The esterase activity of rat liver was mainly concentrated in the microsomal and nuclear fractions, with low activities in other fractions. On the basis of sensitivity t o certain esterase inhibitors, the microsomal esterases were considered to be of a carboxylesterase type. The esterase distribution in sonicated rough microsomes, separated by zone centrifugation, was also investigated.Solubilization of the microsomal esterases was achieved by sodium deoxycholate, trypsin and phospholipase-A treatment. Two esterases were solubilized from rat-liver microsomes by phospholipase-A treatment and were further purified by Chromatography on Sephadex G-100 and DEAE-cellulose. The enzymes were purified 256 and 154 times. The isoelectric points, K , values and molecular weights of the two esterases were determined.Both enzymes are of a carboxylesterase type. One of the esterase, however, was sensitive to HgCl, of low concentrations, which is an unusual property for carboxylesterases. The question of whether the two enzymes constitute a monomer and a dimer of the same esterase or are completely different enzymes, is discussed, The cellular distribution of esterases in the livers of different species has been reported frequently. The microsomal fraction seems to be the main source of the carboxylesterases [l -41, where, as this paper will show, they are bound to the microsomal membrane.

Lactate dehydrogenase and its heart (H) and muscle (M) subunit activities were studied in right ventricular endomyocardial biopsies from eight transplanted human hearts and compared with five chronically failing hearts and six normal human hearts from brain-dead liver/kidney donors. Of the 17 transplant biopsies (taken 5-95 weeks postoperatively), only two showed histologic signs of chronic rejection: They were excluded from the group analysis. A higher proportion of the M subunit of lactate dehydrogenase (M%) was found in the transplanted and the chronically failing hearts than in the normal hearts, presumably reflecting increased myocardial anaerobic glycolytic stress. In the early post-transplantation period, M% was higher in the transplanted than in the chronically failing hearts. Thereafter M% gradually fell, but had not reached normal levels 1-2 years after transplantation. During that time it was similar to the values in the chronic-failure hearts. In the two biopsies with chronic rejection, M% was nearly twice as high as in contemporaneous biopsies showing mild or no rejection. Monitoring of enzymatic adaptation from endomyocardial biopsies may be of clinical interest.

Fractionation of bovine whey concentrate was performed by gel filtration on Sephadex G-75 both on a laboratory scale and on a large scale. By a recycling procedure and improved separation was obtained and the whey proteins were resolved into four fractions in the weight ratio 3:12:1:4. The fractions were analysed by polyacrylamide gel (PAG) electrophoresis and the apparent molecular weights were determined by thin layer gel chromatography (TLG) and by sodium dodecylsulfate (SDS) gel electrophoresis.