Total diet of Kuwait was assessed for the residues of chlorinated pesticides. 140 core samples along with 90 additional samples (collected during 1995–96) were analyzed following US FDA multiresidue ...procedures. The results showed that 17.6% of the core samples contained detectable residues. Chlorpyrifos-methyl was present (ranging from 0.05 to 0.72 mg/kg) in most of the positive samples. Wheat flour was the single important source of this residue in the diet. Residues of chlorpyrifos, vinclozolin, procymidon and captan were also detected in some fresh fruits and vegetable. In general, residue levels were quite low and were significantly below the maximum residue limits (MRLs) established for these pesticides in food.
Breast milk samples, randomly collected from 32 Kuwaiti donors were analysed for chlorinated pesticides. DDE residues ranged from 127 to 3333 micrograms/kg, averaging, 833 micrograms/kg, expressed on ...a fat weight basis. DDT levels ranged from 0.6 to 67 micrograms/kg fat and averaged 12.4 micrograms/kg, fat. High DDE/DDT ratios were found, which indicated that the exposure to DDT, in most cases, happened quite some time ago. In addition many of the samples also contained isomers of HCH, heptachlor-epoxide, aldrin, dieldrin and endrin. Residue levels of non-DDT pesticides were generally low. Overall levels of DDT-pesticides in Kuwaiti milk samples were lower than levels reported from other Middle Eastern countries, although methodologies may not be directly comparable.
Comparative studies were carried out on the interaction of Rhizopus delemar C-lipase with 1, 1, 1-trichloro-2, 2-bis(4-chlorophenyl)ethane (DDT), 2, 2-bis(4-chlorophenyl)ethane (DIM), ...dichlorobenzophenone (DCBP) and aldrin by means of 2-hydroxy-5-nitrobenzylation of tryptophan (Trp) residues on the 1 : 1, 2 : 1 and 9 : 1 (7 : 1 with aldrin) pesticide-lipase complexes.2-Hydroxy-5-nitrobenzylation was carried out under three conditions : modification with a water-soluble modification reagent, with the same reagent in the presence of olive oil emulsion and with a fat-soluble modification reagent in the presence of emulsion. The Trp residues involved in ligand-binding were specified in tems of their modification patterns.Modification revealed that the binding of pesticide involves five exposed Trp residues. The modification patterns are distinctly different depending on the sort of pesticide. This is consistent with the previous observation that the binding of the above four pesticides affects the binding properties of the lipase quite differently depending on the sort of pesticide. It is suggested for DDT, DIM and DCBP that the binding of the first pesticide molecule, which governs the ensuing complex formation, involves the same Trp residue. This would indicate the presence of three overlapping binding sites for each of three pesticides. On the other hand, firstly binding two aldrin molecules bind to a region not involving a Trp residue.
Tryptophan (Trp) residues involved in the binding of 1, 1, 1-trichloro-2, 2-bis(4-chlorophenyl)ethane (DDT), 2, 2-bis(4-chlorophenyl)ethane (DIM) and dichlorobenzophenone (DCBP) by Rhizopus delemar ...C-lipase were identified on the basis of knowledge of amino acid sequences around the Trp residues. Eight Trp- or modified Trp-containing peptides were isolated from each of 1 : 1, 2 : 1 and 9 : 1 pesticide-lipase complexes modified by 2-hydroxy-5-nitrobenzylation under three different conditions, and the peptides were identified.The results confirm the previous tentative assignment of the Trp residues involved in the ligand binding, which was presented on the basis of comparison of their modification patterns.
Rhizopus delemar C-lipase (E) binds 1, 1, 1-trichloro-2, 2-bis(4-chlorophenyl)ethane (D or DDT) to form stable 1 : 1, 2 : 1 and 9 : 1 DDT-lipase complexes as follows.tableCompetitive binding ...experiments with a mixture of E and ED and that of E and E'D2 yielded κ1 : κ2 : κ4=80 : 1 : 400. The κ2 value was estimated to be 1.6×108 M-1s-1 by following the decrease in ED at a low concentration of reactants, ED and DDT, where the reaction was terminated at a given time by scavenging DDT with the addition of excess E'D2. The κ3 value, 0.021s-1, was determined by follwoing the formation of E'D2 from ED2 in the presence of ED. E'D2 was estimated by converting E'D2 rapidly into E*D9 by adding an adequate amount of DDT (ED2 cannont bind DDT), and the excess free DDT was depleted by the pre-existing ED to stop E*D9 formation from newly born E'D2.The continuous slow addition of a limited amount of DDT to ED made the rate of the second order reaction, ED to ED2, comparable to the rate of the slow first order reaction, ED2 to E'D2, thereby favoring the formation of E*D9. The estimation of κ2 and κ3 from the variation in the final population of each DDT-lipase species as a function of the rate of ligand addition was described.
β-Mannosidase was purified to electrophoretic homogeneity from the 20000g supernatant of guinea pig liver homogenate. A highly purified enzyme preparation was also obtained from the acetone powder. ...This enzyme had a pH optimum of 4.0 and molecular weights of ca. 120000 as determined by gel filtration and 110000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was free from other glycosidase activities, as far as was tested. The enzymatic hydrolysis of o- and p-nitrophenyl β-mannosides exhibited an unusual relationship of rate to substrate concentration, indicative of the involvement of two molecules of substrate in the reaction. The rate of hydrolysis was enhanced markedly by several p-nitrophenyl compounds including p-nitrophenyl glycosides, and also by Triton X-100 and chlorinated pesticides such as aldrin.
A method is described for the quantitative and qualitative determination of BHC and DDT isomers and HCB and Methoxychlor (DMDT) in human semen. Pesticide residues were extracted with petroleum ether, ...separated from other co‐extractives on Florisil column, and analyzed by electron‐capture gas chromatography. Recoveries were 96.4 to 110.8% and fortification levels were 0.02 to 0.20 μg/g, respectively.
Studies were undertaken to determine the residues of chlorinated pesticides in human semen, testicles and fat tissues. Samples of semen were taken from a random population and samples of tissues at ...surgery. A preliminary estimation was made to assess the level gradient of environmental pollutants in these types of specimens characterized by a different fat content. Pesticides were considered to show an affinity to fat. The results are an early stage in a programme for a detailed analysis of the effect of pesticides on human reproductive ability and on the value of genetic material.
The effects of three classes of chlorinated pesticides, chloroethanes (DDT, etc.), cyclodienes (aldrin, etc.), and chlorophenols (PCP, etc.), on the activities of porcine pancreatic and Rhizopus ...delemar lipases were studied using water-soluble tripropionin as a substrate. The effects were examined by three different procedures : (I) preincubation of lipase with pesticide and initiation of the enzyme reaction by addition of substrate, (II) preincubation of substrate with pesticide and initiation of the enzyme reaction by addition of lipase, (III) addition of pesticide after initiation of the enzyme reaction. With porcine pancreatic lipase, chloroethanes and cyclodienes exhibited significant activation, increasing the Vmax value and decreasing the Km value, when procedure II was employed, but showed non-competitive inhibition when procedure I or III was employed. With Rhizopus delemar lipase, chloroethanes and cyclodienes exhibited significant activation, increasing only the Vmax value in all three procedures. The activation of pancreatic lipase by chloroethanes was only temporary. Chlorophenols competitively inhibited both lipases in all three procedures.
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