Effects of fat content in the diet on hepatic peroxisomes of the rat

Effects of fat content in the diet on rat liver peroxisomes was examined. In the livers of rats fed for one week on the high-fat diet containing 30% fat, the cyanide-insensitive palmitoyl-CoA oxidation was accelerated to eight times that of control and the enzymic activities of catalase, carnitine acetyltransferase and carnitine palmitoyltransferase were elevated by the factors of 1.3, 5 and 2, respectively. In contrast, the activities of D-amino acid oxidase in addition to the three enzymes mentioned above were all lowered by 20% when the animals were maintained on a fat-free diet for the same period of time. It appears that the high-fat diet-induced increase in the activity of carnitine palmitoyltransferase is a result of the raised activity of this enzyme in mitochondria only while the apparent high activity reflects stimulation of carnitine acetyltransferase in all the subcellular fractions. Another notable effect of the high-fat diet was a remarkable increase in the quantity of a peroxisome-associated polypeptide which was separable by sodium dodecyl sulfate polyacrylamide gel electrophoresis. It is noteworthy that this effect of the high-fat diet resemble that of clofibrate. If the diet was deprived of fat, however, this polypeptide species, with an estimated molecular weight of 80 000, decreased to a level slightly lower than normal. On the basis of the electron micrographic criteria, the high-fat diet provoked a marked proliferation of hepatic peroxisomes.     

Racemization in the Coupling Reaction with the Several Methods beside the Activated Ester Methods

The degree of racemization in the coupling reaction, Pro-Val + Pro, with the several other methods than the activated ester methods was measured and the results were compared with that in the coupling reaction, Leu-Phe + Val, as well as in the previous paper.¹⁾ In the azide and the mixed anhydride methods, no or almost no racemization was detected, whereas in the other tested methods of peptide synthesis (Pachornik-, DCCD- and phosphazo-methods) the significantly large racemization was observed. It can be attributed to the strong nucleo- philic N-atom in the penultimate amino acids (Pro) and the steric hindrance of C-terminal amino acid (Val), which are favourable to the formation of the oxazolone ring.

This assumption was further systematically confirmed in the synthesis of the other several tripeptides with the DCCD method. The separation of the diastereoisomers (LLL and LDL) of the resulting tripeptides by gas chromatography with a packed column was also here reported.     

The isolation and culture of lily pollen protoplasts

Methods for the enzymatic isolation of lily protoplasts and their successful culture are described. When pre-anthesis binucleate pollen (immature pollen grains) was treated in enzyme solution containing macerozyme and cellulase, up to 80% lost their exine and gave rise to intact protoplasts within 1 h. These pollen protoplasts were uniform in size and densely cytoplasmic with two prominent generative and vegetative nuclei. The isolated pollen protoplasts regenerated a cell wall within 1 day of culture and produced a structure resembling a pollen tube after 10–12 days of culture. During this culture period, dividing generative nuclei or 2 sperm nuclei were observed in many protoplasts with regenerated cell walls.     

Interaction between cytochrome c and cytochrome c peroxidase: excited-state reactions of zinc- and tin-substituted derivatives

The effect of cytochrome c peroxidase (CCP) and apoCCP on the fluorescence and phosphorescence of Zn and Sn cytochrome c (cyt c) and the effect of cyt c on the fluorescence and phosphorescence of Zn CCP were examined. We found the following: The fluorescence yields of Zn and Sn cyt c were quenched by about 20% by CCP, consistent with energy transfer between the two chromophores with a separation of about 1.8 nm. The phosphorescence spectrum of Zn cyt c (but not Sn cyt c) shifts by 20 nm to the blue upon complexation with either CCP or apoCCP; at the same time the phosphorescence lifetime of Zn cyt c decreases from 12 +/- 2 to 6 ms with apoCCP addition. Zn CCP phosphorescence decay increases from 8.3 to 9.1 ms upon addition of poly(L-lysine) used to mimic cyt c. It is concluded from these results that binding of the redox partner or an analogue to Zn CCP and Zn cyt c results in a conformational change. The respective phosphorescence lifetimes of Zn and Sn cyt c were 13 and 3 ms in the absence of CCP and 1.6 and 1.1 ms in the presence of CCP; this corresponds to a quenching rate due to CCP of 519 and 570 s-1, for Zn and Sn cyt c, respectively. The phosphorescence of Zn CCP is also affected by native cyt c but is dramatically less than the complementary pair; the quenching rate constant is 17 s-1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Activation of mouse peritoneal macrophages by synthetic glyceroglycolipid liposomes

Summary Liposomes composed of chemically synthesized glyceroglycolipids, such as 1,2-dipalmityl-[-cellobiosyl-(1 3)]-glycerol (Cel-DAG), 1,2-dipalmityl-[-lactosyl-(1 3)]-glycerol, or 1,2-dipalmityl-[-maltosyl-(1 3)]-glycerol, were found to enhance protective immunity against transplantable tumor cells (sarcoma 180) in ICR mice. Peritoneal exudate cells prepared from mice treated in vivo with Cel-DAG showed cytostatic activity in vitro against the mouse leukemia cell line, EL-4. Adherent cells separated from this preparation showed similar activity. Peritoneal cells from polypeptone-injected mice acquired appreciable cytostatic activity when incubated in vitro in the presence of glyceroglycolipid liposomes. The adherent cell fraction alone showed rather weak cytostatic activity when pretreated with the glyceroglycolipids, and full activity was restored by supplementing with the nonadherent cell fraction. The ability of glycolipids to induce tumoricidal effects was affected by cholesterol content: with increasing cholesterol content, the activities decreased. Cholesterol-free glycolipid liposomes were taken more efficiently by macrophages than cholesterol-containing liposomes. Cholersterol modifies the surface property of glyceroglycolipid liposomes. Activation of macrophages is responsible for enhancement of protective immunity against tumor cells by injection of these glycolipids in vivo.This work was supported in part by Grants-in-Aid (Nos. 58010010, and 59870076) for Scientific Research from the Ministry of Education, Science and Culture of Japan     

Electrophoretic Studies on Plant Protoplasts I. pH Dependence of Zeta Potentials of Protoplasts from Various Sources

Electrophoretic mobilities of plant protoplasts from varioussources were measured, as a function of the pH of the medium,by a micro-electrophoresis technique to characterize the protoplastsin terms of curves of zeta potential vs. protoplast surfacepH (pH_s). The shape of the curves of zeta potential vs. pH_scurves differed among preparations of protoplasts isolated fromvarious species and strains. The isoelectric points (pI) ofthe protoplasts measured in this study were between 3.0 and4.0. These differences among the protoplasts suggest that itmay be possible to develop an electrophoretic method for theselection of protoplasts. The shape of the curves of zeta potentialvs. pH_s also indicated that carboxyl groups, as well as phosphategroups, may contribute to the negative charges on the surfaceof protoplasts. (Received October 14, 1988; Accepted February 22, 1989)