Research review: DNA polymerases as molecular markers of the regenerating capacity of hepatocytes

Hepatocyte regeneration has been widely investigated, with the mitotic index and the incorporation of [³H]thymidine being used as regeneration markers. We focused on the induction of DNA replication enzymes, particularly DNA polymerases (pol) α, δ, and ε. Using rat models, we have shown that the activity of pol α in crude liver extract well represents the regenerating capacity of hepatocytes. Using pol α as an indicator, we analyzed liver regeneration in rat models under various conditions: obstructive jaundice, external or internal biliary drainage, and the obstruction of portal vein branches. It has been revealed that the ligation of the common bile duct alone induces a certain amount of hepatocyte proliferation. It was striking that external biliary drainage suppressed regeneration capacity in cholestatic rat liver after partial hepatectomy. The strong regeneration in nonligated lobes induced by portal branch ligation was similar to the liver regeneration seen after partial hepatectomy with respect to the induction of DNA polymerases. Taken together, the aspects of DNA replication, particularly the induction of DNA polymerases, may contribute to shedding new light on the regeneration of human liver. This work was supported in part by a Grant-in-Aid for General Scientific Research and for Cancer Research from the Ministry of Education, Science and Culture, Japan, and by grants from the Uehara Memorial Foundation     

Veno-arterial ECLA (extracorporeal lung assist) for severe respiratory failure due to meconium aspiration

A full term newborn female, 3262g, aspirated meconium at birth and began to suffer from severe hypoxia and acidosis due to progressing pneumonitis, pneumothorax and pneumomediastinum. She also had severe hypotension and anuria. Venoarterial ECLA with a Kolobow membrane lung via the right internal jugular vein and the right common carotid artery was initiated. Blood gas parameters and blood pressure improved, and urine output increased to normal. ECLA permitted a reduction in FIO2 and airway pressure of mechanical ventilation, as well as frequent lavage of the lung. As the physical condition improved, the bypass flow was gradually decreased from 200 ml.kg-1.min-1 at the start to 130 ml.kg-1.min-1 for maintenance, then to 25 ml.kg-1.min-1 at the end. Bleeding throughout the ECLA for 69 hours could be minimized by a meticulous control of the activated coagulation time with a minimum dose of heparin and the transfusion of fresh frozen and platelet rich plasma. After ECLA, the carotid artery was simply ligated, and mechanical ventilatory support was carried out for 5 days. Her condition improved and she left the hospital without any neurological sequelae. ECLA will become an effective means of life support for a baby with severe MAS irresponsive to conventional ventilatory support.     

In-vivo blood-brain barrier transport of a novel adrenocorticotropic hormone analogue, ebiratide, demonstrated by brain microdialysis and capillary depletion methods.

The transport of ebiratide, a novel adrenocorticotropic hormone (ACTH) analogue, [H-Met-(O2)-Glu-His-Phe-D-Lys-Phe-NH(CH2)8-NH2], through the blood-brain barrier was directly demonstrated in-vivo. [125I]Ebiratide (16.9 MBq mL-1) or [14C]sucrose (29.2 MBq mL-1) known to be restrictively transported through the blood-brain barrier was infused into the rat internal carotid artery at a flow rate of 50 microL min-1 for 10 min, and after 15 min infusion the distribution volume of each compound in the brain parenchyma was determined by the capillary depletion method. The distribution volume of [125I]ebiratide was 167.8 +/- 62.2 microL (g brain)-1, which was about seven times higher than that of [14C]sucrose (24.9 +/- 4.0 microL g brain)-1, indicating the uptake of ebiratide into brain parenchymal cells. During the infusion into the internal carotid artery, brain microdialysis was simultaneously performed to directly collect the brain interstitial fluid as the dialysate. Radioactivity was detected in the dialysate during the [125I]ebiratide infusion and HPLC analysis of the dialysate revealed that the intact ebiratide accounted for greater than or equal to 80% total radioactivity. The concentrations of [125I]ebiratide and [14C]sucrose in the brain interstitial fluid were estimated based on the relative recovery obtained in the in-vitro recovery study. The brain interstitial fluid/internal carotid arterial blood concentration ratio for [125I]ebiratide was determined to be 1.47 x 10(-2) +/- 0.17 x 10(-2) and was about eight times higher than that for [14C]sucrose (1.92 x 10(-3) +/- 0.36 x 10(-3)), indicating significant transport of ebiratide to the brain interstitial fluid.(ABSTRACT TRUNCATED AT 250 WORDS)     

Improvement of kidney transplant regraft results by using trauma death donors

Patients who have lost a transplanted kidney are widely recognized as high-risk patients for retransplantation. We have found a profound difference in cadaver kidney regraft survival associated with the age and sex of the donor. Kidneys from male cadaver donors yielded significantly higher graft survival rates than kidneys from female donors. The difference in graft survival at one year was 7% for all first transplants (n = 2974), 14% if the recipient was sensitized, and 18% in 688 patients being regrafted. The difference was even more striking in regraft recipients of kidneys from young male donors (72% one-year graft survival) as compared with recipients of kidneys from older female donors (44% one-year graft survival). The donor age and sex effects correlated well with the cause of donor death. Young male donors accounted for 59% of trauma deaths whereas older female donors made up only 7%. Nontrauma donors, on the other hand, were 38% older female and 14% younger male. The survival of trauma-death donor kidneys in regrafted patients was 69% at one year and 37% for nontrauma donor kidneys, a 32% difference (P less than 0.001). These results indicate that regraft survival could be significantly increased through the use of cadaver kidneys from trauma death donors.     

Extremely High Association Between Appearance of HLA Antibodies and Failure of Kidney Grafts in a Five-Year Longitudinal Study

Longitudinal studies were conducted over a five-year period for HLA antibodies on 493 sera tested from 54 kidney transplant patients. HLA single antigen beads were employed to establish donor specificity of the antibodies. Only 3 of 22 patients without antibodies rejected a graft in contrast to 17 out of 32 patients with posttransplant antibodies (p = 0.003). Using a serum creatinine value of 4.0 mg/dL as the cut-off for a failed graft, 4 of 22 patients without antibodies failed compared to 21 of 32 with antibodies (p = 0.0006). Among patients with donor-specific antibodies (DSA) 13 of 15 failed (p = 0.000004). Even among patients with non-donor specific antibodies (NDSA), 8 of 17 failed (p = 0.05). Among patients who could be identified as making de novo antibodies (since they developed antibodies while not having antibodies for more than six months after transplantation), 6 of 11 failed (p = 0.03). Sequential testing for HLA antibodies shows that antibodies appear prior to a rise in serum creatinine and subsequent graft failure. The very strong association between the production of HLA antibodies after transplantation and graft failure indicates the importance of monitoring for posttransplant HLA antibodies.