Perianth development inAngophora and the bloodwood Eucalypts (Myrtaceae)

The petals ofAngophora flowers are compound structures consisting of two morphologically distinct components that develop along separate morphogenetic pathways. These two components are also evident in the corolline parts of the bloodwood eucalypts. In occasional flowers ofAngophora and some bloodwoods, several adjacent corolline primordia may become continuous due to interprimordial growth, but the petals are mostly free at anthesis. In other bloodwood eucalypt species all the primordia in the corolline whorl become continuous at some stage in development, resulting in an operculum that is anatomically unresolvable into its original petaline parts. The varying degrees of this continuity that are evident within individual trees (and even within single flowers) suggests that operculum formation is an epigenetic event that is determined by morphogenetic processes within the flower. It is suggested that these may relate to differing rates of growth in different regions of the bud.     

An analysis of aortic pressure curves taking into account visco-elastic properties of the aorta and variations in peripheral resistance

The aortic pressure curve necessarily reveals the mechanical properties of the aorta and peripheral resistance as well as of the dynamics of blood flow. The present study uses a reasonable model of visco-elastic properties of the aorta, a reasonable form for variations in peripheral resistance and blood flow to predict an aortic pressure tracing. Numerical values of constants measured experimentally were available in the published literature. These were used in the nonlinear differential equations of motion of the system under analysis. The equations yielded to piece-wise solution, giving the aortic circumference and the aortic pressure as functions of time. The form of both curves resembles clinical tracings, but numerical values of circumference were higher and of pressure lower thanin vivo. The discrepancies between predicted and clinical curves may reveal certain inadequacies in published measurements on visco-elastic constants. These measurements have been made on longitudinal rather than circumferential strips often containing dead rather than living muscle. The discrepancies, therefore, indicate specific gaps in our knowledge of aortic behaviorin vitro. The suggested model of the system aided in the design of experiments which could supply data necessary to substantiate or to revise the model.     

Comparison of Hemolymph and Holotissues of Different Species of Insects as Diet Components forin VitroRearing ofTrichogramma galloiZucchi andT. pretiosumRiley

The aim of this work was to compare pupal holotissues (Diatraea saccharalis, Anticarsia gemmatalis,andBombyx mori) and larval hemolymph of several moth species (Helicoverpa zeaandBombyx mori) commonly produced in Brazilian laboratories as components of artificial diets forin vitrorearing ofTrichogramma galloiandTrichogramma pretiosum.Diets based on larval hemolymph ofH. zeaproduced the best development of both natural enemies, although a diet with pupal holotissues ofB. moriallowed full development ofT. pretiosum.Amino acid analysis showed qualitative differences among the insect derivates and eggs of the natural and alternative hosts, but with a quantitative similarity. Electrophoretic analysis resulting in a diverse protein-stained bands evidenced the qualitative differences among these components.     

Comparison ofin Situ andin Vitro survival ofCandida albicans in seawater

The survival in seawater of several laboratory and field isolates ofCandida albicans was investigated. Initial studies were madein vitro (flasks) to confirm previous reports. Frequent sampling of viable cells showed that flask experiments, even repeated, produced varied patterns of survival in this closed system. As an alternative, multiple experiments were run in untreated seawater in dialysis bags and plexiglas chambers at ambient temperature (17 to 22C) in flowing seawater. Die-off rates of all cultures tested in dialysis bags were very rapid in the first day and may have been related to high levels of dissolved organic carbon in the tubing. Distilled water-or acid-washed bags did not yield significantly higher survival rates in all cases. When plexiglas chambers closed with Nuclepore membranes were used, survival rates decreased to 5% to 15% of the original population after 6 days. Chamber data were more uniform and represented approximately a twofold increase in survival over that shown previously inin vitro (flask) studies. Some evidence was obtained in all three test systems for the greater survival rate of a field isolate ofC. albicans compared with that noted for a laboratory (ATCC) strain. The results are considered to more accurately depict the survival ofC. albicans in summer temperate recreational waters.     

