Development of decision tools to assess migration from plastic materials in contact with food

Testing the specific migration limits of all substances intentionally added to polymer material according to European Union (EU) regulation is a time-consuming and expensive task. Although mathematical modeling offers an interesting alternative, it can significantly overestimate the migration in situations which are strongly conservative due to significant uncertainty in transport properties. In addition, its application is of little use for end-users or enforcement laboratories, which do not have access to the formulation. This paper revises the paradigm of migration modeling by combining modeling with deformulation experiments and iterative modeling in the framework of decision theory. The complete approach is illustrated for polyolefins in contact with 50% ethanol for eight typical migrants, including hindered phenolic antioxidants and low molecular weight surrogates. Results from a French ACTIA project on the identification of formulation fingerprints and on the prediction of partition coefficients with alcoholic and aqueous stimulants is described. When the true migration was close but still lower than the limit of concern, the proposed compact decision tree, including up to four sources of uncertainty, showed that the chance of demonstrating compliance was about 3 : 4 in the presence of one source of uncertainty, whereas it fell below 2 : 4 and 1 : 4 with two and three sources of uncertainty, respectively. The recommendations for further food packaging safety surveys and future developments are discussed.

Modulation of Nr-13 antideath activity by peptide aptamers

Tumor cells are characterized by deregulated proliferation and resistance to proapoptotic stimuli. The Bcl-2 family of antiapoptotic proteins is overexpressed in a large number of chemoresistant tumors. Downregulation or inhibition of antiapoptotic proteins might result in the sensitization of cancer cells to chemotherapeutic agents. In the present study, we took advantage of the peptide aptamer strategy to target Nr-13, a Bcl-2 antiapoptotic protein involved in neoplastic transformation by the Rous sarcoma virus. We isolated peptide aptamers that behave as Nr-13 regulators, in vitro and in mammalian cells in culture. Some of these aptamers have potential proapoptotic activities. These data suggest that peptide aptamers targeting the Bcl-2 family of apoptosis inhibitors may be useful for the development of anticancer molecules.

The zebrafish bcl-2 homologue Nrz controls development during somitogenesis and gastrulation via apoptosis-dependent and -independent mechanisms

Although the role of the b-cell lymphoma (Bcl)-2 family of apoptosis inhibitors is well documented in tumor cells and tissue morphogenesis, their role during the early development of vertebrates is unknown. Here, we characterize Nrz, a new Bcl-2-related inhibitor of apoptosis in zebrafish. Nrz is a mitochondrial protein, antagonizing the death-accelerator Bax. The nrz gene is mainly expressed during gastrulation and somitogenesis. The knockdown of nrz with antisense morpholinos leads to alterations of the somites, correlated with an increase in apoptosis. In addition, earlier during development, in the zebrafish gastrula, nrz knockdown results in an increase of snail-1 expression at the margin and frequent gastrulation arrest at the shield stage, independently of apoptosis. Together these data suggest that Nrz, in addition to its effect on apoptosis, contributes to cell movements during gastrulation by negatively regulating the expression of Snail-1, a transcription factor that controls cell adhesion.

Nrh, a human homologue of Nr-13 associates with Bcl-Xs and is an inhibitor of apoptosis

In search of human homologues of the anti-apoptotic protein Nr-13, we have characterized a human EST clone that potentially encodes a protein, which is the closest homologue of Nr-13 among the Bcl-2 family members, to date known, in humans. Phylogenetic analyses suggest Human nrh, Mouse diva/boo and Quail nr-13 to be orthologous genes. The nrh gene has the same overall organization as nr-13 and diva/boo with one single intron interrupting the ORF at the level of the Bcl-2-homology domain BH2. RT-PCR-based analysis of nrh expression indicated that this gene is preferentially expressed in the lungs, the liver and the kidneys. Interestingly, two in frame ATG codons can lead potentially to the synthesis of two products, one of them lacking 10 aminoacids at the N-terminal end. Sequence alignment with Nr-13 and Diva/Boo in addition to secondary structure prediction of the nrh transcript suggested that the shortest protein will be preferentially synthetized. Immunohistochemical analyses have revealed that Nrh is associated with mitochondria and the nuclear envelope. Moreover, Nrh preferentially associates with the apoptosis accelerator Bcl-Xs and behaves as an inhibitor of apoptosis both in yeast and vertebrate cells.

