Studies on Urea Cycle Enzymes in Rat Liver during Acute Uraemia

Abstract. Activities of urea cycle enzymes were measured in the liver of starved rats 12 and 48 h after bilateral nephrectomy. Control experiments (sham-operated, starved rats) revealed that the activities of only two enzymes of the cycle are altered in the uraemic state: argininosuccinic acid synthetase (EC 6. 3. 4. 5.), which is considered to be rate limiting for urea production and carbamyl phosphate synthetase (EC 2. 7. 2. 5.). Alterations in ornithine concentration of the liver, a possible cause of an increased urea production rate, could not be detected previously (21). Our present results do not support the concept that a decrease of the activity of ornithine-6-amino transferase (EC 2. 6. 1. 13), leading to an increase in the ornithine content of the liver is responsible for the accelerated urea production rate in the liver of acute uraemic rats.     

Therapy of severe aplastic anemia with anti-human thymocyte globulin and androgens: the effect of HLA-haploidentical marrow infusion

Fifty-four patients with severe aplastic anemia were treated with horse anti-human thymocyte globulin (ATG) and androgens. Thirty of these patients also received an infusion of HLA-haploidentical marrow cells. Only those patients having evidence of hematologic recovery within 3 mo after ATG therapy were considered responders to the immunosuppressive regimen. Of 53 patients evaluable for response, 21 had complete or partial responses and 7 had minimal improvement by defined criteria. The remaining patients did not respond or died. Factors correlated with response to therapy included a short duration of aplasia and a high admission granulocyte count. Thirty-six patients (66.7%) are surviving between 18 and 43 mo, and 18 have died. Deaths were due to hemorrhage and/or infection. Short duration of aplasia and high granulocyte counts also correlated with survival, as did younger age. Four patients with complete or partial responses had a recurrence of severe aplasia 6-17 mo after their first course of ATG. Three of these patients were retreated with ATG (and oxymetholone in two cases). All three had second responses to therapy, but two of the three have had second relapses. The fourth patient responded to oxymetholone alone, but died after a second relapse. Mismatched marrow infusion had no effect on the incidence of response or survival.     

Plasma lipoproteins and lecithin:cholesterol acyltransferase distribution in patients on dialysis

Plasma lipoproteins and LCAT activity were studied using a single spin density gradient separation and an exogenous substrate enzyme assay in 41 patients on chronic hemodialysis and in 11 normal subjects. The plasma HDL cholesterol was markedly decreased (33 vs. 63 mg/dl, P less than 0.001) while total and LDL-cholesterol were unchanged in the patients. Plasma LCAT activity was significantly lower in the patient group (42 vs. 59 nmoles/4 hr/ml, P less than 0.001), but the distribution of activity (studied in 13 dialysis patients and 12 control subjects) was not different between the two groups: 90% being associated with HDL and VHDL lipoprotein fractions. To examine the possible genetic influence on the development of hypertriglyceridemia in the patient group, we examined the ratio of apolipoproteins E3/E2 and CII/CIII in ten of the patients and another group of 13 control subjects. The frequency of heterozygotes for E3 deficiency was not different between the patient (one of ten) and the control (two of 13) groups. While the patient group had lower CII/CIII ratio, the figures did not reach statistical significance. The low LCAT activity in the face of higher plasma triglycerides and low HDL may contribute to impaired lipolysis previously documented in uremic patients. A follow-up study performed 1 year after the initial study confirmed the decreased HDL (51 vs. 71 mg/dl, P less than 0.01) and LCAT activity (50 vs. 59 nmoles/hr/ml, P less than 0.02) in an exogenous substrate system (N = 20). LCAT measured using the endogenous substrate was not significantly different from the control group (49 vs. 55 nmoles/hr/ml).(ABSTRACT TRUNCATED AT 250 WORDS)     

Epstein-Barr virus genomes are restricted to secondary neoplastic cells following bone marrow transplantation

DNA from mononuclear blood and tumor cells from 33 patients undergoing bone marrow transplantation for leukemia was examined for the presence of Epstein-Barr virus (EBV) genomes by blot hybridization. Four groups of patients were studied soon after engraftment, during long-term remission, after relapse of the original leukemia, and after development of secondary B cell neoplasms. Only the cells of patients with secondary neoplasms demonstrated EBV genomes, where all five adequately studied samples were positive. Samples from all other patient categories were negative for EBV genomes. We conclude that EBV genomes do not frequently persist in normal engrafted lymphocytes or in mononuclear cells of patients suffering recurrent leukemia. These results are consistent with EBV playing a role in the genesis of secondary B cell neoplasms following bone marrow transplantation.