Normovolaemic haemodilution and hyperoxia have no effect on fractal dimension of regional myocardial perfusion in dogs

Hypervolaemic haemodilution makes myocardial perfusion more homogenous as reflected by reduced fractal dimension of regional myocardial perfusion. The clinically more commonly performed acute normovolaemic haemodilution, however, has not yet been studied in this respect. Hyperoxic ventilation with 100% oxygen is used in conjunction with haemodilution to compensate for low oxygen content by increasing physically dissolved oxygen in plasma. Since hyperoxia is known to cause disturbance in microcirculatory regulation we studied the effects of acute normovolaemic haemodilution to haematocrit (hct) 20 ± 1% and hyperoxia on regional myocardial perfusion heterogeneity in 22 anaesthetized dogs using fractal and correlation analysis. Regional myocardial perfusion was assessed with radioactive microspheres. The results of the study were that heart rate, blood volume and arterial pressure were unchanged during haemodilution. Cardiac index was 3.6 ± 0.7 L min^?1 m^?2 before and 4.6 ± 0.7 L min^?1 m^?2 after haemodilution (P < 0.05). Fractal dimension (D) of regional myocardial perfusion was 1.17 ± 0.10 at baseline. Neither haemodilution (D = 1.19 ± 0.10) nor hyperoxia (D = 1.17 ± 0.10) altered fractal properties of regional myocardial perfusion. Spatial correlation of blood flow to adjacent tissue samples before haemodilution was 0.58 ± 0.15. Haemodilution and hyperoxia did not significantly influence spatial correlation (0.57 ± 0.12 vs. 0.60 ± 0.09; ns). We conclude that neither acute normovolaemic haemodilution nor haemodilution in combination with hyperoxic ventilation alter physiological myocardial perfusion heterogeneity.     

Structural requirements of the oxytocin receptor in rat uterus

Published and newly calculated pA₂-values of 147 neurohypophyseal hormone analogues (7 positions varied) acting as inhibitors of oxytocin on isolated rat uterus in vitro have been subjected to fractionation according to the method by Free and Wilson which was slightly modified for this purpose. The computation was carried out in several steps. After each step, substances with outlying pA₂ -values were el minated. The reduced group containing 73–79% of the original substances displayed a high degree of additivity of side chain contributions (SCC). This group seems to follow the “participation” rule as formulated by Free and Wilson. Analysis of the group of eliminated substances and of the resulting SCC-spectrum (level diagram) enabled us to draw some conclusions concerning the structural requirements of receptor binding: i) The intact ring structure is necessary for the peptide-receptor interaction: linear peptides or peptides with an extended ring are always outliers; ii) Carba analogues (substitution with CH₂ in the disulfide ring) display better affinities than peptides with an S-S ring; d -Arg⁸ substitution decreases the binding affinity; iii) Considerably better additivity is achieved when peptides are divided into subgroups with vasopressin-like and oxytocin-like features; populations of receptors more specific for vasopressin and for oxytocin, respectively, can be assumed. Estimates of the “true” receptor-peptide dissociation constants can be obtained by summation of the corresponding SCC's in each investigated position. The value obtained for oxytocin is identical with the medium affinity binding site on myometrial cells, and not with the high affinity site. A nonlinear relationship exists between SCC's computed from pA₂-values for magnesium-free and magnesium-containing (0.5 mm ) media but no evidence speaks in favor of a Mg-potentiating effect on receptor binding.     

Intracranial aspergillosis in a non-immunocompromised patient treated for muscle-invasive bladder cancer

We report a case of intracerebral Aspergillosis in a patient undergoing radical cystectomy for the treatment of muscle-invasive bladder cancer who did not reveal any deterioration of the immune system. Aspergillus fumigatus is an ubiquitously present, airborne fungus that tends to infect the upper respiratory tract. However, the latter was not observed in the patient presented. Complications in the form of an involvement of the central nervous system are very rarely recognized as a result of an Aspergillus infection and primarily occur in patients who are not immunologically competent. To our knowledge, we present the first case of intracerebral invasive Aspergillosis in an otherwise healthy patient diagnosed with an urological malignancy.     

Unruptured aneurysm of the sinus of Valsalva presenting with ventricular tachycardia

We report a case of a large unruptured aneurysm of the rightsinus of Valsalva which caused severe right ventricular outflowtract obstruction and presented dramatically with a life threateningventricular tachycardia. Despite severe aortic incompetenceprior to surgery it was possible to resect the aneurysm andrepair the aortic root without resort to aortic valve replacementand thus return the anatomy to normal.