Determination of the polymorphic composition of smooth pea starch

A method for estimating the proportions of ‘A’ and ‘B’ polymorphs comprising a sample of ‘C’ type starch is proposed which uses established experimental techniques with commercially available spreadsheet and X-ray analysis software. Waxy maize, potato and smooth pea starches were used to provide X-ray diffraction patterns characteristic of the ‘A’, ‘B’ and ‘C’ starch polymorphs. Samples of amorphous starches were also prepared. The method initially involved subtraction of the amorphous phase and instrumental background from the X-ray diffraction patterns of each starch sample using the spreadsheet program, Lotus 1-2-3. The remainder of the pattern, representing the crystalline portion of the starch sample, was then analysed by profile fitting to elucidate the positions and areas of individual diffraction peaks. The ratio of the total peak area to the areas under peaks characteristic of ‘A’ and ‘B’ type starches, respectively, were used to calculate the relative proportions of these polymorphs in smooth pea starch. These proportions were found to be 56±3% ‘A’ polymorph to 44±3% ‘B’ polymorph. A ‘C’ type pattern was constructed by using Lotus 1-2-3 to combine diffraction patterns from the crystalline portions of ‘A’ and ‘B’ type starches in the proportions given above. Polymorph patterns were obtained by manipulation of the diffraction patterns from the crystalline portions of starches using Lotus 1-2-3. An ‘A’ type pattern was obtained by subtraction of a ‘B’ type pattern from that of a ‘C’ type. Similarly, a ‘B’ type pattern was obtained by subtraction of an ‘A’ type pattern from that of a ‘C’ type.     

A characteristic pharmacological action of ‘Yang-invigorating’ Chinese tonifying herbs: Enhancement of myocardial ATP-generation capacity

In order to investigate the pharmacological basis of ‘Yang-invigorating’ action, the effect of oral treatment with the methanolic extract of ‘Yang-invigorating’ herbs on ATP-generation capacity was examined, using heart homogenates prepared from herb-pretreated mice. Tonifying (i.e., health-promoting) herbs of other functional categories were also included for comparison. The results indicated that ‘Yang-invigorating’ Chinese tonifying herbs could invariably enhance myocardial ATP-generation capacity, with the extent of stimulation varying among the herbs. In contrast, ‘Yin-nourishing’ herbs either did not stimulate or even decreased myocardial ATP-generation capacity. While ‘Qi-invigorating’ herbs produced variable effects on myocardial ATP-generation capacity, most of the ‘blood-enriching’ herbs did not cause any significant changes. The results obtained from studies using myocardial mitochondrial fractions isolated from herb-pretreated mice suggest that ‘Yang-invigorating’ herbs might speed up ATP generation by increasing mitochondrial electron transport. The ensemble of results has provided evidence for the first time to support the pharmacological basis of ‘Yang invigoration’ in Chinese medicine.     

Transitions between cooperative and non-cooperative responding in the 'Pigeon's Dilemma'

Two pigeons played Iterated Prisoner's Dilemma (IPD) against a simulated opponent pre-programmed to play ‘Tit-For-Tat’ (TFT) and ‘Random’ (RND) strategies. Each pigeon received differential amounts of access to food following choices of either ‘cooperate’ or ‘defect’ on a trial. After 1000 trials against TFT and 500 trials against RND, results indicated that choice allocation was optimal when the birds played against RND but was sub-optimal when the birds played against TFT. In order to determine why the pigeons responded suboptimally against TFT, a trial-by-trial analysis of the data was conducted. The analysis revealed that once a pigeon had received the ‘Sucker's’ payoff (S), it was more likely to defect and receive the ‘Temptation’ payoff (T) than to cooperate and receive the ‘Reward’ (R) payoff. Local reinforcement contingencies appear to determine suboptimal responding against TFT in the iterated Pigeon's Dilemma.     

Sequence dependent hydration of DNA

The transitions between the different helical conformations of DNA depend on the base sequence and the ambient conditions such as humidity and counter-ion concentration. In this study energy minimization techniques have been used to locate water molecule sites around nucleotides especially those which form hydrogen bonds between two or more nucleotide atoms and thus form solvent mediated bridges. We have studied several sequences and find that those which are known not to exist in the low hydration ‘A’ form have very similar number of bridging sites in both ‘A’ and ‘B’ conformations. Those sequences which are found in the ‘A’ conformation have considerably more bridging sites in this low hydration form than in the ‘B’ conformation. Sequence related solvent effects for a given conformation have also been analysed.     

