Comparison of cyclopropene, 1-methylcyclopropene, and 3,3-dimethylcyclopropene as ethylene antagonists in plants

A comparison has been made of cyclopropene (CP), 1-methylcyclopropene (1-MCP), and 3,3-dimethyl-cyclopropene (3,3-DMCP) in their ability to protect plants against ethylene. In bananas, both CP and 1-MCP are effective around 0.5 nL L^–1, and 3,3-DMCP was effective at 1 L L^–1. Bananas treated with CP and 1-MCP again become sensitive to ethylene at 12 days and those treated with 3,3-DMCP at 7 days. Mature green tomatoes are protected by 5–7 nL L^–1 of 1-MPC for 8 days at 25°C and tomatoes treated with 3,3-DMCP at 5–10 L L^–1 are protected for 5 days. Carnation flowers are protected with CP or 1-MCP after exposure to 0.5 nL L^–1 for 24 hours and by 1 L L^–1 of 3,3-DMCP. The display life of Campanula flowers is increased from 3.3 to 5.4 days by 10 L L^–1 of 3,3-DMCP and to 9 days by 20 nL L^–1 of 1-MCP. Ethylene inhibition of pea seedlings is reduced by treatment with 1-MCP at 10 L L^–1 of ethylene but as ethylene is increased to 3000 L L^–1 growth inhibition increases. 3,3-DMCP treatment causes very little reduction of the ethylene effect even at very low concentrations.     

Review of mathematica

Mathematica is an extremely powerful tool designed to perform a multitude of mathematical operations and functions. Stephen Wolfram is the creator of the programming language and has long been a leader in the field of scientific computing. The language is rich in options and the task of learning it may seem daunting at first However, if one proceeds with small steps, first learning the basics and then new functions as becomes necessary, they will be rewarded with learning a robust, powerful language that can be used in virtually any application. Here we discuss examples of Mathematica's utility in risk assessment and review a copy of the newly released version 3. It arrives on a multi‐platform CD (i.e., Windows, Macintosh, UNIX) with a password that allows access on only one of the platforms.

Program: Mathematica, Ver. 3.0

Source: Wolfram Research, Inc., 100 Trade Center Drive, Champaign, IL 61820–7237

System: Windows 95 or Windows NT, Ver. 3.51 or higher with at least 8 MB of RAM, though at least 16 MB of RAM is recommended; many other platforms are available

Cost: Commercial price, $1295 for program, standard add‐on packages, and manual; Educational $895; Regular service $195; Premier service $385     

Escherichia coli Population Structure and Antibiotic Resistance at a Buffalo/Cattle Interface in Southern Africa

At a human/livestock/wildlife interface, Escherichia coli populations were used to assess the risk of bacterial and antibiotic resistance dissemination between hosts. We used phenotypic and genotypic characterization techniques to describe the structure and the level of antibiotic resistance of E. coli commensal populations and the resistant Enterobacteriaceae carriage of sympatric African buffalo (Syncerus caffer caffer) and cattle populations characterized by their contact patterns in the southern part of Hwange ecosystem in Zimbabwe. Our results (i) confirmed our assumption that buffalo and cattle share similar phylogroup profiles, dominated by B1 (44.5%) and E (29.0%) phylogroups, with some variability in A phylogroup presence (from 1.9 to 12%); (ii) identified a significant gradient of antibiotic resistance from isolated buffalo to buffalo in contact with cattle and cattle populations expressed as the Murray score among Enterobacteriaceae (0.146, 0.258, and 0.340, respectively) and as the presence of tetracycline-, trimethoprim-, and amoxicillin-resistant subdominant E. coli strains (0, 5.7, and 38%, respectively); (iii) evidenced the dissemination of tetracycline, trimethoprim, and amoxicillin resistance genes (tet, dfrA, and bla_TEM-1) in 26 isolated subdominant E. coli strains between nearby buffalo and cattle populations, that led us (iv) to hypothesize the role of the human/animal interface in the dissemination of genetic material from human to cattle and toward wildlife. The study of antibiotic resistance dissemination in multihost systems and at anthropized/natural interface is necessary to better understand and mitigate its multiple threats. These results also contribute to attempts aiming at using E. coli as a tool for the identification of pathogen transmission pathway in multihost systems.     

