The relationship between hetero-oligomer formation and function of the topological specificity domain of the Escherichia coli MinE protein

MinE is an oligomeric protein that, in conjunction with other Min proteins, is required for the proper placement of the cell division site of Escherichia coli. We have examined the self-association properties of MinE by analytical ultracentrifugation and by studies of hetero-oligomer formation in non-denaturing polyacrylamide gets. The self-association properties of purified MinE predict that cytoplasmic MinE is likely to exist as a mixture of monomers and dimers. Consistent with this prediction, the C-terminal MinE(22-88) fragment forms hetero-oligomers with MinE(+) when the proteins are co-expressed. In contrast, the MinE(36-88) fragment does not form MinE(+)/MinE(36-88) hetero-oligomers, although MinE36-88 affects the topological specificity of septum placement as shown by its ability to induce minicell formation when co-expressed with MinE(+) in wild-type cells. Therefore, hetero-oligomer formation is not necessary for the induction of mini-celling by expression of MinE(36-88) in wild-type cells. The interference with normal septal placement is ascribed to competition between MinE(36-88),nd the corresponding domain in the complete MinE protein for a component required for the topological specificity of septal placement.

T-DNA tagging and characterisation of a novel meristem-specific promoter from tobacco

We have evaluated T-DNA mediated plant promoter tagging, with a left-border-linked promoterless firefly luciferase (luc) construct, as a strategy for the isolation of novel plant promoters. In a population of approximately 300 transformed tobacco plants, IO lines showed LUC activity, including novel tissue-specific and developmental patterns of expression. One line, showing LUC activity only in the shoot and root apical meristems, was further characterised. Inverse PCR was used to amplify a 1.5 kb fragment of plant DNA flanking the single-copy T-DNA insertion in this line. With the exception of a 249 bp highly repetitive element, this sequence is present as a single copy in the tobacco genome, and is not homologous to any previously characterised DNA sequences. Sequence analysis revealed the presence of several motifs that may be involved in transcriptional regulation. Transgenic tobacco plants transformed with a transcriptional fusion of this putative promoter sequence to the beta-glucuronidase (uidA) reporter gene, showed GUS activity confined to the shoot tip and mature pollen. This promoter may be useful to direct the expression of genes controlling the transition to flowering, or genes to reduce losses due to pests and stresses damaging plant apical meristems.

Behavior and interactions of children in cooperative groups in lower and middle elementary grades

The study investigated the behaviors and interactions of children in structured and unstructured groups as they worked together on a 6-week social studies activity each term for 3 school terms. Two hundred and twelve children in Grade 1 and 184 children in Grade 3 participated in the study. Stratified random assignment occurred so that each gender-balanced group consisted of 1 high-, 2 medium-, and 1 low-ability student. The results show that the children in the structured groups were consistently more cooperative and they provided more elaborated and nonelaborated help than did their peers in the unstructured groups. The children in the structured groups in Grade 3 obtained higher reading and learning outcome scores than their peers in the unstructured groups.

Suicide and recency of health care contacts - A systematic review

Background Many countries have set targets for suicide reduction, and suggested that mental health care providers and general practitioners have a key role to play. Method Asystematic review of the literature. Results Among those in the general population who commit suicide, up to 41% may have contact with psychiatric inpatient care in the year prior to death and up-to 9% may commit suicide within one day of discharge. The corresponding figures are I I and 4% for community-based psychiatric care and 83 and 20% for general practitioners. Conclusions Among those who die by suicide. contact with health services is common before death. This is a necessary but not sufficient condition for clinicians to intervene. More work is needed to determine whether these people show characteristic patterns of care and/or particular risk factors which would enable a targeted approach to be developed to assist clinicians in detecting and managing high-risk patients.

