Studies on neutron spectrum characterization for the Pneumatic Fast Transfer System (PFTS) of KAMINI reactor.

Characterization of neutron energy spectrum along with the determination of sub-cadmium to epithermal neutron flux ratio (f) and the epithermal neutron flux shape factor (α) has been carried out at pneumatic fast transfer system (PFTS) of KAMINI reactor. The facility has been extensively used for the neutron activation analysis (NAA) studies using both k0-NAA and relative method. This paper describes the multi-foil activation method to determine the reaction rates followed by the generation of computed guess spectrum to unfold the neutron spectrum using least square minimization approach.

Radiation-induced volatile hydrocarbon production in platelets.

Generation of volatile hydrocarbons (ethane, pentane) as a measure of lipid peroxidation was followed in preparations from platelet-rich plasma irradiated in vitro. The hydrocarbons in the headspace of sealed vials containing irradiated and nonirradiated washed platelets, platelet-rich plasma, or platelet-poor plasma increased with time. The major hydrocarbon, pentane, increased linearly and significantly with increasing log radiation dose, suggesting that reactive oxygen species induced by ionizing radiation result in lipid peroxidation. Measurements of lipid peroxidation products may give an indication of suboptimal quality of stored and/or irradiated platelets.

Rhythms of isolated platelet glutathione, aging, and the internal evolution of species.

Platelet integrity upon reinfusion after storage for varying periods of time constitutes a clinical problem requiring chronobiologic study. For such a study, total glutathione (GSH) served as an index. Blood from healthy volunteers drawn at 0800 was mixed with citrate-citric acid-dextrose (CCD) and centrifuged at 100g to obtain platelet-rich plasma (PRP), transferred to sterile containers, and maintained under ordinary laboratory conditions at room temperature in casually alternating light (L) and darkness (D), in LD 16.8, in continuous light (LL), or in continuous darkness (DD). In 5-ml aliquots of PRP mixed with 500 microliter of 0.34 M EDTA and recentrifuged for 15 min at 200g, a circadian rhythm of GSH per 10(9) platelets was found. The fit to 4-hr data of a linear trend and a 24-hr cosine yields similar acrophases (phi) under the various conditions investigated. With 360 degrees = 24 hr and with 95% limits in parentheses, the acrophases for PRP from a male donor stored in LD, LL, or DD are -64 degrees (-20 degrees, -107 degrees), -67 degrees (-28 degrees, -106 degrees), and -74 degrees (-35 degrees, -112 degrees), respectively. The corresponding values for platelets from a female donor in LD, LL, and DD are -49 degrees (-17 degrees, -80 degrees), -82 degrees (-50 degrees, -113 degrees), and -68 degrees (-29 degrees, -107 degrees), respectively. Six of six best-fitting circadian periods are longer than 24 hr, a result in keeping with a possibly free-running circadian rhythm.(ABSTRACT TRUNCATED AT 250 WORDS)

Isolation of circumferential microtubules from platelets without simultaneous fixation.

Circumferential bands of microtubules (MT) support the discoid shape of resting platelets and participate with the contractile apparatus in shape change and internal contraction following activation. Elucidation of interactions between the circumferential coils and proteins of the stable and contractile cytoskeleton is essential for understanding MT function in platelet physiology. A previous investigation demonstrated that the circumferential rings can be isolated intact from resting platelets following simultaneous exposure to glutaraldehyde and Triton X-100. However, the use of fixation prevented the characterization of protein interactions. The present study has circumvented this problem by developing a procedure for isolating intact microtubule coils from detergent-treated platelets without the use of fixative agents. Incubation of the platelets for intervals of 30 to 60 minutes with the microtubule-stabilizing agent taxol preserved the circumferential bundle after extraction with Triton X-100 even after washing five times. The procedure has made it possible to carry out protein studies on isolated microtubule rings and associated proteins.

Glutathione levels in human platelets display a circadian rhythm in vitro.

