Enhanced activity of deoxyuridine 5′-triphosphatase in regenerating rat liver

An enzyme, dUTPase, that catalyzes the conversion of dUTP to dUMP and PPi, was partially purified from regenerating rat livers. The molecular weight was estimated by gel filtration to be 60,000. The apparent Km for dUTP was 12 μM. No other deoxyribonucleoside triphosphates served as a substrate. This enzyme is active in the absence of added divalent cations or sulfhydryl reagents; the activity could be inhibited by EDTA and shows a broad pH optimum with no decrease in activity from pH 7 to 11. The specific activity of dUTPase in rat liver begins to rise 16 h after partial hepatectomy and reaches a maximum about 24 h after the operation, rising to at least 5 to 6 times the normal level.     

A three-dimensional computerized reconstruction of the rectum, anus and surrounding muscles of the rat fetus at the 20th gestation day

Using fetuses of Wistar/I rats on the 20th gestation day. We designed a three-dimensional computerized reconstruction of the rectum, anus and the surrounding muscles. The tissues were fixed in Bouin's solution sagittally sectioned serially were stained with hematoxylin-eosin. Light microscopic pictures at 40 x magnification were subjected to the analysis using a three-dimensional image processing system, consisting of a drum-scanner, a general purpose computer (Micro VAX II), and a color image processor. The results showed that this system clearly reconstructed the three-dimensional image of the rectum, anus and the surrounding muscles and suggested the presence of the puborectal muscle sling.     

Mechanism of induction of cellular DNA synthesis by the adenovirus E1A 12S cDNA product

The mechanism of induction of DNA synthesis in quiescent rat 3Y1 cells by the adenovirus E1A gene was investigated using the 3Y1 derivative cell lines g12-21, gn12RB1, and gn12RB2. The g12-21 cells express the E1A 12S cDNA and the latter two cells express both the E1A 12S cDNA and the human retinoblastoma susceptibility (Rb) gene at different levels in response to dexamethasone (dex). The cDNA sequences of E1A-inducible cell cycle-dependent genes, clone 3 and clone 16, were isolated by differential screening of a cDNA library constructed from dex-treated g12-21 cells. The quiescent 3Y1 cells induced c-fos and c-myc expression within 2 h after serum stimulation and expressed clone 16 and clone 3 transiently at around 8 h before the onset of DNA synthesis (10 h). In contrast, the quiescent g12-21 cells treated with dex expressed a high level of E1A at 6 to 8 h after treatment and expressed clone 16 and clone 3 at around 8 h without stimulation of c-fos and c-myc expression, suggesting that E1A bypasses the cell cycle early in G1. The half-maximal rate of DNA synthesis was reached in a much shorter time in dex-treated g12-21 cells (12 h) than in serum-treated 3Y1 cells (18 h), suggesting that E1A also bypasses the cell cycle at the G1/S boundary. The gn12RB1 and gn12RB2 cells were unable to induce DNA synthesis in response to dex presumably due to lower levels of E1A expression, although gn12RB2 but not gn12RB1 cells could express clone 16 and clone 3. These results suggest that the level of E1A required for bypass at the G1/S boundary is higher than that required early in G1.     

Alteration of mitochondrial genomes containing atpA genes in the sexual progeny of cybrids between Raphanus sativus cms line and Brassica napus cv. Westar

