Negative inotropic effect of rapamycin on isolated human cardiomyocytes.

Rapamycin is an increasingly important immunosuppressive drug and reduces restenosis after coronary stenting, but its effects on cardiac contractility are largely unknown. We investigated the acute inotropic effects of rapamycin on isolated human cardiomyocytes. Cardiomyocytes were enzymatically isolated from right atrial appendages obtained during routine coronary artery bypass surgery. Cell morphology was examined by confocal microscopy. Cell contraction was recorded after electrical stimulation. Rapamycin elicited a concentration-dependent decrease in fractional cell shortening ranging from 14.3 +/- 2.6% at 10(-8) M rapamycin to 26.4 +/- 4.2% at 10(-5) M. Rapamycin also caused a concentration-dependent decrease in diastolic cell length. Contractile performance of isolated cardiomyocytes was well preserved, as evidenced by the profound positive inotropic effects of high extracellular calcium concentration and the beta-adrenoreceptor agonist isoproterenol. The acute negative inotropic effect of rapamycin on human cardiomyocytes might be due to altered calcium homeostasis through the binding of rapamycin to FKBP12.6 and its regulatory function on the ryanodine receptor, with increased calcium leakage from the sarcoplasmic reticulum.

The stability of insulin in solid formulations containing melezitose and starch. Effects of processing and excipients.

Solid insulin formulations obtained by different methods of preparation were compared with respect to chemical stability and morphology. Spray- and freeze-drying, solution enhanced dispersion by supercritical fluids (SEDS) and precipitation into starch microspheres were the methods used for preparation of solid powders. The excipients applied were melezitose, starch, and sodium taurocholate. The stability of the samples was evaluated after storage in open containers at 25 degrees C and 30% RH for 6 months. All samples were amorphous after processing and storage as detected by XRD, except for the starch microspheres which were semi-crystalline. The spray- and freeze-dried samples containing melezitose and sodium taurocholate experienced a significant water uptake during storage, resulting in changes in morphology and disappearance of Tg. However, the chemical stability of these samples did not seem to be affected by the water uptake. Changes in morphology were not observed for the SEDS powders and the starch microspheres. The chemical stability of the samples was assessed by HPLC. In general, conventional spray- and freeze drying resulted in samples with higher chemical stability compared to SEDS powders and starch microspheres. Nevertheless, the excipients applied were observed to be of major importance, and further optimization of the formulation as well as processing conditions may lead to slightly different conclusions.

Left atrial myxoma diagnosed and characterized by cardiac magnetic resonance imaging.

A 71 year old man was referred for MRI investigation of the heart. He had a history of progressive dyspnea. Due to his echocardiographical findings and the known history of permanent atrial fibrillation, his cardiologist suspected atrial thrombi. MRI investigation of the heart showed a left atrial mass pedunculated at the atrial septum which showed signal enhancement after intravenous administration of gadolinium-DTPA. Left atrial myxoma was suspected. The patient underwent surgery with resection of the tumor and patch-occlusion of the atrial septum. Histology confirmed a polypoid cardial myxoma.

Displacement of adsorbed insulin by Tween 80 monitored using total internal reflection fluorescence and ellipsometry.

PURPOSE: This study was conducted to investigate the mechanism of action in the displacement of adsorbed insulin from a hydrophobic surface by Tween 80 and of the competitive adsorption of the two species. METHODS: Total internal reflection fluorescence (TIRF) and ellipsometry were used as in situ methods to examine the processes taking place at hydrophobic model surfaces in the presence of insulin and Tween 80. RESULTS: TIRF studies showed that the displacement of insulin by Tween 80 could be fitted to a sigmoidal function, indicating a nucleation-dependent process. Furthermore, a linear dependence between the apparent rate constant and the logarithm of the Tween 80 concentration was found. Competitive adsorption from solution mixtures of insulin and Tween 80 indicated that insulin was adsorbed first, but subsequently displaced by the surfactant. This displacement proved also to be dependent on the concentration of Tween 80 in the mixture. CONCLUSIONS: The results indicate that Tween 80 at concentrations above critical micelle concentration can be used to protect insulin against surface adsorption. The presence of a lag phase in the displacement at low surfactant concentration indicates that the mechanism of action for Tween 80 to reduce adsorption of insulin may be by competing for sites at the surface.

Adsorption of human insulin and AspB28 insulin on a PTFE-like surface.

The interactions of human insulin, Zn-free human insulin, and AspB28 insulin with a hydrophobic surface were studied by ellipsometry. All three insulin types investigated adsorbed with high affinity onto the hydrophobic surface, as the plateau of the adsorption isotherm, represented by the irreversible bound fraction, was reached at concentrations >10(-3) mg/ml. The plateau values for human insulin and Zn-free human insulin could not be distinguished with statistical significance, whereas the plateau value for AspB28 insulin was lower than those for the two others, with an adsorbed amount corresponding to a monolayer of insulin monomers. The results observed may be explained by differences in self-association patterns of the insulin types or by enhanced charge repulsion between the AspB28 analog and the negatively charged surface.

[Azathioprine-associated myelodysplastic syndrome with cytogenetic aberrations]. / Azathioprin-assoziiertes myelodysplastisches Syndrom mit zytogenetischen Aberrationen.

HISTORY AND ADMISSION FINDINGS: A 49-years-old female with a history of multiple sclerosis and on medication with azathioprine over 5 years amounting to a cumulative dosage of 45 g presented with fatigue and sinus tachycardia. INVESTIGATIONS: Haematological analysis revealed a pancytopenia with a sustained normochromic anemia (hemoglobin 6,2 g/dl), a mild leukopenia (leucocytes 3500/ microl) and thrombocytopenia (platelets 22000/ microl) requiring platelet substitution. Bone marrow aspirate revealed a dysplasia of all three lineages with reduced thrombopoiesis and ineffective erythropoiesis. Cytogenetic analysis detected a complex aberrant clone including loss of the critically deleted regions in 5q31 and 7q31, as well as structural changes of 12p. The diagnosis was refractory cytopenia with multilineage dysplasia according to the WHO classification of myelodysplastic syndromes. TREATMENT AND COURSE: While allogeneic sibling transplantation was planned the patient developed spontaneous recurrent subdural haematoma and died due to persistent bleeding refractory to platelet substitution. CONCLUSION: Treatment with azathioprine may - depending on its cumulative dosage - lead to pancytopenia and subsequent development of myelodysplasia or secondary leukaemia, respectively. Complex genetic alterations involving chromosome 7 are characteristic. Long-lasting treatment with azathioprine needs critical assessment.

[Incontinentia pigmenti in a male infant]. / Incontinentia pigmenti bei einem männlichen Säugling.

Bloch-Sulzberger incontinentia pigmenti (IP) is a rare X-linked neuroectodermal syndrome. Over 97% of the patients are female. We report on a male baby who developed blisters in linear groups or bands shortly after birth. When the child was 3 months old the blisters were followed by verrucous papules, which cleared after 1 year leaving areas of brownish grey hyperpigmentation. In addition to the skin involvement, our patient showed central motor dysfunction on the right side of the body and also dental and ocular anomalies. Both parents were in good health. Chromosome analysis yielded a normal karyotype (46, XY). The genes for coagulation factor VIII and biglycan in the Xq28 region were not deleted. The presence of the disease in this male infant may be due to an early somatic mutation or a half-chromatid mutation. A further possibility is mosaic expression of an unstable premutation. This model offers a good explanation for the reports in the literature of transmission of the disease from mother to son.