THE ECOLOGICAL IMPACT OF ALLELOPATHY IN AILANTHUS ALTISSIMA (SIMAROUBACEAE)

Compounds inhibitory to the growth of neighboring plant species were found in significant concentrations in the leaves and stems of young Ailanthus altissima ramets. The surrounding soil also contained appreciable concentrations of similarly acting toxins. Individuals of neighboring plant species have either incorporated active portions of inhibitory compounds or responded to Ailanthus by producing growth-inhibiting substances. Under greenhouse conditions, individuals of neighboring plant species previously unexposed to Ailanthus in the field were found to be more susceptible to the Ailanthus toxins than individuals previously exposed. Moreover, seeds produced by unexposed populations were also more susceptible to Ailanthus toxins than seeds produced by previously exposed populations. These differences demonstrated that the allelochemicals of Ailanthus altissima exhibited a measurable impact upon neighboring plant species. Since the progeny of these populations displayed a differential response to Ailanthus toxin, this phenotypic difference between the two populations may have a heritable basis.     

Notes on TYachoma, Tüberolabium and Parapteroceras (Orchidaceae)

The genus Trachoma is considered congeneric with Tüberolabium. All necessary transfers to Tüberolabium are made. Four new combinations are made in the recently established Parapteroceras. A key to the species of Parapteroceras and a key to Parapteroceras and allied genera are provided.     

Regulation of collagenase production by steroids in uterine smooth muscle cells: An enzymatic and immunologic study

An enzyme-linked immunosorbent assay (ELISA) has been developed for rat collagenase. The assay is capable of measuring the enzyme from a variety of rat cell sources at concentrations of 10–;50 ng/ml, approximately 500–;1,000-fold more sensitive than radiolabelled collagen fibril assay systems. The assay is specific to collagenase from the rat: enzymes from human, tadpole, mouse, and bacterial sources failed to cross-react significantly with rat enzyme. The assay is reproducible and accurate, and is capable of detecting enzyme in the presence of serum or tissue inhibitors. Using the ELISA, we have examined the effect of a variety of hormones on the production of collagenase by rat myometrial smooth muscle cells in culture. Of all the reproductive hormones examined, only progesterone and its synthetic derivative medroxyprogesterone acetate were capable of inhibiting the production of the enzyme by these cells. The maximally effective concentration of progesterone was 1 x 10^?6M, and that of medroxyprogesterone acetate was 1 x 10^?7M. The effect of the steroid was selective: no effect on cell proliferation or on general protein synthesis was observed. In addition to the progestational steroids, the glucocorticoids were also capable of inhibiting the production of collagenase by the cells at similar nominal concentrations. However, the myometrial cells were found actively to metabolize progesterone but not hydrocortisone in culture. Thus, the effective inhibitory concentration of progesterone was approximately ten-fold lower than that of hydrocortisone. The results of this study support the concept that progesterone plays a major role in preventing the production of collagenase in the rat uterus.     

1α,25-dihydroxy-24-oxo-16-ene vitamin D3, a metabolite of a synthetic vitamin D3 analog, 1α,25-dihydroxy-16-ene vitamin D3, is equipotent to its parent in modulating growth and differentiation of human leukemic cells

1α,25(OH)₂-16-ene-D₃, a synthetic analog of the steroid hormone, 1α,25(OH)₂D₃, has great potential to become a drug in the treatment of leukemia and other proliferative disorders, because of its minimal in vivo calcemic activity associated with a potent inhibitory effect on cell growth. However, at present, the mechanisms through which 1α,25(OH)₂-16-ene-D₃ expresses its biological activities are still not completely understood. Our previous in vitro study in a perfused rat kidney indicated for the first time that 1α,25(OH)₂-16-ene-D₃ and 1α,25(OH)₂D₃ are metabolized differently. 1α,25(OH)₂-24-oxo-16-ene-D₃, an intermediary metabolite of 1α,25(OH)₂-16-ene-D₃ formed through the C-24 oxidation pathway, accumulated significantly in the perfusate when compared to 1α,25(OH)₂-24-oxo-D₃, the corresponding intermediary metabolite of 1α,25(OH)₂D₃. In a subsequent in vivo study, we also reported that 1α,25(OH)₂-24-oxo-16-ene-D₃ exerted immunosuppressive activity equal to its parent, without causing significant hypercalcemia. In order to establish further the critical role of 1α,25(OH)₂-24-oxo-16-ene-D₃, in generating some of the key biological activities ascribed to its parent, we performed the present in vitro study using a human myeloid leukemic cell line (RWLeu-4) as a model. Comparative target tissue metabolism studies indicated that 1α,25(OH)₂-16-ene-D₃ and 1α,25(OH)₂D₃ are metabolized differently in RWLeu-4 cells, and the differences were similar to the ones we previously observed in the rat kidney. The significant finding was the accumulation of 1α,25(OH)₂-24-oxo-16-ene-D₃ in RWLeu-4 cells because of its resistance to further metabolism. Biological activity studies indicated that both 1α,25(OH)₂-16-ene-D₃ and its 24-oxo metabolite produced growth inhibition and promoted differentiation of RWLeu-4 cells to the same extent, and these activities were several fold higher than those exerted by 1α,25(OH)₂D₃. In addition, the genomic action of each vitamin D compound was assessed in a rat osteosarcoma cell line (ROS 17/2.8) by measuring its ability to transactivate a gene construct containing the vitamin D response element of the osteocalcin gene linked to the growth hormone reporter gene. In these studies, both 1α,25(OH)₂-16-ene-D₃ and its 24-oxo metabolite exerted similar but potent transactivation activity which was several fold greater than that exerted by 1α,25(OH)₂D₃ itself. In summary, our results indicate that the production and slow clearance of the bioactive intermediary metabolite, 1α,25(OH)₂-24-oxo-16-ene-D₃, in RWLeu-4 cells contributes significantly to the final expression of the enhanced biological activities ascribed to its parent analog, 1α,25(OH)₂-16-ene-D₃.     

