Inhibition of thymidine kinase activity by hydroxyurea during highly and less proliferative regions of rat brain

Hydroxyurea, when injected intraperitoneally, exerted marked inhibition on the activity of thymidine kinase in 5 day old postnatal cerebellum and 15 day old embryonic cerebrum. However, it failed to show any sustained inhibition on thymidine kinase activity in 5 day old postnatal cerebrum. In this case, the marginal decrease of thymidine kinase activity noticed during early intervals reversed back to more than normal value at a later time interval. These results along with our earlier findings are taken to indicate the differential action of this drug on thymidine kinase activity in rapidly and slowly proliferating regions of rat brain     

Mobilization and exudation of photo-assimilated14C by developing pods of groundnut (Arachis hypogaea L.)

Summary ‘Pod washings’ were collected from groundnut at three hour intervals for 24 hours after feeding the plants with¹⁴CO₂. Low radioactivity was found in the first four ‘Pod washings’ of 10 day old pods and the radioactivity increased with time. Highest radioactivity was found in washings of 20 and 30 day old pods and was twice the activity found in the washings of 50 day old pods. The radioactivity of both ethanol-soluble and insoluble fractions in pods was determined. The radioactivity mobilized into the pods increased with age and it was highest in 50 day old pods. The influence of the pod exudates on geocarposphere microflora during pod development is discussed.     

Axial dispersion in plate-pulsed columns

The residence time distribution (RTD) of the phase under continuous flow and dispersed flow was measured in a plate-pulsed column under countercurrent liquid-liquid flow, and modelled using (i) the axial dispersion model and (ii) the noninteger ideal stage cascade model. The axial mixing in the continuous phase was found to be significantly higher than in the dispersed phase. The model parameters were related to the operating conditions and system variables.     

Modeling of RNA nanotubes using molecular dynamics simulation

In this study, we construct novel RNA nanoclusters, RNA nanotubes made of several nanorings up to the size of 20 nm, utilizing the molecular dynamics simulation, and study their structural properties [i.e., the root mean square deviation, the radius of gyration and the radial distribution function (RDF)] in physiological solutions that can be used for drug delivery into the human body. The patterns of energy and temperature variations of the systems are also discussed. Furthermore, we study the concentration of ions around the tube as a function of time at a particular temperature. We have found that when the temperature increases, the number of ions increases within a certain distance of the tube. We report that the number of ions within this distance around the tubes decreases in quenched runs. This indicates that some ions evaporate with decrease in temperature, as has been observed in the case of the nanoring. RDF plots also demonstrate a similar trend with temperature, as was found in the case of RNA nanorings.     

Effects of sex hormones on enzymic esterification of 2-(N-hydroxyacetamido)-fluorene by rat liver cytosol

1. Enzymic esterifications of 2-(N-hydroxyacetamido)fluorene and several other hydroxamic acids by liver cytosol were studied. Determination of 2-acetamido-3-methylthiofluorene was used for the assay. 2. With rat liver cytosol, requirement for ATP, Mg²⁺ and SO₄²⁻ suggested formation of phosphate and sulphate esters of 2-(N-hydroxyacetamido)fluorene. 3. Rats showed sex and age differences in their activity. Liver from adult male rat was at least twice as active as liver from adult female rat. No such sex differences were found in mice, hamsters and guinea pigs. 4. Administration of testosterone (300μg/day) subcutaneously for 8 days increased the activity in the female rat by 100%, whereas diethylstilboestrol (100μg/day) had no effect. In the male rat diethylstilboestrol treatment decreased the activity by 60%, whereas testosterone pretreatment was without any effect. 5. Among various endocrine ablations such as adrenalectomy, castration, adrenalectomy–castration and hypophysectomy in the adult male rat, hypophysectomy was found to be the most effective in decreasing the activity of the liver to about 50% of control values. 6. Like 2-(N-hydroxyacetamido)fluorene, various other N-hydroxy derivatives of 2-acetamido-7-fluorofluorene, 2-acetamidophenanthrene, 4-acetamidobiphenyl and 4-acetamidostilbene were also shown to be esterified to different extents by rat liver cytosol.     

Optimization of parameters in the batch kinetic studies of glucose isomerisation by arthrobacter sp.

Vital parameters like temperature, pH and agitation are optimized in the kinetic studies of glucose isomerisation carried out in a batch fashion. A 4-litre fermentor with temperature, pH, agitation and other controls is used. It is found that the two parameters — temperature and pH, do not have an interacting effect on each other. A temperature of 60°C, a pH of 8.0 and a speed of 200 rpm are found to be better suited for the production of fructose syrups starting from glucose by arthrobacter sp. An upper limit of 20 minutes on the residence time is suggested for use in the design of flow reactors.     