Effects of membrane acting-drugs on plasmodium species and sickle cell erythrocytes

The effects of several membrane-acting drugs on malaria and sickle cell anemia was studied. In the initial experiments, propranolol and W-7 were shown to increase red cell density.In vitro, these drugs inhibited the growth ofP. falciparum. However,in vivo experiments using the murine malarial parasite,P. vinckei, demonstrated little, if any, anti-parasite activity with the doses of drugs employed. Subsequently, prostaglandin oligomeric derivatives were found to inhibit the growth ofP. falciparum in vitro andP. vinckei in vivo. Since prostaglandin oligomers inhibited the formation of dense, dehydrated cells (irreversible sickle cells), they may also have therapeutic efficacy in sickle cell anemia.     

Evolution and systematic relationships in theTriticeae (Poaceae)

The evolution and taxonomic relationships in theTriticeae are discussed with the view to highlight aspects of this agronomically important group of plants, which may be of interest to molecular biology. Some of these aspects are addressed in more detail in adjoining papers in which specific genomic loci have been examined at the DNA sequence or isozyme level. Aspects discussed include the systematics and geographic distribution of theTriticeae species, isozyme and chromosome pairing studies on some of the species as well as more recent developments in DNA analyses. A survey of the systematics of theTriticeae indicated that the genomic system ofLöve is probably the most useful starting point for interpreting molecular data even though the system has many problems from a taxonomic point of view. The geographical distribution ofTriticeae species, using both published and unpublished data, suggested that information of this type taken together with the theory of continental drift provides a broad time-span for considering data from DNA sequence studies. The significance, and modes of analyses, of isozyme studies were assessed because they often provide valuable characters in determining relationships between species. The main character underlyingLöve's andDewey's analyses of theTriticeae, namely chromosome pairing, is discussed with particular reference to isozyme studies to show that in some cases, such as species ofHordeum sensu lato, consistent relationships are obtained. Finally, new developments in understanding chromosome structure are considered in relation to the above variables in the taxonomy and evolution of theTriticeae.     

Reconsideration of some results for linear and circular DNA

A reassessment is made of some results for linear and circular DNA. The alternative side-by-side configuration is used in an analysis of situations where some doubt about current double helix based interpretations may exist. The following specific areas are considered: (i) certain linear DNA examples involving duplex interactions, (ii) nucleosome sequence data and (iii) the banding effect observed in gel electrophoresis studies ofin vitro circular DNA.     

Seed set inCichorium intybus L. by pollination of flowers developedin vitro

Formation of viable seeds ofCichorium intybus L. was achieved in anin vitro system. Flower formation, pollination, fertilization, embryogenesis and seed development occurredin vitro on chicory root explants on culture medium lacking plant growth regulators. After flower induction under a 24-h daylength treatment, the explants were transferred to a 16-h daylength at 40 E m^-2s^-1 irradiance for pollination and further seed development. Negative results were obtained when root explants were maintained continuously under a 24-h daylength during the whole culture period. Lower seed set was obtained when the cultures were at low irradiance. The need of a dark period and adequate level of irradiance are suggested as important factors to obtain viable seeds. The developedin vitro system can be used as a model to study the factors controlling the reproductive processes, and for the study of self-incompatibility in chicory.     

All you wanted to know about SELEX

In vitro selection, or SELEX, is a technique that allows the simultaneous screening of highly diverse pools of different RNA or DNA (dsDNA or ssDNA) molecules for a particular feature. Different examples from a great variety of applications ofin vitro selection experiments are described and a detailed overview of the method and its variations will be given. Some especially conclusivein vitro selection experiments are discussed in detail to illustrate the potential power and diversity of this method. Potential restrictions of the methods and possible ways to overcome them are pointed out.     

Acquisition and use of humanin vitro liver preparations

Humanin vitro liver preparations — i.e., slices, hepatocyte suspensions, primary hepatocyte cultures and microsomes — are increasingly used in the drug development process. The main applications are prediction of drug metabolite profiles, drug-drug interactions and toxicity. The use of thesein vitro models is limited, however, because of their erratic availability, the absence of validated protocols and the difficulties of extrapolation ofin vitro data to thein vivo situation.     