Intracellular signalling proteins as ‘smart’ agents in parallel distributed processes

In eucaryotic organisms, responses to external signals are mediated by a repertoire of intracellular signalling pathways that ultimately bring about the activation/inactivation of protein kinases and/or protein phosphatases. Until relatively recently, little thought had been given to the intracellular distribution of the components of these signalling pathways. However, experimental evidence from a diverse range of organisms indicates that rather than being freely distributed, many of the protein components of signalling cascades show a significant degree of spatial organisation. Here, we briefly review the roles of ‘anchor’, ‘scaffold’ and ‘adaptor’ proteins in the organisation and functioning of intracellular signalling pathways. We then consider some of the parallel distributed processing capacities of these adaptive systems. We focus on signalling proteins-both as individual ‘devices’ (agents) and as ‘networks’ (ecologies) of parallel processes. Signalling proteins are described as ‘smart thermodynamic machines’ which satisfy ‘gluing’ (functorial) roles in the information economy of the cell. This combines two information-processing views of signalling proteins. Individually, they show ‘cognitive’ capacities and collectively they integrate (cohere) cellular processes. We exploit these views by drawing comparisons between signalling proteins and verbs. This text/dialogical metaphor also helps refine our view of signalling proteins as context-sensitive information processing agents.     

Quantification of high-frequency sea-level fluctuations in shallow-water carbonates: an example from the Berriasian–Valanginian (French Jura)

When quantifying sedimentary processes on shallow carbonate platforms, it is important to know the high-frequency accommodation changes through time. Accommodation changes in cyclic successions are often analysed by simply converting cycle thickness to Fischer plots. This approach is not satisfactory, because it does not account for differential compaction, possible erosion, sea-level fall below the depositional surface, or subtidal cycles. An attempt is made here to reconstruct a realistic, high-frequency accommodation and sea-level curve based on a detailed facies and cyclostratigraphical analysis of Middle Berriasian to Lower Valanginian sections in the French Jura Mountains. The general depositional environment was a shallow-marine carbonate platform on a passive margin. Our approach includes the following steps: (1) facies interpretation; (2) cyclostratigraphical analysis and identification of Milankovitch parameters in a well-constrained chronostratigraphic framework; (3) differential decompaction according to facies; (4) estimation of depth ranges of erosion and vadose zone; (5) estimation of water-depth ranges at sequence boundaries and maximum flooding intervals; (6) estimation of mean subsidence rate; (7) classification of depositional sequences according to types of facies evolution: ‘catch-up’, ‘catch-down’, ‘give-up’, or ‘keep-up’; (8) classification of depositional sequences according to long-term sea-level evolution: ‘rising’, ‘stable’, ‘falling’; (9) calculation of ‘eustatic’ sea-level change for each depositional sequence using the parameters inferred from these scenarios, assuming that sea-level cycles were essentially symmetrical (which is probable in Early Cretaceous greenhouse conditions); (10) calculation of a sea-level curve for each studied section; (11) comparison of these curves among each other to filter out differential subsidence; (12) construction of a ‘composite eustatic’ sea-level curve for the entire studied platform; (13) spectral analysis of the calculated sea-level curves. Limitations of the method are those common to every stratigraphic analysis. However, the method has the potential to improve the original cyclostratigraphical interpretations and to better constrain the high-frequency sea-level changes that control carbonate production and sediment fluxes.     

Pollen recognition and rejection during the sporophytic self-incompatibility response: Brassica and beyond

Many hermaphrodite flowering plants avoid self-fertilization through genetic systems of self-incompatibility (SI). SI allows a plant to recognize and to reject self or self-related pollen, thereby preserving its ovules for outcrossing. Genes situated at the S-locus encode the ‘male’ (pollen) and ‘female’ (pistil) recognition determinants of SI. In sporophytic SI (SSI) the male determinant is expressed in the diploid anther, therefore haploid pollen grains behave with a diploid S phenotype. In Brassica, the male and the female determinants of SSI have been identified as a peptide ligand and its cognate receptor, respectively, and recent studies have identified downstream signalling molecules involved in pollen rejection. It now needs to be established whether the Brassica mechanism is universal in species with SSI, or unique to the Brassicaceae.     