Reactive phosphate ester of the carcinogen 2-(N-hydroxy)acetamidofluorene

1. Reaction of 2-(N-acetoxy)-acetamidofluorene with orthophosphate buffer at pH7 yielded a large quantity of water-soluble fluorene derivatives, which showed absorption peaks at 303, 290 and 280nm. Tris buffer under similar conditions gave negligible reaction. 2. Hydrolysis of polar material with acid or alkaline phosphatases liberated equimolar amounts of inorganic phosphate and an ether-extractable fluorene derivative. On the basis of its u.v. spectrum, R(F) values after paper chromatography, solubility in alkali and colour with spray reagents, the derivative was characterized tentatively as 2-acetamido-5-hydroxyfluorene. 3. Polar material also contained a reactive fluorene derivative which gave characteristic reaction products with methionine and guanosine. The reactive derivative was characterized as a phosphate ester of 2-(N-hydroxy)-acetamidofluorene. 4. It is suggested that such reactive phosphate esters may also be some of the ultimate carcinogenic metabolites of carcinogenic aromatic hydroxamic acids.     

Induction of experimental autoimmune Graves' disease in BALB/c mice.

We immunized BALB/c mice with M12 cells (H-2d) expressing either mouse (mM12 cells) or human thyrotropin receptor (TSHR) (hM12 cells). Immunized mice developed autoantibodies to native TSHR by day 90 and, by day 180, showed considerable stimulatory Ab activity as measured by their ability to enhance cAMP production (ranging from 6. 52 to 20.83 pmol/ml in different treatment groups relative to 1.83 pmol/ml for controls) by TSHR-expressing Chinese hamster ovary cells. These mice developed severe hyperthyroidism with significant elevations in both tetraiodothyronine and triiodothyronine hormones. Tetraiodothyronine levels in different experimental groups ranged from a mean of 8.66-12.4 microg/dl, relative to 4.8 microg/dl in controls. Similarly, mean triiodothyronine values ranged from 156.18 to 195.13 ng/dl, relative to 34.99 ng/dl for controls. Next, we immunized BALB/c mice with a soluble extracellular domain of human TSHR (TBP), or TBP expressed on human embryonic kidney cells (293 cells) (293-TBP cells). These mice showed severe hyperthyroidism in a manner very similar to that described above for mice immunized with the mouse TSHR or human TSHR, and exhibited significant weight loss, with average weight for treatment groups ranging from 20.6 to 21.67 g, while controls weighed 24.2 g. Early after onset of the disease, histopathological examination of thyroids showed enlargement of colloids and thinning of epithelial cells without inflammation. However, later during disease, focal necrosis and lymphocytic infiltration were apparent. Our results showed that conformationally intact ectodomain of TSHR is sufficient for disease induction. Availability of a reproducible model in which 100% of the animals develop disease should facilitate studies aimed at understanding the molecular pathogenesis of Graves' disease.     

Intermittent hypoxia activates peptidylglycine alpha-amidating monooxygenase in rat brain stem via reactive oxygen species-mediated proteolytic processing

Intermittent hypoxia (IH) associated with sleep apneas leads to cardiorespiratory abnormalities that may involve altered neuropeptide signaling. The effects of IH on neuropeptide synthesis have not been investigated. Peptidylglycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3) catalyzes the alpha-amidation of neuropeptides, which confers biological activity to a large number of neuropeptides. PAM consists of O(2)-sensitive peptidylglycine alpha-hydroxylating monooxygenase (PHM) and peptidyl-alpha-hydroxyglycine alpha-amidating lyase (PAL) activities. Here, we examined whether IH alters neuropeptide synthesis by affecting PAM activity and, if so, by what mechanisms. Experiments were performed on the brain stem of adult male rats exposed to IH (5% O(2) for 15 s followed by 21% O(2) for 5 min; 8 h/day for up to 10 days) or continuous hypoxia (0.4 atm for 10 days). Analysis of brain stem extracts showed that IH, but not continuous hypoxia, increased PHM, but not PAL, activity of PAM and that the increase of PHM activity was associated with a concomitant elevation in the levels of alpha-amidated forms of substance P and neuropeptide Y. IH increased the relative abundance of 42- and 35-kDa forms of PHM ( approximately 1.6- and 2.7-fold, respectively), suggesting enhanced proteolytic processing of PHM, which appears to be mediated by an IH-induced increase of endoprotease activity. Kinetic analysis showed that IH increases V(max) but has no effect on K(m). IH increased generation of reactive oxygen species in the brain stem, and systemic administration of antioxidant prevented IH-evoked increases of PHM activity, proteolytic processing of PHM, endoprotease activity, and elevations in substance P and neuropeptide Y amide levels. Taken together, these results demonstrate that IH activates PHM in rat brain stem via reactive oxygen species-dependent posttranslational proteolytic processing and further suggest that PAM activation may contribute to IH-mediated peptidergic neurotransmission in rat brain stem.