Life cycle assessment standards

The newly emerging LCA standards provide an opportunity to review and improve upon the current LCA methodology. As more industrial practitioners enter the arena, the opportunity arises to not only demand environmental improvement from industrial service and product providers but also to fill LCA data gaps. A framework is suggested for improvement in the current LCA framework that focuses on the business relationships of the industrial practitioner. The framework seeks to promote environmental improvement from industrial sectors through the identification of state-of-the-art technologies used throughout a life cycle. Basing LCAs on the best performers in an industry will create a market for a high level of environmental performance, disperse the responsibility of inventory data gathering, and improve upon the advancements already anticipated through the widespread application of LCA.     

A gene product related to Tral is required for the mobilization of Bacteroides mobilizable transposons and plasmids

The antibiotic-resistance transposon Tn4555 from Bacteroides can be transferred between strains by conjugation. The transposon is not self-transmissible and must be mobilized by resident chromosomal tetracy-cline-resistance elements. In the present report, the mechanism of transfer was examined at the genetic level by deletion analysis and nucleotide sequencing of clones that conferred a transmissible phenotype on a non-mobilizable plasmid. The results suggested that the product of mobA_Tn was required for mobilization and it worked in concert with a cis-acting oriT-like sequence. This mechanism was compared with the mobilization system of a cryptic Bacteroides plasmid, pBl143, and the two systems were found to share a common transfer strategy. The mobA gene products from both genetic elements were related and they had limited homology to the broad group of mobilization proteins (relaxases) typified by Tral of RP4. Phylogenetic analysis of MobA and several other mobilization proteins from commensal gastrointestinal tract organisms suggested that they formed a new subgroup of the Tral superfamily. The mobilization regions of both Tn4555 and pBl143 were located on discrete segments of DNA within the parent genetic element. These segments were delineated by regions of secondary structure, suggesting that they could be defined mobilization cassettes.     

Gene identification in a complex chromosomal continuum by local genomic cross-referencing

Most higher plants have complex genomes containing large quantities of repetitive DNA interspersed with low-copy-number sequences. Many of these repetitive DNAs are mobile and have homology to RNAs in various cell types. This can make it difficult to identify the genes in a long chromosomal continuum. It was decided to use genic sequence conservation and grass genome co-linearity as tools for gene identification. A bacterial artificial chromosome (BAC) clone containing sorghum genomic DNA was selected using a maize Adh1 probe. The 165 kb sorghum BAC was tested for hybridization to a set of clones representing the contiguous 280 kb of DNA flanking maize Adh1. None of the repetitive maize DNAs hybridized, but most of the low-copy-number sequences did. A low-copy-number sequence that did cross-hybridize was found to be a gene, while one that did not was found to be a low-copy-number retrotransposon that was named Reina. Regions of cross-hybridization were co-linear between the two genomes, but closer together in the smaller sorghum genome. These results indicate that local genomic cross-referencing by hybridization of orthologous clones can be an efficient and rapid technique for gene identification and studies of genome organization.     

How many sphygmomanometric cuff inflations are necessary to obtain a hemodynamic baseline?

The purpose of this study was to determine the minimum number of consecutive blood pressure cuff inflations required to obtain seated stable resting baseline measurements of heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP). Sixty male college students aged 18 to 31 years volunteered as study subjects. Thirteen observations of HR, SBP, DBP, and MAP were recorded at 90-second intervals for each subject using a Critikon-Dinamap monitor. Stable readings for SBP and MAP were obtained in 6.5 minutes or 3 to 5 cuff inflations in the population tested. Using this procedure, additional age- and gender-specific norms could be established for normal and hypertensive subjects. Knowing the approximate quantity and frequency of blood pressure cuff inflations needed to generate baseline minimum measurements of HR, SBP, DBP, and MAP will be helpful in studies of cardiovascular reactivity, as well as for clinical and psychophysiologic treatment of hypertension.