Differential regulation of IRP1 and IRP2 by nitric oxide in rat hepatoma cells

Iron-regulatory proteins (IRP1 and IRP2) are RNA-binding proteins that bind to stem-loop structures known as iron-responsive elements (IREs). IREs are located in the 5'- or 3'-untranslated regions (UTRs) of specific mRNAs that encode proteins involved in iron homeostasis. The binding of IRPs to 5' IREs represses translation of the mRNA, whereas the binding of IRPs to 3' IREs stabilizes the mRNA. IRP1 and IRP2 binding activities are regulated by intracellular iron levels. In addition, nitric oxide (NO.) increases the affinity of IRP1 for IREs. The role of NO. in the regulation of IRP1 and IRP2 in rat hepatoma cells was investigated by using the NO.-generating compound S-nitroso-N- acetylpenicillamine (SNAP), or by stimulating cells with multiple cytokines and lipopolysaccharide (LPS) to induce NO. production. Mitochondrial and IRP1 aconitase activities were decreased in cells producing NO(.). NO. increased IRE binding activity of IRP1, but had no effect on IRE binding activity of IRP2. The increase in IRE binding activity of IRP1 was coincident with the translational repression of ferritin synthesis. Transferrin receptor (TfR) mRNA levels were increased in cells treated with NO.-generating compounds, but not in cytokine- and LPS-treated cells. Our data indicate that IRP1 and IRP2 are differentially regulated by NO. in rat hepatoma cells, suggesting a role for IRP1 in the regulation of iron homeostasis in vivo during hepatic inflammation.     

Abnormal prothrombin in the plasma of rats carrying hepatic tumors

Vitamin K is required for the posttranslational formation of gamma- carboxyglutamyl residues in a number of plasma clotting factors. Interference with vitamin K action results in the appearance of abnormal (des-gamma-carboxy) forms of prothrombin in human plasma. Vitamin K-sufficient patients with primary hepatocellular carcinoma also secrete significant quantities of abnormal prothrombin; this response has now been studied in a rat model. Normal Buffalo strain rats had 9 micrograms/mL of circulating plasma abnormal prothrombin, whereas Buffalo strain rats carrying the transplantable Morris hepatoma tumor no. 7777 had 33 micrograms/mL at 3 weeks after transplant. Vitamin K-dependent carboxylase activity was normal in the liver of these rats, but very low in the tumor tissue. Rats carrying Morris hepatoma tumors no. 9618A and 5123D did not secrete significant amounts of abnormal prothrombin. Carboxylase activity in these tumors was 15 times that of the 7777 tumor. The data suggest that the secretion of abnormal prothrombin by hepatocellular tumors is the result of normal expression of the prothrombin gene by those tumors and a failure of the tumor to express the carboxylase gene.     

Experimental acute tubular necrosis: US appearance

Dichromate-induced acute tubular necrosis (ATN) was created in 16 experimental animals and compared with four controls. An increase in cortical echogenicity, greatest on days 4 and 7 after injection, was noted using both histogram analysis and blinded observer readings. These findings closely correlated with proportional outer cortical blood flow. Good interobserver correlation was noted. Based on this experiment, clinical observations, and the literature, we propose that three different entities with different sonographic appearances are included under the term ATN. Drug-induced nephrotoxicity is associated with increased cortical echogenicity; ischemic ATN leads to no change in cortical echogenicity with normal medullary echogenicity; and precipitation of Tamm-Horsfall protein in the pyramids leads to echogenic pyramids with normal cortical echogenicity.     

Efficacy and side effect profile of varying doses of intrathecal fentanyl added to bupivacaine for labor analgesia

The purpose of this randomized, double blinded and controlled study was to determine the optimal dose of intrathecal fentanyl when combined with bupivacaine 2.5 mg for initiation of labor analgesia. Parous parturients with cervical dilation between 3 and 5 cm were randomized to receive intrathecal fentanyl 0 (control), 5, 10, 15, 20 or 25 micrograms, combined with bupivacaine 2.5 mg, followed by a lidocaine/epinephrine epidural test dose. Visual analog pain scores (VAPS) and the presence of side effects were determined every 15 min until the parturient requested additional analgesia. Fetal heart rate (FHR) tracings were compared between groups. All parturients who received fentanyl >/= 15 micrograms had VAPS < 20 mm and duration of analgesia > 15 min, but this was not true for all parturients with fentanyl doses < 15 micrograms. Duration of analgesia was shorter for fentanyl groups 0, 5 and 10 micrograms, compared to groups 15, 20 and 25 micrograms, but there was no difference between the 15, 20 and 25 micrograms groups. There was no difference in the incidence of nausea and vomiting, or in FHR tracing changes. The incidence of pruritus was greater in all fentanyl groups compared to control. These data suggest that, when combined with intrathecal bupivacaine 2.5 mg, fentanyl 15 micrograms provides satisfactory analgesia to all parturients. Higher fentanyl doses produced no additional benefit in duration or quality of analgesia.