Beneficial effect of FR183998, a Na+/H+ exchanger inhibitor, on porcine pancreas allotransplantation retrieved from non-heart-beating donors.

Activation of Na(+)/H(+) exchanger (NHE) may have an important role in the ischemia/reperfusion injury by producing intracellular calcium overload. Recent studies have shown a beneficial effect of an NHE inhibitor on the ischemia/reperfusion injury in the heart. In this study, we examined the effect of FR183998, a potent NHE inhibitor, in porcine pancreas allotransplantation from non-heart-beating Landrace pig donors (NHBDs). The four experimental groups included: untreated with no preservation (group 1; n = 3), treated with no preservation (group 2; n = 5), untreated with preservation (group 3; n = 6), and treated with preservation (group 4; n = 4). The preservation was made in ice-cold University of Wisconsin (UW) solution for 24 hours. The groups treated received 1 mg/kg FR183998 before donor cardiac arrest and 10 mg in the UW solution flush in situ. Serum blood glucose, insulin, and amylase were measured daily. An intravenous glucose tolerance test (IVGTT) was performed on the postoperative day (POD) 7 when pigs were sacrificed for histological examination. Graft survival rates on that day in groups 1,2,3, and 4 were 3 of 3; 5 of 5; 3 of 6; and 4 of 4, respectively. The mean K values of IVGTT in groups 3 and 4 were 0.78 +/- 0.10 and 1.27 +/- 0.16, respectively, which were significantly different (P < .05). Upon histological examination, pancreatic tissue in group 3 showed more severe edema and necrosis than other groups. FR183998 may be considered beneficial for ischemia/reperfusion injury to pancreatic grafts from NHBDs.

Excessive portal flow causes graft nonfunction in small size liver transplantation: an experimental study in pigs.

We investigated the effects of portocaval shunt (PCS) on excessive portal flow in producing sinusoidal microcirculatory injury in small-for-size liver transplants in pigs. The posterior segment of a whole liver (25%) was transplanted orthotopically. The pigs were divided two groups: group A, graft with PCS (n = 11), and group B, graft without PCS (n = 11). The PCS was a side-to-side anastomosis of the portal vein and the inferior vena cava. In group A, eight pigs survived for more than 4 days; all pigs except for one died of graft nonfunction within 24 hours in group B. The portal flow after reperfusion decreased in group A, but increased about three times greater in group B than that before the operation (P < .01). In group B, destruction of the sinusoidal lining and bleeding in the periportal areas were observed after reperfusion, findings that were not recognized in group A. These results suggest that graft nonfunction after small-for-size liver transplantation may be attributable to excessive portal flow producing sinusoidal microcirculatory injury.

Eight UCA codons differentially affect the expression of the lacZ gene in the divE42 mutant of Escherichia coli.

In the divE mutant, which has a temperature-sensitive mutation in the tRNA1(Ser) gene, the synthesis of beta-galactosidase is dramatically decreased at the non-permissive temperature. In Escherichia coli, the UCA codon is only recognized by tRNA1(Ser). Several genes containing UCA codons are normally expressed at 42 degrees C in the divE mutant. Therefore, it is unlikely that the defect is due to the general translational deficiency of the mutant tRNA1(Ser). In this study, we constructed mutant lacZ genes, in which one or several UCA codons at eight positions were replaced with other serine codons such as UCU or UCC, and we examined the expression of these mutant genes in the divE mutant. We found that a single UCA codon at position 6 or 462 was sufficient to cause the same level of reduced beta-galactosidase synthesis as that of the wild-type lacZ gene, and that the defect in beta-galactosidase synthesis was accompanied by a low level of lacZ mRNA. It was also found that introduction of an rne-1 pnp-7 double mutation restored the expression of mutant lacZ genes with only UCA codons at position 6 or 462. A polarity suppressor mutation in the rho gene had no effect on the defect in lacZ gene expression in the divE mutant. We propose a model to explain these results.

Expression of p53, MDM2 protein and Ki-67 antigen in recurrent meningiomas.

Association of p53 gene abnormalities with tumor progression and prognosis of many neoplasms has been demonstrated, but little is known about the clinical significance of p53 abnormalities in meningiomas. The significance of p53 protein expression in recurrent meningiomas and its relationships with MDM2 protein and proliferation activity were investigated by analyzing 39 meningiomas immunohistochemically. p53 protein was expressed in 11 (35%) of 31 non-recurrent and 7 (88%) of 8 recurrent meningiomas. A high frequency of p53 expression was observed in recurrent meningiomas, which tended to have a high p53 positive index (p53 PI), indicating that p53 immunoreactivity may be a marker for predicting tumor recurrence. Four recurrent meningiomas with high p53 PIs were analyzed by the polymerase chain reaction-single strand conformation polymorphism method to detect p53 gene mutations, but none were found in exons 4-8 of this gene. Fifteen (71%) of 21 MDM2-positive and 3 (17%) of 18 MDM2-negative tumors expressed p53 protein, showing that MDM2 expression was more common in meningiomas with p53 expression. p53 immunoreactivity in the absence of mutation may indicate stabilization of the wild type through interaction with the MDM2 protein. The Ki-67/MIB-1 proliferation index (MIB-1 PI) correlated well with recurrence. The p53-positive tumors had a significantly higher mean MIB-1 PI than p53-negative tumors, suggesting that wild-type p53 inactivation by the MDM2 protein may be involved in controlling the proliferative activity in meningiomas. In conclusion, immunohistochemical examination for p53 protein as well as proliferative activity may help predict the malignant potential of tumor recurrence.

An rne-1 pnp-7 double mutation suppresses the temperature-sensitive defect of lacZ gene expression in a divE mutant.

A divE mutant, which has a temperature-sensitive mutation in the tRNA1Ser gene, exhibits differential loss of the synthesis of certain proteins, such as beta-galactosidase and succinate dehydrogenase, at nonpermissive temperatures. In Escherichia coli, the UCA codon is recognized only by tRNA1Ser. Several genes containing UCA codons are normally expressed after a temperature shift to 42 degrees C in the divE mutant. Therefore, it is unlikely that the defect in protein synthesis at 42 degrees C is simply caused by a defect in the decoding function of the mutant tRNA1Ser. In this study, we sought to determine the cause of the defect in lacZ gene expression in the divE mutant. It has also been shown that the defect in lacZ gene expression is accompanied by a decrease in the amount of lacZ mRNA. To examine whether inactivation of mRNA degradation pathways restores the defect in lacZ gene expression, we constructed divE mutants containing rne-1, rnb-500, and pnp-7 mutations in various combinations. We found that the defect was almost completely restored by introducing an rne-1 pnp-7 double mutation into the divE mutant. Northern hybridization analysis showed that the rne-1 mutation stabilized lacZ mRNA, whereas the pnp-7 mutation stabilized mutant tRNA1Ser, at 44 degrees C. We present a mechanism that may explain these results.