Atrial natriuretic peptide and renal adaptation to contralateral nephrectomy in healthy man.

Atrial natriuretic peptide (ANP), angiotensin II (AII), aldosterone (Aldo) and arginine vasopressin (AVP) in plasma were determined in 12 healthy renal transplant donors before and 5, 12, 26, 54 days after uninephrectomy (Nx) in order to study the possible role of these hormones in functional adaptation to acute reduction in renal mass. Glomerular and tubular function was studied by measurements of the clearances of 51Cr-EDTA, lithium, sodium, potassium, and albumin. ANP was 7.4 +/- 3.1 pmol l-1 (mean +/- SD) before Nx and 8.7 +/- 6.1 pmol l-1 at 5 days after Nx and remained at this level through the observation period. Aldo showed a non-significant transient fall at 5 days after Nx. AII and AVP remained normal after Nx. At 5 days after Nx glomerular filtration rate (GFR) of the remaining kidney had risen from 45 +/- 7 ml min-1 before Nx to 57 +/- 8 ml min-1 (p less than 0.01), lithium clearance had risen from 13 +/- 2 ml min-1 before Nx to 20 +/- 7 ml min-1 (p less than 0.01), and sodium and water balance was normal. To conclude, plasma ANP, AII, Aldo and AVP do not appear to be responsible for the hyperfiltration and depression of fractional proximal sodium and water reabsorption observed in recently uninephrectomized man with normal sodium and water balance.     

The Nordic Trueness Project 2002: use of reference measurement procedure values in a general clinical chemistry survey

Up to 136 laboratories participated in a joint effort to assess the trueness of routine measurements for 14 serum components. An unmodified, fresh-frozen human serum ("IMEP-17 Material 1"), produced for an international inter-laboratory comparison, served as the "master material". The serum had assigned values of the highest available metrological quality, and is assumed to involve no or negligible commutability problems. The material was used in the assignment of traceable values to two other reference sera, "CAL" and "X", through parallel measurements on the three materials according to a common protocol. In this transfer process, uncertainty estimates were provided for all values. The material CAL had been supplied with reference measurement procedure values in 1997, and the two sets of assigned values agreed well. A lyophilized control serum "HK02" was also included in the routine analysis series. It, too, had assigned values based on reference measurement procedures. Significant matrix effects were found. The project has provided: Assigned traceable values for 14 components in a fresh-frozen serum, available to Nordic laboratories for the coming years as "NFKK reference serum X"; Confirmation of earlier assigned reference measurement procedure values for a number of components in CAL, the main calibrator in the Nordic Reference Interval project (NORIP). The transferred values will now serve as the primary reference.; Evidence of long-term stability ( > or = 5 years) of the fresh-frozen serum CAL when stored at -80 degrees C; Evidence of substantial matrix effects in the processed serum HK02. The findings should be used to discuss to what extent reference measurement procedure values are useful and cost-efficient for this type of material.     

Regulation of lipoprotein lipase in the diabetic rat.

Diabetes mellitus is associated with a reduction of lipoprotein lipase (LPL) activity and development of hypertriglyceridemia. In the current experiments the mechanisms involved in the regulation of LPL have been examined in control rats, streptozocin-induced diabetic rats, and diabetic rats treated chronically or with a single injection of insulin. Diabetes decreased adipose tissue LPL activity partially by decreasing immunoreactive LPL protein and the steady-state levels of LPL mRNA, but primarily by reducing the catalytic activity of LPL. Both chronic and acute insulin increased adipose tissue LPL activity by correcting the defect in the catalytic activity of LPL and increasing immunoreactive LPL protein; however, only chronic insulin restored LPL mRNA levels to normal. In the heart, LPL activity tended to be elevated with diabetes in parallel to an increase in immunoreactive LPL protein even though levels of LPL mRNA declined. Both chronic and acute insulin normalized LPL activity and immunoreactive LPL protein, while only chronic insulin corrected the levels of LPL mRNA. No changes in the catalytic activity of LPL in heart were detected among the groups. Thus, diabetes and insulin treatment regulate LPL expression pretranslationally, translationally, and post-translationally, with tissue-specific differences apparent in the mechanisms involved.     