Effect of epiphytes on the extent of necrotic injuries of resistant and susceptible poplar clones infected with Dothichiza populea.

Poplar cuttings of a resistant clone, Populus ‘Grandis’, and susceptible clones, Populus nigra ‘Italica’ and Populus ‘Robusta’, were infected with the pathogenic fungus Dothichiza populea alone, or with the pathogen and one of five strains of epiphytes antagonistic towards it (in vitro), isolated from poplar bark. The extent of injury was examined for 28 days after infection by determining the length of necrotic patches and their area as expressed in per cent of the total area of a cutting or the area of necrotic injuries caused by the pathogen alone.

All the poplar cuttings of both the resistant and susceptible clones became diseased when infected with the pathogen alone. Surprisingly enough, however, the least affected clone was the susceptible P. ‘Robusta’, in which necrotic injuries covered 28% of the total area, as against 40% and 70% in the resistant P. ‘Grandis’ and the susceptible P. nigra ‘Italica’, respectively.

When the cuttings were infected simultaneously with Dothichiza populea and its antagonistic epiphytes, the diseased area in the resistant clone diminished by as much as two-thirds, and in the susceptible P. nigra ‘Italica’, by one-third in comparison with the area affected by the pathogen alone. In turn, in the susceptible P. ‘Robusta’ the introduction of three out of five epiphytes stimulated the growth of the pathogenic fungus producing on average a double increase in the necrotic area. The differences in the response of the pathogen to the presence of epiphytes recorded in the susceptible clones indicate a marked influence of the plant on the nature of interactions between its epiphytic microflora and the pathogen.     

Ultrastructure of meristematic cells of dormant and released buds in Tradescantia paludosa

The lateral bud meristems of Tradescantia paludosa show a characteristic cytohistological zonation during dormancy. The cells comprising this so called ‘zone of inhibition’, which is located at the extreme tip of the bud apex, rarely synthesize nuclear DNA or undergo mitotic division. These nuclei are as large as prophase nuclei, yet contain only telophase (2C) amounts of DNA and significantly lower amounts of histone as compared to the 2C nuclei of the actively dividing cells.Ultrastructural observations of the nuclei in the ‘zone of inhibition’ show that a large proportion of the chromatin is organized as less condensed, diffuse, euchromatin fibrils; however, the chromatin of the actively dividing nuclei of the cells outside the ‘zone of inhibition’ or in the released bud meristems is organized to a greater extent as condensed clumps of heterochromatin. When the dormancy is released, the nuclei in the ‘zone of inhibition’ synthesize DNA and histone and undergo cell division in approx. 4 days. Striking changes in the organization of chromatin fibrils take place during this transition period. The diffuse chromatin fibrils of the nuclei in the ‘zone of inhibition’ progressively become more and more condensed as the cell prepares to undergo the first mitotic division after the release of dormancy. This change which is coupled with the synthesis of histones in the nuclei of the ‘zone of inhibition’ suggests a prominent structural role of these basic proteins in the organization of the chromatin. The large volume of 2C nuclei of the ‘zone of inhibition’ seems, therefore, to result not from a great nuclear mass, but probably from a relatively small degree of condensation of chromatin.     

Biosynthesis of Hb in individual fetal liver bursts : γ-Chain production peaks earlier than β-chain in the erythropoietic pathway

The relative synthesis of α-, β-, ^Gγ- and ^Aγ-globin chains has been evaluated in single fetal liver bursts, which were grown in methylcellulose cultures, individually labelled with [³H]leucine and then analysed via iso-electric focusing. Well-hemoglobinized bursts demonstrate a homogeneous globin synthetic pattern, characterized by prevalent HbF (+some HbA) synthesis: thus, they apparently originate from a homogeneously programmed population of erythroid burst-forming unit (BFU-E). On day 8–9 of culture, the synthetic pattern in ‘mature’ (i.e., well-hemoglobinized) bursts has been compared with that in simultaneously-grown, ‘immature’ (i.e., poorly-hemoglobinized) colonies. These patterns have been further compared with that in ‘matured’ bursts (identified in situ as immature on day 8–9 and labelled 2–4 days later when matured). The ‘immature’ colonies showed very low levels of relative β-globin synthesis, while the ‘mature’ ones demonstrated a more elevated production of β-chain. Significantly, the ‘matured’ bursts showed a globin chain synthetic pattern similar to that of previously labelled ‘matured’ colonies. It is postulated therefore that in fetal liver (and also in adult marrow) the synthesis of γ-chain is linked to an early differentiation stage of erythroblasts, while β-globin synthesis is largely activated at a more advanced maturation stage.     