Regulation of cdc2 gene expression by the upstream stimulatory factors (USFs)

cdc2 gene expression is under the control of multiple factors. Although E2F/DP proteins have been reported to play a central role, they cannot account for all aspects of the fine modulation of cdc2 gene expression during cell cycle and embryonic development. To characterize the transcription factors that control cdc2 gene expression during nerve cell differentiation in avians, we have previously cloned the quail cdc2 gene promoter region. We had identified an octamer (CAGGTGGC) containing an E-box, which has important activity in regulating cdc2 transcription. Using in vivo genomic footprinting experiments, we show here that this motif, currently named IG, is the target of binding proteins at different stages of neuroretina development, confirming its importance as a regulatory response element for cdc2 gene expression. A subset of Helix-Loop-Helix family of transcription factors, known as Upstream Stimulatory Factors (USFs) specifically bind to this sequence as dimers. Moreover, our results indicate that USFs transactivate the promoter of cdc2 via the IG motif. These data may help to better understand the mechanisms that control cell division in differentiating nerve cells.

Role of Nr13 in regulation of programmed cell death in the bursa of Fabricius

Apoptotic cell death is developmentally regulated in the chicken bursa of Fabricius. Although apoptosis is low in the embryonic bursa, cell death increases markedly after hatching. The expression of Bcl2 family cell death antagonists was examined to identify the genes that regulate bursal cell apoptosis. The expression of Bcl-xL, A1, and Mcl1 was detected in both embryos and hatched birds, whereas Nr13 was expressed at high levels in embryonic bursa, and decreased significantly after hatching, correlating inversely with apoptosis. The oncogene v-reland phorbol myristate acetate, two known inhibitors of bursal cell apoptosis, induced Nr13 expression. Overexpression of Nr13 in DT40 bursal lymphoma cells protected them from low serum-induced apoptosis. The mechanism of inhibition of apoptosis by Nr13 is likely to involve a critical BH4 domain and interaction with death agonist Bax. Deletion of the BH4 domain converted Nr13 into a death agonist. Bax coimmunoprecipitated with Nr13 and Bax was induced, whereas Nr13 levels diminished when bursal lymphoblasts were induced to apoptosis by dispersion. Bursal transplantation studies demonstrated that Nr13 could prevent the in vivo programmed elimination of bursal stem cells after hatching, suggesting that Nr13 plays a role in maintaining bursal stem cells.

Regulation of E2F-1 gene expression in avian cells

E2F-1 is the prototype of a family of transcription factors playing a central role in the control of cell proliferation and apoptosis. E2F DNA binding activity is down-regulated during cellular differentiation, which is correlated with cell division arrest. We report here that the expression of E2F-1 itself is down-regulated in the developing quail neural retina between embryonic days E8-E10. This event occurs just after the massive arrest of the quail neuroretina cell division (E7-E8). To gain further insight into the regulatory mechanisms monitoring E2F-1 expression in differentiating neurons, we have cloned the quail E2F-1 promoter. In vivo DNA footprintings of this promoter have shown that a number of potential SP-1 and C/EBP response elements are constitutively occupied in the entire quail neuroretina of E5 and E14, whereas the two consensus palindromic E2F binding sites are only protected at E5. This suggests that these E2F elements participate in down-regulation of E2F-1 gene expression during avian neuroretina development. CAT reporter assays have shown that E2F-1 in association with its partner DP-1 transactivates its own promoter, whereas p105Rb inhibits the E2F-1 promoter. Both E2F-1/DP-1 and p105Rh require the presence of the E2F binding sites to mediate their effects. However, experiments performed with deletion mutants of the promoter strongly suggest that other regions located upstream of the E2F binding sites also mediate part of the E2F-1 transactivating effect on its own promoter. Altogether, these results suggest that the down-regulation of E2F-1 gene expression in differentiating neurons could be due, in part, to the E2F/Rb complexes binding to the E2F-1 promoter.

