Abstract: Fishes, in general, follow ammonotelic mode of excretion. However, certain stress factors may provoke them to excrete urea. In the present study, the possible role of ureogenesis to avoid accumulation of toxic ammonia under water-restricted condition was tested in Heteropneustes fossilis. A total of hundred fishes were collected and sacrificed. Excretory urea and ammonia were estimated in the water of the aquarium and glutamate dehydrogenase acitivity was measured in the hepatic tissue. During the experimental period, excretory ammonia in Heteropneustes fossilis was found between 931% to 16% above the baseline ammonia and excretory urea was found between 112% to 898% above the baseline urea. A high degree of correlation with r (coefficient of correlation) above 0.9 is observed between excretory ammonia and urea in Heteropneustes fossilis. However, only a moderate degree of correlation is observed between the activity of glutamate dehydrogenase and excretory ammonia and urea.
Abstract: The kinetic properties of enzymes are often reported
using the apparent KM and Vmax appropriate to the standard
Michaelis-Menten enzyme. However, this model is inappropriate to
enzymes that have more than one substrate or where the rate
expression does not apply for other reasons. Consequently, it is
desirable to have a means of estimating the appropriate kinetic
parameters from the apparent values of KM and Vmax reported for each
substrate. We provide a means of estimating the range within which
the parameters should lie and apply the method to data for glutamate
dehydrogenase from the nematode parasite of sheep Teladorsagia
circumcincta.
Abstract: Influence of octane and benzene on plant cell
ultrastructure and enzymes of basic metabolism, such as nitrogen
assimilation and energy generation have been studied. Different
plants: perennial ryegrass (Lolium perenne) and alfalfa (Medicago
sativa); crops- maize (Zea mays L.) and bean (Phaseolus vulgaris);
shrubs – privet (Ligustrum sempervirens) and trifoliate orange
(Poncirus trifoliate); trees - poplar (Populus deltoides) and white
mulberry (Morus alba L.) were exposed to hydrocarbons of different
concentrations (1, 10 and 100 mM). Destructive changes in bean and
maize leaves cells ultrastructure under the influence of benzene
vapour were revealed at the level of photosynthetic and energy
generation subcellular organells. Different deviations at the level of
subcellular organelles structure and distribution were observed in
alfalfa and ryegrass root cells under the influence of benzene and
octane, absorbed through roots. The level of destructive changes is
concentration dependent. Benzene at low 1 and 10 mM concentration
caused the increase in glutamate dehydrogenase (GDH) activity in
maize roots and leaves and in poplar and mulberry shoots, though to
higher extent in case of lower, 1mM concentration. The induction
was more intensive in plant roots. The highest tested 100mM
concentration of benzene was inhibitory to the enzyme in all plants.
Octane caused induction of GDH in all grassy plants at all tested
concentrations; however the rate of induction decreased parallel to
increase of the hydrocarbon concentration. Octane at concentration 1
mM caused induction of GDH in privet, trifoliate and white mulberry
shoots. The highest, 100mM octane was characterized by inhibitory
effect to GDH activity in all plants. Octane had inductive effect on
malate dehydrogenase in almost all plants and tested concentrations,
indicating the intensification of Trycarboxylic Acid Cycle.
The data could be suggested for elaboration of criteria for plant
selection for phytoremediation of oil hydrocarbons contaminated
soils.