Promoting an agenda for nuclear weapons elimination: The Canberra Commission and dilemmas of disarmament

This paper examines the role of the Canberra Commission in terms of consolidating and influencing the agenda on international negotiations towards the elimination of nuclear weapons. The Commission's Report is significant for two main reasons. First, it represents a unique form of disarmament diplomacy by the Australian Government which combined the post-Cold War international climate of security cooperation with the foreign policy aspirations of an activist middle power. Second, the Report refutes the strategic, technological and political arguments against nuclear elimination in a comprehensive and convincing manner, arguing that without elimination, the world faces increased threats of nuclear proliferation and nuclear terrorism. This paper thus concludes that the Canberra Commission has been instrumental in strengthening the taboo against the possession, testing or use of nuclear weapons.

Tongue piercing: Case report and review of current practice

Although oral piercing has been an uncommon practice in the Western world, the insertion of metal objects into intra-oral and peri-oral pierced sites is growing in popularity. Tongue piercing is one such practice whereby a metal barbell is inserted into the tongue after piercing with a 14-16 gauge needle. Pain, swelling and infection are the most serious consequences associated with this procedure. Other adverse outcomes include mucosal or gingival trauma, chipped or fractured teeth, increased salivary flow, calculus build-up, and interference with speech, mastication and swallowing. This article presents a case report on tongue piercing and highlights the procedure involved. Special attention is given to complications and dental implications associated with such an unusual practice.

In vitro human epidermal and polyethylene membrane penetration and retention of the sunscreen benzophenone-3 from a range of solvents

Purpose. To study epidermal and polyethylene membrane penetration and retention of the sunscreen benzophenone-3 (BP) from a range of single solvent vehicles and evaluate solvent effects on permeability parameters. Methods. The solubility of BP was measured in a number of solvents. Penetration of BP across human epidermis and high density polyethylene (HDPE) membranes was studied from 50% saturated solutions in each solvent. Results. Maximal BP fluxes from the solvents across the two membranes varied widely. Highest fluxes were observed from 90% ethanol (EtOH) for epidermis and from isopropyl myristate (IPM) and C12-15 benzoate alcohols (C12-15 BA) for HDPE membrane. Both the flux and estimated permeability coefficient and skin-vehicle partitioning of BP appeared to be related to the vehicle solubility parameter (delta(v)). The major effects of solvents on BP flux appear to be via changes in BP diffusivity through the membranes. Conclusions. Minimal penetration of sunscreens such as BP is best achieved by choosing vehicles with a delta(v) substantially different to the solubility parameter of the membrane.

Genetic structure and evolution of species in the mangrove genus Avicennia (Avicenniaceae) in the Indo-West Pacific

Allozyme variation in species of the mangrove genus Avicennia was screened in 25 populations collected from 22 locations in the Indo-West Pacific and eastern North America using 11 loci. Several fixed gene differences supported the specific status of Avicennia alba, A. integra, A. marina, and A. rumphiana from the Indo-West Pacific, and A. germinans from the Atlantic-East Pacific. The three varieties of A. marina, var. marina, var. eucalyptifolia, and var. australasica, had higher genetic similarities (Nei's I) and no fixed gene differences, confirming their conspecific status. Strong genetic structuring was observed in A. marina, with sharp changes in gene frequencies at the geographical margins of varietal distributions. The occurrence of alleles found otherwise in only one variety, in only immediately adjacent populations of another variety, provided evidence of introgession between varieties. The varieties appear to have diverged recently in the Pleistocene and are apparently not of ancient Cretaceous origin, as suggested earlier. Despite evidence of high degrees of outcrossing, gene flow among populations was relatively low (N(e)m less than or equal to 1-2), except where populations were geographically continuous, questioning assumptions that these widespread mangrove species achieve high levels of long-distance dispersal.

Simulation and optimization of heated, inviscid flows in scramjet ducts

A space-marching code for the simulation and optimization of inviscid supersonic flow in three dimensions is described. The now in a scramjet module with a relatively complex three-dimensional geometry is examined and wall-pressure estimates are compared with experimental data. Given that viscous effects are not presently included, the comparison is reasonable. The thermodynamic compromise of adding heat in a diverging combustor is also examined. The code is then used to optimize the shape of a thrust surface for a simpler (box-section) scramjet module in the presence of uniform and nonuniform heat distributions. The optimum two-dimensional profiles for the thrust surface are obtained via a perturbation procedure that requires about 30-50 now solutions. It is found that the final shapes are fairly insensitive to the details of the heat distribution.

