Wenn differenzierte Zellen wieder zu Stammzellen werden : über Perspektiven und Grenzen der regenerativen Medizin

Gen- und Stammzelltherapie stehen für das, wovon die Medizin schon immer geträumt hat: geschädigtes Gewebe durch gesundes ersetzen und die Wirkung defekter Gene durch intakte Kopien korrigieren. Wie ist der Stand der weltweiten Forschung? Welche Hindernisse sind zu überwinden, damit mehr Patienten von der regenerativen Medizin profi tieren werden

The effect of sodium valproate in Cushing's disease, Nelson's syndrome and Addison's disease

We investigated the effect of sodium valproate on plasma ACTH and serum cortisol concentrations in different pathological states of ACTH hypersecretion. Five patients with pituitary dependent Cushing's syndrome, two patients with Nelson's syndrome and five patients with Addison's disease were studied. Neither a single dose nor long term administration of sodium valproate resulted in a significant decrease of plasma ACTH levels in patients with Cushing's disease and Nelson's syndrome. Furthermore, the response of ACTH and cortisol to stimulation with lysine-vasopressin was unaffected during acute and chronic treatment. Patients with Addison's disease showed a slight attenuation of the ACTH response to lysine-vasopressin as compared to placebo but the difference was not statistically significant. In conclusion: sodium valproate does not appear to be effective in controlling ACTH hypersecretion in pituitary dependent Cushing's syndrome

Fast and precise underwater transducer characterisation utilising adaptive system identification

Characterising underwater acoustic transducers is essential to optimal signal processing in sound navigation and ranging systems. Precise characterisation allows for equalisation of the input and output hardware, resulting in improved performance of the overall system. A critical quantity of the characterisation is the impulse response of the underwater transducers, which are usually measured in a special low-noise water tank. An established method in other fields to estimate impulse responses of unknown systems is using adaptive filters and include an inherent quality measure. Such approaches allow for very fast and very reliable measurements. However, when using fixed control parameters, a trade-off between convergence speed and final mismatch needs to be found, which can be eliminated using variable control parameters. In this article, a method for determining an optimal step size for adaptive algorithms based on the normalised least mean square method is derived based on a theoretical analysis of the convergence process by taking the reverberation parameters of such measurement tanks into account. The new method is specialised on the application of underwater transducer characterisation and allows a very reliable approximation of the optimal step size and thus a maximally fast adaption behaviour—leading to a very short measurement time. This is firstly shown in simulations and afterwards demonstrated in a real measurement with unknown transducers in a measurement water tank

Nonhypnotic low-dose etomidate for rapid correction of hypercortisolaemia in cushing's syndrome

We determined the adrenostatic potential of low-dose nonhypnotic etomidate in six patients with Cushing's syndrome (ectopic Cushing's syndrome,n=2; Cushing's disease,n=3; bilateral adrenal adenoma,n=1). Etomidate was given as a continuous infusion for 32 h in a dose of 2.5 mg/h (n=5) or 0.3 mg/kg/h (n=3), respectively. Saline was given during a control period. The responsiveness to exogenous ACTH was studied during placebo and 7 and 31 h after commencing etomidate by administration of 250 µg 1–24 ACTH i.v. Etomidate (2.5 mg/h) led to a consistent decrease in serum cortisol in all patients from a mean of 39.4±13.3 to 21.1±5.7 µg/dl after 7 h (P<0.05 compared with placebo). After 24 h cortisol was reduced further to a mean steady state concentration of 12.3±5.7 µg/dl (P<0.05). At the end of the infusion period the cortisol increase in response to ACTH was reduced but not abolished. In contrast, a dose of 0.3 mg/kg/h etomidate induced unresponsiveness of serum cortisol to exogenous ACTH within 7 h. However, sedation was observed in two out of three patients at this dose, while during etomidate in a dose of 2.5 mg/h no side effects were seen. We conclude that low-dose non-hypnotic etomidate reduces serum cortisol to within the normal range in patients with Cushing's syndrome. The possibility to dissociate the adrenostatic effect of etomidate from its hypnotic action, the absence of side effects, and the i.v. route suggest that etomidate in a dose of 0.04–0.05 mg/kg/h may become the drug of choice for rapid initial control of hypercortisolism

Membrane potential stabilizes the O intermediate in liposomes containing bacteriorhodopsin