Glutathione (GSH) levels were measured in platelet-rich plasma (PRP) and concentrates at 4 hour intervals during storage. The values fell steadily during the first several hours after collection at 9:00 a.m., reaching the lowest level at midnight, 14 hours later. Subsequently, the levels rose to a new peak value at 4:00 a.m. GSH levels continued to show cyclic variation over the 48 hours examined in this study. Change in schedules of light and dark under which the platelets were stored had no effect on GSH periodicity. Platelets from night shift workers also displayed a similar periodicity to that of day workers. Erythrocytes failed to demonstrate a similar time related variation in GSH levels during storage.

Irreversible platelet aggregation does not depend on lipoxygenase metabolites.

Previous investigations in our laboratory demonstrated the existence of an intrinsic mechanism, termed membrane modulation, capable of restoring sensitivity to aspirin treated platelets, resulting in irreversible aggregation in response to arachidonic acid (AA). The mechanism underlying correction of aspirin induced inhibition of platelet function, however, was not clear. In the present study we have evaluated the role of lipoxygenase (LO) metabolites of AA in securing irreversible aggregation of drug induced cyclooxygenase (CO) deficient platelets. Platelets treated with aspirin or Ibuprofen did not convert radiolabeled AA to thromboxane, but generated significant quantities of hydroxy acids via the LO pathway. However, drug exposed platelets, when stirred with epinephrine first and then challenged with AA, aggregated irreversibly. Eicosatetraynoic acid (ETYA 1, U53119) inhibited AA conversion by the LO pathway, whereas 5,8,11,14-eicosatetraynoic acid (ETYA 2) inhibited AA conversion by both CO and LO enzymes. Yet, at the inhibitory concentration these fatty acids failed to prevent AA induced irreversible aggregation of CO deficient, alpha adrenergic receptor stimulated platelets. Results of four studies show that the generation of LO metabolites of AA are not essential for securing irreversible aggregation of platelets.

Effect of age and myocardial infarction on serum and heart lactic dehydrogenase.

The effect of isoproterenol (ISO) on the activity of lactic dehydrogenase (LDH) in the serum and heart was investigated in rats belonging to four different age groups. Serum LDH activity increased in all the ages as a result of ISO injection, however, the magnitude and response varied with age. Younger animals were able to recover from the toxicity of ISO much quicker compared to the older ones. An elevation in the LDH enzyme activity in the serum correlated with a decrease in the activity of cardiac muscle LDH in all the age groups of isoproterenol-treated rats.

Effects of training on the extent of experimental myocardial infarction in aging rats.

The effects of exercise on the severity of isoproterenol-induced myocardial infarction were studied in female albino rats of 20,40,60 and 80 weeks of age. The rats were trained to swim for a specific duration and for a particular period. The occurrence of infarcts were confirmed by histological methods. Elevations in the serum GOT and GPT were maximum in the sedentary-isoproterenols and minimum in the exercise-controls. These changes in the serum transaminases were associated with corresponding depletions in the cardiac GOT and GPT. However, age was seen to interfere with the responses exhibited by the young and old rats. Studies dealing with myocardial infarction are more informative when dealt with age.

Metabolism of the glutamate group of amino acids in rat brain as a function of age.

Metabolism of the glutamate group of amino acids--glutamic acid, gamma-amino-butyric acid, glutamine, aspartic acid and alanine--was studied in the brain of rat as a function of age. The levels of glutamic acid, glutamine and aspartic acid decreased while those of gamma-aminobutyric acid, and alanine increased with age. The results on the activity of the twelve enzymes involved in the metabolism showed that five of them (glutamate dehydrogenase, glutamine synthase, gamma-aminobutyric acid transaminase, succinic semialdehyde dehydrogenase and NAD+-isocitrate dehydrogenase) decreased, while four of them (glutaminase, glutamotransferase, glutamic acid decarboxylase, and alpha-ketoglutarate dehydrogenase) increased. The other three enzymes (aspartate aminotransferase, alanine aminotransferase and NADP+-isocitrate dehydrogenase) did not show any significant change in activity. An age-related increase was seen in alpha-ketoglutarate and ammonia, the intermediates involved in the metabolism of these amino acids. The changes in the level of these amino acids are discussed in relation to the altered energy metabolism during aging.

