Systematic aspects of flavonoid biosynthesis and evolution

The Botanical Review - The use of flavonoids in evaluating contemporary taxonomic systems has relied almost exclusively on the distributional patterns of these compounds among plant groups thought...     

Specific leukotriene formation by purified human eosinophils and neutrophils

Human granulocytes isolated from peripheral blood have been described to synthesize both LTB4 and LTC4 from arachidonic acid. We have observed that the amount of LTC4 produced by human granulocyte preparations is strongly dependent on the relative amount of eosinophils. To investigate a possibly significant difference in leukotriene synthesis of the eosinophilic and neutrophilic granulocytes, we developed a purification method to isolate both cell types from granulocytes obtained from the blood of healthy donors. Leukotrienes were generated by incubation of the purified cells with arachidonic acid, calcium ionophore A23187, calcium-chloride and reduced glutathione. Surprisingly, eosinophils were found to produce almost exclusively the spasmogenic LTC4. In contrast, neutrophils produce almost exclusively the chemotactic LTB4, its omega-hydroxylated metabolite 20-hydroxy-LTB4 and two non-enzymically formed LTB4 isomers.     

Flower visiting by hoverflies (Syrphidae)

An account is given of a study of resource-partitioning in hoverflies (Syrphidae) which feed almost exclusively on flowers. Suggestions are made for school project work using hoverflies.     

Types of opioid receptors: relation to antinociception

The endogenous opioid peptides are derived from three large precursors. Pro-opiocortin and proenkephalin yield [Met]enkephalin, carboxy-extended [Met]enkephalins and [Leu]enkephalin. The fragments of prodynorphin are all carboxy-extended [Leu]enkephalins. Three approaches are of importance for an analysis of the physiological functions of the different endogenous opioid peptides. First, since these peptides interact with more than one of the mu-, delta- and kappa-binding sites and thus with their receptors, it is necessary to synthesize peptides or non-peptides, which bind to only one of the sites. As far as narcotic analgesics are concerned, morphine fulfils these conditions since it interacts almost exclusively with the mu-receptor. Secondly, antagonists are required that are selective for only one of the opioid receptors, even when used in high concentrations. Finally, it is important to find circumscribed areas in the nervous system that possess only one type of opioid receptor. It is now known that in the rabbit cerebellum the opioid receptors are almost exclusively of the mu-type whereas in the guinea-pig cerebellum they are almost exclusively of the kappa-type.     

A serologic comparison of Moloney lymphoma cell surface and Moloney oncornavirus antigens.

Moloney lymphomas and Moloney sarcomas share strong tumor antigens. In this report we analyze the cell-surface antigens on a Balb/c Moloney lymphoma, LSTRA, using hyperimmune sarcoma regressor sera (alphaMo) as a primary reagent. We also use heterologous anti-viral p30 and gp70 sera for a direct analysis of virion protein antigens on the LSTRA surface. Using radiolabeled alphaMo-binding assays, we demonstrate that LSTRA tumor antigens detected by these sera are all Moloney viral antigens; approximately 1/3 of these antigenic determinants are expressed on the intact virus, and the other determinants are revealed by detergent lysis of the virus. The major viral antigens expressed on the LSTRA cell surface are viral env gene products, whereas gag gene products are only sparsely represented. We conclude that alphaMo sera detect almost exclusively viral antigens on LSTRA cells, and these antigens are almost exclusively virion env gene products.     

Biosynthesis and emission of terpenoid volatiles from Arabidopsis flowers

Arabidopsis is believed to be mostly self-pollinated, although several lines of genetic and morphological evidence indicate that insect-mediated outcrossing occurs with at least a low frequency in wild populations. Here, we show that Arabidopsis flowers emit both monoterpenes and sesquiterpenes, potential olfactory cues for pollinating insects. Of the 32 terpene synthase genes in the Arabidopsis genome, 20 were found to be expressed in flowers, 6 of these exclusively or almost exclusively so. Two terpene synthase genes expressed exclusively in the flowers and one terpene synthase gene expressed almost exclusively in the flowers were characterized and found to encode proteins that catalyze the formation of major floral volatiles. A beta-glucuronidase fusion construct with a promoter of one of these genes demonstrated that gene expression was restricted to the sepals, stigmas, anther filaments, and receptacles, reaching a peak when the stigma was receptive to cross pollen. The observation that Arabidopsis flowers synthesize and emit volatiles raises intriguing questions about the reproductive behavior of Arabidopsis in the wild and allows detailed investigations of floral volatile biosynthesis and its regulation to be performed with this model plant system.     

