[A rare cause of malignant ascites--peritoneal mesothelioma]. / Eine seltene Ursache für malignen Aszites--das Peritonealmesotheliom.

HISTORY AND CLINICAL FINDINGS: A 56-year-old patient (case 1) with recurrent haemorrhagic ascites for one year was admitted to our hospital for further investigation. Besides massive ascites he did not show abnormal physical signs. In addition, two 45-year-old patients were admitted (case 2 and 3) with clinical signs of acute abdomen--one having muscular guarding in the epigastric angle, the other in the right lower quadrant. All 3 patients did not have serious illnesses in the past; the first 2 patients had occupational asbestos exposure. INVESTIGATIONS: In patient 1 the ultrasound did not reveal abnormal findings besides ascites. Patients 2 and 3 underwent explorative laparotomy. DIAGNOSIS, TREATMENT AND COURSE: In the first case a diagnostic laparoscopy revealed diffuse tumor proliferations with nodular formations over the entire peritoneum--histologically a malignant peritoneal mesothelioma of the epithelial subtype. Patient 2 showed intraoperatively metastatic spread of tumour formations with infiltration of the peritoneum and transverse mesocolon. The histologic finding was similar to that in the first case. Patient 3 had a perforated sigma diverticulitis which was treated by resection of the sigmoid. Incidentally a well differentiated papillary peritoneal mesothelioma was found in the resected specimen. The first two patients were treated with alpha-interferon subcutaneously resulting in a decrease of ascites production. Because patient 3 showed neither ascites nor evidence for malignancy no interferon was administered. CONCLUSION: In case of haemorrhagic ascites of unknown cause a histological clarification by either laparoscopy or laparotomy is mandatory. Immunomodulation with interferon may be a promising approach.

Recombinant troponin I substitution and calcium responsiveness in skinned cardiac muscle.

Using treatment with vanadate solutions, we extracted native cardiac troponin I and troponin C (cTnI and cTnC) from skinned fibers of porcine right ventricles. These proteins were replaced by exogenously supplied TnI and TnC isoforms, thereby restoring Ca2+-dependent regulation. Force then depended on the negative logarithm of Ca2+ concentration (pCa) in a sigmoidal manner, the pCa for 50% force development, pCa50, being about 5.5. For reconstitution we used fast-twitch rabbit skeletal muscle TnI and TnC (sTnI and sTnC), bovine cTnI and cTnC or recombinant sTnIs that were altered by site-directed mutagenesis. Incubation with TnI inhibited isometric tension in TnI-extracted fibers in the absence of Ca2+, but restoration of Ca2+ dependence required incubation with both TnI and TnC. Relaxation at low Ca2+ levels and the steepness of the force/pCa relation depended on the concentration of exogenously supplied TnI in the reconstitution solution (range 20-150 "mu"M), while Ca2+ sensitivity, i.e. the pCa50, was dependent on the isoform, and also on the concentration of TnC in the reconstitution solution. At pH 6.7, skinned fibers reconstituted with optimal concentrations of sTnC and sTnI (120 "mu"M and 150 "mu"M, respectively) were more sensitive to Ca2+ than those reconstituted with cTnC and cTnI (difference in pCa50 approx. 0.2 units). Rabbit sTnI was cloned and expressed in Escherichia coli using a high yield expression plasmid. We introduced point mutations into the TnI inhibitory region comprising the sequence of the minimal common TnC/actin binding site (-G104-K-F-K-R-P-P-L-R-R-V-R115-). The four mutants produced by substitution of T for P110, G for P110, G for L111, and G for K105 were chosen, based on previous work with synthetic peptides showing that single amino acid substitution in this region diminished the capacity of these peptides to inhibit acto-S1 ATPase or contraction of skinned fibers. Therefore, all amino acid residues of the inhibitory region are thought to contribute to biological activity of TnI. However, each of the recombinant TnIs could substitute for endogenous TnI. In combination with exogenous TnC, Ca2+ dependence could be restored when gly110sTnI, thr110sTnI or gly111sTnI was used for reconstitution. The mutant gly105sTnI, on the other hand, reduced the ability of skinned fibers to relax at low Ca2+ concentrations and it caused an increase in Ca2+ sensitivity.

The Ca2+ sensitizer EMD 53998 antagonizes the effect of 2,3-butanedione monoxime on skinned cardiac muscle fibres.

The effects of 2,3-butanedione monoxime (BDM) and 5-[1-(3,4-dimethoxybenzoyl)-1,2,3,4-tetrahydro-6-quinolyl]-6-me thy l-3,6-dihydro-2H-1,3,4-thiadiazin-2-one (EMD 53998) on cardiac muscle were studied in skinned muscle fibres from the right ventricle of the porcine heart. BDM decreases the Ca2+ sensitivity (pCa50 for 50% activation) and it exerts a dose-dependent inhibitory effect on force in troponin I (TnI)-depleted (unregulated) cardiac skinned muscle fibres (IC50 approximately 20 mM) thereby mimicking the effect of the TnI inhibitory peptide (cTnI 137-148, corresponding to the cardiac TnI inhibitory region) and that of inorganic phosphate (Pi). This inhibitory action can be antagonized by the calcium-sensitizing cardiotonic thiadiazinone derivative EMD 53998 that increases the IC50 to about 30 mM. In skinned fibres, BDM (10 mM) also increased the ratio of ATPase activity to isometric force (tension cost), whereas EMD 53998 (20 mu M) decreased it. We propose that BDM antagonizes EMD 53998 because both compounds affect the Pi release step of the crossbridge cycle in an antagonistic manner.

Ca2+ sensitizing effects of EMD 53998 after troponin replacement in skinned fibres from porcine atria and ventricles.

Skinned fibres from porcine ventricles exhibited a higher Ca2+ sensitivity (pCa50, i.e. -log10 Ca2+ concentration required for half-maximal activation, for force generation) than atrial fibres. The thiadiazinone derivative EMD 53998 increased Ca2+ sensitivity and Ca2+ efficacy in both preparations. The drug effect depended on the isoform of troponin (Tn). Using the vanadate method TnI and TnC could be partly extracted and replaced by foreign tropin or by the TnI subunit of added foreign troponins. We investigated the relationship between pCa and force development before and after replacement of TnI with foreign troponin (bovine ventricular troponin, cTn, or rabbit skeletal muscle troponin, sTn) in the presence and absence of EMD 53998. Substitution with bovine cTn increased Ca2+ sensitivity to a value characteristic of bovine ventricular skinned fibres (pCa50 = 5.4) and was further increased by EMD 53998. Substitution with sTn also increased Ca2+ sensitivity, but subsequent addition of EMD 53998 caused little further increase in Ca2+ sensitivity. Following extraction of TnI with vanadate, skinned fibres contracted in a Ca(2+)-independent manner and failed to relax at a pCa of 8. Relaxation could be induced, however, by bovine ventricular TnI and rabbit skeletal muscle recombinant TnI. This relaxation could be reversed by EMD 53998 (100 microM). The Ca(2+)-independent force of contracted fibres could also be depressed by a TnI inhibitory peptide, (cTnI 137-148) and, in addition, this effect was antagonized by EMD 53998.(ABSTRACT TRUNCATED AT 250 WORDS)