Combined effect of nisin and moderate heat on destruction of Listeria monocytogenes in cold-pack lobster meat.

The combined effect of nisin and moderate heat to increase the killing of Listeria monocytogenes in cans of "cold-pack" lobster was investigated. Adding nisin at a level of 25 mg/kg of can contents to the brine surrounding the lobster, in combination with a heat process giving internal can temperatures of 60 degrees C for 5 min and 65 degrees C for 2 min, resulted in decimal reductions of inoculated L. monocytogenes of 3 to 5 logs, whereas heat or nisin alone resulted in decimal reductions of 1 to 3 logs. Such a reduced heat process to that currently commercially used (65.5 degrees C for 13 to 18 min, depending on the can size) results in significant reduction in drained weight loss, thus allowing considerable cost savings to the lobster-processing industry.

Effect of emu oil on auricular inflammation induced with croton oil in mice.

OBJECTIVE: To determine the acute anti-inflammatory effects of topically applied emu oil. ANIMALS: 96 male CD-1 mice assigned randomly to 4 groups, each comprising 24 mice. PROCEDURE: To induce auricular inflammation, 50 microl of a solution comprising 10 microl of croton oil dissolved in 1 ml of acetone was applied to the inner surface of the left auricle (pinna). One hour later, 3 or 5 microl of emu oil (low- and high-dose groups, respectively) or 5 microl of porcine oil (oil-control) was applied to the left pinna. Control mice remained untreated. Six mice per group were euthanatized 3, 6, 12, and 24 hours after induction of inflammation. Specimens of auricular tissue (ear plugs) were obtained, using a 6-mm biopsy punch. Magnitude of swelling was calculated as the weight difference between left (inflamed) and right (noninflamed) ear plugs; degree of edema was determined as the difference between wet and dry weights of the left ear plug. RESULTS: Magnitude of swelling was significantly reduced at 6 and 12 hours in mice treated with emu or porcine oil, compared with controls. The greatest reduction in swelling was detected in the high-dose emu group at 6 hours. Compared with controls, degree of edema was significantly reduced at 6 hours only in the high-dose group, whereas by 12 hours, all groups treated with oils had significantly less edema than controls. At 24 hours, magnitude of swelling and degree of edema did not differ among groups. CONCLUSION: Topically applied emu oil significantly reduced severity of acute auricular inflammation induced by croton oil in mice.

Evaluation of different antimicrobial agents used as selective supplements for isolation and recovery of Yersinia enterocolitica.

Seventeen antimicrobial agents were evaluated separately or in combination for their efficiency as selective supplements in a broth medium against six different serotypes of Yersinia enterocolitica and 20 selected strains of different Gram-negative bacteria. Irgasan (DP300, 5-chloro-2-(2,4- dichlorophenoxy) phenol) at a concentration of 4 micrograms ml-1 inhibited the growth of most Gram-negative bacteria with the exceptions of Aeromonas hydrophila, Morganella morganii, Pseudomonas aeruginosa and Serratia liquefaciens. Other antimicrobial agents incorporated in the growth medium, separately or in combination with Irgasan, either inhibited some strains of Y. enterocolitica or did not inhibit the growth of Irgasan-resistant Gram-negative bacteria.

Evaluation of the ability of primary selective enrichment to resuscitate heat-injured and freeze-injured Listeria monocytogenes cells.

Resuscitation rates of injured Listeria monocytogenes on conventional selective Listeria enrichment broth and nonselective Trypticase soy broth containing 0.6% yeast extract were compared. Cells were heated to 60 degrees C for 5 min or frozen at -20 degrees C for 7 days. Inoculation of Trypticase soy broth-yeast extract with the stressed cells resulted in growth that was superior to that in Listeria enrichment broth. Injured cells were fully recovered at 6 to 8 h.

Evaluation of microsomes isolated from fresh and frozen myotomal tissue of Atlantic cod (Gadus morhua).

Microsomes were isolated from fresh and frozen myotomal tissue of Atlantic cod by two procedures. Electron microscopy revealed one method to yield microsomes containing greater quantities of myofibrillar debris than the other and this was reflected as reduced 5'-nucleotidase, acid phosphatase and succinate dehydrogenase marker enzyme activity. Overnight freezing of myotomal tissue did not affect the marker enzyme activity of microsomes isolated by either procedure. Morphological changes were observed among microsomes prepared from myotomal tissue retained for 8 weeks at -30 degrees C. Accordingly, 5'-nucleotidase was marginally elevated and acid phosphatase and succinate dehydrogenase activity reduced in comparison to fresh microsome preparations.

Free tyrosine levels of rat brain and tissues with sympathetic innervation following administration of L-tyrosine in the presence and absence of large neutral amino acids.

The tyrosine concentration of fasted rats was measured in plasma, brain and tissues receiving sympathetic innervation after L-tyrosine (200 mg/kg) was administered alone or in the presence of an equimolar cocktail containing isoleucine, leucine and valine. In the samples taken at 15, 30, 45, 60, 120 or 180 minutes, the highest concentrations of L-tyrosine were observed in plasma, heart, adrenal gland and kidney at 15 minutes, but in interscapular brown adipose tissue at 15 and 30 minutes and in brain at 15-60 minutes. The decline from peak concentrations was slower in brain, kidney and interscapular brown adipose tissue than in plasma, but in all tissues examined, control levels of free tyrosine were attained by 180 minutes postadministration . Competing large neutral amino acids reduced the maximal uptake of tyrosine in the brain by 48% but had no effect in the other tissues examined.

The effect of high-protein and high-carbohydrate diets on [125I]iodoinsulin binding in skeletal muscle plasma membranes and isolated hepatocytes of rainbow trout (Salmo gairdneri).

[125I]iodoinsulin-binding studies in the presence of a concentration range of bovine insulin were conducted to establish specific insulin-binding levels in skeletal muscle plasma membranes and isolated hepatocytes of rainbow trout (Salmo gairdneri) reared on control, high-protein or high-carbohydrate diets. Negative co-operativity was observed and receptor concentrations and apparent dissociation constants established for each preparation. No differences of specific binding attributed to diet were detected in skeletal muscle plasma membrane preparations; however, the receptor concentration of isolated hepatocytes from high-carbohydrate-reared trout was increased. This contrasted to comparable mammalian studies.