Age-related effects of nutritional vitamin B6 deficiency on B6-dependent enzymes of glutamate, gamma-aminobutyrate and glutamine systems in the rat brain.

Effect of nutritional vitamin B6 deficiency on the activities of enzymes-glutamic acid decarboxylase (GAD), gamma aminobutyric acid transaminase (GABA-T), aspartate amino-transferase (AsAT), alanine aminotransferase (AlAT) and glutamotransferase (GT) was studied in the rat brain of different age groups. Deficiency was induced at one day (group 1), 21 days (group 2), three months (group 3), 12 months (group 4) and 24 months (group 5) for a period of 3-10 weeks. When the holo and apoenzyme levels were compared in control and B6 deficient rats, it was found that GAD, GABA-T, AsAT and AlAT holoenzyme levels were significantly lower in the deficient rats of all the five groups whereas the level of GT holoenzyme was low only in group 1, the other groups did not show any significant change. GAD apoenzyme level was significantly higher in the deficient animals of group 1 and 2 while the reverse was true for GABA-T apoenzyme and no significant variation was seen in the older groups. It is interesting to note that the level of AsAT apoenzyme was significantly low in older age groups (4, 5) as a function of B6 deficiency, while AlAT and GT apoenzymes were not affected in any age group studied.

Murine regional brain monoamine oxidase activity: time- and age-dependent response to inhibitors.

The inhibitory effect of procaine hydrochloride and Gerovital-H3 on monoamine oxidase (MAO) activity in the rat brain was studied at six time points during the 24-hour cycle. It was found that the percent inhibition is time dependent. Both drugs showed maximum inhibition when the MAO activity was at the lowest values during the 24-hour period. In addition to time dependence, these drugs are also age dependent because the MAO activity varies with age.

Circadian variations in the monoamine levels and monoamine oxidase activity in different regions of the rat brain as a function of age.

Time-related changes in the levels of norepinephrine (NE), dopamine (DA), 5-hydroxytryptamine (5-HT) and monoamine oxidase (EC 1.4.3.4, MAO) activity have been studied in the cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum and midbrain of 21 day, 3, 6, 12 and 24 month old rats maintained at 12 hours of light and 12 hours of dark condition. Maximum NE level was seen during the dark phase in all the regions of 3, 6, 12 and 24 month old rats, whereas in 21 day old, the maximum NE level occurred during the light phase. In the cerebral cortex and in the cerebellum of 21 day old rat DA was absent at all times. In all the other age groups, the maximum DA level was seen during the dark phase, while for 5-HT higher level was during the light phase in all the age groups. MAO activity of 3, 6, 12 and 24 month old rats showed the peak activity at the beginning of the light phase (06:00 hours), whereas cerebral cortex, cerebellum and medulla oblongata of 21 day old rat had its peak MAO activity at 14:00 hours and at 22:00 hours in other regions.

Effect of phase shift on monoamine oxidase activity in different regions of the rat brain as a function of age.

The effect of reversed light-dark cycle on the monoamine oxidase activity of different regions of the rat brain in various age groups was studied. Twenty-one-day-old rats showed an irregular pattern of shift in the appearance of the peak activity. In the case of 3-, 6-, and 12-month-old rats, all the regions of the brain became synchronized to the altered environmental condition, and the peak MAO activity was shifted by 180 degrees. In the cerebral cortex of 24-month-old rats the peak was shifted by only 60 degrees, whereas a 120 degrees shift was observed for all the other regions. The present study suggests that the synchronizing effect of the light-dark cycle is age dependent.

