Effects of Cd and Zn waterborne exposure on the uptake and depuration of 57Co, 110mAg and 134Cs by the Asiatic clam (Corbicula fluminea) and the zebra mussel (Dreissena polymorpha)--whole organism study.

Groups of zebra mussels (Dreissena polymorpha) and asiatic clams (Corbicula fluminea) were exposed to cadmium and zinc with the aim of studying the effect of these metals on the 57Co, 110Ag and 134Cs uptake and depuration by these freshwater bivalves. In the presence of zinc, the 57Co concentration factor for the whole organism of the two species was halved, notably because of a decrease of the uptake parameter. Conversely, Zinc and the Cd + Zn mixture increased the 110mAg uptake process by clams and mussels. The two metals also increased the depuration of this radionuclide in mussels, whereas this phenomenon was only observed in clams exposed to cadmium. In comparison with 57Co and 110mAg, the 134Cs bioconcentration was 5-10 times lower in D. polymorpha and not detected in C. fluminea. This weak contamination by this radionuclide resulted from a lower uptake and a higher depuration parameters.

Experimental kinetic rates of food-chain and waterborne radionuclide transfer to freshwater fish: a basis for the construction of fish contamination charts.

A standardized procedure is proposed to obtain from laboratory experiments the kinetic accumulation and release rates necessary to calibrate dynamic models to quantify radionuclide direct and trophic transfer in fish. The model takes into account the food-chain effect, the feeding rate, and the growth of organisms. It takes as examples (54)Mn, (60)Co, and (137)Cs transfer dynamics through a simple pelagic food-chain (phytoplankton, zooplankton, prey fish, and predator fish). The estimated kinetic rates used in quantifying all the transfers of the three radioactive pollutants through the pelagic food chain are compared from the radioecological point of view. For fish, comparison was based on the calculation of concentration factors referring to direct transfer from water and trophic transfer factors. For the prey fish and the predator fish, direct transfer gave the following order for accumulation (60)Co < (137)Cs < (54)Mn. Values reached at equilibrium in L/kg WW were respectively for the prey fish and the predator fish: 8.7 < 27.4 < 107 and 4.14 < 6.59 < 13.4. For the trophic route, (137)Cs is the most accumulated (TTF(eq) = 0.485 in 291 days for the prey fish and TTF(eq) = 1.45 in 17 years for the predator fish). A sensitivity analysis adapted to the case of a chronic contamination scenario of a watercourse was run. It showed that the phytoplankton biomass, the contact time of these drifting particles from a release point to the station where they are ingested and the feeding rates of the fish are the most influential parameter with regard to the concentration in fish, whatever the trophic level. Contamination charts are constructed for the predator fish to illustrate the relationship between the most influential ecological parameters and the radionuclide concentration in fish for simple contamination scenarios. They are shown to be effective tools for helping in the choice of the most relevant value of aggregated concentration factors (ACFs: radionuclide concentration ratio between the organism and the water, referred to steady-state and to all possible transfer pathways) for a given key ecological situation in a given ecosystem. An example is given of a simple chronic release scenario of 1 Bq/L and a phytoplanktonic bloom period. For (137)Cs, the ACF increases with increasing contact time and increasing feeding rate, to nearly 550 L/kg WW at equilibrium. For (54)Mn, ACF reaches 65 L/kg WW. For (60)Co, the general pattern of the relationship is due to the rapid kinetic rates governing the distribution of the radionuclide between dissolved and solid (phytoplankton) phases with a maximum value for ACF of 7.2 L/kg WW for the case study. Analysis of these charts provides a basis for overall guidelines for chronic releases in a given watercourse.

60Co transfer from water to the rainbow trout (Oncorhynchus mikiss Walbaum).

60Co uptake from natural water, release and tissue distribution were investigated in the rainbow trout (Oncorhynchus mikiss), which is representative of the third order consumers of the freshwater trophic chains. The experiments were carried out on two groups of fingerling trout placed in 0.45 microm filtered river water, maintained at 12 +/- 0.5 degrees C, contaminated with about 30 Bq ml-1 of 60Co and renewed three times a week. After a 8-week exposure phase, the fish of one group were dissected to determine the contamination of the tissues and organs and the distribution of the accumulated 60Co. The fish of the other group were placed in non-contaminated water, renewed daily, to monitor radionuclide release. After a 42-day depuration phase, the specimens were dissected to study the tissue distribution of the residual 60Co.60Co accumulation from water by trout can be described by a one-compartment exponential model. The concentration factor, calculated from the ratio of the radionuclide concentration in filtered water and in the fish, reached a maximum value of 4.6 (w.w.) after 30 days exposure. After the 42-day depuration phase, the fish retained about 29% of the accumulated radionuclide. A single-compartment exponential model was fitted to the 60Co elimination data, and the corresponding radionuclide half-life was 21 days. At the end of the exposure phase, tissue contamination study showed 60Co accumulation by the gills, viscera (air bladder, heart and spleen) and kidneys, to be the highest. At the end of the depuration phase, the kidney was the most contaminated organ, followed by the viscera, head, gills, and liver. In both cases, 60Co concentration was by far the lowest in the muscle, which accounted for about 45% of the total body weight and only 20% of the total radionuclide body load.

Uptake from water, release and tissue distribution of 54Mn in the Rainbow trout (Oncorhynchus mikiss Walbaum).