p34(cdc2) and mitotic cyclin expression in the developing quail neuroretina

After an initial proliferation phase, neurons of the central nervous system (CNS) of higher eukaryotes remain postmitotic during their entire lifespan. This requires that a very stringent control be exerted on the cell division apparatus, whose molecular mechanisms remain quite elusive. Here we have used quail neuroretina as a model to study the control of cell division in the developing CNS. In vertebrates, embryonic neuroretinal cells (NR cells) stop their proliferation at different times depending on the cell type. Most NR cells in the quail embryo become postmitotic between E7 and E8. To acquire a better understanding of the molecular events leading to quiescence in NR cells, we have analyzed the expression of cdc2 and of two activators of p34(cdc2): cyclin A and cyclin B2 in the developing neuroretina. We report that these three proteins are downregulated between E7 and E9, suggesting that a common mechanism could block their transcription in differentiating neurons. We also report, using an immunohistochemical approach, that p34(cdc2) downregulation is correlated with the appearance of the microtubule-associated protein tau. These results strongly suggest that inhibition of cdc2 gene expression is closely linked to the achievement of terminal differentiation in neurons. However, we also show that postmitotic ganglion cells precursors begin to synthesize the early neuronal differentiation marker beta3-tubulin while p34(cdc2) is still detectable in these cells, suggesting that p34(cdc2) or a closely related kinase could play a role in some "young" postmitotic neurons.

The product of the v-src-inducible gene nr-13 is a potent anti-apoptotic factor

Tumorigenesis can be induced either by activating cell proliferation or by inhibiting metabolic pathways regulating programmed cell death (apoptosis). There is evidence suggesting that p60(v-src) and other tyrosine kinases protect cells against apoptosis. This effect could contribute to cell transformation by the Rous sarcoma virus. Mechanism of cell death inhibition by p60(v-src) remains largely unknown. We have recently reported that in avian cells p60(v-src) activates the expression of nr-13, a bcl-2-related gene. In this paper, we demonstrate, using the bone marrow derived cell line Baf-3 as an experimental model, that the product of this avian gene (nr-13) is a potent anti-apoptotic factor. In addition, we report that, in quail neuroretinal cells, nr-13 expression is activated upon infection by the Rous sarcoma virus (RSV) but not by other oncogenic retroviruses like FSV or MH2, suggesting that nr-13 is a specific target of v-src. Activation of nr-13 expression may be a key step in cellular transformation by v-src.

Viral inhibition of apoptosis

Viral propagation is limited both by the host immune response and by apoptosis of infected cells. Viruses circumvent apoptosis by different mechanisms: direct inhibition of particular proteases involved in cell death, stimulation of anti-death pathways or regulation of the activity of transcription factors monitoring cell survival.

Two distinct regulatory elements control quail cdc2 transcription: possible involvement in the control of retinoblast differentiation

It is a characteristic of the central nervous system of higher eukaryotes that neurons, after an initial proliferation phase, remain postmitotic for their whole life span. In the developing quail neuroretina, most retinoblasts become postmitotic after 7-8 days of incubation. They also cease to express cdc2, which is presumably necessary to allow retinoblasts to definitively leave the cell cycle. The molecular mechanisms monitoring cdc2 expression during differentiation remain partly understood. To further study the control of cdc2 transcription in avian cells, we have cloned the quail cdc2 promoter. Two functional regulatory elements have been characterized. One of them contains an E2F-binding site. Human E2F-1 was found to transactivate the quail cdc2 promoter very efficiently in avian and human cells. Gel retardation experiments are presented, suggesting that E2F, in association with different partners, is a major regulatory of cdc2 transcription during the development of the neuroretina. Our data also indicate that another transcription factor binds to the octamer CAGGTGGC located 115 nucleotides above the main transcription start site. This motif is thus another important regulatory element participating in the control of cdc2 expression.

