Transformation of a psychrotrophic bacterium with a plasmid from a mesophile

The psychrotrophic bacteriumBacillus psychrophilus was transformed with the broadhost-range plasmid pC194. The ability of the transformant to express chloramphenicol (CAM) resistance and the possible effects of such expression on the physiology of the psychrotroph were examined. The transformant exhibited growth rates, filament formation at elevated temperatures, synthesis of cold shock proteins and cold acclimation proteins, similar to the parentalB. psychrophilus.     

Living inside a sponge skeleton: the association of a sponge,a macroalga and a diatom

The relationships between sponges and macroalgae have been poorly investigated, especially in temperate waters. This work describes the consortium between the dictyoceratid sponge Dysidea pallescens and the red alga Acrochaetium spongicola permeating spongin fibres in the Mediterranean Sea; moreover, this is the first report of a diatom, Amphora pediculus, living also inside the spongin skeleton. The annual trend of the total algal biomass did not vary over time in relation to the temperature, irradiance and incorporation of foreign bodies. Our analyses, conducted by light and electron microscopy, suggest that both the macroalga and the diatom invade the skeleton of the sponge from the external environment, and that the benthic diatom, epiphyte of the macroalga, is passively carried inside the fibres through the growth of Acrochaetium spongicola. All the examined samples of D. pallescens showed that the macroalga permeated at least some fibres, while the presence of the diatom was occasional. The superficial layer of the sponge, thin and reticulate, likely allows the passage of the light and ensures the algal survival inside the sponge tissue. The high occurrence of the association with A. spongicola, together with the morphological adaptations of the sponge favouring the algal life, suggest that the relationship is mutualistic. The possible benefits for the involved partners are hypothesized. The taxonomy and ecology of endozoic Acrochaetiales are controversial due to the reduced size of thalli, the absence of peculiar diagnostic characters and unknown reproductive structures. Therefore, detailed studies on the relationships between the algae and their hosts will provide helpful information for the algal identification.     

Testing a Primary and a Secondary Endpoint in a Group Sequential Design

Summary We consider a clinical trial with a primary and a secondary endpoint where the secondary endpoint is tested only if the primary endpoint is significant. The trial uses a group sequential procedure with two stages. The familywise error rate (FWER) of falsely concluding significance on either endpoint is to be controlled at a nominal level α. The type I error rate for the primary endpoint is controlled by choosing any α‐level stopping boundary, e.g., the standard O'Brien–Fleming or the Pocock boundary. Given any particular α‐level boundary for the primary endpoint, we study the problem of determining the boundary for the secondary endpoint to control the FWER. We study this FWER analytically and numerically and find that it is maximized when the correlation coefficient ρ between the two endpoints equals 1. For the four combinations consisting of O'Brien–Fleming and Pocock boundaries for the primary and secondary endpoints, the critical constants required to control the FWER are computed for different values of ρ. An ad hoc boundary is proposed for the secondary endpoint to address a practical concern that may be at issue in some applications. Numerical studies indicate that the O'Brien–Fleming boundary for the primary endpoint and the Pocock boundary for the secondary endpoint generally gives the best primary as well as secondary power performance. The Pocock boundary may be replaced by the ad hoc boundary for the secondary endpoint with a very little loss of secondary power if the practical concern is at issue. A clinical trial example is given to illustrate the methods.     

Characterization of a new strain of a purple nonsulfur bacterium from a thermal spring

A new budding purple nonsulfur bacterium of the genus Rhodobacter (strain Ku-2) was isolated from a mat of a moderately thermal spring (Baikal rift zone, Buryatia, Russia). The bacterium had lamellar photosynthetic membranes, which are typical of only one Rhodobacter species, Rba. blasticus. The cells contained spheroidene carotenoids and bacteriochlorophyll a (Bchl a). In vivo absorption spectrum of the cells, with the major maximum at 863 nm and an additional peak at 887 nm, is characteristic of the pigment-protein complexes of Bchl a-containing membranes. The previously described Rba. blasticus strains do not exhibit the 887-nm maximum. The new isolate was photoheterotrophic, with optimal growth occurring at 35°C, 3 g/L NaCl, and pH 7–8. The DNA G+C content was 64.4 mol %. The similarity between the 16S rRNA gene sequences of strain Ku-2 and the Rba. blasticus type strain was 98.7%. The PufM amino acid sequences of strain Ku-2 and the earlier studied Rba. blasticus type strain were 89.5 % identical. Thus, strain Ku-2 belongs to the genus Rhodobacter and is phylogenetically close to Rba. blasticus.     