Role of the 6-20 disulfide bridge in the structure and activity of epidermal growth factor

Two synthetic analogues of murine epidermal. growth factor, [Abu6, 20] mEGF4-48 (where Abu denotes amino-butyric acid) and [G1, M3, K21, H40] mEGF1-48, have been investigated by NMR spectroscopy. [Abu6, 20] mEGF4-48 was designed to determine the contribution of the 6-20 disulfide bridge to the structure and function of mEGF The overall structure of this analogue was similar to that of native mEGF, indicating that the loss of the 6-20 disulfide bridge did not affect the global fold of the molecule. Significant structural differences were observed near the N-terminus, however, with the direction of the polypeptide chain between residues four and nine being altered such that these residues were now located on the opposite face of the main beta-sheet from their position in native mEGF Thermal denaturation experiments also showed that the structure of [Abu6, 20] mEGF4-48 was less stable than that of mEGF. Removal of this disulfide bridge resulted in a significant loss of both mitogenic activity in Balb/c 3T3 cells and receptor binding on A431 cells compared with native mEGF and mEGF4-48, implying that the structural changes in [Abu6, 20] mEGF4-48, although limited to the N-terminus, were sufficient to interfere with receptor binding. The loss of binding affinity probably arose mainly from steric interactions of the dislocated N-terminal region with part of the receptor binding surface of EGF [G1, M3, K21, H40] mEGF1-48 was also synthesized in order to compare the synthetic polypeptide with the corresponding product of recombinant expression. Its mitogenic activity in Balb/c 3T3 cells was similar to that of native mEGF and analysis of its H-1 chemical shifts suggested that its structure was also very similar to native.

Efficient transformation and regeneration of diverse cultivars of peanut (Arachis hypogaea L.) by particle bombardment into embryogenic callus produced from mature seeds

Peanut, one of the world's most important oilseed crops, has a narrow germplasm base and lacks sources of resistance to several major diseases. The species is considered recalcitrant to transformation, with few confirmed transgenic plants upon particle bombardment or Agrobacterium treatment. Reported transformation methods are limited by low efficiency, cultivar specificity, chimeric or infertile transformants, or availability of explants. Here we present a method to efficiently transform cultivars in both botanical types of peanut, by (1) particle bombardment into embryogenic callus derived from mature seeds, (2) escape-free (not stepwise) selection for hygromycin B resistance, (3) brief osmotic desiccation followed by sequential incubation on charcoal and cytokinin-containing media; resulting in efficient conversion of transformed somatic embryos into fertile, non-chimeric, transgenic plants. The method produces three to six independent transformants per bombardment of 10 cm(2) embryogenic callus. Potted, transgenic plant lines can be regenerated within 9 months of callus initiation, or 6 months after bombardment. Transgene copy number ranged from one to 20 with multiple integration sites. There was ca. 50% coexpression of hph and luc or uidA genes coprecipitated on separate plasmids. Reporter gene (luc) expression was confirmed in T-1 progeny from each of six tested independent transformants. Insufficient seeds were produced under containment conditions to determine segregation ratios. The practicality of the technique for efficient cotransformation with selected and unselected genes is demonstrated using major commercial peanut varieties in Australia (cv. NC-7, a virginia market type) and Indonesia (cv. Gajah, a spanish market type).

