A note on the microbial spoilage of undercooked chub-packed luncheon meat

Contrary to expectations slight undercooking (68.5°C instead of 70°C for 90 min) dramatically increased the shelf-life of chub-packed luncheon meat stored at 25°C. The pH of undercooked chubs fell rapidly to below 5.0 as a result of the growth of enterococci. The accumulated acid prevented the growth of Bacillus spores and gave the luncheon meat a not unpleasant tangy flavour. Degradative changes associated with the spoilage of commercially cooked chub-packed luncheon meat did not occur, even after 42 d storage. Apparently, post-cooking fermentation by enterococci can effectively convert a perishable product into a 'shelf stable' one by lowering the pH below 5.0.     

Safety evaluation of nuclear polyhedrosis virus replication in pigs

To evaluate the hygienic risk involved in using baculoviruses for insect pest control, safety studies are required. Pigs were chosen as representative test animals of commercial and agricultural importance. The tests were aimed at detecting virus propagation, immune reactions, and signs of acute infection (changes in body temperature and hematology profile, swelling of lymph nodes). Four of five animals inoculated with nuclear polyhedrosis virus showed a slight temperature rise at day 2 postinfection. After day 4 postinfection, no differences between infected animals and controls were observed. In the bioassay, virus activity could be recovered from fecal samples; however, no activity was found in organ extracts. The data did not indicate hygienic risks involved in the application of nuclear polyhedrosis virus, especially that from Mamestra brassicae, in biological pest control.     

Two possible conformations of the repetitive site of the immunoglobulin G3 hinge region

Conformational analysis of immunoglobulin G3 (IgG3) hinge region repeating part was performed. In approximation of backbone regular conformations for the case of C2 symmetry (the symmetry axis is perpendicular to S-S bridges and passes through their midpoint) on the basis of total analysis of ring geometry possibilities and estimation of steric conditions, the existence of two conformations with n = 3 (3(10) helix type and polyproline II type) was inferred. A possible role of these conformations in the immunoglobulin functioning was discussed.     

Standardization of high-resolution flow cytometric DNA analysis by the simultaneous use of chicken and trout red blood cells as internal reference standards

Determination of nuclear DNA content by flow cytometry requires comparison with a reference standard. The use of external standards such as lymphocytes or granulocytes is time-consuming and inaccurate. Chicken red blood cells (CRBC) have a DNA content of 35% of the human diploid value and have been widely used as internal standard. The ratio calculated on the basis of the peak channel numbers of the standard and the sample and used to indicate the DNA content (DNA ratio) is, however, very sensitive to changes in the zero level adjustment of the flow cytometer. If two internal standards are used the DNA ratio becomes independent of the zero level. Rainbow trout red blood cells (TRBC) have a DNA content of 80% of human diploid cells. A mixture of CRBC and TRBC was prepared and stored in small aliquots at -80 degrees C. This mixture was added to the sample before staining. The day-to-day variation of the DNA ratio obtained by use of the two standards was smaller than that obtained by CRBC alone. The possibility of sex related differences in DNA content of CRBC and TRBC was examined. The results indicated that a new batch of standards should be tested against the old batch to avoid the introduction of a systematic error.     

Effect of vitamin B3-active compounds on the content of free and combined gamma-aminobutyric acid and glutamic acid in the brain of mice

The bound and free GABA and glutamic acid content in the brain of F1 (CBA X C57B1/6) hybrid mice was investigated by the Eliott method. A tendency to a decrease of GABA and glutamate content in the brain with their practically constant bound/free ratio was observed 24 h after calcium-D-pantothenate injections (150 mumole/kg, 9 injections for 3 days). Calcium-D-homopantothenate injected in the same way caused a significant decrease in the GABA content, and a sharp drop of the bound/free GABA ratio. The effect is not associated with the influence of calcium ions in the composition of the injected compounds.     

Effect of various respiration substrates and growth marker proteins on oxygen consumption in rabbit heart mitochondria

Oxygen uptake by myocardium mitochondria of healthy, carcinomatous and new-born rabbits in the presence of different substrates was studied under the effect of immunoglobulin G and beta-globulin peculiar to the normal and malignant growth. It is stated that the growth marker proteins representing a subfraction of immunoglobulin G of tumour patients blood serum and beta-globulin of new-born rabbits blood serum in the presence of pyruvate, alpha-ketoglutarate and glutamate inhibit the oxygen uptake by healthy rabbits heart mitochondria. Studies conducted on mitochondria of new-born and carcinomatous rabbits show that the action of the proteins under study depends on the respiration substrate. In the presence of succinate the proteins under study activate the oxygen uptake and pyruvate, alpha-ketoglutarate and glutamate inhibit this process. A conclusion is drawn that the effect of proteins peculiar to the growth process on the biological oxidation depends both on the substrate and structural state of mitochondria.     

Studies on (K+ + H+)-ATPase V. Chemical composition and molecular weight of the catalytic subunit

(1) A (K+ + H+)-ATPase preparation from porcine gastric mucosa is solubilized in sodium dodecyl sulfate, and is subjected to gel filtration. (2) A main subunit fraction is obtained, which is a protein carbohydrate lipid complex, containing 88% protein, 7% carbohydrate and 5% phospholipid. The Detailed composition of the protein and carbohydrate moieties are reported. (3) Sedimentation analysis of the subunit preparation, after detergent removal, reveals no heterogeneity, but the subunits readily undergo aggregation. (4) Acylation of the subunit preparation with citraconic anhydride causes a clear shift of the band obtained after SDS gel electrophoresis, but the absence of broadening and splitting of the band pleads against subunit heterogeneity. (5) Treatment of the subunit preparation with dansyl chloride indicates that the NH2 terminus is blocked, which favors the assumption of homogeneity of the protein. (6) Binding studies with concanavalin A indicate that at least 86% of the subunit preparation is composed of glycoprotein. (7) These findings, taken together, strongly suggest that there is a single subunit which is a glycoprotein and which represents the catalytic subunit of the enzyme. From sedimentation equilibrium analysis a molecular mass value of 119 kDa (S.E. 3, n = 6) is calculated for protein + carbohydrate and of 110 kDa (S.E. 3, N = 6) for protein only. (8) In combination with the molecular mass of 444 kDa (S. E. 10, n = 4) obtained for the intact enzyme by radiation inactivation we conclude that the enzyme appears to be composed of a homo-tetramer of catalytic subunits.