Vegetation as a component of a non-nested hierarchy: a conceptual model

Abstract. A general conceptual model of vegetation based on hierarchy theory is presented. The model emphasizes that prediction of vegetation requires consideration of both mechanisms of vegetation change and the constraints within which it occurs. The mechanisms of vegetation change are the responses to and effects upon their surroundings of individual plants. The most general constraints upon vegetation are aspects of the environment not affected by vegetation over successional time, and the pool of species within dispersal range. Examples of such environmental factors include macroclimate and soil parent material. In some cases, vegetation may alter important labile environmental factors such as soil nutrient and water availability. Some vegetation compositions appear to be resistant to changes in the general constraints. Due to both sources, there are multiple possible vegetation compositions given the same general constraints. Disturbance is defined as an abrupt change in the constraints on the vegetation resulting in a change in the vegetation's state or dynamics. Both the recognition of disturbance and the distinction between independent and labile environmental factors depend on the spatial and temporal scale of observation. For example, a particular wildfire at a given stand may be a disturbance, whereas at a larger scale of observation the same event may contribute to the wildfire regime, part of the constraints at that scale. Similarly, levels of soil organic matter may constrain vegetation over short time scales, due to influencing availability of water and nutrients. Over long time scales, the vegetation itself is a primary determinant of soil organic matter content. This model contains elements of both the initial, holistic theory of vegetation and recent, reductionistic approaches. It reiterates the need to considerboth mechanisms and constraints, stressed by contemporary and earlier workers. Hierarchy theory provides new insights concerning sufficient conditions for prediction, possible limits on predictability, and appropriate research strategy.     

How a G protein binds a membrane

Heterotrimeric G proteins interact with receptors and effectors at the membrane-cytoplasm interface. Structures of soluble forms have not revealed how they interact with membranes. We have used electron crystallography to determine the structure in ice of a helical array of the photoreceptor G protein, transducin, bound to the surface of a tubular lipid bilayer. The protein binds to the membrane with a very small area of contact, restricted to two points, between the surface of the protein and the surface of the lipids. Fitting the x-ray structure into the membrane-bound structure reveals one membrane contact near the lipidated Ggamma C terminus and Galpha N terminus, and another near the Galpha C terminus. The narrowness of the tethers to the lipid bilayer provides flexibility for the protein to adopt multiple orientations on the membrane, and leaves most of the G protein surface area available for protein-protein interactions.     

Carotenoids in floral parts of a narcissus, a daffodil and a tulip

1. The qualitative and quantitative distribution of carotenoids of the floral parts of three monocotyledons, the narcissus Scarlet Elegance, the daffodil King Alfred and the tulip Golden Harvest, were studied. β-Carotene, lutein or epoxy-β-carotenes were usually the main pigments, depending on the floral part and on the flower. When β-carotene was the major pigment there were only small amounts of, or sometimes no, epoxycarotenes. 2. Anthers, stigmas and styles of the three flowers did not possess any specific carotenoids but in some cases contained appreciable amounts of epoxycarotenoids. The possibility that these take part in reproduction is discussed. 3. The generalization that yellow flowers contained large amounts of xanthophylls and only traces of carotenes, whereas deep-orange flowers seemed to be characterized by the presence of large amounts of one carotene, was not always the correct one. It is suggested that the floral parts are yellow or orange depending on what carotenoids are present, which is the major one and the amount of total carotenoids, and also on the presence of other non-carotenoid pigments. 4. Two new probable isomers of 5,6:5′,6′-diepoxy-β-carotene were isolated and found together in various floral parts of the tulip Golden Harvest.     

Some properties of a neutral phosphatase of a bacterium isolated from a trickling filter effluent

Summary The partial purification and some of the properties of a neutral phosphatase from a Gram-negative oxidative bacterium isolated from a sewage works effluent are described. The enzyme is active against a variety of organic and inorganic phosphates and, of a number of ions tested, cadmium, copper, mercury and zinc and tungstate and molybdate were the most powerful inhibitors of enzyme action. Inhibition by phosphate is competitive. The possible significance of bacterial neutral phosphatases in purification processes is discussed.     

Characterization of a novel amylolytic enzyme encoded by a gene from a soil-derived metagenomic library

It has been estimated that less than 1% of the microorganisms in nature can be cultivated by conventional techniques. Thus, the classical approach of isolating enzymes from pure cultures allows the analysis of only a subset of the total naturally occurring microbiota in environmental samples enriched in microorganisms. To isolate useful microbial enzymes from uncultured soil microorganisms, a metagenome was isolated from soil samples, and a metagenomic library was constructed by using the pUC19 vector. The library was screened for amylase activity, and one clone from among approximately 30,000 recombinant Escherichia coli clones showed amylase activity. Sequencing of the clone revealed a novel amylolytic enzyme expressed from a novel gene. The putative amylase gene (amyM) was overexpressed and purified for characterization. Optimal conditions for the enzyme activity of the AmyM protein were 42 degrees C and pH 9.0; Ca2+ stabilized the activity. The amylase hydrolyzed soluble starch and cyclodextrins to produce high levels of maltose and hydrolyzed pullulan to panose. The enzyme showed a high transglycosylation activity, making alpha-(1, 4) linkages exclusively. The hydrolysis and transglycosylation properties of AmyM suggest that it has novel characteristics and can be regarded as an intermediate type of maltogenic amylase, alpha-amylase, and 4-alpha-glucanotransferase.     

