Activation of TIMP-2/progelatinase A complex by stromelysin.

Progelatinase A was purified as a complex with TIMP-2 from the conditioned medium of a human glioblastoma cell line. The TIMP-2/progelatinase complex was resistant to the activation by p-aminophenylmercuric acetic acid (APMA), and showed less than 10% of the activity of the TIMP-2-free active enzyme. When the complex was incubated with stromelysin in the presence of APMA, the 64-kDa progelatinase was effectively converted to the 57-kDa mature enzyme, increasing its gelatinolytic activity about 8-fold. These results suggest that stromelysin is a natural activator of TIMP-2-bound progelatinase A.     

VP-16-induced nucleotide pool changes and poly(ADP-ribose) synthesis: the role of VP-16 in interphase death

Exposure of human promyelocytic leukemia cell line (HL-60) to VP-16 resulted in accumulation of DNA strand breaks. Concomitantly, intracellular NAD levels fell at 1 h, followed by declines in ATP at 2 h and in GTP, CTP, and UTP at 3 h. Furthermore, marked morphological changes, such as loss of microvilli or bleb formation, appeared at 4 h and cell death by 8-10 h. The addition of an inhibitor of poly(ADP-ribose) polymerase, 3-aminobenzamide (5 mM), theophylline (2 mM), or thymidine (1 mM), prevented these sequential reductions of nucleotide pools and cell death. In fact, the activation of poly(ADP-ribose) synthesis was detectable within a few hours after treatment with VP-16, although it was smaller than that induced by N-methyl-N'-nitro-N-nitrosoguanidine. These results may suggest the possible role of activation of poly(ADP-ribosyl)ation in VP-16-induced nucleotide pool changes and subsequent interphase death.     

Flowering and Endogenous Levels of Plant Hormones in Lemna Species

The occurrence and endogenous level of various plant hormoneswere measured for the short-day plants Lemna paucicostata 151and 381 and the long-day plant Lemna gibba G3 to determine whetherany of them are involved in the photoperiodic control of flowering.ABA, IAA, GA₁, GA₂₉, GA₃₄, GA₅₃, trans- and cis-zeatin, trans-and cis-ribosyl zeatin, N⁶-(²-isopentenyl) adenine and N⁶-(²-isopentenyl)adenosine were definitely detected in each species, while GA₄was only detected in L. gibba G3 and GA₂₀ was only detectedin L. paucicostata 151. The endogenous levels of ABA and IAAwere in the range of 1–7 ng/g fr wt and were not significantlydifferent in vegetative and flowering plants. The endogenousgibberellin levels were generally higher in Lemna grown underlong-day rather than short-day conditions. The endogenous cytokininlevels were almost the same in both flowering and vegetativeplants of L. paucicostata 151 and 381. In L. gibba G3, however,the level of cis-ribosyl zeatin, N⁶-(²-isopentenyl) adenineand N⁶-(²-sopentenyl) adenosine were higher in vegetative thanin flowering plants. These results indicate that there is not necessarily a directrelation between endogenous plant hormone levels and flowering,and that the chemical basis for the photoperiodic control offlowering cannot be explained solely by changes in hormone levels.The possibility remains, however, that one or more of the planthormones has some influence of secondary importance on the floweringprocess in Lemna. (Received January 29, 1986; Accepted July 12, 1986)     

Synergistic effects of the myc and ras oncogenes on ganglioside synthesis by BALB/c 3T3 fibroblasts

The effects of oncogene activation on glycosphingolipid (GSL) synthesis by a mouse fibroblast clonal cell line were studied. A transfectant that expressed the activated ras gene showed a definite change in the composition of acidic GSLs, probably an increase in polysialoganglioside, while one that expressed the myc gene showed only a slight change. Neither transfectant grew in soft agar. However, another transfectant, which expressed both the myc and ras genes, and grew in soft agar, showed a more dramatic increase in the acidic GSL component. Thus, activations of the myc and ras oncogenes have a synergistic effect on GSL synthesis during transformation.     

