Expression and loss of the pBR322 plasmid in Klebsiella aerogenes NCTC 418, grown in chemostat culture

Klebsiella aerogenes harbouring the plasmid pBR322 was grown in continuous culture at various growth rates under glucose, phosphate or ammonia limitation. With tetracycline in the medium, the maximum culture -lactamase activity was found at the higher growth rates. When tetracycline was absent, loss of resistance to the drug occurred. Concomitant with the occurrence of drug-sensitive cells, the culture -lactamase activity decreased. At the higher growth rates the enzyme activity decreased at a slightly higher rate than did the resistance to tetracycline. From this it was concluded that the -lactamase activity per mg cellular dry weight of the drug-resistant fraction of the population was still decreasing during the appearance of drug-sensitive cells. At the higher growth rates, this decrease was independent of the nutrient that was growth-limiting.     

Dose dependent hypoglycemic effect of aqueous extract of Enicostemma littorale blume in alloxan induced diabetic rats.

Previous studies in our lab had confirmed the blood glucose lowering effect of E. littorale Blume in alloxan induced diabetic rats with no change in normoglycemic control rats. Present paper deals with dose dependent (0.5, 1.0, 1.5, 2.5, 3.5 g dry plant equivalent extract/100 g body wt., p.o.) blood glucose lowering effect of aqueous extract of E. littorale Blume in alloxan induced diabetic rats. The effective dose was found to be 1.5 g dry plant equivalent extract/100 g body wt.. The above dose caused significant decrease in glycosylated haemoglobin, liver glucose-6-phosphatase activity and significant increase in serum insulin levels of the diabetic rats. No significant changes were observed in the toxicity parameters of extract treated diabetic rats as compared to diabetic control rats. The above results suggest that E. littorale is a potent antidiabetic agent without any toxic effect at this particular dose (1.5 g dry plant equivalent extract/100 g body wt.).     

A comparative study of raw garlic extract and tetracycline on caecal microflora and serum proteins of albino rats

Studies conducted on the comparative action of raw garlic extract and tetracycline hydrochloride on equal concentrations showed the raw garlic extract to be a more potent antimicrobial agent than tetracycline. The reversion to normalcy of caecal microflora and serum proteins after the withdrawal of test materials indicated an inverse relation between intestinal microflora and serum globulins.     

The Influence of an Extract from the Marine Brown Alga <Emphasis Type="Italic">Sargassum pallidum</Emphasis> on the Metabolic Reactions in the Liver under Experimental Toxic Hepatitis

This study explores the influence of an extract enriched with polyphenol substances obtained from the brown alga Sargassum pallidum and the effect of the Legalon commercial reference preparation on the biochemical indices of the blood at acute hepatic injury induced in rats with carbon tetrachloride (CTC). Administration of S. pallidum extract exhibited a pronounced antioxidant and hepatoprotective effect revealed in reduction of alanine aminotransferase (AlAT) activity in blood plasm, in normalization of superoxide dismutase activity and reduced glutathione contents, of the level of lipid peroxidation, and the liver antiradical activity. We observed recovery of lipid metabolism and elimination of liver fatty infiltration. The S. pallidum extract was as effective as the reference Legalon hepatoprotector and even surpassed it in its ability to restore the phospholipid metabolism. In our opinion, this hepatoprotective effect of S. pallidum extract is associated with the action of polyphenols contained in brown algae, that is, phlorotannins, which are highly active antioxidants and restore the liver metabolic reactions after toxic hepatic injury with CTC.     

Isolation and identification of tetracycline resistant lactic acid bacteria from pre-packed sliced meat products