Isolation of a retrovirus and a herpesvirus from a captive California sea lion

A non-oncogenic retrovirus was isolated from an explanted skin biopsy from a captive California sea lion (Zalophus californianus) with a history of recurring skin lesions. The morphology of the viral particles in electron photomicrographs was characteristic of a foamy virus, a retrovirus in the subfamily Spumavirinae. Viral cytopathic effects consistent with foamy virus infection were observed in subsequent explants of skin and lymph nodes and co-cultivated peripheral blood leukocytes. The sea lion with the persistent foamy virus infection later died from pericarditis caused by Pasteurella multocida. A herpesvirus was isolated from explants of lung.     

Histochemical localization of cholinesterase in a rodent,a sub-primate and a primate brain

Summary The distribution of acetylcholinesterase (AChE) was studied in the various rhinencephalic structures of the brains of the coypu rat, the galago and the Grivet monkey. Serial sections of the brains of these animals, stained by the classical neurohistological methods, were available and were used for the identification of the nuclear arrangements. Although there are minor differences there seems to be a general similarity between the coypu, galago and monkey in so far as the distribution of cholinesterase is concerned. The intensity of staining is nearly the same in the coypu and galago brains. Although the staining is less intense in the brain of the monkey, yet one must be fairly cautious before drawing any conclusions simply from the intensity of staining. So much may depend on the method, for example the optimum pH for one animal may not be appropriate for another. In all these animals the most intense reaction is observed in the olfactory tubercle, amygdala and the caudate-putamen. The fibres of the anterior commissure and lateral olfactory tract stain only very faintly. These comparative histochemical studies suggest that cholinesterase — containing fibres in general are better developed, in the phylogenetically older parts of the brain.     

Bifurcation from a limit cycle in a two predator-one prey ecosystem modeled on a chemostat

Pattern formation in a unicomponent reaction-diffusion system with trigger type dynamics and combined boundary conditions is considered. The boundary permeabilities and reservoir concentrations as well as the dimension of the system are the control parameters. The whole assemblage of steady states, their bifurcations and changes under the variation of these parameters is described. Among all steady distributions possible for given values of the parameters, only the simplest ones prove to be asymptotically stable. The relation to catastrophe theory is discussed.     

Biomechanics of a muscular hydrostat: a model of lapping by a reptilian tongue

We have developed a quantitative model of an example of a muscular hydrostat, a reptilian tongue, and have used this model to study a functional movement, protrusion and retrusion, a form of lapping. The model tongue consists of a longitudinal muscle that shortens the tongue when it contracts, and a circumferential muscle wrapped around the longitudinal muscle that lengthens the tongue when it contracts. The anatomy of the model tongue and the pattern of activation of its muscles are based on studies of the tongue of the lizard Tupinambis nigropunctatus (Smith 1984). The mechanics of pressure vessels were used to derive a relationship between the forces in the two muscles. Muscle force production was modelled as the product of length/tension properties, force/velocity properties, and activation due to neural inputs (incorporating both recruitment and firing period). Passive forces were modeled as a force in parallel with the longitudinal muscle. Muscle activation dynamics were modeled as a first order low pass filter. When the model tongue is short, the two muscles can lengthen or shorten it with comparable forces, but as it lengthens, the force that the circumferential muscle can exert drops precipitously. When the tongue is long, it can neither be very stiff, nor can it generate much force. The model also reproduces the kinematics of lapping movements actually observed in Tupinambis.     

Facile synthesis of a D-galactono-1,6-lactone derivative, a precursor of a copolyester

2,3,4,6-Tetra-O-methyl-d-galactonic acid (5) was readily prepared from d-galactono-1,4-lactone (1) in 47% yield. The sequence involves tritylation of HO-6 of 1, followed by O-permethylation and deprotection. Lactonization of 5 led to the per-O-methyl-d-galactono-1,6-lactone, which was copolymerized with epsilon-caprolactone by ring-opening polymerization catalyzed by scandium triflate. The incorporation of the sugar comonomer into the polyester chain was about 10%.     

