Effects of diethyldithiocarbamate (ddtc) on the plasma biotransformations of tetrachloro(d,i-trans)-1,2-diaminocyclohexaneplatinum(iv) (tetraplatin) in fischer 344 rats

We have studied the effects of diethyldithiocarbamate (DDTC) on the biotransformations of toxic doses of tetrachloro (d,l-trans)1,2-diaminocyclohexaneplatinum(IV) (tetraplatin) in Fischer 344 rats. In animals not treated with DDTC, tetraplatin was rapidly converted to dichloro(d,I-trans)1,2-diaminocyclohexaneplatinum(II) [PtCl₂(dach]. Subsequent biotransformations included the transient formation of the (d,I-trans)1,2-diaminocyclohexane-aquachloroplatinum(II) [Pt(H₂O)(Cl)(dach)]+ complex, followed by formation of the platinum (Pt)-methionine and either Pt-cysteine or Pt-ornithine complexes. Significant amounts of free (d,I-trans) 1,2-diaminocyclohexane (dach) were observed in plasma as a result of intracellular trans-labilization reactions. DDTC caused a marked decrease in both total and protein-bound platinum in the circulation. A significant increase in the plasma concentration of free dach was also observed as a result of formation of the Pt(DDTC)₂ complex. Some of the free dach could have arisen from intracellular reactions with DDTC, but the displacement of platinum from plasma proteins was more than sufficient to account for the increase in free dach in the circulation. DDTC treatment also decreased plasma concentrations of tetraplatin, PtCl₂(dach), [Pt(H₂O)(Cl)(dach)]⁺, the Pt-methionine complex, and one unidentified biotransformation product, but had no effect on the Pt-cysteine (or Pt-ornithine) complex. These effects of DDTC on protein-bound platinum and low-molecular-weight biotransformation products in plasma may contribute to the decrease in tetraplatin toxicity seen in DDTC-treated rats.     

Effects of diethyldithiocarbamate (DDTC) on the plasma biotransformations of tetrachloro(d,l-trans)-1,2-diaminocyclohexaneplatinum(IV) (tetraplatin) in Fischer 344 rats.

We have studied the effects of diethyldithiocarbamate (DDTC) on the biotransformations of toxic doses of tetrachloro (d,l-trans)1,2-diaminocyclohexaneplatinum(IV) (tetraplatin) in Fischer 344 rats. In animals not treated with DDTC, tetraplatin was rapidly converted to dichloro(d,l-trans)1,2-diaminocyclohexaneplatinum(II) [PtCl2(dach)]. Subsequent biotransformations included the transient formation of the (d,l-trans)1,2-diaminocyclohexane-aquachloroplatinum(II) [Pt(H2O)(Cl)(dach)]+ complex, followed by formation of the platinum (Pt)-methionine and either Pt-cysteine or Pt-ornithine complexes. Significant amounts of free (d,l-trans) 1,2-diaminocyclohexane (dach) were observed in plasma as a result of intracellular trans-labilization reactions. DDTC caused a marked decrease in both total and protein-bound platinum in the circulation. A significant increase in the plasma concentration of free dach was also observed as a result of formation of the Pt(DDTC)2 complex. Some of the free dach could have arisen from intracellular reactions with DDTC, but the displacement of platinum from plasma proteins was more than sufficient to account for the increase in free dach in the circulation. DDTC treatment also decreased plasma concentrations of tetraplatin, PtCl2(dach), [Pt(H2O)(Cl) (dach)]+, the Pt-methionine complex, and one unidentified biotransformation product, but had no effect on the Pt-cysteine (or Pt-ornithine) complex. These effects of DDTC on protein-bound platinum and low-molecular-weight biotransformation products in plasma may contribute to the decrease in tetraplatin toxicity seen in DDTC-treated rats.     

