Self-oscillations in an open biochemical substrate-inhibited reaction interacting with the enzyme-producing system

An open biochemical reaction with substrate inhibition is analysed under conditions of a continuous turnover of its enzyme maintained by the enzyme-producing system (EPS). In this reaction, self-oscillations of a long period may occur in addition to the resonance phenomena found in a simple biochemical reaction with the EPS. A distinctive property of this reaction is also superadaptation with which the total enzyme concentration increases as a square of the substrate influx rate.     

Significance of adrenal hormones in brain energy metabolism

Intensity of glycolysis was studied under conditions of immobilization stress and adrenalectomy as well as with administration of adrenaline and hydrocortisone. The processes of aerobic glycolysis, activity of enzymes of the tricarboxylic acid cycle and mitochondria respiratory chain, content of total, free and protein-bound glycogen, glucose-I-phosphate, glucose-6-phosphate, pyruvate, alpha-ketoglutarate, cytrate and macroergs in the brain are shown to depend on the level of adrenal hormones producing a multilateral effect on a series of energy metabolism links.     

Effect of thymic polypeptide factor on the cyclic nucleotide system of immunocompetent cells

Thyramine, a polypeptide factor from thymus, at wide range of concentrations increased the cAMP content in rat thymocytes. Increase in the cAMP content was less distinct in spleen lymphoid cells. Thyramine decreased the cGMP content in thymocytes; minimal nucleotide level was found within 15 min of incubation. The data obtained suggest that the rate of lymphocyte maturation is important for response of the cells to the effect of immunoregulating agents.     

Influence of Neotyphodium coenophialum on copper concentration in tall fescue

Poor performance of livestock that graze tall fescue (Festuca arundinacea Schreb.) has been associated with the endophyte fungus Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). Recent evidence suggests lowered Cu status and a depression of Cu-related immune function in steers that graze endophyte-infected (E+) tall fescue. Greenhouse and field studies investigated relationships between the endophyte and Cu concentrations in tall fescue. Seventeen infected 'Kenhy' clones were divided, and one plant of each pair was treated three times with Benomyl to remove the endophyte (E-). Plants were watered with nutrient solution in a greenhouse for 6 mo before sampling. Copper concentrations were greater (P < .001) in E- than in E+ clones (3.4 vs 2.8 microg/g; SE, .06). In the second greenhouse experiment, genetically similar E+ and E- 'Kentucky'-31 (KY-31) and 'Georgia Jessup' were grown from seed and fertilized with nutrient solution to produce mature plants. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (8.6 vs 7.6 microg/g; SE, .3). In a field plot experiment in Texas, E+ and E- KY-31 were grown with 0, 50, and 100% replacement of potential evapotranspiration. By September, Cu concentrations were higher (P < .05) in E- than in E+ tall fescue (7.3 vs 6.6 microg/g; SE, .2). In pasture experiments, KY-31 E+ (> 70% infection level) and E- (< 5% infection level) tall fescue were grown in Virginia at two locations with three rates of N fertilizer. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (4.8 vs 4.5 microg/g; SE, .1) and increased (P < .01) linearly in response to N. Our data demonstrate that the presence of the endophyte is associated with lower Cu concentrations in tall fescue, which may contribute to lowered Cu status in animals and thus contribute to the etiology of fescue toxicity.     

The effect of superhigh doses of gamma radiation on the energetics of rat liver mitochondria

The effect of high dose of gamma radiation (200 Gy) on energy of rat liver mitochondria was studied. 1 hour after irradiation state 3 (V3) increased by 32 +/- 7%, state 4 (V4)- by 25 +/- 8%, the rate of ATP synthesis by 52 +/- 11%. 48 hours after irradiation these parameters decreased to control levels inspite of accumulation of lipid peroxidation products.     

Pulmonary function changes after nebulised and intravenous frusemide in ventilated premature infants

AIMS: To compare the effects of a single dose of frusemide administered either intravenously or by nebulisation on pulmonary mechanics in premature infants with evolving chronic lung disease. METHODS: The effect of frusemide on pulmonary mechanics was studied at a median postnatal age of 23 (range 14-52) days in 19 premature infants at 24 to 30 weeks gestational age, who had been dependent on mechanical ventilation since birth. Frusemide (1 mg/kg/body weight) was administered, in random order, intravenously and by nebulisation, on two separate occasions 24 hours apart. Pulmonary function studies were performed before and at 30, 60, and 120 minutes after administration of frusemide. Urine was collected for six hours immediately before and for six hours after administration of frusemide. RESULTS: Nebulised frusemide increased the tidal volume 31 (SE 11.5)% and compliance 34 (SE 12)% after two hours, whereas no change in either was noted for up to two hours after intravenous frusemide administration. Neither intravenous nor nebulised frusemide had any effect on airway resistance. Six hour urine output increased from a mean (SE) of 3.3 (0.4) ml/kg/hour to 5.9 (0.8) ml/kg/hour following intravenous frusemide administration while nebulised frusemide had no effect on urine output. Urinary sodium, potassium, and chloride losses were also significantly higher after intravenous frusemide, whereas nebulised frusemide did not increase urinary electrolyte losses. CONCLUSION: Single dose nebulised frusemide improves pulmonary function in premature infants with evolving chronic lung disease without adverse effects on fluid and electrolyte balance.