As part of a research programme on the transfer of several radionuclides along a pelagic trophic chain, two groups of 12 trout were kept for 8 weeks in water contaminated with 30 Bq ml(-1) of (54)Mn. In order to simulate chronic contamination and limit alterations in the physical and chemical characteristics of the medium, the water was renewed every 2 days. The kinetics of the accumulation and elimination of the radionuclide were monitored in one group of fish. The second group was used to study the contamination of the main organs and tissues at the end of the accumulation phase. The dynamics of contamination can be described by a bi-compartmental model, taking into account the fluctuations in the concentration of (54)Mn in the water, as well as the biological dilution resulting from the growth of the fish. The theoretical value of the steady-state concentration factor for zero growth is 13 (w.w.) and the radionuclide release is characterised by two biological half-lives of 6 and 97 days. At the end of the accumulation phase, the (54)Mn is preferentially fixed in the bone, gills, skin and brain. The data obtained at the end of the depuration phase allow one to classify the organs in two groups with different elimination kinetics. The first group consists of organs of penetration or transit, such as the skin, gills, kidneys, liver, primary and secondary gut and viscera, whereas the second group is made up of the receptor and storage organs and tissues such as the bone, head, fins and muscle.

60Co accumulation from sediment and planktonic algae by midge larvae (Chironomus luridus).

This paper reports the results of several experiments carried out to evaluate uptake and retention by a limicolous midge larva of 60Co retained in sediment, either adsorbed on mineral particles or bound to planktonic algae. In order to determine their relative contributions in radionuclide accumulation, the different vectors (water, algae and sediment) were first labelled individually and then simultaneously. 60Co accumulation from water and from algae results in a maximum concentration factor of 30 and in a mean trophic transfer factor of 4.5 x 10(-3). The level of contamination of midge larvae from sediment is markedly influenced by the presence of endogenous organic matter. Thus the radionuclide transfer factor is about twice as high for larvae placed in labelled raw sediment than for larvae placed in labelled incinerated sediment, in the presence as in the absence of contaminated planktonic algae. Irrespective of the contamination conditions, 60Co depuration from midge larvae is a very rapid phenomenon that corresponds, in all cases, to a radionuclide half-life of only a few days.

60Co retention by a freshwater planktonic alga Scenedesmus obliquus.

This paper presents the results of various decontamination experiments aimed at evaluating (60)Co retention by Scenedesmus obliquus, and the respective roles played by absorption and adsorption in the contamination of the alga by this radionuclide. The physiological condition of cells is not involved in radiocobalt desorption, which seems to indicate that the phenomenon is of a passive nature. When the precontamination time is extended, the proportion of adsorbed (60)Co decreases, and the final percentage of radionuclide retained increases. These results are confirmed by bringing cells into contact with a strong chelating agent. The elimination of (60)Co in the presence of EDTA undergoes a sharp decrease which is correlated with the increase in the duration of the precontamination phase. The use of a weaker complexing agent, such as NaCl, leads to the hypothesis of there being 2 types of (60)Co receptor on cell membranes.

[Cylindroma on a pleomorphic adenoma. Apropos of 2 case reports]. / Cylindrome sur adénome pléomorphe. A propos de 2 observations.

Among a group of 863 patients with epithelial tumors of the salivary glands, including 470 with pleomorphic adenomas, the latter were associated with carcinomas in 20 cases and of these two were adenoid cystic carcinoma. In both cases these were isolated parotid tumors, lacking functional symptomatology and failing to recur 2 and 4 years respectively after parotidectomy. Diagnosis was mainly by histology and was based on the finding of a co-existing pleomorphic adenoma and an authentic adenoid cystic carcinoma, not to be confused with the benign pseudo-cylindromatous appearance sometimes detected in simple pleomorphic adenomas. This association of adenoid cystic carcinoma and pleomorphic adenoma increases the risk of recurrence and of metastases--long-term follow up is necessary. Prognosis is dependent mainly on the quality of the initial surgical excision.

[Diagnostic and therapeutic problems occasioned by a voluminous cervical schwannoma (author's transl)]. / Problèmes diagnostiques et thérapeutiques posés par un volumineux schwannome cervical.

A tumour of the nervous sheath, the schwannoma often entails difficult diagnostic problems linked to its anatomopathological polymorphism. A medical case of a benign schwannoma of the neck has been reported. In this case, it concerns a tumour moreworthy for its size, its adherence, elements which are unusual in a regular tumour which is well inserted in a capsule, and which has entailed difficult therapeutic problems. Its atypical histological shape brought up a debate between its diagnostic on the one of a fibro-myxoma.

[Pulmonary-mediastinal sarcoidosis presenting as parotiditis. A report on two cases (author's transl)]. / Deux cas de parotidite, révélateurs d'une sarcoöidose médiastino-pulmonaire.

The authors report on two cases in which parotid localization enabled diagnosis of an unsuspected sarcoidosis io be made. They feel that, apart from Sjogren-Goygerot's syndrome, all patients with parotiditis, even non-specific, should be examined systematically to exclude the possibility of a latent sarcoidosis.

[A poorly reduced fracture with spontaneous consolidation in good position]. / Une fracture mal réduite et spontanément consolidée en bonne position.

The authors present a case of double mandibular fracture in a partially edentulous patient, which was poorly reduced but nevertheless evolved spontaneously to consolidation in a satisfactory position. They feel that only the influence of muscular forces can explain this fortunate outcome. The technique involving the use of plate and screws is felt to be preferable to osteosynthesis using steel wires in such cases.