The effect of varying sea salt concentration in the growth medium on the chemical composition of a purified membrane fraction fromPlanococcus citreus Migula

Membrane preparations were prepared from cells ofPlanococcus citreus grown in the presence of three final concentrations of sea salt in a basic growth medium. The concentration of salt in the medium affects the amount of membrane in the cell. The three preparations were subjected to chemical analysis and no significant changes in chemical composition were seen as the salt concentration in the medium was increased. Values for the various components generally were within normal ranges and were similar to those of non-halophiles rather than extreme halophiles. The protein levels were slightly higher and it is suggested that this may be advantageous in selectively maintaining the correct cellular ion balance. Atomic absorption analysis of the major cations associated with the membranes showed that divalent ions were present in a 2:1 ratio with 1971; Oliver and Colwell, 1973; Stern and Tietz, 1973; Kushwaha et al., 1974; Lanyi, 1974). However, changes in the overall membrane composition in mild halophiles in response to various concentrations of salt have received little attention, even though it has been known for some time (Salton and Freer, 1965) that the composition of a growth medium may alter the chemical composition of a bacterial membrane. This investigation was undertaken to determine whether any gross changes in composition occurred in membranes isolated from cells ofPlanococcus citreus Migula when it is grown in a basic medium supplemented with various amounts of sea salt.     

An evaluation of the stoichiometry ofin vitro nitrate assimilation inZea mays

Summary Reported non-stoichiometry in the reduction of nitrate to nitrite was investigated in leaves ofZea mays L.. The nitrogen balance sheet forin vitro nitrate assimilation was influenced by enzyme protectants in the extraction media and by the method employed to terminate the reaction. A number of limitations were found in the generally acceptedin vitro nitrate reductase assay, in particular the presence of endogenous components which interfered with the assay of nitrite were considered. A stoichiometric balance for thein vitro reduction of nitrate to nitrite was obtained when interfering factors were minimized. The absence of back reactions from ammonia in the assay was confirmed.     

Periodicity of endocytosis inTetrahymena pyriformis

Summary Starved cells ofTetrahymena pyriformis show marked periodicity in the rates of uptake of digestive vacuoles when presented with a mixture of peptone and polystyrene latex particles. Rates of egestion also show some periodicity. The results show that the supply of membrane is not the sole factor (and possibly not even a main factor) restricting vacuolar uptake. The rates of egestion also do not appear to be greatly influenced by the amounts of digestive vacuole membrane to be reincorporated into the cell membrane. It is suggested that energy and lysosomal supplies may be more important than membrane supply for uptake and that reduction in the supply of uncombined lysosomes may in some way cause cessation of vacuole formation.Fed cells ofTetrahymena also show variations in the rate of digestive vacuolar uptake with time. The maximum rate of uptake is about three times as great as that found in starved cells.     

Requirement ofwingless signaling andengrailed action in the development and differentiation of reproductive system inDrosophila

The segment polarity geneswingless (wg) andengrailed (en) have been shown to play important roles in pattern formation at different stages ofDrosophila development in the thoracic imaginai discs. We have studied the patterns of expression of these genes in genital discs from wild type larvae, pupae and pharate adults and also from hetero-allelic mutant combinations of these genes. Our results suggest that these genes play vital roles in the normal development and differentiation of genital discs and gonads. In the absence of normalwg oren functions, the flies showed a complete lack of internal accessory reproductive organs and specific defects in the external genitalia. In addition, the testes in such males were small, rounded and with an abnormal cellular organization, although the ovaries in females appeared normal. Temperature shift experiments using the conditional mutant allele ofwg, (wg ^IL-114 ) indicated a requirement ofwg signaling from second instar onwards for normal development and differentiation of the accessory reproductive organs. Using a heat-shock allele (Hs-wg) we also show that the spatially regulated expression ofwg as a pre-requisite for normal development and differentiation. Based on the expression patterns ofen andhedgehog (hh) we suggest that even in the genital disc development and differentiation the action ofen is mediated throughhh.     

