Publisher Correction: GloPL, a global data base on pollen limitation of plant reproduction.

J. H. Burns was omitted in error from the author list of the original version of this Data Descriptor. This omission has now been corrected in both the HTML and PDF versions.

GloPL, a global data base on pollen limitation of plant reproduction.

Plant reproduction relies on transfer of pollen from anthers to stigmas, and the majority of flowering plants depend on biotic or abiotic agents for this transfer. A key metric for characterizing if pollen receipt is insufficient for reproduction is pollen limitation, which is assessed by pollen supplementation experiments. In a pollen supplementation experiment, fruit or seed production by flowers exposed to natural pollination is compared to that following hand pollination either by pollen supplementation (i.e. manual outcross pollen addition without bagging) or manual outcrossing of bagged flowers, which excludes natural pollination. The GloPL database brings together data from 2969 unique pollen supplementation experiments reported in 927 publications published from 1981 to 2015, allowing assessment of the strength and variability of pollen limitation in 1265 wild plant species across all biomes and geographic regions globally. The GloPL database will be updated and curated with the aim of enabling the continued study of pollen limitation in natural ecosystems and highlighting significant gaps in our understanding of pollen limitation.

Reflections on, and visions for, the changing field of pollination ecology.

Since the launch of Ecology Letters in 1998, the field of Pollination Ecology has changed considerably in its focus. In this review, we discuss the major discoveries across the past two decades. We quantitatively synthesise the frequency by which different concepts and topics appeared in the peer-reviewed literature, as well as the connections between these topics. We then look forward to identify pressing research frontiers and opportunities for additional integration in the future. We find that there has been a shift towards viewing plant-pollinator interactions as networks and towards understanding how global drivers influence the plants, pollinators and the ecosystem service of pollination. Future frontiers include moving towards a macroecological view of plant-pollinator interactions, understanding how ecological intensification and urbanisation will influence pollination, considering other interactions, such as plant-microbe-pollinator networks, and understanding the causes and consequences of extinctions. Pollination Ecology is poised to advance our basic understanding of the ecological and evolutionary factors that shape plant-animal interactions and to create applied knowledge that informs conservation decision making.

The ghost of competition present.

Communities have been viewed as the end product of an assembly process that results in increasing stability through time as progressively better competitors eventually dominate the other species that can emigrate from a regional pool. Previous work has explained species assemblages based on the traits of the successful species. We suggest that the traits of unsuccessful species in the regional pool may also be important for understanding which species are successful in communities. We constructed a simulation model to study what distinguishes stable, uninvasible assemblages from other possible assemblages from a regional pool of species. Our model demonstrates that both the interactions among the successful species and the interactions between these species and unsuccessful species attempting to invade the community contribute significantly to determining success in the final stable community. Understanding the structure of natural communities may require some knowledge of the unobserved "ghost" species that fail to establish in that same community yet still have significant effects on structure.

A psyllium-enriched cereal for the treatment of hypercholesterolemia in children: a controlled, double-blind, crossover study.

Psyllium, a water-soluble fiber, has been shown to lower total serum and low-density-lipoprotein (LDL)-cholesterol concentrations in adult hypercholesterolemic subjects and may be effective in the treatment of hypercholesterolemia in children. The effects of a psyllium-enriched cereal were compared with a matched control cereal in a double-blind, crossover fashion in 25 children, 6-18 y old, with hypercholesterolemia. After an 8-wk diet-stabilization period, the subjects were randomly assigned to receive the active or control cereals for 6 wk, followed by a 6-wk washout period and a 6-wk crossover treatment period. Whereas no changes were noted in total and LDL-cholesterol concentrations during consumption of the control cereal, significant changes were seen during the psyllium-cereal periods [0.31 mmol/L (12.1 mg/dL) and 0.28 mmol/L (10.9 mg/dL); P = 0.03 and 0.01, respectively]. The psyllium-enriched cereal was well tolerated throughout the trial. Consumption of the psyllium-enriched cereal resulted in a modest 7% reduction in LDL-cholesterol concentrations compared with the control cereal when used in this pediatric hypercholesterolemic sample. Psyllium offers a potential adjunct to a low-fat diet for the treatment of hypercholesterolemia in the pediatric population because of its ease of incorporation into various foods.

Maintenance of lower proportions of (n - 6) eicosanoid precursors in phospholipids of human plasma in response to added dietary (n - 3) fatty acids.

