The Use of the Pressure Chamber Technique for Measurement of the Water Potential of Transpiring Plant Organs

The existence of water potential gradients in flowering shoots and leaves of roses (Rosa sp., cv. Baccara) and along flag leaves of wheat (Triticum aestivum L.) were studied by means of the Scholander pressure chamber. In roses grown in greenhouse, the water potential measured in transpiring shoots was higher than in leaves detached from these shoots, whereas the potential differences between leaf and shoot after equilibration in the dark were small or negligible. A progressive decrease in water potential was found upon repeated measurement on the same organ; this decline was steeper in leaves than in shoots. Extrapolating this decline to excision time resulted in water potential values which, in transpiring shoots, were 3 to 5 bars higher than in leaves. Detopping the flower bud did not alter this pattern, indicating that the highest water potential in the shoot was in the stem. In field-grown wheat, the water potential measured in a whole flag leaf was about 6 bars higher than that measured in the apical one-third of the leaf, and this difference disappeared after equilibrating the detached leaf for 1 h in the dark. These potential differences indicate the presence of resistances along the water path in the organ. The results obtained by the pressure chamber represent the highest water potential in the organ, rather than the average water potential.     

A new method for the assay of glutaminase activity: direct measurement of product formation by an ammonia electrode

A simple, reliable procedure is described for the quantitative assay of glutaminase reaction by measuring product formation using an ammonia electrode. The ammonia electrode is a gas-detecting electrode, sensing the level of dissolved ammonia in aqueous solutions. Ammonia concentration can be read from calibration curves after converting ammonium ion to ammonia by adding sufficient base. Sample color and turbidity do not affect measurements, and samples need not be distilled. The concentrations of the three glutaminase isoenzymes from rat tissues measured by this method are strictly comparable to those measured by other methods.     

Frequency, time and type of metastasis of different transplantable tumors in mice

The character of metastasis of 9 strains of transplantable mouse tumours in conventional subcutaneous inoculation was studied. There were differences in the frequency, intensity, and types of metastasis of different tumours. Periods of onset of metastases of Lewis lung carcinoma and RL-67, and also of sarcoma-37 were established. Sarcoma, Lewis and RL-67 lung carcinomas, adenocarcinoma of the colon AKATOL, Cloudman's melanoma and B-16 metastasized most intensively. Sarcoma-37 metastasizing into the regional and remote lymph nodes, Lewis lung carcinoma and melanomas metastasizing into the lungs, RL-67 lung carcinoma metastasizing into the lungs, kidneys, adrenal glands, ovaries, the heart, and also adenocarcinoma of the colon AKATOL metastasizing into the lymph nodes and the liver can be used as models for the research in the field of drug action upon metastases and the metastasis process.     

Regulatory factors produced by lymphocytes. I. The occurrence of multiple alpha-lymphotoxins associated with ribonuclease activity.

Supernatant fluids of mitogen-activated human tonsil lymphocytes contain large amounts of a factor toxic to mouse L cells. This substance, with a m.w. of 80,000 +/- 5,000 daltons, is called alpha-lymphotoxin (alpha-LT), to differentiate it from another toxin elaborated by mitogen activated human blood lymphocytes, called beta-lymphotoxin (beta-LT), which differs from alpha-LT in size (45,000 +/- 5,000 daltons), antigenicity, and stability. Further purification of alpha-LT by sequential phosphocellulose and DEAE-cellulose chromatography and polyacrylamide gel electrophoresis (PAGE) identifies a series of cytotoxins differing in ion exchange characteristics and electrophoretic mobilities. The three PAGE fractions (PAGE Ia, Ib and II), recovered in 2, 4.6, and 21% yield from the starting serum-free culture supernatant, represent purifications of 24-, 24- and 1851-fold, respectively. Each cytotoxic fraction has a ribonuclease activity. Comparison of RNase and mouse L cell cytotoxic activities of the three alpha-LT fractions shows that both activities for all three fractions have a similar temperature stability pattern and that both are similarly inhibited by DNA, single strand forms better than double strands, by glycerol in 5 to 20% concentration, and by protein denaturing reagents. These observations suggest, but do not prove, that mouse L cell toxicity and RNase activity are mediated by the same substance, which appears to occur in multiple or isozymic forms.