Long lasting cadmium intake is associated with reduction of insulin receptors in rat adipocytes.

The effects of chronic cadmium exposure on adipose tissue have not been extensively reported. In adult Wistar male rats we investigated in vivo effect of 6 weeks lasting cadmium intake in drinking tap water (CdCl2 9,7 mg/l). Insulin receptors in isolated adipocytes from epididymal fat and glucose transporter protein GLUT4 content in fat tissue plasma membranes were determined. Control and Cd treated rats had similar water intake with subsequent heavy augmentation of Cd content in liver of experimental animals. In comparison with controls, Cd intake did not influence body mass increment and fat cell size, but significantly increased serum glycemia and moderately elevated insulinemia. Cadmium intake significantly reduced (approximately 50%) both, total insulin receptors number and density of the receptors in fat cells. No differences in the content of GLUT4 in crude plasma membranes of adipose tissue were observed. Diminished insulin receptors in adipocytes could account for diabetogenic effect of long lasting cadmium intake.

Effect of cadmium and mercury on the nuclear retinoic acid receptors.

The actions of retinoic acids (RA) are mediated by their cognate nuclear receptors--ligand inducible transcription factors (retinoic acid receptors (RAR)). Possible interactions of toxic heavy metals on the RAR system are of interest due to involvement of the RAR system in multiple systemic processes. We assayed cadmium chloride and mercury chloride for their influence on the RAR system in rat and in cell culture. Mercury chloride was observed to decrease the maximal binding capacity in vitro of RARs for all-trans RA in liver nuclear fraction containing sets of nuclear receptors by seventy percent at a concentration of 0.1 mmol/l, though not cadmium chloride. Neither mercury chloride nor cadmium chloride induced any changes with respect to mRNA levels of RAR and binding properties of nuclear receptor fraction for RA or retinoic acid responsive elements (RARE) in male Wistar rats receiving tap water with cadmium chloride (9.7 mg/l) or mercury chloride (11.5 mg/l) for six weeks. In rat pituitary GH4C1 cells, neither mRNA levels nor binding properties for RARE in cell culture were affected by non-toxic concentrations of these heavy metals. From the data obtained it is suggested that, in vivo, cadmium or mercury have no significant impact on RA nuclear receptor system.

Role of astrocytes in trimethyltin neurotoxicity.

Although the neurotoxicity of trimethyltin (TMT) is well known, mechanisms are still not clear. Glia have been proposed to mediate the toxic action of TMT on nerve cells. Accordingly, the effects of TMT were tested in primary neuronal cultures from rat cerebellum and compared to effects in astrocytes and mixed cultures. Neuronal damage observed following TMT exposure was less in the presence of astrocytes and astrocytes alone were resistant to TMT. Thus, astrocytes have a protective effect against TMT-induced neurotoxicity. TMT caused an oxidative stress in granule cell cultures involving a variety of oxidative species (O2)*-, H2O2, NO), but astrocytes were less sensitive to TMT-induced oxidative species generation. Antioxidants, glutathione and 7-nitroindazole attenuated neuronal cell death induced by TMT. It appears that oxidative stress mediates a large part of the destructive action of TMT in neuronal cultures. The presence of astrocytes appears to modulate TMT-induced oxidative stress so that TMT causes only a small increase in lipid peroxidation in mouse brain after systemic administration. Thus, TMT induces a pronounced oxidative stress in cultured neurons, but when astrocytes are present, oxidative species play a lesser role in the neurotoxic action of TMT.

Effect of cadmium chelating agents on organ cadmium and trace element levels in mice.

In experiments performed on male mice (CD-1, Charles River), the mobilizing effects of repeated administration of the carbodithioate analogue BLDTC [N-benzyl-4-O-(beta-D-galactopyranosyl)-D-glucamine-N-carbodithioate+ ++] and CaDTPA (calcium trisodium pentetate) on cadmium deposits in the liver, kidneys, brain and testes were compared. The antidotes were injected alternately every 48 h over a period of 16 d (8 doses in total) following a previous loading with 20 doses of CdCl2.2.5 H2O (single doses of 3 mg kg-1 i.p.). The experiments confirmed BLDTC to be one of the most effective cadmium mobilizing agents. The administration of CaDTPA, which is known as a useful antidote in acute cadmium intoxication, increased the mobilizing effect of BLDTC. Cadmium elevated the concentration of zinc in all organs examined and the level of copper in the liver, kidneys and testes. This accumulation of trace elements was only partially corrected by the chelators. The antidotes administered alone exert only a negligible effect on the trace element levels in the organs.

[Listeria monocytogenes in food]. / Listeria monocytogenes v potravinách.

As in recent years laboratory diagnostics of listeria has become part of food microbiology, the frequency of occurrence of the bacteria Listeria monocytogenes has been followed in various kinds of foods for a year. A total of 51 strains of L. monocytogenes (7.2%) was isolated from 700 kinds of samples (raw milk, pasteurized milk, meat surface, poultry, cheeses, thermally not treated meat products, food--industry machinery). As can be seen in Tab. I, the highest number of strains was isolated from meat surfaces (13.5%), followed by meat--industry machinery (12.72%), poultry (10%) and cheeses (5%). The lower numbers of strains were found out in thermally not treated meat products (3.8%) and in raw milk (3.3%). Pasteurized milk did not contain any strains. Our findings in raw milk (3.3%) and in pasteurized milk (0) are in agreement with the data cited e. g. by authors from the USA (Lovett et al., 1987), who mention the value of 4.2% in raw milk and the zero value in pasteurized milk. The percentage of strains monitored in cheeses (5%) can be evaluated as low as the assortment of investigated cheeses was small (all strains were isolated from soft ripening cheeses). German authors (Tham et al., 1988) speak about the 2.5% percentage of L. monocytogenes strains; this is in keeping with our findings. The findings in thermally not treated meat products (3.8%) can be evaluated as low although the number of strains found in raw meat was high.(ABSTRACT TRUNCATED AT 250 WORDS)

[Occurrence of Yersinia enterocolitica, particularly serovar 03, biovar 4 in pork and beef]. / Výskyt Yersinia enterocolitica, zvláste sérovaru 03, biovaru 4 ve veprovém a hovezím mase.

