Some Biochemical Abnormalities Caused by Cypermethrin in Adults of Tribolium castaneum (Herbst.)

Biochemical effects of sub lethal doses LC₁₀ and LC₂₀ of cypermethrin were studied on some enzymes and macromolecule activities of adult beetles of Tribolium castaneum (Herbst.). Cypermethrin caused disturbances in levels of all biochemical components under study. The dose of 0.78 ppm caused abnormalities in α‐amylase and FAA by increasing their activities i.e., 45.45% and 21.97% significantly. The higher sub lethal dose of 2.62 ppm disturbed all the parameters (AcP, α‐amylase, soluble protein and FAA) except AkP, which was decreased by 93.06%. Moreover, sub lethal doses either increased or decreased the levels of all parameters non‐significantly except AkP and FAA which were effected significantly by 87.92% and 14.29% at lower and higher doses, respectively. In the present studies, cypermethrin significantly enhanced the activity of AkP in both susceptible and resistant strains of T. castaneum adult beetles while FAA contents were increased significantly in resistant strain only. The activity of α‐amylase was significantly lowered in susceptible strain only.     

Effect of pH and calcium on short-term NO3- fluxes in roots of barley seedlings

The effect of pH and Ca2+ on net NO3- uptake, influx, and efflux by intact roots of barley (Hordeum vulgare L.) seedlings was studied. Seedlings were induced with NO3- or NO2-. Net NO3- uptake and efflux, respectively, were determined by following its depletion from, and accumulation in, the external solution. Since roots of both uninduced and NO2(-)-induced seedlings contain little internal NO3- initial net uptake rates are equivalent to influx (M. Aslam, R.L. Travis, R.C. Huffaker [1994] Plant Physiol 106: 1293-1301). NO3-, uptake (influx) by these roots was little affected at acidic pH. In contrast, in NO3(-)-induced roots, which accumulate NO3-, net uptake rates decreased in response to acidic pH. Under these conditions, NO3- efflux was stimulated and was a function of root NO3- concentration. Conversely, at basic pH, NO3- uptake by NO3- and NO2(-)-induced and uninduced roots decreased, apparently because of the inhibition of influx. Calcium had little effect on NO3- uptake (influx) by NO2(-)-induced roots at either pH 3 or 6. However, in NO3(-)-induced roots, lack of Ca2+ at pH 3 significantly decreased net NO3- uptake and stimulated efflux. The results indicate that at acidic pH the decrease in net NO3- uptake is due to the stimulation of efflux, whereas at basic pH, it is due to the inhibition of influx.     

Native Enzyme Mobility Shift Assay (NEMSA): a new method for monitoring carboxyl group modification of carboxymethylcellulase from Aspergillus niger

A simple, sensitive, accurate and more informative assay for determining the number of modified groups during the course of carboxyl group modification is described. Monomeric carboxymethylcellulase (CMCase) from Aspergillus niger was modified by 1-ethyl-3(3-dimethylaminopropyl)carbodiimide (EDC) in the presence of glycinamide. The different time-course aliquots were subjected to non-denaturing PAGE and the gel stained for CMCase activity. The number of carboxyl groups modified are directly read from the ladder of the enzyme bands developed at given time. This method showed that after 75 min of modification reaction there were five major species of modified CMCases in which 6 to 10 carboxyls were modified.     

Presynaptic Adenosine A2 and N-Methyl-D-Aspartate Receptors Regulate Dopamine Synthesis in Rat Striatal Synaptosomes

Dopamine synthesis rate and cyclic AMP concentration were measured in synaptosomes prepared from rat striatum. Dopamine synthesis rate was decreased by the addition of either adenosine deaminase or 8-phenyltheophylline, an adenosine receptor blocker, and was increased by the addition of 2-chloroadenosine. The addition of L-glutamate in the absence of adenosine deaminase decreased both dopamine synthesis rate and cyclic AMP concentration; in the presence of adenosine deaminase, glutamate had no effect on basal dopamine synthesis, but enhanced K(+)-stimulated synthesis. Both these effects of glutamate were abolished in Ca2(+)-free medium or in the presence of 2-amino-5-phosphonovalerate, an N-methyl-D-aspartate (NMDA) receptor blocker. In Mg2(+)-free medium with adenosine deaminase, glutamate enhanced both basal and K(+)-stimulated synthesis. These results suggest that dopaminergic terminals have A2 adenosine receptors, whose activation can stimulate dopamine synthesis by a cyclic AMP-dependent mechanism, and NMDA receptors, which modulate dopamine synthesis by a Ca2(+)-dependent mechanism.     

Glutamine Synthetase in Oligodendrocytes and Astrocytes: New Biochemical and Immunocytochemical Evidence

The results of recent immunocytochemical experiments suggest that glutamine synthetase (GS) in the rat CNS may not be confined to astrocytes. In the present study, GS activity was assayed in oligodendrocytes isolated from bovine brain and in oligodendrocytes, astrocytes, and neurons isolated from rat forebrain, and the results were compared with new immunochemical data. Among the cells isolated from rat brain, astrocytes had the highest specific activities of GS, followed by oligodendrocytes. Oligodendrocytes isolated from white matter of bovine brain had GS specific activities almost fivefold higher than those in white matter homogenates. Immunocytochemical staining also showed the presence of GS in both oligodendrocytes and astrocytes in bovine forebrain, in three white-matter regions of rat brain, and in Vibratome sections as well as paraffin sections.     