Diel infestation dynamics of gnathiid isopod larvae parasitic on Caribbean reef fish

Infestation dynamics of parasitic gnathiid isopods on Caribbean reefs were studied throughout the 24-h diel cycle. Gnathiid infestation on caged longfin damselfish (Stegastes diencaeus) peaked strongly at dawn, remained low during the remainder of the day, and increased again at night until about midnight. Gnathiids were less abundant during the pre-dawn period. Peak loads on fish retrieved at dawn were the highest reported in any study thus far. The dawn peak consisted almost exclusively of individuals from the smallest size class, whereas nocturnal activity consisted almost exclusively of individuals of the largest size class. Because of the high rates of infestation at night and dawn, and the high variation in parasite loads on fish collected during that time, reduction of parasite infestation may play an important role in the selection of nocturnal and crepuscular shelter holes and settlement sites by reef fishes.     

Transposition of the Responder Element (Rsp) of the Segregation Distorter System (Sd) to the X Chromosome in Drosophila Melanogaster

In order to test whether the meiotic drive system Segregation distorter (SD) can operate on the X chromosome to exclude it from functional sperm, we have transposed the Responder locus (Rsp) to this element. This was accomplished by inducing detachments of a compound-X chromosome in females carrying a Y chromosome bearing a Rsps allele. Six Responder-sensitive-bearing X chromosomes, with kappa values ranging from 0.90 to 1.00, were established as permanent lines. Two of these have been characterized more extensively with respect to various parameters affecting meiotic drive. SD males with a Responder-sensitive X chromosome produce almost exclusively male embryos, while those with a Rsp-Y chromosome produce almost exclusively female embryos. This provides a genetic system of great potential utility for the study of early sex-specific differentiation events as it allows the collection of large numbers of embryos of a given sex.     

An analysis of genetic stock identification on a small geographical scale using microsatellite markers,and its application in the management of a mixed‐stock fishery for Atlantic salmon Salmo salar in Ireland

A genetic stock identification (GSI) study was undertaken in a fishery for Atlantic salmon Salmo salar to determine the effects of restrictive fishery management measures on the stock composition of the fishery, and if accurate and precise stock composition estimates could be achieved on the small geographical scale where this fishery operates, using a suite of only seven microsatellite loci. The stock composition of the Foyle fishery was shown to comprise almost exclusively of Foyle origin fish in the 3 years after restrictive measures were introduced in 2007, compared to 85% the year before. This showed that the restrictive measures resulted in the Foyle fishery being transformed from a mixed‐stock fishery to an almost exclusively single‐stock fishery, and showed how GSI studies can guide and evaluate management decisions to successfully manage these fisheries. Highly accurate and precise stock composition estimates were achieved in this study, using both cBAYES and ONCOR genetic software packages. This suggests accurate and precise stock composition is possible even on small geographical scales.     

The current landscape of the FDA approved companion diagnostics

Predictive biomarker is an important element in the realization of precision medicine and with the introduction of the drug-diagnostic codevelopment model, the number of regulatory approved companion diagnostics (CDx) have steadily increased. This short perspective is based on an analysis of the FDA List of Cleared or Approved Companion Diagnostic Devices and focus on the biomarkers, drugs, clinical indications, analytical platforms, regulatory paths and status related to the different assays. By the end of 2020, the total number of CDx assays approved by the FDA had reached 44. These assays are almost exclusively linked to different hematological and oncological drugs. Without an accurate and reliable CDx assay these drugs will lose their value. The analytical platforms are diverse and cover technologies like immunohistochemistry, in situ hybridization, polymerase chain reaction, next generation sequencing, and imaging. CDx assays are high risk devices and the regulatory path almost exclusively requires submission of a Premarket Application (PMA); however, a relatively large group of the CDx assays is PMA approved Laboratory Developed Test.     

The evolution of density-dependent dispersal

Despite a large body of empirical evidence suggesting that the dispersal rates of many species depend on population density, most metapopulation models assume a density-independent rate of dispersal. Similarly, studies investigating the evolution of dispersal have concentrated almost exclusively on density-independent rates of dispersal. We develop a model that allows density-dependent dispersal strategies to evolve. Our results demonstrate that a density-dependent dispersal strategy almost always evolves and that the form of the relationship depends on reproductive rate, type of competition, size of subpopulation equilibrium densities and cost of dispersal. We suggest that future metapopulation models should account for density-dependent dispersal     

A T cell receptor goes public

The crystal structure of a human T cell receptor, which is used almost exclusively in the immune response to an Epstein-Barr virus protein, highlights the importance of noncontact residues in antigen recognition.     

Instantaneous flux control analysis for biochemical systems.

Linear sensitivity analysis of steady-state control of enzymic systems has been extended to non-steady states yielding sensitivity coefficients which provide non-intuitive insights into the behavior of the system and the sites of metabolic control, and which are quantitative counterparts to traditional qualitative concepts. Because this information is provided in a readily understood format, these coefficients serve as convenient indices of metabolic control. This treatment was applied to a simple test system, consisting of two enzymes and one non-enzymatic reaction, which exhibits oscillatory behavior. The results indicate that oscillations in the concentrations of the intermediate metabolites are regulated almost exclusively by the second enzyme. Control of the flux through the pathway is apportioned equally among the three reactions during periods of low net flux, but it is due almost exclusively to the second enzyme during periods of high net flux.     