Glucose-6-phosphate dehydrogenase in barley roots: kinetic properties and localisation of the isoforms

Two different isoforms of glucose-6-phosphate dehydrogenase (Glc6PDH; EC 1.1.1.49) have been partially purified from barley (Hordeum vulgare L., cv. Alfeo) roots. The procedure included an ammonium sulfate step, Q-Sepharose and Reactive Blue agarose chromatography, and led to 60-fold and 150-fold purification for the two enzymes, respectively. The Glc6PDH 1 isoform accounts for 17% of total activity of the enzyme in roots, and is very sensitive to the effects of NADP⁺/NADPH ratio and dithiothreitol; the Glc6PDH 2 isoform is less affected by reducing power and represents 83% of the total activity. The isoforms showed distinct pH optima, isoelectric points, K _m for glucose-6-phosphate and a different electrophoretic mobility. The kinetic properties for the two enzymes were affected by ATP and metabolites. Both enzymes are inhibited to different extents by ATP when magnesium is omitted from the assay mixture, whereas the addition of ATP-Mg²⁺ had no effect on Glc6PDH activities. The Glc6PDH isoforms are usually present in the plastids and cytosol of plant cells. To verify the intracellular locations of the enzymes purified from barley roots, Glc6PDH was purified from isolated barley root plastids; this isoform showed kinetic parameters coincident with those found for Glc6PDH 1, suggesting a plastid location; the enzyme purified from the soluble fraction had kinetic parameters resembling those of Glc6PDH 2, confirming that this isoform is present in the cytosol of barley roots. Received: 21 June 2000 / Accepted: 28 July 2000     

Plasminogen activator production in a rat model of Pneumocystis carinii pneumonia

Several studies have indicated that the serine protease urokinase-plasminogen-activator (uPA) is an important factor in host defense against pulmonary pathogens. To gain a better insight into the role of uPA in Pneumocystis carinii (P. carinii) pneumonia (PCP), we evaluated PA production in alveolar macrophages (AMs) obtained from rats with steroid-induced PCP. Treatment with cortisone acetate favored PCP in 91% of rats. In the bronchoalveolar lavage (BAL) samples of immunosuppressed rats both with and without PCP, we observed a decrease in uPA activity as well as a decrease in cell number. Urokinase-PA production by AMs was reduced in rats treated with cortisone alone. However, an increase in cell-associated uPA was observed in rats with PCP. This increase appears to be produced in response to P carinii infection. In fact, when AMs obtained from untreated healthy or immunosuppressed uninfected rats were challenged with P carinii, a significant increase in PA activity in cell lysates was observed, though a lower response was obtained in cortisone-treated animals. Our results suggest that healthy AMs respond to the presence of P carinii with an increase in uPA production and that this response in immunodepressed rat-AMs is partially impaired.     

Glutamate synthesis in barley roots: the role of the plastidic glucose-6-phosphate dehydrogenase

Evidence is provided for a close link between glutamate (Glu) synthesis and the production of reducing power by the oxidative pentose phosphate pathway (OPPP) in barley ( Hordeum vulgare L. var. Alfeo) root plastids. A rapid procedure for isolating organelles gave yields of plastids of over 30%, 60% of which were intact. The formation of Glu by intact plastids fed with glutamine and 2-oxoglutarate, both substrates of glutamate synthase (GOGAT), depends on glucose-6-phosphate (Glc-6-P) supply. The whole process exhibited an apparent K(m Glc-6-P) of 0.45 mM and is abolished by azaserine, a specific inhibitor of GOGAT; ATP caused a decrease in the rate of Glu formation. Glucose and other sugar phosphates were not as effective in supporting Glu synthesis with respect to Glc-6-P; only ribose-5-phosphate, an intermediate of OPPP, supported rates equivalent to Glc-6-P. Glucose-6-phosphate dehydrogenase (Glc6PDH) rapidly purified from root plastids showed an apparent K(m Glc-6-P) of 0.96 mM and an apparent K(m NADP)(+) of 9 micro M. The enzyme demonstrated high tolerance to NADPH, exhibiting a K(i) (NADPH) of 58.6 micro M and selectively reacted with antibodies against potato plastidic, but not chloroplastic, Glc6PDH isoform. The data support the hypothesis that plastidic OPPP is the main site of reducing power supply for GOGAT within the plastids, and suggest that the plastidic OPPP would be able to sustain Glu synthesis under high NADPH:NADP(+) ratios even if the plastidic Glc6PDH may not be functioning at its highest rates.     