AbstractIn the bacteriorhodopsin-containing proteoliposomes, a laser flash is found to induce formation of a bathointermediate decaying in several seconds, the difference spectrum being similar to the purple–blue transition. Different pH buffers do not affect the intermediate, whereas an uncoupler, gramicidin A, and lipophilic ions accelerate decay of the intermediate or inhibit its formation. In the liposomes containing E204Q bacteriorhodopsin mutant, formation of the intermediate is suppressed. In the wild-type bacteriorhodopsin liposomes, the bathointermediate formation is pH-independent within the pH 5–7 range. The efficiency of the long-lived O intermediate formation increases at a low pH. In the wild-type as well as in the E204Q mutant purple membrane, the O intermediate decay is slowed down at slightly higher pH values than that of the purple–blue transition. It is suggested that the membrane potential affects the equilibrium between the bacteriorhodopsin ground state (Glu-204 is protonated and Asp-85 is deprotonated) and the O intermediate (Asp-85 is protonated and Glu-204 is deprotonated), stabilizing the latter by changing the relative affinity of Asp-85 and Glu-204 to H+. At a low pH, protonation of a proton-releasing group (possibly Glu-194) in the bacteriorhodopsin ground state seems to prevent deprotonation of the Glu-204 during the photocycle. Thus, all protonatable residues of the outward proton pathway should be protonated in the O intermediate. Under such conditions, membrane potential stabilization of the O intermediate in the liposomes can be attributed to the direct effect of the potential on the pK value of Asp-85

Detection of the DCC gene product in normal and malignant colorectal tissues and its relation to a codon 201 mutation.

Protein expression of the putative tumour-suppressor gene DCC on chromosome 18q was evaluated in a panel of 16 matched colorectal cancer and normal colonic tissue samples together with DCC mRNA expression and allelic deletions (loss of heterozygosity, LOH). Determined by a polymerase chain reaction (PCR)-LOH assay, 12 of the 16 (75%) cases were informative with LOH occurring in 2 of the 12 cases. For DCC mRNA, transcripts could be detected in all analysed normal tissues (eight out of eight) by RT-PCR, whereas 6 of the 15 tumours were negative. DCC protein expression, investigated by immunohistochemistry using the monoclonal antibody 15041 A directed against the intracellular domain, was homogeneously positive in all normal tissue samples. In tumour tissues, no DCC protein was seen in 11 out of 16 samples (69%). For the DCC codon 201, we found a loss of a wild-type codon sequence caused by mutation or LOH in at least 8 out of 15 cases (53%) compared with the corresponding normal tissue. DCC protein expression was undetectable in eight of the nine tumours missing both wild-type codons. Only one of the five tumours with retained DCC protein expression had no detectable wild-type codon 201. In addition, 9 out of 15 normal tissue specimens were mutated in codon 201. In two out of three cases with homozygous wild-type codons in peripheral blood lymphocyte (PBL) DNA, mutations were already observed in the tumour adjacent normal colonic mucosa. We conclude that DCC immunostaining should be introduced in the clinicopathological routine because of its strong correlation with the known prognostic markers 18q LOH and mutation of codon 201

Adrenostatische Therapie mit Metyrapon und Aminoglutethimid beim ACTH-abhängigen Cushing-Syndrom

Bei zehn Patienten mit ACTH-abhängigem Cushing-Syndrom, vier mit ektopem Cushing-Syndrom und sechs mit M. Cushing, wurde retrospektiv die Wirksamkeit einer adrenostatischen Therapie mit Metyrapon (Metopiron®) und Aminoglutethimid (Orimeten®) untersucht. Unter Metyrapon allein (n = 5) sowie in Kombination mit Aminoglutethimid (n = 5) kam es bei allen Patienten zu einer dauerhaften Senkung der Serum-Cortisol-Konzentration. Die Beobachtungszeit betrug 2 Wochen bis 4 Jahre. Der angestrebte therapeutische Bereich von < 16 µg/dl wurde bei sieben Patienten erreicht. Im Verlauf der Therapie wurde ein Anstieg der mittleren Plasma-ACTH-Konzentration beobachtet; dabei kam es nicht zu einem »Escape« der Cortisol-Konzentration. Eine Einschränkung erfuhr die adrenostatische Therapie allein durch die Nebenwirkungen, die bei zwei Patienten zu einer Beendigung der Therapie führten. Folgerung: Die adrenostatische Therapie mit Metyrapon und Aminoglutethimid ist wirksam und praktikabel. Sie eignet sich nicht nur zur akuten Behandlung des floriden Cushing-Syndroms, sondern auch zur Langzeittherapie, wenn eine kurative Therapie nicht möglich ist.The adrenostatic effect of metyrapone (Metopiron®) and aminoglutethimide (Orimeten®) was assessed retrospectively in ten patients with ACTH-dependent Cushing's syndrome, four of them with the ectopic form. Five patients received metyrapone only, the other five both metyrapone and aminoglutethimide. Persistent lowering of the serum cortisol level was achieved in all, after an observation period of two weeks to four years. The intended therapeutic level of below 16 µg/100 ml was achieved in seven patients. In the course of treatment there was a rise in mean plasma ACTH concentration, but without an »escape« phenomenon. The adrenostatic treatment had to be limited, if at all, only because of side effects, which in two patients required that the drug administration be terminated. It is concluded that adrenostatic treatment with metyrapone and aminoglutethimide is effective and practical. It is suitable not only in the management of florid Cushing's syndrome, but also for long-term treatment when complete cure is not possible