Isolation and initial characterization of a temperature-sensitive mutant of mouse FM3A cells defective in cytokinesis

A temperature-sensitive mutant, designated tsFT101, was isolated from a mouse mammary carcinoma cell line, FM3A, and given an initial characterization. In this cell line, cytokinesis was blocked at a non-permissive temperature (39 degrees C), but DNA synthesis and nuclear division proceeded normally for at least 24 h at 39 degrees C as detected respectively by autoradiography and cytofluorometric analysis. As a result, multinucleate cells accumulated at 39 degrees C (more than 95% in 36 h). When the culture was returned to a permissive temperature (33 degrees C) after 24 h of arrest at 39 degrees C, cytokinesis was resumed and there was a rapid decrease in the number of multinucleate cells. At 39 degrees C, tsFT101 cells had less F-actin than cells at 33 degrees C, indicative of the existence of an abnormality in actin polymerization in this mutant.     

Effects of Some Growth Regulators and Benzoic Acid Derivatives on Flower Initiation and Root Elongation of Pharbitis nil, Strain Kidachi

Seedlings of Pharbitis nil, strain Kidachi, were grown undercontinuous light at 20°C in vessels containing 5,000-mlnutrient solution, 24 plants per vessel. NAA (0.005–0.5µM), GA₃ (0.1–0.5 µM), kinetin (0.5–5µM), benzyladenine (0.05–5 µM) or abscisicacid (4 µM) added to the nutrient solution induced long-dayflowering, and the flowering was always accompanied by suppressionof root elongation. 3,4-Dichlorobenzoic acid (0.05–10µM) and some other benzoic acid derivatives which arehighly effective for the induction of flowering in Lemna paucicostataalso showed similar effects. Neither NAA, kinetin nor 3,4-dichlorobenzoicacid applied via the apical part of the hypocotyl could causeflowering or suppression of root elongation. Thus, the flower-inducingeffect of the above substances was presumed to be secondaryto the suppression of root elongation. Ethrel (1–50 µM)added to the nutrient solution suppressed root elongation, butdid not induce flowering probably because it has flower-inhibitingactivity. ¹ This paper is dedicated to the memory of Dr. Joji Ashida,the first president of the Japanese Society of Plant Physiologists. (Received December 15, 1982; Accepted February 25, 1983)     

Flowering behavior of the hybrids between strains 6746 and 371 of Lemna paucicostata hegelm

Lemna paucicostata Hegelm. 6746, a short-day plant, flowers even under continuous light when CuSo₄, AgNO₃, K₃[Fe(CN)₆], or benzoic acid are added to the medium, or when blue light is given exclusively. All other strains tested, including strain 371, did not flower under any of these conditions. Crossing between strains 371 (♀) and 6746 (♂) produced some seeds, although the reciprocal crossing did not. None of the hybrids flowered in response to AgNO₃, or blue light, and only a few flowered in response to CuSO₄. Most of the hybrids, on the other hand, flowered in response to K₃[Fe(CN)₆] or benzoic acid, although the responses were lower than the mean of the parental. Further analysis could not be made because self-pollination or crossing between the hybrids did not produce any seeds. However, since sensitivities to the above 5 factors were passed on to the F₁ hybrids in varying degrees, the extraordinary high sensitivities to these factors of strain 6746 are considered to be governed by different genes. Otherwise, a single (or a few) gene(s) governing the sensitivities to these factors would be differently expressed in the hybrids.     

The androgen-dependent rat prostate protein,probasin, is a heparin-binding protein that co-purifies with heparin-binding growth factor-1

Summary Rat prostate extracts contain an abundant 20–22 kilodalton heparin-binding protein with near identical chromatographic properties, but only 0.2–1% of the mitogenic activity, of bovine brain heparin-binding growth factor-1 (acidic fibroblast growth factor). Amino terminal amino acid sequence (met-met-thr-asp-lys-asn-leu-lys-lys-lys-ile-glu-gly-asn-trp-arg-thr-val-tyr-leu-ala-ala-ser-?-val-glu-lys-ile-asn-glu-gly-ser-pro) and immunochemical analysis revealed that the protein is identical to the androgen-dependent protein “probasin”. This work was supported in part by NCI grant CA37589 (W. L. M., J. W. C.) and the Medical Research Council of Canada (R. J. M.).