Acta microbiologica Hungarica最新文献

A two phase slug flow tubular heat exchanger was used for the thermal inactivation of Listeria monocytogenes in natural infected milk from seven cows. L. monocytogenes serotype 4b inoculated UHT sterilized milk was monitored in a parallel study. The two milks were heated at 71.1 degrees C for holding times of 2, 4, 10, 15, 20 and 30 s. Milk was assayed for survivors immediately after heat treatment and weekly thereafter for 4 weeks during storage at 4 degrees C. No survivors were detected in the naturally infected milk at any of the holding times. Survivors were found at 2 and 4 s in the inoculated UHT milk with initial titres of 8 x 10(2) to 7.1 x 10(3) c.f.u./ml, only after storage at 4 degrees C for 28 days. No survivors were detected for 10 through 30 s holding times.

Enterohaemorrhagic Escherichia coli O157:H7 is of major concern to the food industry due to high pathogenicity of this foodborne organism. For the detection of these bacteria a special agar medium with a fluorogenic substrate has been developed. The medium uses the characteristics of this E. coli serotype not to ferment sorbitol and not to produce beta-glucuronidase. In contrast, approximately 96% of all other strains of E. coli are sorbitol-positive and nearly all of them are beta-glucuronidase-positive. For discrimination between Proteus and E. coli O157:H7 which are both sorbitol- and beta-glucuronidase-negative, sodium thiosulphate and ferrio ammonium citrate were added. This leads to a brownish colour of the Proteus colonies due to their production of hydrogen sulphide. Growth of the gram-positive flora was inhibited by the addition of sodium deoxycholate.

Hydrophobic property of 136 Escherichia coli strains was examined by salt aggregation test (SAT). Out of the tested strains 61 were SAT positive. The correlations among the surface properties characterized by SAT and other phenotypical properties, e.g. mannose resistant haemagglutinating activity (MRHA), mannose sensitive haemagglutinating activity (MSHA), presence of antigen K1 and adsorption to Al(OH)3 gel were examined. The results showed that (i) Possession of antigen K1 provides the bacterial cell a hydrophilic character and covers its relative surface hydrophobicity; (ii) Correlation exists between the relative hydrophobicity of the bacteria determined by SAT and their haemagglutinating activity. SAT values are also influenced by non haemagglutinating fimbriae and also by other non fimbrial structures; (iii) The hydrophilic surface characters are mainly expressed by the results of adsorption to Al(OH)3 gel and the hydrophobic characters rather by the SAT values.

The connective tissue content of four different human liver tumors (Fibrolamellar carcinoma, FLC; hepatocellular carcinoma, HCC; focal nodular hyerplasia, FNH and hepatocellular adenoma, HCA) was investigated by computer aided morphometry. A significantly higher connective tissue content was found in FNH and FLC as compared to HCA and HCC. The distribution of the connective tissue was homogeneous in the cases of FNH, HCA and HCC, while a highly unhomogeneous distribution was observed in FLC cases.

The cellular localization of the p21 protein was studied by immunoelectron microscopy in human fibrosarcoma cells with different N-ras gene expression. The tumorigenic HT1080 cells--expressing equally the normal and mutant N-ras genes--contained the p21 in the plasma membrane, in pinocytotic areas as well as in the intracellular vesicles. The non-tumorigenic revertants--expressing more normal N-ras gene than the mutant one--contained p21 in the plasma membrane, especially at the cell junctions. These results suggest, that the mutant p21 may locate to the membrane areas connected with pino- or endocytotic functions.

The macromolecular composition and ultrastructure of the myotendineal junction (MTJ) of slow-twitch (type 1) and fast-twitch (type 2) muscle fibers were studied in the gastrocnemius-soleus-Achilles unit of the rat. Both proteoglycans and glycosaminoglycans, type III collagen, fibronectin and laminin could be detected at the MTJ. Due to membrane folding, finger-like processes were seen at the myotendineal junction. The processes of the type 1 fibers are greater in size, however, due to subdivisions, the processes of type 2 muscle fibers had a greater surface than type 1 fibers. The macromolecular composition is similar in both type 1 and type 2 muscle fibers.

In attempts to grow viruses from tumour cells and circulating lymphocytes, we isolated an oncogenic infectious adenovirus type 18 strain from the phytohaemagglutinin-stimulated peripheral T-lymphocytes of a patient with bladder tumour. The virus genome is assumed to play certain role in the development of the tumour in interaction with other DNA viruses and the damaged immune system.

Concanavalin-A (Con-A) gave rise to a moderate aggregation in untreated (control) Tetrahymena pyriformis GL populations. The cells pretreated (imprinted) with insulin or lectins underwent aggregation earlier and to a greater degree than the untreated control cells. Lens lectin, although of the same sugar specificity as Con-A, was considerably less active than the latter. Helix lectin and phytohaemagglutinin (PHA), although of similar sugar specificity, accounted for a dissimilar extent of cell aggregation, in that Helix lectin was comparable in activity to Con-A. Pretreatment (imprinting) with insulin enhanced the aggregation inducing effect of those lectins which were capable of overlapping on the insulin receptor owing to similar specificity.

Taking advantage of a mathematical equation applied so far in different fields the calculation of ATGCAT recognition sequence of restriction endonuclease from Streptococcus mutans serotype C (SmuC I) is reported together with confirming computer and physical mapping data.

One hour after treatment with 3H-benzpyrene, grains appeared for the most part above the hepatocellular surface, heterochromatin and dense vacuoles, whereas 24 h later they were associated mainly with the dense vacuoles and smooth-surfaced endoplasmic reticulum and only, a few were still present above the heterochromatin. Neonatal pretreatment (imprinting) with benzpyrene accounted for an earlier appearance of benzpyrene in the hepatocytes relative to the non-pretreated control, but while labelled benzpyrene had practically disappeared from the liver of imprinted rats within 24 h, it still persisted in the liver of control rats at a level approximating the 4 h value.