Effect of low ambient temperature on protein turnover and heat production in chicks

1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks.     

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.     

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     

Mapping and disruption of the cybB gene coding for cytochrome b561 in Escherichia coli

Abstract The cybB gene on a plasmid encoding cytochrome b ₅₆₁ in Escherichia coli was disrupted by insertion of Km^rl determinant DNA. The cromosomal cybB gene was replaced by the inactivated cybB gene on the plasmid by homologous recombination using λ phage lysogenization and heat-induction. The replacement was confirmed by Southern and Western blotting analyses. Deficiency on the cybB gene product did not affect the growth properties of the cells, and the oxidase activities of the cells dependent on various substrates were similar to those of the parental strain. Cytochrome b ₅₆₁ is concluded to be expressed in E. coli , but may not play a major role in cell growth. In the genetic map of E. coli , the cybB gene was determined by conjugational and transductional crosses to be at 31 min between trg and terC .     

Exposure of Leaves of Cucumis sativus L. to Low Temperatures in the Light Causes Uncoupling of Thylakoids II. Non-Destructive Measurements with Intact Leaves

To examine the effects of chilling of leaves of cucumber (Cucumissativus L.) in moderate light on the coupling state of thylakoidsin situ, changes in fluorescence, changes in light scatteringand flash-induced changes in absorbance at 518 nm were examinedin intact leaves. After chilling of leaves at 5?C in the lightfor 5 h, the non-photochemical quenching of fluorescence, ameasure of energisation of thylakoids, was largely suppressed.The treatment also caused a suppression of light-induced changesin the light scattering by leaves, which depends on the formationof a pH gradient across thylakoid membranes. When thylakoidswere prepared by very gentle methods from the leaves chilledin the light, through a step of preparation of intact chloro-plasts,the transport of electrons from H₂O to ferricyanide was uncoupled,being insensitive to an uncoupler, methylamine. These data provide consistent evidence that the thylakoids areuncoupled in situ by the chilling of leaves in the light and,as a consequence of the uncoupling, the energisation of themembranes is suppressed. However, the decay of the flash-inducedchange in absorbance at 518 nm in leaves was not markedly acceleratedby the treatment. The thylakoids isolated from leaves chilledin the light, which were in the uncoupled state, also did notshow a rapid decay, unless an efficient uncoupler such as gramicidinwas added. These results suggest that even a considerable uncouplingof thylakoids, brought about by chilling of leaves in the light,is not sufficient to cause a marked acceleration of the decayof the flash-induced change in absorbance at 518 nm. Therefore,analysis at 518 nm is not always a sensitive method for assessingthe coupling state of thylakoids. (Received July 1, 1991; Accepted October 4, 1991)