Buried seed population in the herbaceous lomas on Loma Ancon in the coastal desert of central Peru

Herbaceous lomas in the Peruvian coastal desert, of South America establish in spring, and its habitat is limited to the southern or southwestern slopes along the coast that are affected by thick fog. The time of appearance, the duration and the thickness of the fog vary greatly from year to year, so the lomas can grow only in habitats with enough water to, sustain seed germination and plant growth. This paper studies the species composition and density of the buried seed population, of the herbaceous lomas of Loma Ancon in order to clarify the mechanisms of the lomas' establishment. The mean number of species with viable seeds was about, 12 spp. m⁻² and that of dead seeds was about 22 spp. m⁻². The dominant species wereSolanum tuberiferum, S. pinnatifidum andNolana humifusa, both in viable and dead seeds. Viable seed density was about 5000–8000 seeds m⁻², which is comparable with the seed densities of other herbaceous communities. Dead seed density was about 15000–27000 seeds m⁻², or nearly three times the viable seed density, because the rate of decomposition was slow in the extremely dry conditions. The net increase of viable seeds by seed production was estimated at about 5000 seeds m⁻² in 1980, and the increase in the number of dead seeds was 2200 seeds m⁻².     

Chemotaxis away from thiocyanic and isothiocyanic esters in Pseudomonas aeruginosa

Abstract A novel mycoplasmal species designated as Mycoplasma penetrans has recently been isolated from patients infected with human immunodeficiency virus. The 16S rRNA gene from this mycoplasma was cloned and its nucleotide sequence determined. This sequence was aligned with previously published homologous sequences from several mycoplasmas and with related Gram-positive bacteria and a phylogenetic tree was constructed. The results indicate that M. penetrans belongs to the evolutionary group Pneumoniae.     

A specific concanavalin A-mediated binding of bovine serum α-mannosidase to cultured human skin fibroblasts

A specific elevation of cell-associated α-mannosidase was observed in human skin fibroblasts cultured with concanavalin A for 12–72 hours. There was a latency of several hours before the increase of the enzyme activity occurred. When the cells were washed with α-methylmannoside, α-mannosidase activity was not increased. Other lysosomal enzymes including β-mannosidase showed a slight decrease in activity. It was concluded that the elevation of this enzyme activity was the result of a specific binding to the cell surface mediated by concanavalin A.     

Hypoxia-Induced Reactive Oxygen Species Cause Chromosomal Abnormalities in Endothelial Cells in the Tumor Microenvironment

There is much evidence that hypoxia in the tumor microenvironment enhances tumor progression. In an earlier study, we reported abnormal phenotypes of tumor-associated endothelial cells such as those resistant to chemotherapy and chromosomal instability. Here we investigated the role of hypoxia in the acquisition of chromosomal abnormalities in endothelial cells. Tumor-associated endothelial cells isolated from human tumor xenografts showed chromosomal abnormalities, >30% of which were aneuploidy. Aneuploidy of the tumor-associated endothelial cells was also shown by simultaneous in-situ hybridization for chromosome 17 and by immunohistochemistry with anti-CD31 antibody for endothelial staining. The aneuploid cells were surrounded by a pimonidazole-positive area, indicating hypoxia. Human microvascular endothelial cells expressed hypoxia-inducible factor 1 and vascular endothelial growth factor A in response to either hypoxia or hypoxia-reoxygenation, and in these conditions, they acquired aneuploidy in 7 days. Induction of aneuploidy was inhibited by either inhibition of vascular endothelial growth factor signaling with vascular endothelial growth factor receptor 2 inhibitor or by inhibition of reactive oxygen species by N-acetyl-L-cysteine. These results indicate that hypoxia induces chromosomal abnormalities in endothelial cells through the induction of reactive oxygen species and excess signaling of vascular endothelial growth factor in the tumor microenvironment.     

The Effects of Caffeine and Caffeine-containing Beverages on the Disposition of Brain Serotonin in Rats

Caffeine and caffeine-containing beverages (instant coffee, black tea, green tea, or oolong tea) caused a significant decrease in serum tryptophan, and significant increases in brain tryptophan, serotonin, and 5-hydroxyindole acetic acid over those in rats fed a control diet. Adenosine supplementation partially counteracted the increase of brain serotonin caused by caffeine. These results are interpreted as indicating that caffeine-containing beverages may have some nutritional and behavioral effects.     