In recent years, the food chain has been recognised as one of the main routes for transmission of antibiotic resistant bacteria between the animal and human population. In this regard, the current study aimed to investigate if tetracycline resistant (tetR) lactic acid bacteria (LAB) are present in ready-to-eat modified atmosphere packed (MAP) sliced meat products including fermented dry sausage, cooked chicken breast meat and cooked ham. From population graphs based on doubling tetracycline concentrations between 0 and 256 microg ml(-1), only fermented dry sausage was shown to contain a high-level retR LAB population (5.10(1) - 2,23.10(4) CFU/g), and this in four out of ten examined sausages. From these four positive sausages, a total of 100 strains were isolated on de Man, Rogosa and Sharpe-sorbic acid (MRS-S) agar without tetracycline (n = 45) and on MRS-S agar supplemented with a tetracycline breakpoint concentration of 64 microg ml(-1) (n = 55). Using resistance histograms derived from the disc diffusion method, all these strains were grouped as sensitive to rifampicin, erythromycin and ampicillin. All strains from the tetracycline-containing MRS-S plates were resistant to tetracycline. Identification with whole-cell protein profiling revealed that the total strain set represented four different species: Pediococcus pentosaceus, Lactobacillus plantarum, Lactobacillus sakei subsp. carnosus and Lactobacillus curvatus. All species are commonly associated with fermented dry sausage, either as starter culture or as natural contaminants. The latter three species were found to comprise all tetracycline resistant strains. To our knowledge, this is the first report providing evidence for the presence of tetR LAB in final ready-to-eat pre-packed fermented dry sausages.     

Mechanism of the pro-oxidant activity of tetracycline

It was shown on male rats that like ethanol tetracycline increased lipid peroxidation (LPO) in the hepatocyte membranes, evident from increased levels of diene conjugates and malone dialdehyde in the liver homogenates, especially on their combination. The signal amplitude of the EPR-forms of cytochrome P-450 and Cu-, Mo- and Fe-containing proteins did not change, while the content of the EPR-forms of the free radicals increased. High efficiency of antioxidants, such as tocopherol acetate, sodium selenite and tincture of Astragalus L. is indirect evidence of the role of the free radicals in initiation of LPO in tetracycline affections of the liver.     

Upon the observation of superbeads in chromatin.

There exist some indications that nucleases recognize "superbeads" in chromatin. We show that a chromatin extract of rat liver which contains so-called "superbead"-peaks can be separated in a Mg++ soluble and a Mg++ insoluble fraction. The Mg++ insoluble fraction contains the full complement of histones and the expected DNA fragments, but has lost the characteristic peaks in sucrosegradient profiles. These discrete peaks are found in the Mg2+ soluble fraction of the chromatin extract. We give evidence that these peaks are RNP particles on the basis of their protein- and nucleic acid contents.     

The antioxidant and stress-protective properties of an extract from the green alga <Emphasis Type="Italic">Ulva lactuca</Emphasis> Linnaeus, 1753

The effects of an extract from the green alga Ulva lactuca and the Essentiale® commercial preparation, which was used as a reference, on the weight indexes of the viscera and the biochemical markers of the liver have been studied in a model of acute stress in rats. Acute stress was simulated by suspending animals in the upright position by their neck dorsal skin fold for 24 hours. Administration of the U. lactuca extract to rats exposed to the extreme stress resulted in a pronounced preventive action, which was manifested in the support of the weight index of their viscera, lipids metabolism, the antioxidant defense system of liver, and a reduction of lipid peroxidation. The extract from U. lactuca was no less effective in protecting the metabolic reactions of the liver under acute stress than the Essentiale® commercial preparation. The pronounced protective properties of the U. lactuca extract are explained by the combined effects of phospholipids of marine origin, n-3 PUFAs, and antioxidant polyphenols that comprise it.     

Determination of the biological activity of antibiotics by using dry nutrient media

The possibility of using available dry nutrient media Nos. 5 to 12 in assays of antibiotic biological activity with the agar diffusions method was studied with respect to benzylpenicillin, gramicidin S, kanamycin sulfate, kanamycin B, oleandomycin, novobiocin, tetracycline and erythromycin. The dry media were used instead of the respective media prepared with meat hydrolyzate. Optimal conditions of the assays on such media were determined.     