Oxidative metabolism of zolpidem by human liver cytochrome P450S

The aim of this study was to identify the form(s) of cytochrome P450 (CYP) responsible for the biotransformation of zolpidem to its alcohol derivatives which, after rapid conversion to carboxylic acids, represents the main way of metabolism in humans. In human liver microsomes, zolpidem was converted to alcohol derivatives. Production of these correlated with the level of CYP3A4 and with cyclosporin oxidation and erythromycin N-demethylation activities, but not with the level of CYP1A2 nor with ethoxyresorufin O-deethylation or S-mephenytoin 4'-hydroxylation activities. Liver microsomes from CYP2D6-deficient patients exhibited normal activity. Production of alcohol derivatives was significantly inhibited by anti-CYP3A antibodies and by ketoconazole. Antibodies directed against other CYP forms (including CYP1A1, CYP1A2, CYP2A6, CYP2B4, and CYP2C8), and CYP-specific substrates or inhibitors (including propranolol, coumarin, mephenytoin, sulfaphenazole, quinidine, aniline, and lauric acid) produced a moderate or no inhibitory effect. cDNA-expressed CYP3A4 and CYP1A2 generated significant amounts of one of the alcohol derivatives, whereas CYP2D6 generated both of them in similar amounts. In human hepatocytes in primary culture, zolpidem was extensively and almost exclusively converted to one of the carboxylic acid derivatives, the main species identified in vivo. Treatment of cells with inducers of CYP1A (beta-naphthoflavone) and CYP3A (rifampicin and phenobarbital) greatly increased the rate of production of this metabolite. We conclude that the formation of alcohol derivatives of zolpidem is rate-limiting and principally mediated by CYP3A4. Both CYP1A2 and CYP2D6 participate in alcohol formation; but, because of their low relative level of expression in the human liver, their contribution is minor.

A Bcl-2-related gene is activated in avian cells transformed by the Rous sarcoma virus

The oncoprotein p60v-src encoded by the Rous sarcoma virus (RSV) genome is the prototype of non-receptor tyrosine kinases. More than 50 targets of p60v-src have been described to date. However, the precise mechanisms of RSV transformation remain to be elucidated. Here, we present the study of a new v-src-activated gene, NR-13, which encodes a protein identified as a new member of the Bcl-2 family. This protein is localized in the membrane with a pattern already observed with Bcl-2. In quail embryos, this gene is mainly expressed in neural and muscular tissues. Its expression is dramatically down-regulated after embryonic day 7 (E7) in the optic tectum. To evaluate a possible role for NR-13 in the control of apoptotic processes in this particular brain area, in situ hybridization and DNA ladder fractionation studies were performed to correlate NR-13 expression with typical situations of apoptosis during brain development. Our results support the idea that RSV could activate anti-apoptotic functions of the host cell resulting in an increase of their lifespan, which could be particularly relevant to tumour formation.

Serum factors and v-src control two complementary mitogenic pathways in quail neuroretinal cells in culture

Quail neuroretinal cells (QNR cells) from 7-day-old embryos do not proliferate even in the presence of 8% fetal calf serum. After infection by the Rous sarcoma virus (RSV) they proliferate actively and exhibit a transformed phenotype; this effect is mediated by the oncoprotein pp60v-src. Secondary cultures infected by the thermosensitive strain tsNY68 of RSV are blocked in G0 either by thermal inactivation of pp60v-src at 41.5 degrees C or by serum deprivation at the permissive temperature (36.5 degrees C). Cell division is reinduced either by pp60v-src thermal renaturation or by subsequent serum addition. Our results indicate that v-src and serum control two synergic pathways leading to G0/G1 transition in QNR cells. In order to characterize genes related to the mitogenic and transforming effects of v-src in nerve cells, we have constructed a cDNA library from QNR cells transformed by tsNY68. We report the properties of five molecular clones isolated by differential screening of this library. Unlike immediate-early genes like c-fos, they are induced in mid and late G1. Four of them correspond to unknown mRNAs and the last one codes for nucleolin. This set of v-src-regulated genes is likely to code for functions deficient in terminally differentiated QNR cells and necessary for the progression in G1.