Hypochromic reticulocytes, hypochromic erythrocytes and p-transferrin receptors in diagnosing iron-deficient erythropoiesis

BACKGROUND: The purpose of this study was to test the hypothesis that hypochromic reticulocytes, hypochromic erythrocytes and p-transferrin receptors are sensitive variables in detecting iron-deficient erythropoiesis in healthy subjects and hemodialysis patients. METHODS: Study 1: Twenty-one blood donors donated 450 mL blood. During the following 2 weeks blood samples were analyzed for the variables mentioned above. Study 2: Twenty-eight blood donors received 10,000 U recombinant human erythropoietin (rHuEPO) twice in the first week or placebo, after they had donated 450 mL blood. During the following 3 weeks the blood samples were analyzed for the variables mentioned in Study 1. Study 3: Eighteen hemodialysis patients receiving rHuEPO and iron treatment had either iron treatment discontinued for 4 weeks, after which iron was resumed, or received unchanged treatment. During 8 weeks blood samples were analyzed for the variables mentioned in Study 1. RESULTS: Study 1: Blood donation induced an increase in hypochromic reticulocytes of 178%, in hypochromic erythrocytes the increase was 267%, and in p-transferrin receptors 32%. Study 2: Treatment with rHuEPO induced a more pronounced increase than placebo in hypochromic reticulocytes (232% vs. 158%) and hypochromic erythrocytes (1240% vs. 300%), but not in p-transferrin receptors. Study 3: Discontinuation of iron treatment did not cause any significant differences in the variables mentioned above between the two groups, but caused a 25% decrease in p-ferritin. When iron treatment was resumed, p-ferritin increased by 19%. We found no significant changes in the control group. CONCLUSIONS: Hypochromic reticulocytes, hypochromic erythrocytes and p-transferrin receptors are sensitive variables in the early detection of iron-deficient erythropoiesis in healthy subjects, but in this study the iron withdrawal period was too short to show the value of these variables in the detection of iron-deficient erythropoiesis in hemodialysis patients.     

A balance between tissue factor and tissue factor pathway inhibitor is required for embryonic development and hemostasis in adult mice

Inactivation of the murine tissue factor (TF) gene or tissue factor pathway inhibitor 1 (TFPI) gene results in embryonic lethality, indicating that both are required for embryonic development. We have shown that expression of low levels of TF from a transgene (hTF) rescues TF-null embryos. However, low-TF mice (mTF(-/-)/hTF+) have hemostatic defects in the uterus, placenta, heart, and lung. In this study, we hypothesized that the death of TFPI-/- embryos was due to unregulated TF/FVIIa activity and that the hemostatic defects in low-TF mice were due to insufficient TF expression. Therefore, we attempted to rescue TFPI-/- embryos by reducing TF expression, and to restore hemostasis in low-TF mice by abolishing TFPI expression. Intercrossing TFPI(+/-)/mTF(+/-)/hTF+/- mice generated close to the expected number of TFPI(-/-)/low-TF mice at weaning age from 128 offspring, indicating rescue of TFPI-/- embryos from embryonic lethality. Conversely, a decrease in TFPI levels dose-dependently prolonged the survival of low-TF mice and rescued the hemorrhagic defects in the lung and placenta but not in the heart or uterus. These results indicate that the correct balance between TF and TFPI in different organs is required to maintain hemostasis during embryonic development and in adult mice.     

Prüfung chemotherapeutischer Substanzen auf Verursachung reversibler und irreversibler Zellschäden am Modell der Gewebekultur

Zusammenfassung Die Verwendbarkeit von Gewebekulturen zur Austestung chemotherapeutischer Substanzen im Hinblick auf reversible oder irreversible Zellschäden wird am Beispiel alkylierend wirkender Substanzen der N-Lost- und Äthylenimin-Gruppe beschrieben. Das Verfahren könnte verwendet werden, um rechtzeitig zu erkennen, ob bei der Applikation einer Substanz Spätschäden drohen.