Disruption of a Silencer Domain by a Retrotransposon

A galactose-inducible Ty element carrying the HIS3 gene has been used as an insertional mutagen to generate alpha-factor resistant mutants. This collection of Ty-induced mutations includes insertions into the gene for the alpha-factor receptor (STE2), several nonspecific STE genes, and mutations that lead to the expression of the normally silent HML alpha locus. The hml alpha "on" mutations fall into two classes, those that disrupt trans-acting regulators involved in silencing HML alpha and a novel class of mutations that activate HML alpha by insertion at that locus. The hml alpha::Ty "on" mutations illustrate the unusual ability of these retrotransposons to activate genes by overcoming gene silencing mechanisms. The hml alpha::Ty "on" mutations include examples of multimeric Ty arrays. Single Ty and solo delta insertion derivatives of these Ty multimers restore the ability of the silencing mechanism to repress HML alpha.     

Study of hydrodynamic instabilities of a Z-pinch during a high-current explosion of a thin wire

Results are presented from laboratory and numerical experiments on the influence of the core and associated hydrodynamic instabilities on the high-current implosion of a plasma of exploding metal wires. The experimental investigation of the discharge structure was carried out using the multiframe X-ray backlighting technique with high temporal and spatial resolution (<1 ns and 1 μm, respectively); X-pinches were used as small-sized radiation sources. The implosion of a dense Z-pinch was modeled by the free-point method with the use of a two-dimensional radiative MHD code. The onset of instabilities at the corona-core boundary was modeled by the NUTCY Eulerian code. The results show that hydrodynamic processes in the core are primarily responsible for the formation of small bright regions observed in X-rays. After the reflection of a shock wave from the axis, the rapid onset of hydrodynamic instabilities can occur at the corona-core boundary. __________ Translated from Fizika Plazmy, Vol. 26, No. 9, 2000, pp. 797–810. Original Russian Text Copyright ? 2000 by Gus’kov, Ivanenkov, Mingaleev, Nikishin, Pikuz, Rozanov, Stepniewski, Tishkin, Hammer, Shelkovenko.     

Development of a herbicide biosensor using a peptide receptor screened from a combinatorial library

The purpose of this study was to screen for peptides that bind herbicides with a chlorinated aniline chemical structure. A tetrapeptide library was constructed using a solid phase split synthesis approach. Peptide beads were suspended in a buffer containing fluorescent-labeled dichloroaniline (DCA) as the bait. Eighteen fluorescent peptide beads were selected which bound to the bait after two rounds of staining screenings. The beads were then stained and suspended in a solution containing an excess of DCA and five quenched peptide beads were subsequently selected that recognized the DCA moiety. The screened peptides had many sequence similarities. The binding affinity of the screened peptides to herbicides was analyzed using surface plasmon resonance (SPR). N′-(3,4-dichlorophenyl)-N,N-dimethylurea [3-(3,4-dichlorophenyl)-1,1-dimethylurea] solution was injected over the peptide immobilized SPR chip. The SPR signal was found to increase in proportion to the DCMU concentration, whereas no signal was obtained from the negative control, 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP). From these results it is suggested that the screened peptide selectively recognizes the chemical structure of DCA.     

Care in a birth room versus a conventional setting: a controlled trial.

A controlled clinical trial was carried out to assess whether a birth room setting would influence the care of mothers and newborns. Of the 163 low-risk women enrolled, 49 (30%) manifested some prenatal risk and were excluded. The remaining 114 were allocated by strict alternation to a birth room or a conventional setting. Of the 56 women allocated to the birth room, 63% of the primiparas and 19% of the multiparas were later transferred. The numbers in the two settings who had oxytocin stimulation, epidural anesthesia, forceps delivery or cesarean section did not show statistically significant differences. The episiotomy rates were slightly lower in the birth room than in the conventional setting, and the rates of an intact perineum were higher in the birth room. Neither the Apgar scores nor the morbidity rates of the infants showed statistically significant differences related to the setting to which the mother had been allocated, although more infants from the conventional setting were admitted to a special care unit. Both "experimental" groups of women less often received routine perineal shaving, enemas or intravenous infusions than did an obstetrically similar nonexperimental comparison group. Despite the apparent inability in this setting for the birth room to influence the rate of major obstetric procedures (except for episiotomy) and outcomes, the authors believe that a birth room is desirable in tertiary care centres as well as in community hospitals.     

Study of a DC gas discharge with a copper cathode in a water flow

A dc gas discharge between copper electrodes in the current range of 5–20 А was studied experimentally. The discharge gap length was varied within 45–70 mm. The cathode was a 10-mm-diameter rod placed in the water flowing out from a dielectric tube. Three discharge configurations differing in the position of the cathode upper end with respect to the water surface were considered: (i) above water; (ii) flush with the water surface, and (iii) under water. The electric and optical characteristics of the discharge in the second configuration were studied in more detail. It is established that the discharge properties are similar to those of an electric arc. Considerable cathode erosion was observed in the third configuration. It is revealed that fine-dispersed copper grains form in the course of erosion.