Identification of the rabbit and human cytochromes P-450IIIA as the major enzymes involved in the N-demethylation of diltiazem

Oxidative metabolism of diltiazem (DTZ), a calcium channel blocker, was investigated in rabbit and human liver microsomes as well as in primary cultures of human hepatocytes. DTZ N-demethylation, the major metabolic pathway in man, was strongly increased by treatment of animals, patients, and hepatocyte cultures with rifampicin and other inducers of the P-450IIIA subfamily. In a reconstituted system with purified forms of P-450 and NADPH cytochrome P-450 reductase, P-450IIIA7 exhibited the highest DTZ N-demethylase activity. In both rabbit and human liver microsomes, this activity was highly correlated with erythromycin demethylase, a characteristic substrate of P-450IIIA, or with an immunoquantitated level of P-450IIIA, and was specifically inhibited by anti-P-450IIIA7 polyclonal and monoclonal antibodies. Cyclosporin A, another specific substrate of P-450IIIA in rabbit and human, competitively inhibited DTZ N-demethylase in both species. In primary cultures of human hepatocytes treated with various inducers, including rifampicin, dexamethasone, phenobarbital, phenylbutazone or beta-naphthoflavone, the rate of release of N-demethyl-DTZ in the extracellular medium was highly correlated with the intracellular level of P-450IIIA, which appeared to be strongly induced by rifampicin and phenobarbital and to a lesser extent by dexamethasone and phenylbutazone. In aggregate, these results are consistent with the view that in both rabbit and human, cytochromes P-450 from the P-450IIIA subfamily are the major enzymes involved in the N-demethylation of DTZ. Accordingly, drugs which may be specific substrates or inducers of this P-450 are likely to influence both the side effects and the efficacy of this molecule.

Down regulation by p60v-src of genes specifically expressed and developmentally regulated in postmitotic quail neuroretina cells

The avian neuroretina (NR) is composed of photoreceptors and different neurons that are derived from proliferating precursor cells. Neuronal differentiation takes place after terminal mitosis. We have previously shown that differentiating NR cells can be induced to proliferate by infection with Rous sarcoma virus (RSV) and that cell multiplication requires expression of a functional v-src gene. We speculated that the quiescence of NR cells could be determined by specific genes. Cell proliferation could then result from the negative regulation of these genes by the v-src protein. By differential hybridization of a cDNA library, we isolated eight clones corresponding to genes expressed in postmitotic NR cells from 13-day-old quail embryos, transcriptional levels of which are significantly reduced in NR cells induced to proliferate by tsNY68, an RSV mutant with temperature-sensitive mitogenic activity. Partial sequencing analysis indicated that one RNA encoded the calmodulin gene, whereas the other seven showed no similarity to known sequences. By using v-src mutants that induce NR cell proliferation in the absence of transformation, we showed that transcription of six genes was negatively regulated by the v-src protein and that of four genes was correlated with NR cell quiescence. We also report that a subset of genes are specifically transcribed in neural cells and developmentally regulated in the NR. These results indicate that the v-src protein regulates expression of genes likely to play a role in the control of neural cell growth or differentiation.

Direct enantiomeric separation of betaxolol with applications to analysis of bulk drug and biological samples

A direct method is described for the resolution of the enantiomers of betaxolol, a novel cardioselective beta-adrenergic blocking agent, using a tris(3,5-dimethylphenylcarbamate)cellulose chiral column. An excellent resolution of the two antipodes is obtained (Rs greater than 2) with high peak symmetries. The method is simple and ideally suited to the routine control of the enantiomeric excess in the bulk drug and the analysis of the enantiomers of betaxolol in hepatocyte suspensions. With modification of the polar modifier in a hexane-based mobile phase, most commercially available beta-blockers can be baseline resolved.

