Identification of cyclopentenyl fatty acids by gas liquid chromatography and mass spectrometry

The straight chain fatty acids and the cyclopentenyl fatty acids present in the lipids of Hydnocarpus wightiana seeds were separated as their pyrrolidides by means of gas chromatography. A gas chromatography-mass spectrometry system confirmed the complete separation and permitted the identification of the individual components in the sample.     

In-vitro modulation of protein kinase C activity by environmental chemical pollutants

A number of environmental chemical pollutants have been reported to cause tumors or help in the propagation of tumors in experimental animals. The in-vitro effects of a few chemical contaminants were studied on the histone phosphorylation and 3H Phorbol dibutyrate (PdBu) binding of partially purified Ca2+/phospholipid dependent protein kinase c (PKC) from the brains of Fischer F344 and B6C3F1 mice. The enzyme was prepared by a modified method which gave approximately 75-fold purification. A differential effect of various compounds was observed on the phosphorylation activity and PdBu binding of PKC from rats and mice. The reported tumor promoting ability and effect on protein kinase C activity appeared to be related in the case of the rat enzyme, although causality cannot be inferred.     

The two pathways for oxygen exchange by actomyosin and myofibrils and their dependence on temperature

At an intermediate stage in the hydrolysis of MgATP by actomyosin there is an exchange of oxygen between water and the terminal phosphoryl group of MgATP, tightly bound to the myosin active site. This intermediate oxygen exchange results from the reversible hydrolysis of the bound MgATP. The rate of the exchange cycle (hydrolysis and the reverse) is assumed to be determined by the rate of reverse hydrolysis; and the average time available for exchange is determined by the post-exchange reaction that immediately follows the cycle. Past analytical studies of the exchange, using actomyosin mixtures and myofibrils at room temperature, have revealed two pathways for hydrolysis, operating at a comparable flux but differing greatly in the extent of exchange they support. It is shown here that these pathways also appear over a range of temperatures from 5 to 30 degrees C and that temperature had little effect on their relative fluxes. At each temperature, the flux ratio (%) for the low exchange pathway: high exchange pathway was near 50:50 for actomyosin mixtures and 60:40 for myofibrils. Apparently, the rate-limiting steps that determine the fluxes of the two pathways have a similar temperature dependence. However, the analysis indicates that one or both of the steps that determine the extent of exchange (reverse-hydrolysis and/or the post-exchange reaction) shows a different temperature dependence for the two pathways. We interpret this to reflect a difference in the temperature dependence of the post-exchange reaction, which we propose is exceedingly fast and independent of actin concentration along the low exchange route, but slow and dependent on the actin concentration along the high exchange route. Thus at all temperatures over a broad range of actin concentration there are two pathways of comparable flux that differ primarily in the time available for exchange.     

Effects of dispersal on the stability of a prey-predator system with functional response

Using Liapunov's direct method, effects of dispersal on the linear and nonlinear stability of the equilibrium state for a prey-predator system with functional response are investigated. It is noted that the functional response has a destabilizing effect. It is shown that an otherwise linearly or nonlinearly stable equilibrium state of the system remains so with dispersal as well, even with functional response. It is further established that if the equilibrium state is linearly stable a subregion of the positive quadrant can be found in the phase plane where it is nonlinearly stable with or without dispersal.     

Crocodilian Nest in a Late Cretaceous Sauropod Hatchery from the Type Lameta Ghat Locality,Jabalpur, India

The well-known Late Cretaceous Lameta Ghat locality (Jabalpur, India) provides a window of opportunity to study a large stable, near shore sandy beach, which was widely used by sauropod dinosaurs as a hatchery. In this paper, we revisit the eggs and eggshell fragments previously assigned to lizards from this locality and reassign them to crocodylomorphs. Several features point to a crocodilian affinity, including a subspherical to ellipsoidal shape, smooth, uneven external surface, discrete trapezoid shaped shell units with wide top and narrow base, basal knobs and wedge shaped crystallites showing typical inverted triangular extinction under crossed nicols. The crocodylomorph eggshell material presented in this paper adds to the skeletal data of these most probably Cretaceous-Eocene dryosaurid crocodiles.     

Acetate and Bicarbonate Assimilation and Metabolite Formation in Chlamydomonas reinhardtii: A 13C-NMR Study

Cellular metabolite analyses by ¹³C-NMR showed that C. reinhardtii cells assimilate acetate at a faster rate in heterotrophy than in mixotrophy. While heterotrophic cells produced bicarbonate and CO₂ ^aq, mixotrophy cells produced bicarbonate alone as predominant metabolite. Experiments with singly ¹³C-labelled acetate (¹³CH₃-COOH or CH₃-¹³COOH) supported that both the ¹³C nuclei give rise to bicarbonate and CO₂ ^aq. The observed metabolite(s) upon further incubation led to the production of starch and triacylglycerol (TAG) in mixotrophy, whereas in heterotrophy the TAG production was minimal with substantial accumulation of glycerol and starch. Prolonged incubation up to eight days, without the addition of fresh acetate, led to an increased TAG production at the expense of bicarbonate, akin to that of nitrogen-starvation. However, such TAG production was substantially high in mixotrophy as compared to that in heterotrophy. Addition of mitochondrial un-coupler blocked the formation of bicarbonate and CO₂ ^aq in heterotrophic cells, even though acetate uptake ensued. Addition of PSII-inhibitor to mixotrophic cells resulted in partial conversion of bicarbonate into CO₂ ^aq, which were found to be in equilibrium. In an independent experiment, we have monitored assimilation of bicarbonate via photoautotrophy and found that the cells indeed produce starch and TAG at a much faster rate as compared to that in mixotrophy and heterotrophy. Further, we noticed that the accumulation of starch is relatively more as compared to TAG. Based on these observations, we suggest that acetate assimilation in C. reinhardtii does not directly lead to TAG formation but via bicarbonate/CO₂ ^aq pathways. Photoautotrophic mode is found to be the best growth condition for the production of starch and TAG and starch in C. reinhardtii.