Brain enzyme activity in irradiated sympathectomized rats

The results are reviewed from studies of activity of hexokinase (2.7.1.1.EC), dehydrogenase glucose-6-phosphate (1.1.1.49 EC), and cholinesterase (3.1.1.7 EC) in subcellular fractions of rat brain at the background of chemical sympathectomy induced by long-term administration of guanethidine and subsequent irradiation with a dose of 7 Gy. In conditions of sympathectomy, the enzyme activity is inhibited; in irradiated sympathectomized rats, activity of hexokinase and cholinesterase increases to reach the level of that of intact animals while dehydrogenase remains inhibited.     

The level and immunochemical characteristics of fibronectin in the plasma of irradiated rats

The electrophoretic and immunoelectrophoretic methods were used to study fibronectin of blood plasma of intact Wistar rats and of those exposed to 1-10 Gy radiation. The increase in the fibronectin concentration 3 days after irradiation was a function of radiation dose. Possible mechanisms of the hyperfibronectinemia development involving mechanisms of endogenous proteolytic fragmentation of glycoprotein, the increase in the protein synthesis and complexation and inhibition of the rate of fibronectin degradation and elimination are discussed.     

Ribonucleic acid synthesis in regenerating liver of irradiated adrenalectomized rats.

The effect of whole-body irradiation on RNA synthesis in regenerating and non-growing livers was studied in intact and adrenalectomized rats. The animals were divided into four sub-groups: (1) control; (2) irradiation only; (3) partially-hepatectomized; and (4) irradiated partially-hepatectomized. Newly-synthesized RNA was determined by 30 or 40 min uptake of (6-14C) orotic acid. Both nuclear and polyribosomal RNA synthesis in regenerating livers of adrenalectomized rats were depressed below their control levels, regardless of whether irradiation was 2 hours before or 2 hours after partial hepatectomy. Specific radioactivity values of regenerating livers of adrenal intact and adrenalectomized rats were elevated above those of the non-growing livers from irradiated and unirradiated rats.     

Changes in the level of pyrimidine nucleoside phosphates in the liver of irradiated rats

Content of uridyl and cytidyl nucleoside-phosphates in the liver of rats irradiated by gamma-rays (60Co) in a dose of 774 mC/kg (3000 P) was studied 0.5, 1, 3, 6 and 24 h after the effect. A trustworthy decrease of UTP and CTP as well as UDP and CDP content 24 h after irradiation was found. The number of pyrimidine nucleoside monophosphates increases after 24 h of the effect.     

Kininogenesis and the effect of bradykinin on the level of blood plasma glucocorticoids in irradiated rats

Kininogenesis is activated after irradiation as well as after the injection of hydrocortisone. Bradykinin, the main component of the kinin system, is a factor that limits the level of blood plasma 11-oxycorticosteroids after its intravenous injection to exposed rats.     

Diffusion resistance and enzyme activity decay in a pellet

The effective enzyme activity decay can be decreased by diffusion limitation in the immobilized pellet. Thiele modulus changes and/or poisoning of various enzyme forms are two phenomena which are influenced by diffusion limitation. This article considers these effects on enzyme decay as applied to glucose isomerase.     

Dietary whey protein modulates liver glycogen level and glycoregulatory enzyme activities in exercise-trained rats

This study compared the effects of dietary whey protein with dietary casein or soy protein on glycogen storage and glycoregulatory enzyme activities in the liver of sedentary and exercise-trained rats. Male Sprague-Dawley rats (ca. 130 g) were divided into one sedentary and three exercise-trained groups, with eight animals in each group. Casein was provided as the source of dietary protein in the sedentary group while the exercise-trained groups were fed casein, whey, or soy protein. Rats in the exercise-trained groups ran for 30 mins/day, 4 days/week on a motor-driven treadmill. In the exercise-trained rats, animals fed whey protein had higher liver glycogen content than animals in the other two diet groups. Glucokinase activity was significantly higher in rats fed whey protein compared to that in rats fed soy protein, while glucose 6-phosphatase activity was significantly decreased in animals on the whey protein diet compared with those the other two diets. Although 6-phospho-fructokinase activity was significantly lower in the whey protein group than in the soy protein group, we found that fructose 1,6-bisphosphatase activity was significantly higher in the whey group compared with either the casein or soy groups. Pyruvate kinase activity in rats fed the casein diet was significantly higher than in rats fed either the whey or soy protein diets. In addition, hepatic alanine aminotransferase activity and serum alanine level were also increased in the whey protein group compared with the casein or soy protein groups. Taken together, these results demonstrate that the whey protein diet in exercise-trained rats results in significantly higher levels of liver glycogen, because of the combined effects of regulation of rate limiting glycolytic and gluconeogenic enzyme activities and activation of glycogenesis from alanine via alanine amino-transferase.     

DNA synthesis in irradiated intestinal epithelium

• 1.1. DNA synthesis in the intestinal epithelium of X-irradiated mice was studied by means of autoradiography following labeling with tritiated thymidine. Radiation doses used varied from 200 to 3000 rads whole-body irradiation. The label was administered once or 5 times, at times ranging from one day before to 3 days after irradiation. The time from irradiation to sacrifice varied from 0 to 3 days.
• 2.2. Irradiation results in reduction of thymidine incorporation. The rapidity of development and the ultimate severity of this effect increase with dose.
• 3.3. An analysis of possible mechanisms indicates that the initial phase of the effect observed is a block of DNA synthesis in cells in the DNA synthesis phase.
• 4.4. The fate of cells irradiated while in DNA synthesis phase was studied. Some of them die, the majority mature precociously and emigrate into the region occupied by mature cells, and some remain in the zone of proliferation.
• 5.5. After moderate to heavy doses, DNA synthesis is resumed long before cell division. In heavily irradiated mice, the remaining crypt cells go through one to two cycles of DNA synthesis not followed by division.
• 6.6. The migration of mature cells along the villi is not markedly affected by irradiation. Emptying of the crypts occurs in heavily irradiated animals chiefly on the first and third day after irradiation, at times when there is no or little DNA synthesis.
• 7.7. These observations, combined with the results of previous studies, shed some light on the mechanisms which control cell movements, particularly the transitions from crypts to villi.
• 8.8. Qualitative and quantitative changes in the population of mature cells on the villi reflect the lack of cell proliferation and changes of cell retention in the crypts.