Tryptophan-dependent biosynthesis of auxins in soil

The presence of auxins in soil may have an ecological impact affecting plant growth and development. A rapid and simple colorimetric method was used to assess California soils for their potential to produce auxins upon the addition of L-tryptophan (L-TRP). The auxin content measured by colorimetry was expressed as indole-3-acetic acid (IAA)-equivalents. A substrate (L-TRP) concentration of 5.3 g kg^-1, glucose concentration of 6.7 g kg^-1, no nitrogen, pH 7.0, 40°C, shaking (aeration) and 48 h incubation time were selected as standardized conditions to assay for auxin biosynthesis in soil. IAA was confirmed as a major microbial metabolite derived from L-TRP in soil by use of high performance liquid chromatography (HPLC). Under standardized conditions, L-TRP-derived auxins in 19 soils varied greatly ranging from 18.2 to 303.2 mg IAA equivalents (auxins) kg^-1 soil. This study suggests that the phenotypic character of the soil microbiota has more of an influence on auxin production than the soil physicochemical properties (e.g., pH, organic C content, CEC, etc.).     

Enzymatic studies during spontaneous cell rupture of Saccharomyces cerevisiae

Summary Some of the extract and intracellular enzyme activities in K2nB strain of Saccharomyces cerevisiae that growing in the condition which induce spontaneous cell rupture, were measured. B-1-3-glucanase, invertase, acid phosphatase and active chitin synthetase zymogen showed a reduced activity in ruptured cell while alkaline phosphatase shows no differences in its activity.     

Mechanistic studies on C-19 demethylation in oestrogen biosynthesis

Mechanistic aspects of the biosynthesis of oestrogen have been studied with a microsomal preparation from full-term human placenta. The overall transformation, termed the aromatization process, involves three steps using O₂ and NADPH, in which the C-19 methyl group of an androgen is oxidised to formic acid with concomitant production of the aromatic ring of oestrogen: [Formula: see text] To study the mechanism of this process in terms of the involvement of the oxygen atoms, a number of labelled precursors were synthesized. Notable amongst these were 19-hydroxy-4-androstene-3,17-dione (II) and 19-oxo-4-androstene-3,17-dione (IV) in which the C-19 was labelled with ²H in addition to ¹⁸O. In order to follow the fate of the labelled atoms at C-19 of (II) and (IV) during the aromatization, the formic acid released from C-19 was benzylated and analysed by mass spectrometry. Experimental procedures were devised to minimize the exchange of oxygen atoms in substrates and product with oxygens of the medium. In the conversion of the 19-[¹⁸O] compounds of types (II) and (IV) into 3-hydroxy-1,3,5-(10)-oestratriene-17-one (V, oestrone), it was found that the formic acid from C-19 retained the original substrate oxygen. When the equivalent ¹⁶O substrates were aromatized under ¹⁸O₂, the formic acid from both substrates contained one atom of ¹⁸O. It is argued that in the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), the C-19 oxygen of the former remains intact and that one atom of oxygen from O₂ is incorporated into formic acid during the conversion of the 19-oxo compound (IV) into oestrogen. This conclusion was further substantiated by demonstrating that in the aromatization of 4-androstene-3,17-dione (I), both the oxygen atoms in the formic acid originated from molecular oxygen. 10β-Hydroxy-4-oestrene-3,17-dione formate, a possible intermediate in the aromatization, was synthesized and shown not to be converted into oestrogen. In the light of the cumulative evidence available to date, stereochemical aspects of the conversion of the 19-hydroxy compound (II) into the 19-oxo compound (IV), and mechanistic features of the C-10–C-19 bond cleavage step during the conversion of the 19-oxo compound (IV) into oestrogen are discussed.     

Glycerol Phosphate Dehydrogenase, Glucose-6-Phosphate Dehydrogenase, and Lactate Dehydrogenase: Activities in Oligodendrocytes, Neurons, Astrocytes, and Myelin Isolated from Developing Rat Brains

Abstract: Glycerol phosphate dehydrogenase (GPDH), glucose-6-phosphate dehydrogenase (G6PDH), and lactate dehydrogenase (LDH) activities were determined in Oligodendrocytes, neurons, and astrocytes isolated from the brains of developing rats. The activity of each enzyme was significantly lower in both neurons and astrocytes than in Oligodendrocytes. The GPDH activity in Oligodendrocytes increased more than 4-fold during development, and at 120 days cells of this type had 1.4-fold the specific activity of forebrain homogenates. The G6PDH activities in Oligodendrocytes from 10-day-old rats were 1.4-fold the activities in the forebrain homogenates. The activities of this enzyme in Oligodendrocytes were progressively lower at later ages, such that at 120 days the cells had 0.8 times the specific activities of homogenates. The Oligodendrocytes had 0.6 times the homogenate activities of LDH at 10 days, and this ratio had decreased to 0.2 by 120 days. These enzymes were also measured in myelin isolated from 20-, 60-, and 120-day-old rats. By 120 days the specific activities of G6PDH and LDH in myelin were <8% of the respective activities in homogenates. The GPDH activity in myelin was, however, at least 20% the specific activity in the homogenates, even in the oldest animals. It is proposed that LDH could be used as a marker for oligodendroglial cytoplasm in subfractions of myelin and in myelin-related membrane vesicles.