Summary We have investigated the fate of the mitochondrial genomes of cybrids derived from donor-recipient protoplast fusion between X-irradiated Raphanus sativus (cms line) and iodoacetamide-treated Brassica napus cv. Westar. Two out of ten fusion products were male-sterile with the diploid chromosome number of B. napus. The mitochondrial (mt) genomes of the cybrids and their progeny were further analyzed by DNA-DNA hybridizaion using the pea mitochondrial ATPase subunit gene (atpA) as a probe. One cybrid, 18-3, had a 3.0 kb fragment characteristic of B. napus and a 2.0 kb non-parental fragment when the BamHI-digested DNA was hybridized with the probe. In the first-backcrossed progeny of this cybrid, the hybridization pattern was not stably inherited. A 4.0 kb radish fragment, not detectable in the cybrid, appeared in one of the BC₁ generation siblings, and the 2.0 kb non-parental fragment was lost in another. The hybridization patterns in BC₁ progeny siblings of cybrid 12-9 were also varied. The alteration of mtDNA in the cybrid progeny continued to the BC₂ generation. There was no clear evidence of a heteroplasmic state or of sub-stoichiometric molecules in the mt genome of cybrid 18-3. A possible cause of the observed alteration in the mt genome is discussed.     

DNA ligase I mRNA and enzyme levels in human hematopoietic cells under dimethyl sulfoxide-induced growth-arrest and differentiation.

About half the activity level of DNA ligase I in cycling human lymphoblastoid cells (Raji and Akata) remained in the cells arrested at G1 by a 4-day treatment with 1.5% dimethyl sulfoxide (DMSO), and one-third the enzyme activity in actively growing promyelocytic leukemia cells HL-60 was detected in the terminally differentiated cells after DMSO-treatment. In contrast, DNA ligase I mRNA was negligible in the G1-arrested Raji and differentiated HL-60 cells. The steady-state mRNA level was increased 9 h after release from DMSO in the G1-arrested Raji cells and reached a maximum at 18 h. These results indicate that gene expression of human DNA ligase I, but not activity level of the enzyme, is closely correlated with activity of cell proliferation.     

Local formation and degradation of endothelin-1 in guinea pig airway tissues

Endothelin(ET)-1 and big ET-1 caused potent and sustained constriction of isolated guinea pig bronchus. The response to ET-1 was enhanced by phosphoramidon in a simple dose-related manner (0.01-1000 microM), while the response to big ET-1 was enhanced at lower doses (0.01-0.1 microM) but was suppressed at higher doses (100-1000 microM) of phosphoramidon. Big ET-1, when given intravenously (i.v.) to anesthetized guinea pigs, increased both bronchopulmonary inflation pressure and mean arterial blood pressure (2.5, 5, 10 nmol/kg i.v.). The pressor response to big ET-1 was attenuated by phosphoramidon dose-relatedly, while the pulmonary response was modified in a complex fashion composed of delayed onset and prolonged duration of action. These results suggest that ET converting as well as degrading enzymes coexist in the airway tissue and both enzymes are sensitive to phosphoramidon, so that phosphoramidon acts bifunctionally to reduce and stimulate the airway responses to big ET-1.     

Immunological detection of propolypeptide of von Willebrand factor on platelet surface

Recently we have found that propolypeptide of von Willebrand factor (pp-vWF) obtained from platelets binds to type I collagen. It is known that pp-vWF is present in platelet alpha-granules and is secreted upon activation. In this paper, we demonstrate the two following evidences to show that it is also present on the surface of resting platelets. [1] The antibody against pp-vWF bound to the surface of platelets. [2] The antibody induced aggregation of platelets. The binding of the antibody and the antibody-induced aggregation of platelets were inhibited in a dose-dependent manner by Fab fragment of the antibody. Platelets from von Willebrand disease patients bound less of the antibody and responded weakly to the antibody.     

Growth of a human yolk sac tumor cell line with yolk sac-derived functions in selenium-supplemented chemically defined synthetic medium