The paper deals with the incidence of Yersiniae in pork and beef, focused in particular on the prevalence of Yersinia enterocolitica, serovar 3, biovar 4. The author uses for detection the method of cold shock, alkalization of the sample, taking advantage of the tolerance of Yersinias of diluted alkalis and suppressing the contaminating microflora, and the the selective medium CIN agar with a locally manufactured supplement. Cultivation was either direct or after propagation in phosphate buffer pH 7.6. The authors isolated 84 strains of Yersinias, i.e. 60% of the total number of examined specimens. Four strains were Yersinia enterocolitica, serovar 03, biovar 4 from pork by direct cultivation. Twenty strains did not agglutinate with commercial serum O-Yersinia IMUNA; they were included in the group "Yersinia enterocolitica other biovars" and 60 strains were "Environmental Yersinia isolates". The author proved a seasonal incidence of Yersinie enterocolitica, serovar 03, biovar 4. The applied method of detection and the the selective medium CIN agar with supplement proved suitable. It is important to respect hygienic provisions during processing in the slaughterhouse with regard to the high incidence of environmental Yersinias and the possible incidence of pathogenic serovars of Yersinias.

[Pseudomonas aeruginosa in raw and pasteurized milk]. / Pseudomonas aeruginosa v syrovém a pasterovaném mléce.

Eighteen strains of Pseudomonas aeruginosa, i.e. 8.87%, were isolated during a year from 203 samples of raw milk. Two Pseudomonas aeruginosa strains, i.e. 4%, were isolated from 50 samples of pasteurized milk. The strains were isolated using propagation techniques in meat-peptone broth with malachite green and on selective media--on centrimide agar (CEM) and on Pseudomonas F agar. All the isolated strains produced protease, whereas lipase was produced by only five strains. The strains were devitalized when exposed to pasteurization temperatures (72 degrees C) for 20 seconds. At cold store temperatures (4 degrees C), Pseudomonas aeruginosa strain cells propagated on average by two orders, inhibitory effects of low temperatures were recorded only with one strain. Inhibitory effects of milk cultures (cream, yogurt) on Pseudomonas aeruginosa were observed; their effects were more clear-cut at the temperature of 4 degrees C. The strains were markedly susceptible to gentamycin.

[Campylobacter jejuni in poultry processed in slaughterhouses]. / Campylobacter jejuni u jatecne opracované drubeze.

The frequency of occurrence of Campylobacter jejuni germs in dressed poultry was studied for a year. The samples--smears from the body cavities of chickens--were collected during the technological dressing of the chickens; 101 strains of Campylobacter jejuni (i. e. 28.69%) were isolated from the 352 samples analyzed. The occurrence of the germs exhibited a considerable seasonal variance with peak rates in spring and summer. The use of a suitable culture medium, the technique of cultivation and the properties of the isolated strains were studied at the same time. The culture medium (Agar no. 3 IMUNA enriched with supplement C, horse blood and ingredients increasing the aerotolerance of the germs--sodium pyruvate and iron sulphate) used during the investigation was found to be suitable. The technique of cultivation by means of an anaerostat manufactured by the Development Station in Brno, atmosphere regulation (5% CO2) and with a pre-set cultivation temperature (43 degrees C) was found to be suitable for the screening of the Campylobacter jejuni germs.

Characteristics of Staphylococcus aureus strains, isolated from slaughtered poultry.

The extent of contamination in slaughtered poultry by strains of Staphylococcus aureus was investigated, as well as the origin of strains and the way of their transfer during operation of the poultry slaughterhouse. 45 strains were isolated from 175 swab samples from the surface and the body cavity of poultry and 8 strains from 23 workers of the slaughterhouse. 22 strains of St. aureus from the poultry were classified as biotype A (of human origin), according to the biochemical identification scheme by Hájek and Marsálek (1971), and 20 strains as biotype B (of poultry origin). 3 strains were not typable. 7 strains from the workers handling the poultry were classified as biotype A and one strain was not typable. Enterotoxins were produced mostly by strains of biotype A (13), by one strain of biotype B, and by one strain which could not be typified. The transfer of staphylococci from workers into the poultry was verified.

[Use of a selective sulfite-reducing medium for the isolation of Clostridium perfringens]. / Pouzití selektivního sulfitredukcního média pro izolaci Clostridium perfringens.

The effect of sulphite-reduction in 33 sample bacterial strains was tested. With regard to the capacity of reducing sulphite in modified sulphite-reduction media in a wide scale of bacterial strains the possibility of an application of selective media with an addition of various concentrations of antibiotic solutions was checked. A concentration of 750 microgram of D-cycloserine per 1 ml of the sulphite-reduction medium appeared to be the most advantageous for the isolation and detection of sulphite-reductive clostridia, above all of Clostridium perfringens. This concentration ensured also a sufficient inhibition of undesirable bacteria without any affection of the growth and capacity of Clostridium perfringens to reduce sulphite in the applied medium.