Vasopressin effects on food-rewarded learning tasks might be due to its action on carbohydrate/lipid metabolism, not memory

Vasopressin (VP) has been implicated in memory processes on the basis of effects observed in aversively motivated learning situations. Therefore researchers have tried to confirm this role by using food-motivated learning tasks. However, the well-established physiological influences of VP on carbohydrate and lipid metabolism were not taken into consideration. At various times following administration, VP might act as a feeding stimulant or as a satiating agent. Experimental designs should allow for these effects when food-rewarded learning paradigms are used to determine whether VP acts on memory.     

5-substituted 2′-deoxyuridines: Correlation between inhibition of tumor cell growth and inhibition of thymidine kinase and thymidylate synthetase

A large variety of 5-substituted 2′-deoxyuridines (dUrds) and 2′-deoxyuridylates (dUMPs) have been evaluated for their inhibitory effects on the thymidine (dThd) kinase or thymidylate (dTMP) synthetase isolated from mouse leukemia L1210 cells. The most potent inhibitors of dThd kinase were 5-chloro-, 5-bromo- and 5-iodo-dUrd. Their K_i/K_m values ranged from 0.57 to 0.82. All dUrd analogs tested showed competitive kinetics with respect to dThd. However, there was little, if any, correlation between the inhibitory effects of the compounds on L1210 cell growth and their inhibitory activities against dThd kinase (r = 0.16). The most potent inhibitors of dTMP synthetase were (in order of decreasing activity): 5-nitro-dUMP > 5-formyl-dUMP > 5-fluro-dUMP > 5-oxime of 5-formyl-dUMP > 5-azidomethyl-dUMP > (E)-5-(2-bromovinyl)-dUMP. The k_i/K_m values for these compounds ranged from 0.001 to 0.665. All dUMP analogs tested showed competitive kinetics with respect to dUMP (if not preincubated with the enzyme at 37°). There was a strong correlation (r = 0.833) between the inhibitory effects of these compounds on L1210 cell growth and their inhibitory activities against dTMP synthetase. Thus, the suppressive action of 5-substituted dUrd derivatives on tumor cell growth would involve prior conversion of the nucleoside analogs to the corresponding 5′-monophosphates followed by an inhibition of dTMP synthetase.     

Temporary reversible post and core restoration for multirooted teeth

A restoration for endodontically treated multirooted teeth has been described. This procedure is used for endodontically treated teeth that require temporary restorations.     

St. Thomas Cardioplegia Versus Topical Cooling: Ultrastructural and Biochemical Studies in Humans

Transmural left ventricular biopsies were studied from 28 patients undergoing cardiopulmonary bypass with anoxic cardiac arrest. The myocardium was protected by topical cooling (20° C) (Group 1, 15 patients) or by cardioplegia with St. Thomas' solution (Group 2, 13 patients). Biopsies were taken at the start of bypass and 3 to 5 minutes after unclamping of the aorta. Mean cross-clamp time was not significantly different between the groups (50 minutes for Group 1 and 53 minutes for Group 2; p > 0.05).The ultrastructural changes induced by ischemia and subsequent reperfusion were almost exclusively related to the mitochondria. The degree of mitochondrial damage was evaluated by a semiquantitative analysis based on mitochondrial fine structure. The frequency of severe postischemic mitochondrial damage was significantly higher in Group 1 (20.1% verus 2.7% in Group 2; p < 0.05).Biochemical analysis of the biopsies indicates that the myocardial concentration of creatine phosphate decreases by about 50% after topical cooling (p < 0.05). With St. Thomas cardioplegia, no significant change in the tissue level of this high-energy phosphate takes place. The results show evidence of the superiority of the St. Thomas cardioplegia to topical cooling alone.     

Quantitative study of left bundle branch fibrosis in left anterior hemiblock: A stereologic approach

Serial sectioning of the interventricular septum was carried out in 16 hearts, 8 from elderly subjects with no conduction disturbance and 8 from patients with chronic left anterior hemiblock. The histologic slides were studied stereologically, and the relative density of fibrosis was quantitatively assessed by the point counting technique at various levels of the main subdivisions of the left bundle branch system.Statistical analysis revealed the following: (1) Although some fibrosis was found in the control hearts, the density of fibrosis was consistently and significantly greater throughout the conduction system in patients with left anterior hemiblock. (2) In the group with hemiblock, the relative density of fibrosis tended to increase significantly from the posterior ramification to the midseptal fibers and, finally, to the anterior fascicle. (3) Among the eight patients with hemiblock, fibrosis appeared to be evenly distributed throughout the conduction system in four. It was predominantly located in the anterior and midseptal fibers in one patient and showed an increasing severity from the posterior to the midseptal and anterior fibers in the remaining three patients.From this quantitative study, it is concluded that left anterior hemiblock is a reliable sign of left bundle branch disease but that the underlying lesions are more widely distributed than would be from the expected electrocardiographic terminology since they were found predominantly in the anterior ramifications in only half of the studied cases.