Effect of docosahexaenoic acid (DHA) on arachidonic acid metabolism and platelet function.

Studies from our laboratory have suggested a role for ferrous iron in the metabolism of arachidonic acid and demonstrated that inhibitors of prostaglandin synthesis exert their effect by complexing with the heme group of cyclooxygenase. Docosahexaenoic acid (DHA) is a potent competitive inhibitor of arachidonic acid metabolism by sheep vesicular gland prostaglandin synthetase. In this study we have evaluated the effect of exogenously added DHA on platelet function and arachidonic acid metabolism. DHA at 150 microM concentration inhibited aggregation of platelets to 450 microM arachidonic acid. At this concentration DHA also inhibited the second wave of the platelet response to the action of agonists such as epinephrine, adenosine diphosphate and thrombin. Inhibition induced by this fatty acid could be overcome by the agonists at higher concentrations. DHA inhibited the conversion of labeled arachidonic acid to thromboxane by intact, washed platelet suspensions. However, platelets in plasma incubated first with DHA then washed and stirred with labeled arachidonate generated as much thromboxane as control platelets. These results suggest that the polyenoic acids, if released in sufficient quantities in the vicinity of cyclooxygenase, could effectively compete for the heme site and inhibit the conversion of arachidonic acid.

Monoamine levels and monoamine oxidase activity in different regions of rat brain as a function of age.

The levels of norepinephrine, dopamine, 5-hydroxytryptamine and the activity of monoamine oxidase were estimated in cerebral cortex, cerebellum, medulla oblongata, hypothalamus, striatum and midbrain of 21-day-old, 3-, 6-, 12- and 24-month-old male albino rats of Wistar strain. No significant change with age was found in the levels of all the three amines in cerebral cortex and cerebellum, while medulla oblongata showed a significant decrease of all the amines by 24 months of age. Hypothalamic norepinephrine, dopamine and striatal dopamine showed a highly significant decrease by 24 months of age, whereas 5-hydroxytryptamine in hypothalamus, norepinephrine and 5-hydroxytryptamine in striatum and dopamine in midbrain did not show any appreciable change with age. Monoamine oxidase activity in all the regions except cerebellum showed a significant increase by 24 months of age compared to 3- and 6-month-old rats.

Effect of exercise on protein degradation: 3-methylhistidine and creatinine excretion.

The effect of 1 hr of intensive exercise per day on protein breakdown was studied in a group of young male volunteers (20-25 years old) who were on a meat-free diet during the entire period of the study. Urinary 3-methylhistidine and creatinine were estimated as index of protein degradation. When studied over a period of 24 hr at different time points, the mean rates of 3-methylhistidine excretion were 2.4 and 2.9 nmole/min/kg for the day of exercise and nonexercise, respectively. Immediately following the exercise period, 3-methylhistidine and creatinine excretion rates decreased significantly.

Age-related changes in cardiac muscle of rat.

Study of the age-related changes in cardiac muscle of 5, 10, 15, 20, and 25 months old albino rats showed that the muscle mass decreased by 10% while the ratio of the weight of cardiac muscle to body weight decreased by 30% between 5 and 25 months. Autolytic and proteolytic activity of sarcoplasmic proteins increased remarkably (70% and 200%, respectively) between 5 and 25 months of age. Although the total protein content decreased, the amount of fibrous protein (collagen) increased by 50%. Levels of salt soluble and labile collagen (free hydroxyproline released at 65 degrees C in Ringer solution) decreased by 65% and 50%, respectively, while insoluble collagen increased by 180% with advance in age from 5 to 25 months. Increase in acid soluble collagen was seen only up to 20 months of age. The acid mucopolysaccharide content decreased, whereas the activity of beta-glucuronidase showed an increase from 110-148 units between 10 and 15 months of age. beta-N-acetylglucosaminidase increased by 25% as the age increased from 5 to 25 months.