Intercellular exchange of lysosomal hydrolases between mutant human fibroblasts and other cell types

Human fibroblasts with a genetic deficiency of a single lysosomal enzyme and fibroblasts from a patient with ‘I-cell’ disease with a multiple deficiency of lysosomal hydrolases were used as recipient cells in studies on recognition and uptake of β-N-acetylhexosaminidase (hexosaminidase), β-glucuronidase and β-galactosidase. Normal human fibroblasts, and fibroblasts, hepatocytes and hepatoma cells from the rat were used as donor cells. The release of hexosaminidase was found to be similar among these different cell types, but the extracellular activities of β-glucuronidase and β-galactosidase were much higher in the rat cell cultures than in cultures of normal human fibroblasts. The enzymes released by rat fibroblasts were ingested by deficient human fibroblasts; enzyme from normal human fibroblasts was shown to be taken up by rat fibroblasts by means of electrophoresis. This indicates that reciprocal transfer of lysosomal hydrolases occurs between human and rat fibroblasts. Rat hepatocytes released hydrolases that were poorly taken up by human recipient fibroblasts and uptake of human fibroblast enzyme was not detected in the hepatocytes. Rat hepatoma cells, on the other hand, released lysosomal enzymes that were taken up by human deficient cells with a higher efficiency than those from fibroblasts. The uptake was subject to competitive inhibition by mannose 6-phosphate, the kinetics of which were comparable with those reported for ‘high-uptake’ forms of lysosomal enzymes [1–2]. Electrophoretic studies showed that rat hepatoma cells were not only capable of ingesting hexosaminidase from normal human fibroblasts, but also defectively processed enzyme [4–5] released by ‘I-cells’. These findings make rat hepatoma cells a useful model for the study of recognition and uptake of lysosomal enzymes.     

Pharmacogenomics: out of the lab and into the community

Pharmacogenomics is the study of the inherited basis of differences in response to drugs. These interindividual differences are often more than tenfold; a ‘slow metabolizer’ or ‘low-responsive’ individual might therefore require ten times less than the recommended dose of a drug than a ‘rapid metabolizer’ or ‘high-responsive’ person, and the slow metabolizer is often more likely to experience drug toxicity than a rapid metabolizer. Our knowledge is developing rapidly to the point that the physician will soon use DNA-based tests to aid in decision-making with respect to the most appropriate drug and dosage given to each patient. If the patient's DNA is available, however, what boundaries should be placed on that DNA? If the patient's genotype becomes known to the physician (and presumably to the patient him- or herself), what ethical questions might arise and how will they be resolved? This article discusses these issues and outlines some of the possible solutions.     

Plant-parasite interactions: has the gene-for-gene model become outdated?

The detection of pathogens by plants is often described as a ‘gene-for-gene’ interaction.

However, recent work from several laboratories indicates that, in some instances, a single gene product in the plant can mediate the recognition of multiple pathogen signals, and that multiple plant genes are required for the recognition of, and response to, a single pathogen signal.     

Different architectures of the collagen fibril: morphological aspects and functional implications

Several tissues known to contain collagen fibrils with a ‘helical’ arrangement were studied by t.e.m. and freeze-fracture. In all the tissues examined, the diameter of the collagen fibrils appeared to be tissue-specific and fairly constant within the same tissue. No statistical differences, on the contrary, were detectable in the coiling angle which appeared similar in all the tissues and independent of both diameter and age of the fibril. Rat tail tendon was also examined under the same technical conditions and showed collagen fibrils of large and very heterogeneous diameter and with a consistent ‘straight’ arrangement. These data seem to suggest that the ‘helical’ and ‘straight’ arrangements may actually identify different types of collagen fibrils. The authors discuss the possible functional significance of these arrangements and present two hypotheses on the three-dimensional structure of the ‘helical’ fibril.     

Fatty acid composition in microspore-derived secondary embryos of Brassica napus L.