Nutrient-induced competition between two species of marine diatoms

Competition experiments betweenPhaeodactylum tricornutum andSkeletonema costatum showed that even at temperatures higher than 10°C (i.c. 14°C), the development ofSkeletonema can be favoured by adjusting nutrient levels and nutrient ratios. Low NSi ratios were found to favourSkeletonema. Additionally, high NP ratios further enhanced the ability ofSkeletonema to dominate the cuftures. Contrary to some statements in literature, it seems that high concentrations of silicates are more important for the dominance ofSkeletonema costatum in large-scale cultures than just low temperatures. This finding is important with regard to stimulating the blooming ofSkeletonema costatum in natural phytoplankton populations as food for bivalve molluscs.     

Observations on the source of acid in empoldered mangrove soils

Summary Formation of elemental sulphur as an intermediate in polysulphide oxidation in mangrove soils has been demonstrated both in laboratory experiments and in the field. The oxidation of soil polysulphides occurred in the absence of more reactive sulphur compounds and it is suggested that these are not essential for the initiation of sulphur oxidation in high sulphur soils. Field experiments contained some evidence of instability of soil polysulphides at pH values near neutrality, but laboratory experiments suggested that early decomposition of polysulphides may be accelerated by non-biological oxidations which lower the soil pH value.Maximum population ofThiobacillus thio-oxidans was reached much earlier than maximum oxidative activity, although an early peak in oxidative activity could be obtained by adding elemental sulphur to soil. It is suggested that while conditions in the early stages of the oxidation may be suitable for multiplication of the organisms, maximum oxidative activity is limited by the rate of release of sulphur from the decomposing polysulphide.     

THE DEVELOPMENTAL MORPHOLOGY OF GONGROSIRA DEBARYANA1

The development and asexual cycle of Gongrosira debaryana have been studied in unialgal culture. Zoospores may settle singly and develop a Pleurotham-mon-like thallus, or they may clump and so produce a thallus characteristic of Gongrosira. It is suggested that Borzi's Pleurothamnion papuasicum be considered a synonym of Gongrosira debaryana.     

Reassessing Models of Hepatic Extraction

The aim of this investigation is to compare different mathematical models of the liver in the context of in vitro-in vivo correlation. We reanalyze drugs from the Houston reviews [1, 2], and compare the mathematical models. For the well-stirred model, a particular form of the distributed tubes model, and the dispersion model, fits are done to in vitro and in vivo intrinsic clearance data from microsomal and hepatocyte experiments. The distributed and dispersion models have decreased residuals as compared to the well-stirred model, but neither is to be clearly preferred over theother. It seems likely that drug-specific factors have a major impact on the quality of IVIVC correlations. While new experiments are needed to validate IVIVC models, our results indicate that improved correlation of in vitroand in vivo data is possible for high clearance drugs by using either a dispersion or distributed tube model rather than a well-stirred model.     

FTIR protein secondary structure analysis of human ascending aortic tissues

The advent of moderate dilatations in ascending aortas is often accompanied by structural modifications of the main components of the aortic tissue, elastin and collagen. In this study, we have undertaken an approach based on FTIR microscopy coupled to a curve‐fitting procedure to analyze secondary structure modifications in these proteins in human normal and pathological aortic tissues. We found that the outcome of the aortic pathology is strongly influenced by these proteins, which are abundant in the media of the aortic wall, and that the advent of an aortic dilatation is generally accompanied by a decrease of parallel β‐sheet structures. Elastin, essentially composed of β‐sheet structures, seems to be directly related to these changes and therefore indicative of the elastic alteration of the aortic wall. Conventional microscopy and confocal fluorescence microscopy were used to compare FTIR microscopy results with the organization of the elastic fibers present in the tissues. This in‐vitro study on 6 patients (three normal and three pathologic), suggests that such a spectroscopic marker, specific to aneurismal tissue characterization, could be important information for surgeons who face the dilemma of moderate aortic tissue dilatation of the ascending aortas. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)