Competition between the (n - 3) and (n - 6) types of highly unsaturated fatty acids can diminish the abundance of (n - 6) eicosanoid precursors in a tissue, which in turn can diminish the intensity of tissue responses that are mediated by (n - 6) eicosanoids. The mixture of 20- and 22-carbon highly unsaturated fatty acids maintained in the phospholipids of human plasma is related to the dietary intake of 18:2 (n - 6) and 18:3 (n - 3) by empirical hyperbolic equations in a manner very similar to the relationship reported for laboratory rats (Lands, W.E.M., Morris, A. and Libelt, B. (1990) Lipids 25, 505-516). Analytical results from volunteers ingesting self-selected diets showed an inter-individual variance for the proportion of (n - 6) eicosanoid precursors in the fatty acids of plasma phospholipids of about 5%, but the variance among multiple samples taken from the same individual throughout the day was less (about 3%), closer to the experimental variance of the analytical procedure (about 1%). The reproducibility of the results makes it likely that analysis of fatty-acid composition of plasma lipids from individuals will prove useful in estimating the diet-related tendency for severe thrombotic, arthritic or other disorders that are mediated by (n - 6) eicosanoids. Additional constants and terms were included in the equations to account for the effects of 20- and 22-carbon highly unsaturated (n - 3) fatty acids in the diet. A lower constant for the 20- and 22-carbon (n - 3) fatty acids compared to that for the 18-carbon (n - 3) fatty acid in decreasing the ability of dietary 18:2 (n - 6) to maintain 20:4 (n - 6) in tissue lipids confirmed the greater competitive effectiveness of the more highly unsaturated n - 3 fatty acids in the elongation/desaturation process. Also, a lower constant for direct incorporation of 20-carbon fatty acids of the n - 6 vs. the n - 3 type indicated a greater competitive effectiveness of 20:4 (n - 6) relative to 20:5 (n - 3) in reesterification after release from tissue lipids. The equations may be used in reverse to estimate the dietary intakes of the (n - 3) and (n - 6) fatty acids by using the composition of the fatty acids that had been maintained in plasma lipids.

Marine oil capsule therapy for the treatment of hyperlipidemia.

Because marine oil capsules may vary widely in their content of omega-3 fatty acids, saturated fat, and cholesterol composition and, therefore, their biologic potency, we compared the lipid-lowering effects of three representative preparations in patients with different forms of hyperlipidemia. The ester and triglyceride forms of marine oil both effectively lowered triglyceride, but the response of low-density lipoprotein cholesterol was variable; it declined modestly in patients with hypercholesterolemia and was either unchanged or increased in those with hypertriglyceridemia. The saturated fat and cholesterol content of the marine oil preparation appeared to influence the low-density lipoprotein cholesterol response. Therefore, marine oil capsules are useful for lowering levels of very-low-density lipoprotein cholesterol, but the large dose required to achieve and sustain this effect (4.5 g of omega-3 fatty acids, or nine to 18 capsules daily) may limit long-term compliance.

The hypocholesterolemic effects of beta-glucan in oatmeal and oat bran. A dose-controlled study.

Oat cereals rich in the water-soluble fiber beta-glucan have been studied as a dietary therapy for hypercholesterolemia. To determine the hypocholesterolemic response of beta-glucan in the diet, 156 adults with low-density lipoprotein cholesterol (LDL-C) levels above 4.14 mmol/L (160 mg/dL) or between 3.37 and 4.14 mmol/L (130 and 160 mg/dL) with multiple risk factors were randomized to one of seven groups. Six groups received either oatmeal or oat bran at doses (dry weight) of 28 g (1 oz), 56 g (2 oz), and 84 g (3 oz). A seventh group received 28 g of farina (beta-glucan control). At week 6 of treatment, significant differences were found for both total cholesterol and LDL-C levels among the farina control and the treatment groups who were receiving 84 g of oatmeal, 56 g of oat bran, and 84 g of oat bran, with decreases in LDL-C levels of 10.1%, 15.9%, and 11.5%, respectively. Fifty-six grams of oat bran resulted in significantly greater reductions in LDL-C levels than 56 g of oatmeal. Nutrient analysis shows no difference in dietary fat content between these treatment groups; therefore, the higher beta-glucan content of oat bran most likely explains the significantly greater LDL-C reductions. A dose-dependent reduction in LDL-C levels with oat cereals supports the independent hypocholesterolemic effects of beta-glucan.

Differentiation stage-specific expression of a gene during granulopoiesis.

Differential screening of a recombinant cDNA library using cDNAs transcribed from poly(A)+ RNA of normal or leukemic leukocytes revealed a number of recombinants homologous to mRNAs characteristic of particular leukemias. The occurrence of one of these (pCG14) in high abundance was shown to be sufficiently characteristic of the circulating leukocyte population of chronic granulocytic leukemia (CGL) patients to distinguish them from all other populations of leukocytes. We have now characterized the gene encoding this mRNA and shown that its expression is specific to the granulocyte lineage in hemopoietic cells and is, moreover, limited to a narrow stage of differentiation during granulopoiesis. Our results explain why high levels of pCG14 RNA are characteristic of chronic granulocytic leukemia peripheral blood leukocytes.

