin signal is mediated by the breakdown of inositol phosphates and the release of inositol-triphosphates and diacylglycerol. Inositol triphosphates were found to be responsible for the intracellular mobilization of calcium. The localization of vasopressin binding sites at the hair cell membranes, therefore, suggests that vasopressin contributes to the breakdown and release of phospholipid messenger molecules and is thus probably involved in cochlear and vestibular signal transduction.
The effects of isoflurane (1 MAC) and enflurane (1 MAC) on cerebral blood flow and cerebral oxygen consumption were studied in 20 male patients without intracranial disease undergoing coronary artery bypass surgery (mean age 57 and 59 years respectively). The aim of the study was to investigate whether both agents diminish autoregulation of cerebral blood flow and CO2 reactivity of cerebral blood vessels. Patients were randomly assigned to one of two groups (10 patients each) receiving either isoflurane 1.15 vol.% or enflurane 1.68 vol.% endexpiratory. Measurements were performed and blood samples were taken in the awake state (I); 15 min after achievement of steady-state conditions with 1.68 vol.% enflurane or 1.5 vol.% isoflurane without blood pressure support (II); during norepinephrine-induced hypertension at a cerebral perfusion pressure of 110 mmHg (III); and during controlled hyperventilation at a PaCO2 of 27 mmHg and normotension (IV). Cerebral blood flow was measured by the argon wash-in technique. Isoflurane and enflurane produced a significant drop in cardiac index and cerebral perfusion pressure and reduced cerebral blood flow significantly by 35% and 39% respectively. Cerebral oxygen consumption was also significantly decreased by 49% (isoflurane) and 50% (enflurane). Induced hypertension with norepinephrine increased cerebral blood flow significantly by 32% (isoflurane) and 26% (enflurane), while hypocapnia reduced cerebral blood flow significantly by 26% (isoflurane) and 29% (enflurane).(ABSTRACT TRUNCATED AT 250 WORDS)
To assess mitochondrial function and test the hypothesis of an underlying oxidative phosphorylation defect in Alzheimer disease (AD), we evaluated the activities of mitochondrial respiratory chain enzyme complexes I+III, complexes II+III, complex IV (cytochrome c oxidase, COX), succinate dehydrogenase, and citrate synthase in the frontal cortex, temporal cortex, hippocampus, and cerebellum of 23 AD patients and 13 normal human brains. The major finding was a significant decrease in COX activity in AD temporal cortex and hippocampus, both whether activities were expressed per noncollagen protein content (49 +/-4.6 versus 78+/-10.8 nmol/min/mg NCP, P = 0.006; 23+/-1.9 versus 48.6+/-8.1 nmol/min/mg NCP, p = 0.003) or corrected for citrate synthase activity (1.6+/-0.2 versus 3+/-0.4, P = 0.001; 0.76+/-0.1 versus 1.76+/-0.26, P = 0.0009). There were no significant differences in the activities of complexes I+III, II+III, and of succinate dehydrogenase in any of the brain regions examined. Our results suggest a specific defect of COX in the AD brain versus the normal human brain, which may contribute to impaired energy generation. Biochemically, the defect is confined to selected brain regions, suggesting anatomic specificity.
Cardiac ischemia is associated with an impairment in long-chain fatty acid metabolism. We studied carnitine palmitoyltransferase (CPT) in left ventricular biopsies of 6 transplant recipients with ischemia due to atherosclerosis, 4 patients with dilated cardiomyopathy, and 5 donor hearts. Total CPT activity was not significantly different between the three groups (7.9 +/- 3; 6.7 +/- 2, and 8 +/- 3 nmol/min/mg noncollagenous protein). Residual CPT activity after inhibition by malonyl-CoA (0.4 mM) was 38 +/- 11, 36 +/- 5 and 38 +/- 7%. There were no difference in IC50 values. Residual CPT activity after the addition of the detergent Triton X-100 (0.5%) was 58 +/- 17, 54 +/- 2 and 50 +/- 8% (nonsignificant). Our results suggest that (i) total CPT activity and (ii) the sensitivity of the interaction of CPT I with its regulator malonyl-CoA are not affected by cardiac ischemia, and (iii) the ratio of CPT I to CPT II is not altered in cardiac ischemia.
A fourteen year old boy with Rubinstein-Taybi-syndrome presented with a severe congenital subvalvular fibrous aortic stenosis with associated aortic regurgitation. Transthoracic echocardiographic imaging and left heart angiography showed a transvalvular peak systolic pressure gradient of 90 mmHg and a regurgitant fraction of 30%. The surgical treatment consisted of resection of the subvalvular fibrous tissue and subsequent aortic valvuloplasty. Intraoperative transesophageal echocardiography revealed a wide systolic opening of the aortic valve and good coaptation of the aortic valve leaflets in diastole. Two-dimensional color-coded and contrast echocardiography were successfully used to confirm a satisfactory reconstruction. Transesophageal echocardiography therefore represents a valuable tool in the assessment of the morphologic and haemodynamic status, especially in rare cases of congenital heart disease in older children.