Fatty acid (FA) composition was determined in secondary embryos (SeEs) of Brassica napus L. of the cv. ‘Topas’ and ‘Janetzki’, and compared with the FA composition in microspore-derived embryos (MDEs) and seeds. SeEs of ‘Topas’, a rapessed cultivar with low erucic acid, revealed the same FA composition as observed in the MDEs. The FA pattern was, in most of the cases, independent of the procedures used for induction of SeEs e.g. low density cultures, transversal wounding, auxin treatment, and light conditions. However, non-embryogenic calli, as well as leaves from greenhouse- and in vitro-grown material had a FA composition distinctly different from the MDEs or SeEs. SeEs with an abnormal phenotype revealed differences in FA composition compared to MDEs or SeEs, but was distinct from the composition of non-embryogenic tissues. Virtually no erucic acid (22:1) or eicosaenoic acid (20:1) could be detected in SeEs of ‘Topas’. However, its presence in SeEs of ‘Janetzki’, a high erucic acid rapeseed cultivar, demonstrates that SeEs contain embryo-specific FAs. Under standard culture conditions, the levels of 22:1 and 20:1 were the same as observed in MDEs, which was approximately half the content observed in the seeds. The similarity in FA composition between SeEs and MDEs, of both low and high erucic acid rapeseed cultivars, is a unique characteristic which differs from most other somatic embryogenic systems.     

Comparative assessment of two algorithms for calibrating stereophotogrammetric systems

In this paper, a comparison is carried out between two photogrammetric algorithms aimed at camera calibration and three-dimensional target point reconstruction by ‘absolute’ distributions of control points; the first is Marzan and Karara's DLT, the second is CESNO, by the author, an algorithm quite close to Hatze's modified DLT (MDLT). The comparative assessment is especially aimed at testing the capability of the two methods to produce good results when calibration data are to be extrapolated beyond the space spanned by the control distribution. The assessment was carried out not by a real stereophotogrammetric system, but by the computer simulation of a two-camera set-up. Various combinations of internal camera parameters, such as the scaled principal distances, were tried out. As for the magnitude of the simulated non-linear lens distortion, three configurations were used which produced ‘low’, ‘medium’ and ‘strong’ distortion. The influence of decreasing the number of control (calibration) points on the accuracy performance of the two algorithms was also investigated. The results show the superiority of CESNO, especially with medium or strong lens distortion, or when the two camera principal distances sensibly differ.     

Influence of gene-linkage and recombination of evolutionary algorithms on the rate of evolution, genetic diversity and the response of evolving populations to disturbance

Both biological populations and fault tolerant evolvable hardware systems need to respond rapidly to changes in their dynamic environmental niche. Such changes can be caused by a disturbance event or fault occurring. Here I examine evolutionary algorithms, based on eukaryote sexual selection, which allow different levels of recombination of ‘genes’. The differences in recombination are based on ‘genes’ related to the optimisation process being either linked on a single ‘chromosome’ or being present on separate ‘chromosomes’. When genes are present on separate chromosomes the initial rate of evolution of a randomly generated population is faster than if the genes are linked on the same chromosome. However, when the optimisation problem is changed during the optimisation period, indicating a disturbance or fault occurring, the initial fitness of the linked population is higher and the rate of optimisation immediately after the disturbance is more rapid than for the non-linked populations. The genotypic and phenotypic diversity of the linked populations are also significantly higher immediately prior to the disturbance event. I propose this diversity provides the necessary variation to allow more rapid evolution following a disturbance. The results demonstrate the importance of population diversity in response to change, supporting theory from conservation biology.     

Human and machine factors in algae monitoring performance

We all take our visual systems for granted, and often assume we are always ‘near perfect’ observers. This is not the case; expert visual recognition is complex and can be error prone. Starting with examples that define the problem I will explore some of the issues of recognition where expert judgements are required.

In addition to ‘expert’ effects, there are a number of cognitive factors that can severely affect performance, including fatigue, boredom, recency effects, positivity bias and short-term memory effects. Experimental evidence of the impact of these on performance are presented and discussed.

The specimen identifications generated by experts are useful not only to ecology, but to researchers developing systems for automatic labelling of marine plankton. Comparisons of performance are presented, where human experts have been pitted against machines to label plankton. Consensus of opinion is important in reducing errors, yet it is the norm for experts to operate alone. The shortcomings of man and machines engaged in plankton recognition are reviewed and the future of automation is assessed.