Effect of TPA on the mutagenicity of caffeine in the soybean mutation test

12-O-Tetradecanoylphorbol-13-acetate (TPA) is a well-known tumor promoter in mouse-skin carcinogenesis. Its effects on mutagenesis in a soybean test system were examined, and the effects were judged from the appearance of spots of various colors on the leaves. When soybean seeds were treated with TPA plus 0.03% caffeine, the frequency of spots per leaf decreased significantly and in proportion to the concentration of TPA. TPA alone at concentrations of 1–20 μg/ml did not induce any mutations. Mutations induced by γ-rays were not affected by administration of TPA either before or after exposure to γ-rays. The mechanism of suppression by TPA of mutations induced by caffeine is discussed.     

Weak Light-Induced Oxygen Consumption Observed during Photoreactivation Is Coupled to the Recovery of Oxygen Evolving Activity

During photoreactivation of the O₂-evolving center in Tris-inactivated/Mn-depletedthylakoids, a slow O₂-consumption occurred. This O₂-consumptionbecame detectable when the O₂-evolving activity of thylakoidswas inactivated by Tris-treatment and decreased as photoreactivationproceeded. The O₂-consumption and photoreactivation similarlyrequired Mn²⁺ at µM levels in addition to PSII electrondonors and shared severa common characteristics. Stimulationof O₂-consumption and photoreactivation by these cofactors werealways accompanied by enhancement in chlorophyll fluorescenceinduction, suggesting the involvement of a Mehler-type reactionin photoreactivation. Although the electron transport due tothis O₂-consumption was rapid enough to oxidize 4 Mn²⁺ ionsto reconstitute the tetranuclear Mn-cluster in each O₂-evolvingcenter in a few seconds, actual recovery of O₂-evolving activityoccurred more slowly in a few minutes. It was inferred thatphotoreactivation in Tris-inactivated thylakoids is not a simplephotooxidation of Mn2²⁺ but involves more complicated processeswhich are coupled to the Mehlertype electron transport fromPSII to oxygen via PSI. (Received July 11, 1994; Accepted August 23, 1996)     

N-acetyl conjugates of basic amino acids newly identified in rat urine

Ninhydrin-negative conjugates of basic amino acids were isolated from rat urine and were characterized. The following conjugates of basic amino acids are the compounds newly identified in animal urine specimens, N^α-acetyl-N^π-methylhistidine, N^α-(N-acetyl-β-alanyl)histidine (N-acetylcarnosine), N^α-acetyl-N^G,N^′G-dimethylarginine, N^α-acetyl-N^G,N^G-dimethylarginine, and N^α-acetyl-N^?,N^?,N^?-trimethyllysine.     

Tanycyte absorption affected by the hypothalamic deafferentation in Japanese quail,Coturnix coturnix japonica

In Japanese quail, Coturnix coturnix japonica the tanycytes of the median eminence absorbed peroxidase injected into the third ventricle. The number of tanycytes showing peroxidase reaction was greater in the posterior median eminence than in the anterior median eminence. Following hypothalamic deafferentation, the tanycyte absorption was augmented both in the posterior and anterior median eminence. These findings suggest that axons of some neurons, which have inhibitory action on the tanycyte absorption, were transected by deafferentation resulting in augmentation of tanycyte absorption. A considerable number of ependymal cells lining the upper portion of the third ventricle and those of the pars nervosa also absorbed peroxidase. In birds with a deafferented hypothalamus, photostimulated ovarian growth was completely inhibited.     

A retrospective analysis of germline competence in rat embryonic stem cell lines

The factors responsible for conferring germline competence in embryonic stem (ES) cell lines remain unidentified. In the present study, rat ES cell lines (n = 17) were established with 3i medium (SU5402, PD0325901, CHIR99021), 2i medium (PD0325901, CHIR99021) or 2iF medium (PD0325901, CHIR99021, forskolin), and their potential for germline transmission to the G1 generation was examined. Rat strains were divided into an albino group (F344, Wistar or CAG/Venus transgenic rats with the Wistar background) or a colored coat group (Brown-Norway, Dark-Agouti, or BLK rats selected from >F3 generations of Wistar × Dark-Agouti rats based on their black coat color). Successful germline transmission was observed in 57 % (4/7), 40 % (2/5) and 100 % (5/5) of the ES cells established with 3i, 2i and 2iF media, respectively. ES cell lines from the homozygous CAG/Venus transgenic rats were established in all three media, but only the lines established with the 2iF medium were germline-competent. Neither coat-color (albino: 64 %, 7/11; colored: 67 %, 4/6) nor gender of the ES cell lines (XX: 67 %, 2/3; XY: 64 %, 9/14) were likely to affect germline transmission.     

cDNA cloning and characterization of an osmotically sensitive TRP channel from ascidian eggs

The transient receptor potential (TRP) ion channels are thought to be involved in the entry of calcium ion into cells. In this study, we isolated a cDNA clone, HrTRPV, that shows high homology to Caenorhabditis elegans OSM-9, a TRPV subfamily member of the TRP family, from a Halocynthia roretzi fertilized egg cDNA library. We analyzed its properties using HrTRPV-transfected cells. Upon reduction of extracellular osmolarity, the intracellular calcium concentration was found to increase in HrTRPV-transfected cells. This increase in intracellular calcium concentration was dependent on the presence of extracellular calcium ion and was inhibited by treatment with gadolinium ion, a stretch-activated calcium channel blocker. Thus, these results indicate that ascidian egg HrTRPV is an osmotically sensitive TRP channel.     

A missense mutant myostatin causes hyperplasia without hypertrophy in the mouse muscle

Myostatin, which is a member of the TGF-beta superfamily, is a negative regulator of skeletal muscle formation. Double-muscled Piedmontese cattle have a C313Y mutation in myostatin and show increased skeletal muscle mass which resulted from an increase of myofiber number (hyperplasia) without that of myofiber size (hypertrophy). To examine whether this mutation in myostatin gene affects muscle development in a dominant negative manner, we generated transgenic mice overexpressing the mutated gene. The transgenic mice exhibited dramatic increases in the skeletal muscle mass resulting from hyperplasia without hypertrophy. In contrast, it has been reported that a myostatin mutated at its cleavage site produces hypertrophy without hyperplasia in the muscle. Thus, these results suggest that (1) the myostatin containing the missense mutation exhibits a dominant negative activity and that (2) there are two types in the dominant negative form of myostatin, causing either hypertrophy or hyperplasia.     

Specific and sensitive detection of Alcaligenes species from an agricultural environment

A quantitative real‐time PCR assay to specifically detect and quantify the genus Alcaligenes in samples from the agricultural environment, such as vegetables and farming soils, was developed. The minimum detection sensitivity was 106 fg of pure culture DNA, corresponding to DNA extracted from two cells of Alcaligenes faecalis. To evaluate the detection limit of A. faecalis, serially diluted genomic DNA from this organism was mixed with DNA extracted from soil and vegetables and then a standard curve was constructed. It was found that Alcaligenes species are present in the plant phytosphere at levels 10²–10⁴ times lower than those in soil. The approach presented here will be useful for tracking or quantifying species of the genus Alcaligenes in the agricultural environment.