Purification and characterization of a plant antimicrobial peptide expressed in Escherichia coli

MiAMP1 is a low-molecular-weight, cysteine-rich, antimicrobial peptide isolated from the nut kernel of Macadamia integrifolia. A DNA sequence encoding MiAMP1 with an additional ATG: start codon was cloned into a modified pET vector under the control of the T7 RNA polymerase promoter. The pET vector was cotransformed together with the vector pSB161, which expresses a rare arginine tRNA. The peptide was readily isolated in high yield from the insoluble fraction of the Escherichia coil extract. The purified peptide was shown to have an identical molecular weight to the native peptide by mass spectroscopy indicating that the N-terminal methionine had been cleaved. Analysis by NMR spectroscopy indicated that the refolded recombinant peptide had a similar overall three-dimensional structure to that of the native peptide. The peptide inhibited the growth of phytopathogenic fungi in vitro in a similar manner to the native peptide. To our knowledge, MiAMP1 is the first antimicrobial peptide from plants to be functionally expressed in E. coil. This will permit a detailed structure-function analysis of the peptide and studies of its mode of action on phytopathogens. (C) 1999 Academic Press.

Architecture and morphogenesis of grain sorghum, Sorghum bicolor (L.) Moench

Plant architecture has been neglected in most studies of biomass allocation in crops. To help redress this situation for grain sorghum (Sorghum bicolor (L.) Moench), we used a 3D digitiser to measure the dimensions and orientations of vegetative and reproductive structures and derived thermal time-based functions for architectural changes during morphogenesis. Our plants, which were grown in a greenhouse, controlled environment cabinets and the field, covered a large, three-fold, size range when mature. This allowed us to detect some general architectural relationships and to fit morphogenetic functions common across the size range we observed. For example, the relationship between the lengths of successive fully-expanded leaves within a plant was nearly constant for all plants. The lengths of existing leaf blades were accurate predictors of the lengths of up to six subsequently-formed blades in our plants. Similar constant relationships were detected for internode lengths in the panicle and for heights above ground of the collars of successive leaves, even though these traits varied a lot between growth conditions. We suggest that such architectural relationships may be used to link the effect of previous growth conditions to future growth potential, and in that way to predict future partitioning. Our results provide the basis for a preliminary model of sorghum morphogenesis which could eventually become useful in conjunction with crop models by allowing resource acquisition to be related to changes in plant architecture during development. (C) 1999 Elsevier Science B.V. All rights reserved.

Determination of chemical shielding tensor of an indole carbon and application of tryptophan orientation of a membrane peptide

Using tryptophan C-13-enriched at the C-4 (C epsilon(3)) of the indole, the orientation of the C epsilon(3) chemical shift tensor relative to the C epsilon(3)-H dipolar axis was determined from the C-13 chemical shift/C-13-H-1 dipolar 2D NMR powder pattern. The principal values obtained were 208, 137 and 15 ppm with sigma(33) perpendicular to the indole plane, and sigma(11) (least shielded direction) 5 degrees off the C epsilon(3)-H bond toward C xi(3). The side off the C epsilon(3)-H bond was determined by comparing the reduced chemical shift anisotropies obtained by solid-state NMR and from molecular dynamics calculations of [4-C-13] tryptophans in gramicidin A aligned in phospholipid membranes. (C) 1999 Elsevier Science B.V. All rights reserved.

Phylogenetic relationships among members of the Comamonadaceae, and description of Delftia acidovorans (den Dooren de Jong 1926 and Tamaoka et al. 1987) gen. nov., comb. nov.

The phylogenetic relationships among members of the family Comamonadaceae and several unclassified strains were studied by direct sequencing of their PCR-amplified 16S rRNA genes. Based on the 16S rRNA gene sequence analysis, members of the family formed a coherent group. The closest relatives are species of the Rubrivivax sub-group: Leptothrix discophora, Ideonella dechloratans and Rubrivivax gelatinosus. The genus Hydrogenophaga formed two subclusters, as did the species of Acidovorax, whereas the five species of the genus [Aquaspirillum] were polyphyletic. Comamonas acidovorans was phylogenetically distant from the type species of Comamonas, Comamonas terrigena. On the basis of this work and previous studies, Comamonas acidovorans is removed from the genus Comamonas and renamed as Delftia acidovorans gen. nov., comb, nov. Descriptions of the new genus Delftia and of the type species Delftia acidovorans, for which the type strain is ATCC 15668(T), are presented.