The relative abundances of specific RNA sequences can be used to classify the myeloid leukaemias.

The relative concentrations of pCG14 RNA (a myelocyte-specific mRNA), pAM6 RNA (a monocyte-lineage specific marker), and c-myc RNA (present at higher concentrations in more primitive cells) were measured in the RNAs from peripheral blood leucocytes from leukaemic samples and normal individuals. The potential of differences in the relative abundances of these three RNAs in a series of 34 leukaemias was assessed as a means of distinguishing among the myeloid leukaemias. The chronic phase CGL samples were clustered with a high pCG14 RNA, a medium to low c-myc RNA abundance, and a variable pAM6 RNA level. The ANLL samples could be distinguished from the chronic phase CGL by virtue of different relative abundances of these RNAs: low pCG14, medium to high c-myc and a variable pAM6. The acute phase CGL samples showed a variety of relative RNA abundances with some samples sited within the ANLL region. Using samples obtained during the progression of CGL we have shown a shift in the relative abundances of these RNAs from the CGL region towards the ANLL region, and have suggested that the use of these parameters may allow the progression to acute phase to be monitored and, possibly, predicted.

Expression of the myc gene locus in populations of leukocytes from leukaemia patients and normal individuals.

The relative abundances of c-myc-related RNA in the total cellular RNA of peripheral blood leukocytes from 36 patients with leukaemia have been compared with those in normal peripheral blood leukocytes and in HL60 cells. Varying amounts of c-myc-related RNA were found in RNAs from leukocytes from patients with ANLL, CGL and ALL. High concentrations (comparable with that in HL60 cells) were found in 13 (36%) of the leukaemias and lower, but still significant, concentrations in a further 15 (42%). Low concentrations of c-myc-related RNA, comparable to that in normal leukocytes, were found in 2 of 8 CGLs, 1 of 12 ANLLs, and 5 of 5 CLLs. DNAs from 11 leukaemia patients' leukocytes, in which c-myc-related RNA concentrations ranged from very high to very low, were examined for rearrangements and/or amplification of the c-myc gene. No rearrangements were detected, and the small degree of amplification (2- to 4-fold at most) found was not correlated with increased levels of c-myc RNA. There was, however, a noteworthy (though incomplete) correlation between elevated levels of c-myc-related RNA and the occurrence of higher proportions of blast cells in leukocyte populations from leukaemic patients. It is suggested that high levels of c-myc-related RNA in a population of peripheral blood leukocytes indicate the presence of a high proportion of leukaemic leukocytes that are maturation-arrested at early stages of development.

Characterization of digoxin binding and daunorubicin uptake by isolated mature rat cardiac myocytes.

Myocytes isolated from ventricular muscle of mature rat heart have been used for characterization of digoxin binding and to establish whether a relationship exists between digoxin binding and uptake of daunorubicin. High- and low-affinity digoxin binding sites have been identified; respectively, 0.9 +/- 0.1 X 10(7) sites/myocyte, Kd 70-77 nM and 7 +/- 2 X 10(7) sites/myocyte, Kd 1.4-1.7 microM. Myocytes accumulate daunorubicin to an intracellular concentration 30-40 times that in the medium. We find no evidence that saturation of digoxin binding sites alters daunorubicin uptake or that daunorubicin influences binding of digoxin. Alteration of sarcolemmal membrane properties is demonstrated by inhibition of amino acid transport reflected in protein synthesis rates. Calmodulin activation of phosphodiesterase appears insensitive to daunorubicin.

Subdivision of the acute non-lymphoblastic leukaemias by measurement of the relative abundance of a specific RNA sequence.

A recombinant plasmid library representing the more abundant polyadenylated RNA of a relapsed acute myelomonocytic leukaemic (FAB class M4) has been constructed. One recombinant, designated pAM6, contains a DNA sequence complementary to an RNA of about 1100 nucleotides in length. The relative concentrations of pAM6 RNA in the RNAs from cloned human haematopoietic cell lines and from fractionated leukaemic leukocytes and normal bone marrow cells, measured by an RNA dot hybridization method, indicated that pAM6 RNA occurs in myeloid cells, probably those of the monocyte lineage at the earlier stages in differentiation. Similar assays showed that pAM6 RNA could not be detected in the peripheral blood leukocytes of normal individuals, or of ALL and CLL patients, but that the relative abundance of pAM6 RNA varied widely in leukocytes from CGL chronic phase, CGL acute phase, and ANLL. No correlation between pAM6 RNA occurrence and FAB classification of ANLL could be made; thus it would appear that the relative abundance of pAM6 RNA in ANLL leukocytes can be used to subdivide the ANLLs in a novel manner. It is suggested that this criterion, in conjunction with existing diagnostic markers, may provide a subclassification of the ANLLs that could be of some prognostic and therapeutic value.