Isolation of desmosomes from the epidermis of Xenopus laevis and immunochemical characterization of the Xenopus desmosomal cadherins

Here we report a new method of isolating epidermal desmosomes from Xenopus laevis, and a major constituent of desmosomes designated as Xenopus desmogleins (XDsg). Isolation of desmosomes from Xenopus laevis epidermis was carried out by a two step-incubation with different concentrations of NP-40. After discontinuous sucrose gradient centrifugation at 30,000 g for 60 min, a pure desmosomal fraction was obtained at 30%/40% interface. In the SDS-PAGE of isolated desmosomes, at least 12 bands (XDB1 to XDB12) were observed over a 75 kD region. Among them, three bands (XDB3, XDB7, XDB8; estimated MW 175, 124, and 112 kD respectively) were recognized as glycoproteins based on ConA binding. Monospecific polyclonal antibody against XDB3 cross-reacted with bovine Dsgs and vis-a-vis anti-bovine Dsgs with XDB3. By contrast, monospecific antibody against bovine Dsc a/b did not cross-react with either XDB7 or XDB8. Heterogeneous molecular constituents of desmosomal adhesion molecule, which have been observed among different bovine tissues, were confirmed in a phylogenetically different animal, Xenopus laevis. Combined results with other evidence could suggest an alternative system for desmosome-mediated cell adhesion.     

Activin receptors are expressed on human lung fibroblast and activin A facilitates fibroblast-mediated collagen gel contraction

Activin A is a member of the transforming growth factor-beta superfamily that exerts its diverse biological effects through bindings to activin specific transmembrane serine/threonine kinase receptors. The fibroblast-mediated contraction of a collagen gel is thought to be a model of part of the wound-repair response and tissue contraction. In this study, we found the expression of activin type I receptors (ActR-I and ActR-IB) and type II receptor (ActR-II) on human fetal lung fibroblasts (HFL-1) by RT-PCR and immunocytochemistry. We also examined the effects of activin A on the HFL-1-mediated collagen gel contraction. Activin A stimulated collagen gel contraction in a dose dependent manner and its effect was abolished by an activin-binding protein, follistatin, that specifically suppresses activin A activities. This study demonstrated that ActR-I, ActR-1B and ActR-II are expressed on human fetal lung fibroblast and that activin A regulates fibroblast-mediated collagen gel contraction, suggesting that activin A might contribute to human lung fibroblast activities and structural remodeling observed in pulmonary fibrosis.     

Small‐molecule auxin inhibitors that target YUCCA are powerful tools for studying auxin function

Auxin is essential for plant growth and development, this makes it difficult to study the biological function of auxin using auxin‐deficient mutants. Chemical genetics have the potential to overcome this difficulty by temporally reducing the auxin function using inhibitors. Recently, the indole‐3‐pyruvate (IPyA) pathway was suggested to be a major biosynthesis pathway in Arabidopsis thaliana L. for indole‐3‐acetic acid (IAA), the most common member of the auxin family. In this pathway, YUCCA, a flavin‐containing monooxygenase (YUC), catalyzes the last step of conversion from IPyA to IAA. In this study, we screened effective inhibitors, 4‐biphenylboronic acid (BBo) and 4‐phenoxyphenylboronic acid (PPBo), which target YUC. These compounds inhibited the activity of recombinant YUC in vitro, reduced endogenous IAA content, and inhibited primary root elongation and lateral root formation in wild‐type Arabidopsis seedlings. Co‐treatment with IAA reduced the inhibitory effects. Kinetic studies of BBo and PPBo showed that they are competitive inhibitors of the substrate IPyA. Inhibition constants (K_i) of BBo and PPBo were 67 and 56 nm , respectively. In addition, PPBo did not interfere with the auxin response of auxin‐marker genes when it was co‐treated with IAA, suggesting that PPBo is not an inhibitor of auxin sensing or signaling. We propose that these compounds are a class of auxin biosynthesis inhibitors that target YUC. These small molecules are powerful tools for the chemical genetic analysis of auxin function.