The effect of ionizing irradiation on the lipid biosynthesis by thymus and liver

New Zealand rabbits, fasted for 12 hours, were subjected to 500 rads of whole-body irradiation. Analysis of thymus lipids, at various time intervals following irradiation, showed a threefold increase of triglycerides at 24 hours. Fatty acid composition of the 600 X g supernatant was not affected at 24 hours after irradiation. Lipid biosynthesis from acetate-1-14C by the thymus homogenates was increased to a small extent at 4 hours following irradiation, while the radioactivity distribution into fatty acids was not considerably affected. Contrary to the above findings, fatty acid synthesis from acetate-l-14C by the liver preparations showed a decreased incorporation between the fourth and twelfth hour following irradiation. Counting of the radioactivity of the separated fatty acids suggested that the system for synthesis of short-chain fatty acids was impaired as early as 4 hours following irradiation.     

The effect of ionizing radiation on lipid metabolism in lymphoid cells

Lipid metabolism was studied in lymphoid tissues of rats after whole body irradiation with doses producing damage of different degrees to lymphoid cells (4-10 Gy). The content of free cholesterol, cholesterol esters, and total phospholipids was determined in peripheral blood lymphocytes and thymocytes 1-2 h after exposure. Simultaneously, the rate of in vitro incorporation of 2 14C-acetate into total lipids, phospholipids, and cholesterol of lymphoid cells was estimated. It was shown that exposure of rats to ionizing radiation caused activation of lipogenesis. Cholesterol synthesis was activated after a dose of 4 Gy and decreased with increasing dose.     

Perturbations in phosphoinositide metabolism and protein kinase C activity in mouse liver following whole body irradiation

The involvement of the signal transduction pathway in mouse liver following whole body irradition was investigated. Mice were exposed to 60Co gamma rays (3 Gy) and sacrificed after different time intervals. Various elements of phosphatidyl inositol signal transduction pathway were investigated. Alterations could be seen as early as 15 min of irradiation. These changes are reflected in elevation in DAG levels and increased activation of PKC, an enzyme which is involved in tumorigenesis. The chronological appearance of various transducers following whole body irradiation is of significance since these early effects may set the stage for radiation-induced tumorigenesis and hence may be used to manipulate tumor response to radiotherapy.     

Proliferation kinetics and PCNA expression of HL-60 cells following ionizing irradiation and granulocytic differentiation

The human promyelocytic leukaemia cell line, HL-60, was investigated with regard to proliferation and terminal differentiation following irradiation. The cells were X-irradiated and induced with 1.25% dimethyl sulfoxide (DMSO) towards the granulocytic lineage. Proliferation was measured via cell growth, clonogenicity and the bromodeoxyuridine/DNA incorporation assay. Immunohistochemical detection of proliferating cell nuclear antigen (PCNA) expression was used to discriminate cycling from non-cycling cells. The differentiation obtained was proved by testing for the immune function of the respiratory burst (NBT reduction test). The HL-60 cells studied revealed a high radiosensitivity (D₀= 0.63 Gy). After induction with DMSO, declines in cell growth, clonogenicity and PCNA positivity of the cells indicated a decrease in proliferation and an increase in differentiation. Starting on day 2 in culture, irradiation after seeding with 1 Gy accelerated the loss of the PCNA expression in induced cells (46%v. 3% PCNA-negative control cells on day 3). Induced cells gained the capability of exerting the respiratory burst, which was found to be dose-dependent radiosensitive (42% and 12% NBT-positive cells after 1 and 2 Gy, respectively, v. 53% NBT-positive control cells on day 8). Subpopulations in the cell line were evident in all parameters investigated. We discuss the HL-60 cell, not only as a model comparable to human progenitor cells, but also as a suitable tool in radiobiological research with regard to proliferation and differentiation following ionizing irradiation.     

Plasmatic heparinic activity following lipid load

Changes of hemocoagulability and of plasmatic fibrinolysis have induced us to study PHA following the administration of the lipid load. We have studied the effects induced by the administration of a lipid load, constituted by 1/2 g of olive oil and by 1/2 g of butter dissolved in 200 ml of vaccine milk. PHA has been estimated in all our subjects under basal conditions and after 4 1/2 hours from the lipid load. The statistical analysis of the results we have obtained shows a significant PHA reduction following the lipid load. Concluding, our results indicates that the lipid load very frequently causes a reduction of PHA which is due to a consumption of heparin. This consumption is more probably due to the activation of lipoprotein-lipase by heparin.     

Alterations in rat lipid metabolism following ecdysterone treatment

The influence of ecdysterone on the lipid metabolism in liver and adipose tissue from rat was investigated using 14C-acetate and 32P-orthophosphate as precursors. Ecdysterone produced an increase in 14C-acetate incorporation into triglycerides. A concomitant decrease in free fatty acids and diglycerides was observed. The effect of ecdysterone on triglyceride lipase activity was investigated and a significant decrease was found. Ecdysterone produced a significant increase in the specific activity of phosphatidylethanolamine and phosphatidylserine in liver. On the contrary, the specific activity of phosphatidylcholine was reduced. In adipose tissue, the most evident effect observed was the increase of specific activity of phosphatidylcholine. These results contribute to knowledge of the heterophylic action of ecdysterone.     

The inheritance of lipoxidase activity and pigment content in durum wheat

Summary Analysis of a 10-parent diallel of durum wheat (Triticum turgidum L. var. durum) grown at two diverse locations revealed that for enzyme lipoxidase activity, wheat and predicted macaroni pigment contents, heterosis was environmentally dependent. Both additive and dominance genetic effects were significant for each of these quality traits studied, but in one location, the additive genetic effect was consistently more pronounced than the dominance genetic effect, while the reverse was the case in the other location. There was no evidence of epistatic gene effect for any of the three characters in either location.Contribution No. 333.     

Action and interaction of red and far-red radiation on lipoxidase metabolism of squash seedlings

Lipoxidase, in the cotyledons of squash (Cucurbita moscata) seedlings grown in the dark, reached its peak activity on the fifth day and then declined to its lowest activity on the eighth day. Under continuous irradiation, the rate of enzyme disappearance was accelerated by red (655 mμ) and was retarded by far-red (735 mμ) radiation. Acceleration of enzyme disappearance caused by red light was reversed repeatedly by far-red light in seedlings that received an initial exposure to red radiation. These responses were independent of the duration of irradiation at each of the alternating wavebands. No change was observed when the white light was administered either 24 hours before or 24 hours after the red, far-red treatment.

The lipoxidase system of the seedlings given an initial exposure to far-red radiation also responded reversibly to alternating far-red, red extended exposures, but it failed to respond reversibly when short exposures were employed. Similarly, no change occurred in these seedlings when either pre- or post-treatment with the white light was applied.

These results demonstrate that the capacity of lipoxidase to act reversibly depends primarily on the duration of exposure and on the kind of light (red or far-red) to which the seedlings were exposed initially. In spite of these variations, lipoxidase metabolism can be considered an additional biochemical manifestation of red, far-red reaction that operates in the photomorphogenesis of plants.