The role of parathyroid hormone and calcitonin in magnesium absorption in the rat small intestine

Summary We studied duodenal and ileal magnesium (Mg) absorption in intact, parathyroidectomized (PTX), thyroid-(TX) and thyroparathyroidectomized (TPTX) rats with iodine hormones replaced, and, additionally, in PTX rats receiving bovine parathyroid hormone 1–34 and 1,25-dihydroxyvitamin D₃, respectively. Ma absorption was reduced after PTX and TPTX in the duodenum, but not in the ileum, whereas TX had no influence on duodenal or ileal Mg absorption. Both bovine parathyroid hormone 1–34 and 1,25-dihydroxyvitamin D₃ increased Mg absorption in the duodenum and the ileum in PTX rats.Acknowledgments. We are grateful to B. Schreiber, K. Schwille and I. Goldberg for technical and secretarial help. Supported by Deutsche Forschungsgemeinschaft (Schw 210/3). Reprint requests to P.O.S., University Hospital, Maximiliansplatz, D-8520 Erlangen.     

Protective effect of lidocaine in the experimental foot-and-mouth disease pancreatitis

Experimental infection of mice with foot-and-mouth disease virus (FMDV) induces a necrotizing pancreatitis of the exocrinar portion of the organ. The lesions are characterized by vascular congestion, edema and interstitial polymorphonuclear leukocyte (PMN) infiltrates. When infected mice were treated with different amounts of lidocaine (a local anesthetic, chemically defined as a tertiary amide compound), reduction in intensity of the pancreatic necrosis and in the number of PMN were observed. Even though lidocaine could interfere with FMDV post-replicative cytolytic mechanisms, it appears that protection against pancreatic necrosis is by attenuation of PMN presentation in the infected tissue.     

Depression of experimental gastric ulcers and acute pancreatitis in rats treated by 5-azacytosine, 5-azacytidine and their N-methyl derivatives

5-Azacytosine, 1-methyl-5-azacytosine and 5-azacytidine administered to rats with a ligated pylorus block gastric secretion, gastric acidity, the extent of hemorrhage and the number and size of gastric defects. The same drugs also depress the development of experimental acute pancreatitis mediated in rats by interstitial administration of 7.5% natrium cholate into the pancreas in vivo. The drugs affected the amount of abdominal fluid and 6 h after the treatment the pathological changes were significantly decreased.     

Depression of experimental gastric ulcers and acute pancreatitis in rats treated by 5-azacytosine, 5-azacytidine and their N-methyl derivatives

Summary 5-Azacytosine, 1-methyl-5-azacytosine and 5-azacytidine administered to rats with a ligated pylorus block gastric secretion, gastric acidity, the extent of hemorrhage and the number and size of gastric defects. The same drugs also depress the development of experimental acute pancreatitis mediated in rats by interstitial administration of 7.5% natrium cholate into the pancreas in vivo. The drugs affected the amount of abdominal fluid and 6 h after the treatment the pathological changes were significantly decreased.     

Hyperglucagonemia,hypocalcemia and diminished gastric blood flow-evidence for an etiological role in stress ulcer of rat

Zusammenfassung Unter Zwangshaltung entwickeln intakte, scheinoperierte und adrenalektomierte Ratten eine Drosselung der Magenperfusion und unterschiedlich häufig Nekrosen und Erosionen in der Magenmukosa. Dieses Phänomen ist von einem erheblichen Anstieg an Pankreasglucagon begleitet, während Gastrin unter Stress eher abfällt.

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Acknowledgment. We are gratefully indebted toK. Schwille, A. Wellmann andG. Besold for skillful technical assistance.     

Making the abstract concrete: The role of norms and values in experimental modeling

Experimental modeling is the construction of theoretical models hand in hand with experimental activity. As explained in Section 1, experimental modeling starts with claims about phenomena that use abstract concepts, concepts whose conditions of realization are not yet specified; and it ends with a concrete model of the phenomenon, a model that can be tested against data. This paper argues that this process from abstract concepts to concrete models involves judgments of relevance, which are irreducibly normative. In Section 2, we show, on the basis of several case studies, how these judgments contribute to the determination of the conditions of realization of the abstract concepts and, at the same time, of the quantities that characterize the phenomenon under study. Then, in Section 3, we compare this view on modeling with other approaches that also have acknowledged the role of relevance judgments in science. To conclude, in Section 4, we discuss the possibility of a plurality of relevance judgments and introduce a distinction between locally and generally relevant factors.     