Serotonin inhibits acetylcholine release from rat striatum slices: evidence for a presynaptic receptor-mediated effect

Rat brain striatum slices were incubated with [3H]choline, perfused with a physiological buffer, and stimulated by perfusion with a K+-enriched buffer for 2 min. The tritium overflow evoked by K+ was decreased by 5-hydroxytryptamine (serotonin, 5-HT) (maximal inhibition 10(-6) M). This effect of 5-HT was mimicked by several agonists (5-methoxytryptamine, N,N-dimethyl-tryptamine, bufotenin) and blocked by serotonergic antagonists (methiothepin, methysergide, cinanserin) but not by haloperidol; methiothepin and methysergide alone slightly increased the K+-evoked overflow of tritium (3H). Inhibition of the tritium release by 5-HT was not suppressed in the presence of tetrodotoxin (TTX) (10(-6) M). These results suggest that 5-HT tonically inhibits acetylcholine (ACh) release from striatal cholinergic neurons by acting on a presynaptic receptor localized on cholinergic terminals.

Multiple high affinity binding sites for 5-hydroxytryptamine: a new class of sites distinct from 5-HT1 and S2

Two different classes of binding sites probably related to serotonergic receptors have already been reported: 5-HT1 binding sites recognize [3H]5-hydroxytryptamine with a high affinity (Kd = 3 nM) and S2 binding sites recognize [3H]spiroperidol and [3H]ketanserine. An additional population of sites has been observed in crude membrane preparations or fractions enriched with synaptosomal membranes obtained from rat brain cortex. This population was observed as a single class of sites in a synaptosomal fraction (L fraction--according to Laduron (1977)). It corresponded to a dissociation constant Kd = 13-15 nM, and Bmax = 0.80 +/- 0.15 pmol/mg protein. Displacement experiments showed that it recognized preferentially the 5-HT structure (bufotenin, 5-MeO-tryptamine). Tryptamine was a weak displacer and 5,7-dihydroxytryptamine totally inefficient. Neither 8-OH-DPAT, nor quipazine had any effect. Methiothepin, cinanserin and cyproheptadine displaced 5-HT from these sites whereas ergot derivatives did not. Contrary to 5-HT1 binding, this recently observed binding was not altered by GTP; alpha-MSH reduced the corresponding Bmax whereas Leu-enkephalin did not. The degenerative lesion of the serotonergic fibers led to a slight increase in the Bmax of the binding without altering the Kd which means that corresponding sites are not located on serotonergic fibers and might be postsynaptically located.

Solubilization and characterization of [3H] 5HT high affinity binding sites (5HT1 and 5HT3)

The solubilization of the serotonergic 5HT1 and 5HT3 sites was performed with digitonin and sodium cholate at 1% (final concentration). Two binding sites for [3H]5HT were observed on rat or horse brain synaptosomal membranes solubilized with these detergents. The corresponding dissociation constants (KD) were 1-3 nM and 13-30 nM respectively. These values were closely similar to those corresponding to 5HT1 and 5HT3 sites located in intact membranes. The solubilized sites specifically bound 5HT. The effect of GTP decreasing the binding to 5HT1 sites was lost on solubilized 5HT1 sites; it was recovered, however, by addition of phospholipids (asolectin 0,2%). The apparent molecular weights of these sites were determined using the gel filtration method (438 and 235 K daltons). The photoactivation of [3H]5HT by U.V. light was used to label 5HT1 and 5HT3 sites irreversively in membranes. The binding of [3H]5HT following U.V. irradiation was not dissociated after dilution; it was saturable and prevented by serotonergic drugs and not by adrenergic or dopaminergic antagonists. Moreover, GTP added prior to the irradiation reduced it markedly thus showing that 5HT1 sites were labelled. Electrophoretic and fluorographic analyses of the labelled material evidenced a 60 K dalton-band specifically labelled with [3H]5HT (5 or 20 nM). These results tend to indicate that the 60 K dalton-proteic band might represent a proteic subunit constituting part of 5HT1 and 5HT3 sites.