Seasonal variation in nutritional composition and anti-proliferative activity of brown seaweed, <Emphasis Type="Italic">Sargassum oligocystum</Emphasis>

This study investigated the nutritional components and anti-proliferative activity of Sargassum oligocystum against an adriamycin-resistant human small cell lung carcinoma cell line (GLC4/Adr). The seaweed samples were collected from Nang Rong Beach, Chonburi Province, Thailand in February (the hot/dry season), May (the early monsoon season), August (the monsoon season) and December (the cool/dry season) of 2012. In general, the nutritional composition of S. oligocystum was high during the hot dry and early monsoon season. Additionally, four different types of extract were obtained: ethanolic extract (E1), lipophilic extract (E2), acidic extract (E3) and alkali extract (E4). The highest anti-proliferative activity was found in samples collected during the monsoon season. It is noteworthy that the E2 extract collected during the monsoon season was the most effective, with an IC₅₀ (half maximal inhibitory concentration) value of 2.52 ± 0.54 μg mL^?1. The anti-proliferative activity showed a positive correlation with vitamin E (α-tocopherol) in the extracts. However, there were no clear correlations between the total phenolic or fucoxanthin contents and anti-proliferative activity. These results indicate that S. oligocystum has potential as an alternative source for functional food or cancer treatments in the future.     

Cost-effective multiplication of the entomopathogenic fungus Nomuraea rileyi (F) Samson

Cost-effective and rapid multiplication of Nomuraea rileyi is reported. The spore yields in semi-synthetic media were comparable or significantly higher to the standard medium. Maltose and peptone, carbon and nitrogen sources could be effectively replaced with 2% barley extract and 1% soybean extract respectively. However, replacement of yeast extract with dry yeast resulted in lower spore yields. Sporulation of the fungus multiplied on solid substrate was possible only when the bags used had a 0.2 m filter to facilitate passive exchange of sterile air. A high spore yield of 2.8 × 10⁹/g of substrate was realized on crushed sorghum.This revised version was published online in October 2005 with corrections to the Cover Date.     

Doxycycline regulation in a single retroviral vector by an autoregulatory loop facilitates controlled gene expression in liver cells

The tetracycline system has limitations in liver cells, such as toxic effects and low controllability. We generated different retroviral vectors for controlled gene expression in liver cells, in which the regulatory elements were arranged in different patterns. Only the organization of the tetracycline system in an autoregulatory loop in the sense orientation results in high retroviral titres and in tight regulation of gene expression in highly differentiated hepatoma cells. Because of the toxicity of the transactivator tTA, it was impossible to establish doxycycline-dependent stable HepG2 cell lines. To avoid sequelching-related toxicity in liver cells, we replaced tTA with new non-toxic transactivators. By using tTA2, tTA3 and tTA4, we observed tight doxycycline-dependent gene expression in 23, 49 and 45% of the isolated clones. The tTA4 vector was used to transduce hepatocytes of mice in vivo. Tight doxycycline-controllable gene regulation was also observed in the liver of mice, confirming our hypothesis that retroviral vectors with autoregulatory loops of the tetracycline system facilitate inducible gene expression in the liver in vivo. Our new retroviral vector system allows rapid isolation of controllable clones in a very high yield and should make the tetracycline system more applicable to liver-derived cells and in liver gene therapy in vivo.     

Effect of antimicrobials on cholesterol synthesis and content in liver and small intestines.

The antimicrobials tetracycline, ampicillin and bactrim (cotrimoxazole) decreased HMG CoA reductase activity in liver and small intestines of albino rats. Diminished incorporation of 1, 2, 14C acetate into cholesterol of small intestines in bactrim group was noted. There was a significant fall in cholesterol content of liver, duodenum, jejunum and ileum of the bactrim group and jejunum only in tetracycline group.     

Effect of benzylpenicillin and tetracycline on the phagocytic, nonspecific humoral and biochemical activity of uninfected animals

The effect of benzylpenicillin and tetracycline on the activity, intensity and completion of phagocytosis with the leucocytes of the peritoneal exudate, on the activity of lysozyme and beta-lysins of the blood serum, on the content of nucleic acids, the activity of succinate dehydrogenase and total and acid phosphatase in the liver and kidney cells was studied experimentally on noninfected albino mice. The study showed that administration of benzylpenicillin and tetracycline to the animals for 5 days induced a decrease in the activity of the cell and humoral defence and the activity of the above enzymes in the liver and kidney cells. The content of the nucleic acids did not change under the effect of the antibiotics.     

Partial purification and some properties of a liver alkaline ribonuclease from the frog Rana esculenta.