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Summary Chemotherapeutic substances cause reversible and irreversible cell damage in tissue culture. By this technique it is possible to test them, as shown in the studies with alkylating substances of the nitrogen mustard and ethylenimine groups. The procedure might be used to detect early, whether the application of a substance threatens late damage.

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Antilipolytic effect of prostaglandin E2 in perifused rat adipocytes

Previously, the antilipolytic effect of prostaglandin E2 (PGE2) has been investigated in conventional adipocyte incubations. To define the effect of PGE2 on lipolysis more clearly, isolated epididymal adipocytes were studied with the perifusion system. PGE2 inhibited isoproterenol (100 nM)- and theophylline (1 mM)-stimulated lipolysis in a concentration-dependent manner in both the perifusion system and conventional incubations. However, the half-maximally inhibitory concentration (ED50) of PGE2 on isoproterenol-induced lipolysis was about 0.4 nM in the perifusion system, whereas the ED50 was 8 nM in the static adipocyte incubations. The ED50 values of PGE2 on theophylline-induced lipolysis were 0.8 nM (perifusion) and 5 nM (incubation), respectively. Thus, the sensitivity of stimulated lipolysis to PGE2 was about 10 times higher in the perifusion system than in conventional adipocyte incubations. In addition, the maximal antilipolytic effect of PGE2 was greater in the perifusion system. At a concentration of 100 nM PGE2 inhibited theophylline-induced lipolysis by 82 +/- 5% in adipocyte incubations, whereas lipolysis was inhibited by 100 +/- 3.5% in the perifusion system (P less than 0.05). When lipolysis was stimulated by isoproterenol the maximal antilipolytic effect of PGE2 was an inhibition of 90 +/- 2.5% in the perifusion system and 55 +/- 5% in adipocyte incubations (P less than 0.05). Moreover, the maximal antilipolytic effect was obtained at a PGE2 concentration of 20 nM in the perifusion system, but at a concentration of 100 nM in static incubations. The release of immunoreactive PGE2 from adipocytes was measured by RIA. In the perifusion system no PGE2 could be detected in the effluent under basal conditions; however, during exposure to 100 nM isoproterenol a small amount of PGE2 was detected (3-4.5 pg/10(6) cells X min). Exogenous PGE2 was almost totally (90%) recovered in the effluent. In adipocyte incubations basal PGE2 production was 103 +/- 22 pg/10(6) cells X 60 min, whereas both isoproterenol and theophylline increased these amounts of PGE2 2-fold (P less than 0.01). It is concluded that exogenous PGE2 has pronounced antilipolytic properties at very low concentrations (subnanomolar) in perifused adipocytes. The reduced sensitivity and maximal responsiveness of PGE2 in static incubations may be related to accumulation of FFA and endogenous PGs, which may partially obscure the interaction of exogenous PGE2 with the adenylate cyclase complex.     

Chronic pulmonary thromboembolism in dogs treated with tranexamic acid

BACKGROUND. Many questions remain regarding the pathogenesis, natural history, diagnosis, and treatment of chronic thromboembolic pulmonary hypertension in patients. To answer such questions, we developed an animal model of this disorder. The brisk thrombolytic response of canines to acute embolism has, previously, prevented the establishment of such a model. METHODS AND RESULTS. The fibrinolytic inhibitor tranexamic acid was given orally to canines before, and for intervals after, pulmonary emboli were released from venous thrombi formed in vivo in femoral veins or the inferior vena cava. Preliminary studies disclosed that embolic residuals from femoral vein thrombi were not sufficient to cause significant, persistent pulmonary hypertension. With repetitive, larger thrombi embolized from the inferior vena cava, however, persistent pulmonary hypertension was achieved in most animals. CONCLUSIONS. Resolution of emboli in the canine can be inhibited by tranexamic acid. As in humans, a spectrum of embolic residuals is encountered, and the perfusion lung scan consistently underestimates the extent of embolic residuals. Studies of this animal model continue.