The metabolism and kinetics of tiflorex in the rat

14C-Tiflorex given either orally or intravenously to male rats (10 mg/kg; 250 microCi) was well absorbed orally; greater than 70% of the dose was excreted in the urine in the first 48 hr after dosing by either route of administration. Inasmuch as part of the dose (10%) was excreted in the feces after iv administration, it is probable that biliary excretion is a route of elimination. This was shown to be so by cannulation of the bile duct. The major route of metabolism was S-oxidation to give the sulfoxides and sulfones of tiflorex (7% each) and nortiflorex (10 and 20%, respectively) which were excreted together with the unchanged drug (1%) in the 0- to 48-hr urine. Examination of the plasma for the unchanged drug and its metabolites showed the drug to be rapidly absorbed orally, maximum levels being attained within 30 min. The plasma half-life for the elimination phase of the unchanged drug was relatively long (7.5 hr) compared with the metabolites (2.5 hr) with the exception of nortiflorex sulfone (9.8 hr) and two as yet unidentified metabolites which had half-lives in excess of 24 hr. The latter three compounds were responsible for the relatively long plasma half-life of total radioactivity (ca. 13 hr). The ratio of the areas under the plasma curve for unchanged drug indicated a low bioavailability (30%). It appears that the predominant route of metabolism of this group of compounds in the rat, p-hydroxyltation had been blocked by the trifluoromethylthio group, with consequent emphasis on S-oxidation.

[Polychlorinated biphenyl intoxication and nutrition. I. Effect of dietary variations on PCB storage in the rat (author's transl)]

Rats were fed three dietary variations containing 100 ppm of Phenoclor DP6 (a commercial PCB mixture) for 30 days. Compared to the normal diet, rats on high fat (20%, and low protein (3,5%) diets had a same curve of PCB storage in liver and carcase fat. However the DP6 in whole body (as per cent of ingested dose) was lower in rats receiving unbalanced diets. Intestinal absorption of DP6 was unaffected by higher-fat diet ingestion.

[Effect of polychlorinated biphenyls in the rat. IV - Metabolic alterations and residual effects of DP6 dietary exposure (author's transl)]

In the first experiment, rats fed diet containing Phenoclor DP6 at a level of 100 ppm (wet weigh) were sacrificed after 1, 3, 8, 15 and 30 days of treatment. Metabolic alterations such as enlarged liver, increased protein and lipid liver contents and hyperlipemia were established within 8 days. The glucid metabolism and muscle metabolic parameters show a low sensibility to DP6 treatment. In the second experiment, rats fed diet containing Phenoclor DP6 (100 ppm) for 15 days were subsequently removed from the experimental diet and placed on control diet. The metabolic alterations described above disappear within 52 days after removal DP6 diet, although the remaining liver PCB stays elevated. These data attest the early effect of DP6 exposure in rats and the reversibility of induced metabolic alterations.

[Effect of polychlorinated biphenyls in the rat. III - PCB distribution, storage and elimination relation time (author's transl)]

The study of accumulation and elimination of Phenoclor DP6 (a commercial PCB mixture) was carried out in three experiments : 1) Rats were fed diet containing 100 ppm of DP6 and were sacrificed after 1, 3, 8, 15 and 30 days. 2) Rats fed DP6 diet during 15 days were subsequently fed with a control diet and sacrificed 8, 15, 52 and 78 days after removal DP6 diet. 3) Bile was collected from surgically treated rats fed DP6 diet during 15 days. Polychlorobiphenyls were spotted in fat carcasses, liver, brain, kidney, muscle, feces and urine to determine absorption, distribution in the animal organism and the clearence rates in urine and feces. We found a very hight DP6 absorption and retention. The low excretion and metabolisation of DP6 result in low decrease after removal DP6 diet.

[Effect of polychlorinated biphenyls in the rat: I. -- Relation tissue level dose (author's transl)]

Rats were fed with a diet containing Phenoclor DP6, a French commercial polychlorinated biphenyl (PCB) mixture, for 30 days. Diet PCB levels were 10, 100, 500 and 1000 ppm (wet weight). At 500 ppm, a 50 per cent mortality was found after 8 days, while a 100 per cent mortality was noted after 6 days with 1000 ppm. Our principal findings include: loss of body weight (at major doses), central nervous system stimulation, inflammation of lungs and gastro-intestinal tractus, and fatty degeneration of the hepatic cells. Ingested PCB is found in all organs and tissues tested and was largely stored in liver and muscle. PCB levels in the major tissues are related to dietary doses.