Morphological and thermal properties of cellulose-montmorillonite nanocomposites

Cellulose-layered montmorillonite (MMT) nanocomposites were prepared by precipitation from N-methylmorpholine- N-oxide (NMMO)/water solutions. Two hybrid samples were obtained to investigate the influence of the reaction time on the extent of clay dispersion within the matrix. It was observed that longer contact times are needed to yield nanocomposites with a partially exfoliated morphology. The thermal and thermal oxidative properties of the hybrids, which might be of interest for fire-resistant final products, were investigated by thermogravimetry and chemiluminescence (CL). The nanocomposites exhibited increased degradation temperatures compared to plain cellulose, and the partially exfoliated sample showed the maximum stability. This result was explained in terms of hindered transfer of heat, oxygen, and degraded volatiles due to the homogeneously dispersed clay filler. Kinetic analysis of the decomposition process showed that the degradation of regenerated cellulose and cellulose-based hybrids occurred through a multistep mechanism. Moreover, the presence of nanoclay led to drastic changes in the dependence of the activation energy on the degree of degradation. CL analysis showed that longer permanence in NMMO/water solutions brought about the formation of carbonyl compounds on the polymer backbone. Moreover, MMT increased the rate of dehydration and oxidation of cellulose functional moieties. As a consequence, cellulose was found to be less stable at temperatures lower than 100 degrees C. Conversely, at higher temperatures, the hindering of oxygen transfer prevailed, determining an increase in thermo-oxidative stability.     

Degradation of waste waters from olive oil mills by Yarrowia lipolytica ATCC 20255 and Pseudomonas putida

Waste waters from olive oil processing may cause severe pollution in the Mediterranean area, since they have a high level of chemical oxygen demand (COD) (100–200 g/l) and contain other organic and inorganic compounds. In all olive oil producing countries, the reduction of pollution in olive oil mill waste waters at reasonable costs and using techniques suitable for most industrial applications is an unsolved problem. For this paper, the yeast Yarrowia lipolytica ATCC 20255 was grown on waste waters from an olive oil mill in a 3.5 1 fermenter under batch culture conditions. The results showed that the yeast was capable of reducing the COD value by 80% in 24 h. In this way, a useful biomass of 22.45 g/l as single cell protein (SCP) and enzyme lipase were produced. During this process, most of the organic and inorganic substances were consumed, only aromatic pollutants were still present in the fermentation effluents. Therefore, we used a phenol degrader, namely Pseudomonas putida, to reduce phenolic compounds in the fermentation effuents after removing Yarrowia lipolytica cells. P. putida was effective in reducing phenols in only 12 h.     

Properties of the two common electrophoretic variants of phosphoglucomutase in Drosophila melanogaster

Phosphoglucomutase (PGM) of adult stage in Drosophilia melanogaster has been characterized by gel filtration, ion-exchange chromatography, and isoelectric focusing. The two common electrophoretic variants, PGMA and PGMB, differ with respect to their kinetic and stability parameters. PGMA is more thermostable than PGMB but shows the same pH optimum, equal dependence on Mg2+, and identical molecular weight. There is no significant kinetic difference between the two allozymes at the optimum pH values, but at pH 6.0 the Km value for glucose-1,6-diphosphate of PGMB is significantly higher than that of PGMA. This difference might explain the observed selective advantage of the PgmA allele in population studies.