Summary A human yolk sac tumor cell line, TG1, which was established from a testicular yolk sac tumor, was found to replicate continuously in a chemically defined medium supplemented with Na₂SeO₃ (ISRPMI). TG1 produced several plasma proteins and growth factors: albumin, alpha-fetoprotein (AFP), ferritin, carcinoembryonic antigen, beta-2-microglobulin, polyamine, neuron specific enolase, tissue polypeptide antigen, transferrin (Tf), epidermal growth factor, and platelet derived growth factor. By analysis of lectin (LcHA)-affinity electrophoresis, to examine the microheterogeneity of carbohydrate chains of synthetic glycoproteins, TG1 cells cultured with ISRPMI produced only LcHA reactive Tf and AFP based on core fucose attached to asparagine-linkedN-acetylglucosamine residues instead of LcHA-nonreactive Tf and AFP produced by TG1 cells cultured with fetal bovine serum (FBS)-containing medium.α1-6 Fucosyltransferase activity was significantly greater in the TG1 cells cultured with ISRPMI (39.9±1.5 pmol · h⁻¹ · mg⁻¹ protein) than cultured with FBS-containing media (18.2±1.2 pmol · h⁻¹ · mg⁻¹ protein). These results have indicated that the selective increase ofα1-6 fucosyltransferase occurred when the cells were cultured with the FBS-free synthetic media.     

Molecular cloning and nucleotide sequence of cDNA encoding the rat kidney S-adenosylmethionine synthetase.

We previously reported the isolation of a cDNA encoding the liver-specific isozyme of rat S-adenosylmethionine synthetase from a lambda gt11 rat liver cDNA library. Using this cDNA as a probe, we have isolated and sequenced cDNA clones for the rat kidney S-adenosylmethionine synthetase (extrahepatic isoenzyme) from a lambda gt11 rat kidney cDNA library. The complete coding sequence of this enzyme mRNA was obtained from two overlapping cDNA clones. The amino acid sequence deduced from the cDNAs indicates that this enzyme contains 395 amino acids and has a molecular mass of 43,715 Da. The predicted amino acid sequence of this protein shares 85% similarity with that of rat liver S-adenosylmethionine synthetase. This result suggests that kidney and liver isoenzymes may have originated from a common ancestral gene. In addition, comparison of known S-adenosylmethionine synthetase sequences among different species also shows that these proteins have a high degree of similarity. The distribution of kidney- and liver-type S-adenosylmethionine synthetase mRNAs in kidney, liver, brain, and testis were examined by RNA blot hybridization analysis with probes specific for the respective mRNAs. A 3.4-kilobase (kb) mRNA species hybridizable with a probe for kidney S-adenosylmethionine synthetase was found in all tissues examined except for liver, while a 3.4-kb mRNA species hybridizable with a probe for liver S-adenosylmethionine synthetase was only present in the liver. The 3.4-kb kidney-type isozyme mRNA showed the same molecular size as the liver-type isozyme mRNA. Thus, kidney- and liver-type S-adenosylmethionine synthetase isozyme mRNAs were expressed in various tissues with different tissue specificities.     

Late quaternary dynamics of pollen influx at mineral lake,Washington

Pollen influx analysis at Mineral Lake, Washington, indicates that immediately south of the Puget Lobe of the Fraser Glaciation, tundra was a characteristic vegetation until 16,300 years ago. Invasion ofPinus contorta began 17,500 years B.P., and boreal climax conifers (Abies, Picea andTsuga mertensiana), 16,300, but was temporarily interrupted by the Vashon advance (14,500–14,000 yr B.P.).Pseudotsuga menziesii began to grow in population 10,750 years ago, and woodland was established within a time span of 1,000 years. Modern lowland coniferous forests began to form 7,000 years ago. Logistic analysis of pollen abundance changes show that the intrinsic growth rate,r (yr⁻¹), of pioneer species (e.g. 0.024–0.026 inPteridium aquilinum) is higher than that of climax species (e.g. 0.003 inThuja plicata).P. menziesii, a subclimax species, shows an intermediater value (0.013) between these two ecologically different taxa. The absoluter value ofP. contorta (−0.011) is only slightly lower than that ofP. menziesii, although their replacement began almost simultaneously. Thus competition between these species was intense before the inflection point ofPinus curve 10,100 years ago. At this time, forest gaps became abundantly available forPseudotsuga, as indicated by a peak of the diagnostic factor (the reciprocal of the pollen influx).