The effect of calcitonin on calcium uptake in mouse molars in vitro

Summary Mouse maxillary second molars were removed at either 24 or 96 h of age and maintained in vitro. Half of the teeth, of each age group, were treated with 50 m-units of synthetic salmon calcitonin. By comparing the initial and final calcium concentrations in the medium, the net uptake or release of calcium was inferred. The treated molars took up significantly more calcium than the untreated groups.     

The role of volume expansion,of prostaglandins and catecholamines in the development of acute renal failure

Summary A single injection either of isotonic or hypertonic saline solutions protected rats against acute renal failure (ARF) induced with glycerol. This protection was accompanied by increased urinary prostaglandin E (PGE) concentration. On the contrary, a single s.c. injection either of hypotonic saline or isotonic glucose solution, which did not increase urinary PGE concentration, or depletion of the endogenous catecholamines, using reserpine, did not protect the animals against acute renal failure.The authors wish to thank Miss Sylvie Bompis and Miss Ermione-Loukia Ghikas for their technical assistance and Mr Richard Irvine B.A. for his help with the English.     

The role of hsp70 in protection and repair of luciferase activity in vivo; experimental data and mathematical modelling

The stably transfected rat cell line HR24 expressing high levels of the inducible human hsp70 and its parental cell line Rat-1 were used for in vivo studies to analyse the role of hsp70 during thermal protein denaturation and the subsequent renaturation. In order to monitor denaturation and renaturation of a cellular protein in vivo, both cell lines were transiently transfected with firefly luciferase (Luc). The continuous monitoring of Luc activity during and after heat stress allowed a detailed analysis of the inactivation and reactivation kinetics in cells grown in monolayers. The aim of these studies was to distinguish a protective effect of increased hsp70 levels during heat shock-induced protein inactivation from a stimulation of reactivation. In this paper we show that in cells that are stably transfected with hsp70, thermal Luc inactivation decreased, and subsequent reactivation yielded higher activity levels, compared with the parental cells. The difference in early inactivation kinetics observed in the two cell lines suggests an immediate effect of the presence of an extra amount of hsp70 on enzyme inactivation. Using different mathematical models, the heat-induced inactivation and reactivation kinetics was compared with simulations of denaturation and renaturation. It is concluded that the model in which it is assumed that hsp70 is able to interact with partially denatured proteins, which did not yet lose their enzymatic activity, most optimally explains the experimental observations. Received 2 December 1998; received after revision 19 February 1999; accepted 18 March 1999     

The use of crocetin in experimental atherosclerosis

Résumé L'action préventive de la crocetine de l'apparition de l'artério-sclerose sur l'aorte du lapin soumis à un régime hypercholestérolémiant est démontrée. Par contre le mécanisme d'action de cette substance n'est pas élucidé par les expériences relatées.     

The role of repair in radiobiology

Apart from cancer and mutation induction, radiobiological effects on mammals are mostly attributable to cell 'death', defined as loss of proliferative capacity. Survival curves relate retention of that capacity to radiation dose, and often manifest a quasi-threshold ('shoulder'). The shoulder is attributable to an initial mechanism of repair ('Q-repair') which is gradually depleted as dose increases. Another form of repair, which is not depleted ('P-repair'), increases the dose required to deliver an average of one lethal event per cell (dose 'D0'). Neither form of repair can unambiguously be linked with repair of defects in isolated DNA. An important initial lesion may well be disruption of the complex structural relationship between the DNA, nuclear membrane and associated proteins. One form of P-repair may be restoration of that structural relationship.     

The role of repair in radiobiology

Summary Apart from cancer and mutation induction, radiobiological effects on mammals are mostly attributable to cell death, defined as loss of proliferative capacity. Survival curves relate retention of that capacity to radiation dose, and often manifest a quasi-threshold (shoulder). The shoulder is attributable to an initial mechanism of repair (Q-repair) which is gradually depleted as dose increases. Another form of repair, which is not depleted (P-repair), increases the dose required to deliver an average of one lethal event per cell (dose D₀). Neither form of repair can unambiguously be linked with repair of defects in isolated DNA. An important initial lesion may well be disruption of the complex structural relationship between the DNA, nuclear membrane and associated proteins. One form of P-repair may be restoration of that structural relationship.