CNS thermosensitivity and control of latent heat dissipation in the pigeon

Thermoregulatory responses to heat exposure were studied in 12 hand-reared, acclimated pigeons (Columbia livia). Measurements of body temperature (Tcl), brain temperature (Tbr), cutaneous water evaporation (CWE) and respiratory frequency (fr) were carried out in intact conscious heat exposed birds. In a second group of lightly restrained birds, fr and CWE were taken when temperatures of the trunk, brain and air (Ta) were independently changed. Increasing Tbr to 43.5–43.8°C induced a pronounced polypnea (deep and fast, (300 breaths min⁻¹) when Tcl regulated at 42.4°C. Moreover, when hyperthermia (Tcl = 43.0°C) was combined with increased Tbr (43.0–43.8°C) shallow and fast panting (>500 breaths min⁻¹) was evoked. CWE was probably elicited by inputs generated by the skin warm receptors as a result of increased Ta. Moreover it was demonstrated that warming the brain to 42.5°C elicits cutaneous water evaporation in birds exposed to 26°C. When a high Ta (60°C) is accompanied by a high relative humidity (17%), the combined effect generates inputs eliciting intensive panting. The integration of the present and earlier data allows us to generate a model demonstrating the distinguished significance of the trunk, skin and brain thermosensors in the regulation of both respiratory and cutaneous latent heat dissipation. The present model also emphasizes the fact that the highly thermosensitive pigeon brain responds in a similar pattern to that found in mammals     

Membrane Lipoteichoic Acid Is Not a Precursor to Wall Teichoic Acid in Pneumococci

The distribution of a pulse of teichoic acid-specific radiolabel between wall and membrane teichoic acids in pneumococci was constant over a subsequent chase period, suggesting that wall and membrane teichoic acids are biosynthesized simultaneously and independently.     

Initial glycosylation and acidic pH in the Golgi apparatus are required for multimerization of von Willebrand factor

Two conditions were identified that interfered with the complex polymerization process in biosynthesis of von Willebrand factor (vWf). Treatment of human umbilical vein endothelial cells with tunicamycin inhibited N-linked glycosylation of nascent vWf and the resulting pro-vWf monomers failed to dimerize. The single subunits accumulated in the endoplasmic reticulum and were neither processed further nor secreted. In the presence of a weak base (ammonium chloride or chloroquine), interdimer disulfide bond formation was inhibited in a dose-dependent manner. This process appeared therefore to be pH sensitive and likely to be initiated in the acidic trans-Golgi apparatus (Anderson, R. G. W., and R. K. Pathak, 1985, Cell, 40: 635-643). The weak base had no obvious effect on the other processing steps, i.e. dimerization, complex carbohydrate formation and sulfation, and produced only slight inhibition of prosequence cleavage. On the other hand, the weak base interfered with the targeting of newly synthesized vWf into Weibel-Palade bodies, with all of the vWf being secreted constitutively and none stored in the Weibel-Palade bodies. In summary, initial glycosylation of the nascent vWf protein and low pH in the trans-Golgi apparatus were important conditions for the successful polymerization of human vWf. Genetic defects disrupting any one of these conditions could result in the phenotype of von Willebrand disease.     

Growth of a pogonophore: a study of Polybrachia canadensis with a discussion of the development of taxonomic characters

Heptabrachia canadensis , previously known from one juvenile specimen, has been redescribed from new material and transferred to the genus Polybrachia. About 1400 specimens were available for study, including a series of developmental stages ranging from juveniles less than 0.1 mm in diameter to adults 0.6 mm in diameter. The smallest juveniles have one tentacle while most adults have 30 to 40 tentacles. Juveniles differ from adults in diameter, length, number of tentacles and type of tube. The most important observation to emerge is the variability of characters hitherto thought to distinguish different genera, and the need for care in the diagnosis of new species from limited material.