Lineage-specific and differentiation-stage-specific gene expression in normal and leukaemic human myeloid cells.

One example of each of two approaches to the isolation of molecular hybridization probes and their use for the comparative investigation of gene expression and its control during differentiation of normal and leukaemic leukocytes is described. RNA preparations from the peripheral blood leukocytes of human leukaemias of various types were assayed for the relative abundance of the mRNA homologous with a cellular oncogene, c-myc. All types of leukaemia except chronic lymphatic leukaemia (CLL) showed varying levels of myc-related RNA; the highest concentrations occurred in cell populations in which blast cells predominated. In contrast, a recombinant plasmid (pCG14), isolated from a cDNA recombinant plasmid library that represented polyadenylated RNAs from the peripheral blood leukocytes of a chronic granulocytic leukaemia (CGL), hybridized with an mRNA whose occurrence is diagnostic of CGL leukocytes. This mRNA was also found in normal bone marrow cells; in both bone marrow and in CGL leukocytes, pCG14-homologous RNA occurs only in cells around the myelocyte stage in differentiation. It is suggested that these probes, and others for mRNAs whose occurrence is specific to a particular cell lineage and/or stage in differentiation, detect a new series of potential diagnostic markers. These might usefully supplement existing ones to provide a more detailed, objective subclassification of the leukaemias which could have important implications for diagnosis and therapy.

A new approach to the classification of human leukaemias: measurement of the relative abundance of a specific RNA sequence by means of molecular hybridisation.

A recombinant plasmid library representing polyadenylated RNAs in the leucocytes of a Ph1-positive chronic granulocytic leukaemia (CGL) has been constructed. One recombinant (designated pCG14) isolated from this library contains a DNA sequence complementary to a small polyadenylated RNA that is abundant in RNA from CGL leucocytes. The relative concentrations of pCG14 RNA in the RNAs from a variety of normal and leukaemic leucocytes and human haemopoietic cell lines have been measured with a molecular hybridisation assay. This has shown that pCG14 RNA is 10 to 50 times more abundant in RNA from CGL leucocytes than in the RNAs from these other cells. The data indicate that the occurrence of pCG14 RNA in high abundance is sufficiently characteristic of a CGL leucocyte population to distinguish it from other populations of leucocytes. They suggest that the measurement of the concentrations of specific RNA species in leucocyte RNA by means of molecular hybridisation with cloned complementary DNAs may provide additional markers for the objective classification of human leukaemias which could be particularly useful since the method exploits a criterion different from any currently in use.

Differences among the polyadenylated RNA sequences of human leucocyte populations: an approach to the objective classification of human leukaemias.

We have constructed a complementary DNA (cDNA) library representing expressed sequences of the white blood cells from a patient with chronic granulocytic leukaemia. The library was screened by colony hybridization of 32P-labelled cDNAs synthesized from the polyadenylated RNAs of the white blood cells from patients with chronic granulocytic or chronic lymphocytic leukaemia. The autoradiographic patterns were compared and 70 recombinants were selected to comprise a panel which distinguished between these two types of leukaemia. Hybridization of this panel with complementary DNAs transcribed from the polyadenylated RNAs of a variety of normal and neoplastic leucocyte populations showed that the RNA sequences in high abundance in leucocytes from chronic granulocytic leukaemias differ quite radically from those in other leucocytes. The patterns of hybridization seen when this panel was challenged with cDNAs representing the RNAs of normal and leukaemic leucocyte populations were sufficiently different to distinguish clearly the peripheral blood leucocytes of chronic granulocytic leukaemias from other populations of white blood cells, both normal and leukaemic. We suggest that this approach might provide additional markers useful in the classification of the acute leukaemias, especially the undifferentiated leukaemias whose identification by conventional methods is uncertain.

Amino acid transport and protein synthesis in energetically-stable calcium-tolerant isolated cardiac myocytes.

Myocytes isolated by enzymic dispersion from adult rat ventricular tissue are shown to be energetically stable in the presence of 0.5 mM CaCl2. ATP and ADP content and rates of lactate production are comparable with those of intact myocardial tissue and consistent with these cells being tightly coupled. Addition of 2,4-dinitrophenol precipitates rapid changes in adenine nucleotide concentrations and a 10-fold increase in lactate production. Cardiac myocytes selectively transport neutral amino acids of the A and L classes. Transport of the amino acid analogue alpha-aminoisobutyric acid is an active, temperature-dependent and insulin-sensitive process. The apparent Km for alpha-aminoisobutyric acid transport is similar to that determined for embryonic cardiac cells. Mature myocytes incorporate labelled amino acids into cytoplasmic proteins with molecular weights ranging from 10 000 to 150 000. Newly synthesised protein is metabolically stable. The data establishes calcium-tolerant myocytes as an experimental system offering many advantages over whole hearts for short- and long-term studies of protein synthesis and catabolism.