1. RNAases varying in pH optimum, activation with pCMB, sensitivity towards temperature and acid treatment, as well as electrophoretic mobility were found in Rana esculenta liver extract. 2. Of the three activity peaks of alkaline ribonuclease separated on CM-cellulose with 2000-fold purification, RNAase of peak C is thermo- and acid-stable and exhibits specificity for pyrimidine bases, preferring poly(U) over poly(C). 3. Differences in the specific "inhibitory effect" of frog liver supernatant on the frog liver alkaline RNAase were observed.     

Effects of an extract of adult rat liver on Reuber H-35 hepatoma cells in vitro]

The effects of an extract from adult liver on hepatoma cells cultivated in vitro (line H-35) are studied with cytological and quantitative cytochemical methods. This extract inhibits cell multiplication and premitotic DNA synthesis. The treated cells form "trabeculae" looking like those observed when normal adult hepatocytes are cultivated in vitro.     

Stabilization of rat liver tyrosine aminotransferase by tetracycline.

Rat liver tyrosine aminotransferase was purified 200-fold and an antiserum raised against it in rabbits. 2. Hepatic tyrosine aminotransferase activity was increased fourfold by tyrosine, twofold by tetracycline, 2.5-fold by cortisone 21-acetate and ninefold by a combination of tyrosine and cortisol administered intraperitoneally to rats. 3. Radioimmunoassay with 14C-labelled tyrosine aminotransferase, in conjunction with rabbit antiserum against the enzyme, revealed that cortisol stimulates the synthesis of the enzyme de novo, but that tetracycline has no such effect. 4. Incubation of rat liver homogenates with purified tyrosine aminotransferase in vitro leads to a rapid inactivation of the enzyme, which tetracycline partially inhibits. 5. The inactivation is brought about by intact lysosomes, and the addition of 10mM-cysteine increases the rate of enzyme inactivation, which is further markedly increased by 10mM-Mg2+ and 10mM-ATP. Here again tetracycline partially inhibits the decay rate, leading to the inference that the increase of tyrosine aminotransferase activity in vivo by tetracycline is brought about by the latter inhibiting the lysosomal catheptic action.     

Doxycyline regulation in a single retroviral vector by an autoregulatory loop facilitates controlled gene expression in liver cells

The tetracycline system has limitations in liver cells, such as toxic effects and low controllability. We generated different retroviral vectors for controlled gene expression in liver cells, in which the regulatory elements were arranged in different patterns. Only the organization of the tetracycline system in an autoregulatory loop in the sense orientation results in high retroviral titres and in tight regulation of gene expression in highly differentiated hepatoma cells. Because of the toxicity of the transactivator tTA, it was impossible to establish doxycycline-dependent stable HepG2 cell lines. To avoid sequelching-related toxicity in liver cells, we replaced tTA with new non-toxic transactivators. By using tTA2, tTA3 and tTA4, we observed tight doxycycline-dependent gene expression in 23, 49 and 45% of the isolated clones. The tTA4 vector was used to transduce hepatocytes of mice in vivo. Tight doxycycline-controllable gene regulation was also observed in the liver of mice, confirming our hypothesis that retroviral vectors with autoregulatory loops of the tetracycline system facilitate inducible gene expression in the liver in vivo. Our new retroviral vector system allows rapid isolation of controllable clones in a very high yield and should make the tetracycline system more applicable to liver-derived cells and in liver gene therapy in vivo.     

Interaction of a bovine thymic peptide extract with vasoactive intestinal peptide (VIP) receptors

Bovine t hymic peptide extract (1–100 g/ml) is shown to completely inhibit the binding of [¹²⁵I]VIP to rat blood mononuclear cells, lymphoid cells of spleen, and liver plasma membranes. In the three models, the bovine thymic peptide extract inhibits [¹²⁵I]VIP binding with a potency that is 4000–7000 times lower than that of the native VIP, on a weight basis. In rat liver plasma membranes, the bovine thymic peptide extract stimulates adenylate cyclase with a maximal efficiency that is similar to that of VIP. At maximal doses, VIP and thymic peptide extract do not exert an additive effect on adenylate cyclase, suggesting that the activation of the enzyme by the bovine thymic peptide extract occurs through VIP receptors. Finally, no VIP-like immunoreactivity was detected in the thymic peptide extract using an antiserum raised against mammalian VIP. All these data suggest the presence in the bovine thymic peptide extract of a new substance which behaves as a VIP agonist in rat.