A snail with unbiased population sex ratios but highly biased brood sex ratios

Extraordinary sex ratio patterns and the underlying sex-determining mechanisms in various organisms are worth investigating, particularly because they shed light on adaptive sex-ratio adjustment. Here, we report an extremely large variation in the brood sex ratio in the freshwater snail, Pomacea canaliculata. In eight rearing series originating from three wild populations, sex ratios were highly variable among broods, ranging continuously from almost exclusively males to almost exclusively females. However, sex ratios were similar between broods from the same mating pair, indicating that sex ratio is a family trait. Irrespective of the large variations, the average sex ratios in all rearing series were not significantly different from 0.5. We argue that Fisher's adaptive sex-ratio theory can explain the equal average sex ratios, and the results, in turn, directly support Fisher's theory. Polyfactorial sex determination (in which sex is determined by three or more genetic factors) is suggested as the most likely mechanism producing the variable brood sex ratio.     

“Killer Character” of Saccharomyces cerevisiae: Curing by Growth at Elevated Temperature

Normal "killer" strains of Saccharomyces cerevisiae, when grown at 37 to 40 C, produce almost exclusively nonkiller cells due to loss or mutation of at least part of the non-chromosomal killer genome.     

Boeckella antiqua n. sp. (Copepoda,Calanoida, Centropagidae) from Patagonia

Boeckella antiqua n. sp. from samples collected in an ephemeral pond on the Patagonian plateau is described and illustrated. Diagnostic features of B. antiqua are almost exclusively related to the male fifth pair of legs, females being almost indistinguishable from those of the closely related B. poppei. The two-segmented, spine-bearing left endopod of the male fifth leg suggests that it may be the basal species in the genus.     

Imaging the K,Mg, Na and Ca Distributions in Flax Seeds using SIMS Microscopy

Taking advantage of the sensitivity, the lateral resolution and the ability of secondary ion mass spectrometry (SIMS) for elemental imaging, we have shown that the main alkaline and alkaline-earth cations exhibited clear-cut regionalization in flax seeds. Calcium, and even more magnesium were almost exclusively located within the protein bodies (PBs); and they were practically absent from the tissue areas with no PBs, such as the provascular tissue. By contrast, sodium was almost exclusively located outside the PBs; moreover, most of the seed sodium was in the tissues at the seed periphery (chiefly the teguments). Among the studied cations, potassium was the only one with a non-negligible concentration both in and outside the PBs.     

Exogenous thymidine is preferentially incorporated into human cytomegalovirus DNA in infected human fibroblasts.

The effect of human cytomegalovirus infection on cellular DNA synthesis in human fibroblasts was measured by fluorometry and by incorporation of radiolabeled thymidine. The results show that although HCMV infection stimulates cellular DNA synthesis in both quiescent and serum-stimulated cells, radiolabeled thymidine is almost exclusively incorporated into viral DNA.     

Polyploidy,flowering phenology and climatic adaptation in Heteropogon contortus (Gramineae)

Chromosome numbers of 2n = 39, 40, 50, 60, 69, 70, 80 and 90 are reported for Heteropogon contortus from a world collection. The numbers 2n = 39, 69, 70 and 90 are new to the literature. The cytogeographic distribution indicates that the tropical latitudes are almost exclusively occupied by tetraploids while the sub-tropical latitudes are characterized by a wide range of ploidy levels from tetraploid to nonaphid. Observations on the time of flowering of these accessions using uniform grass garden techniques indicate that pan-tropical populations are made up almost exclusively of late flowering lines and those from subtropical areas are of mixed lines showing great diversity from early to late flowering types. The association of polyploidy and flowering time are discussed in relation to the possible origin of H. contortus, to its adaptation and migration. It seems reasonable to suggest that polyploidy and the development of an earlier flowering response are both adoptively advantageous and have been selected for the species’migration into sub-tropical latitudes.     

Ontogenetic Behaviour Changes in Larvae of the Damselfly Ischnura verticalis (Odonata: Coenagrionidae)

Larvae of most animals go through large changes in size. Because change in size can lead to changes in ability to gain food and in predation risk, changes in behaviour are predicted to reflect this. Models consider change in amounts of the same behaviour, but different selective pressures on different larval sizes may also lead to qualitative differences in behavioural repertoire. In the damselfly Ischnura verticalis we observed ontogenetic changes in behaviour under controlled laboratory conditions. We found that frequency and duration of feeding behaviour and behaviour related to activity were increased in larger instars. Larger larvae also had higher transition probabilities to the behaviour abdomen wave, straight abdomen raise, and rotate + head out. We also found that the behavioural repertoire of damselfly larvae changed with development: some behavioural patterns were performed almost exclusively by smaller larvae (F - 4 to F - 7) while others were performed almost exclusively by larger larvae (F - 3 to F - 0).