Citrus limonoid effects on Colorado potato beetle larval survival and development

The effects of citrus limonoids, applied topically to potato (Solanum tuberosum L. var. Katahdin) foliage, on Colorado potato beetle (Leptinotarsa decemlineata) (Say) (Chrysomelidae) larval development, growth, and survival were quantified in laboratory assays and a small-plot field test. In laboratory assays, survival, development rate, and body weight decreased with increasing limonoid concentration, however these measures of larval response did not significantly differ among varying periods of limonoid exposure (three, six, or nine days). Significant limonoid application concentration and frequency effects on survival, development rate, and defoliation were observed in the field test. These results indicate the potential utility of lethal and non-lethal effects of citrus limonoids for management of the Colorado potato beetle.     

Determinants of Dominance in the Tree Lizard Urosaurus ornatus: the Relative Importance of Mass,Previous Experience and Coloration

A determination of some of the factors that predict the outcome of contests between male tree lizards, Urosaurus ornatus, was made using logistic regression modelling on matched-pair data. Two-day-long encounters were staged between pairs of males differing in size (snout-vent length and mass), previous contest status (previous winners and previous losers), and coloration (dorsal coloration during their previous contest and throat coloration, a fixed trait). Mass proved to be the best single predictor of contest outcome, resulting in an 80% correct classification rate for predicting winners and losers, far better than the less than 57% correct classification rate for snout-vent length. Previous social status (winner or loser) also was a powerful single predictor of contest outcome with a 793% correct classification rate, as was previous dorsal coloration (76.7%). When combined, mass and previous status produced the strongest combination of predictors with a better than 86% correct classification rate. Contrary to several previous studies, which implicated throat coloration as an important status signal of dominance, our results failed to show that throat coloration is a strong predictor of contest outcome. Possible reasons for this discrepancy with earlier findings are discussed. The logistic regression models also allow prediction of the magnitude of difference in mass between two contestants for there to be an equal chance of winning, given a second asymmetry in contest predictors.     

Modelling the spatial patterning of teeth primordia in the alligator

We propose a model mechanism for the initiation and spatial positioning of teeth primordia in the alligator, Alligator mississippiensis. Detailed embryological studies by Westergaard and Ferguson (1986, 1987, 1990) have shown that jaw growth plays a crucial role in the developmental patterning of the tooth initiation process. Based on biological data we develop a dynamic patterning mechanism, which crucially includes domain growth. The mechanism can reproduce the spatial pattern development of the first seven teeth primordia in each half jaw of A. mississippiensis. The results for the precise spatio-temporal sequence compare well with experiment. Simulation of the model also predicts that certain transplantations can alter the spatial sequence of teeth primordia initiation.     

Exclusion of epidermal growth factor and high-resolution physical mapping across the Rieger syndrome locus.

We have evaluated the 4q25-4q26 region where the autosomal dominant disorder Rieger syndrome has been previously mapped by linkage. We first excluded epidermal growth factor as a candidate gene by carrying out SSCP analysis of each of its 24 exons using a panel of seven unrelated individuals with Rieger syndrome. No evidence for etiologic mutations was detected in these individuals, although four polymorphic variants were identified, including three that resulted in amino acid changes. We next made use of two apparently balanced translocations, one familial and one sporadic, to identify a narrow physical localization likely to contain the gene or to be involved in regulation of gene function. Somatic cell hybrids were established from individuals with these balanced translocations, and these hybrids were used as a physical mapping resource for, first, preliminary mapping of the translocation breakpoints using known sequence tagged sites from chromosome 4 and then, after creating YAC and cosmids contigs encompassing the region, for fine mapping of those breakpoints. A cosmid contig spanning these breakpoints was identified and localized the gene to within approximately 150 kb of D4S193 on chromosome 4. The interval between the two independent translocations is approximately 50 kb in length and provides a powerful resource for gene identification.     

Differences between observed and predicted energy costs at rest and during exercise in three subsistence-level populations

Estimates of daily energy expenditure are important for many areas of research in human ecology and adaptability. The most common technique for estimating human energy expenditure under field conditions, the factorial method, generally relies on activity-specific energy costs derived from published sources, based largely on North American and European subjects. There is concern that such data may not be appropriate for non-Western populations because of differences in metabolic costs. The present study addresses this concern by comparing measured vs. predicted energy costs at rest and during sub-maximal exercise in 83 subjects (52 males, 31 females) from three subsistence-level populations (Siberian herders and high-land and coastal Ecuadorian farmers). Energy costs at rest (i.e., lying, sitting and standing) and while performing a standard stepping exercise did not significantly differ among the three groups. However, resting energy costs were significantly elevated over predicted levels (+16% in men, +11% in women), whereas exercising costs were comparable to predicted values (?6% in men, +3% in women). Elevations in resting energy needs appear to reflect responses to thermal stress. These results indicate that temperature adjustments of resting energy costs are critical for accurately predicting daily energy needs among traditionally living populations. o 1996 Wiley-Liss, Inc.     

Seasonal variation in the effects of hard substratum biofilming on settlement of marine invertebrate larvae

The effect of season on "biofilming";, as a cue for the settlement of marine invertebrate larvae, was investigated in a long-term field study during the years 1992-1994. The series of settlement experiments was conducted in a tidal rapid on the west coast of Scotland, and involved manipulations of artificial panels. Biofilming of substrata, whilst excluding larval settlement, was achieved by the enclosure of panels within tight-fitting (but removable) mesh screens so that the number of settlers on filmed and unfilmed substrata were counted in the initial absence of other incumbent post-larvae. Depending on larval species, the effects of biofilming were found to be either facilitatory or inhibitory. Significant within- and between-species seasonal differences in the settlement responses were detected, and a reversal of the effect of biofilming on larval settlement response, from inhibitory to facilitatory and vice versa, was noted with season in the case of some taxonomic groups and species (e.g. Tubulipora sp., Plagioecia sp., Electra pilosa (L.)). The present study emphasizes the need for extended field studies of larval responses to environmental cues, when the focus of interest is in drawing general inferences about naturally occurring behavioural patterns at settlement.     

Analysis of stimulatory and inhibitory amino acids for development of hamster one-cell embryos in vitro

Hamster embryo development to the blastocyst stage in vitro can be modulated by amino acids. This series of experiments employed both empirically and statistically designed approaches to elucidate which of 20 amino acids inhibit or stimulate development and to devise a complement of amino acids that best supports in vitro development of hamster 1-cell embryos. Development and/or mean cell number were significantly inhibited by the presence of leucine, tyrosine, valine, isoleucine, phenylalanine, arginine, methionine, or cysteine (at 0.5 mM) and isoleucine, phenylalanine, or tryptophan (at 0.05 mM). Three amino acids—glutamine, taurine, and glycine—were stimulatory and in combination improved development; the culture medium containing these amino acids was designated Hamster Embryo Culture Medium-5. Moreover, addition of another eight amino acids—asparagine, aspartic acid, serine, glutamic acid, histidine, lysine, proline and cysteine (medium designated HECM-6)—had a significant stimulatory effect on development over previously formulated culture media for hamster embryos. These results demonstrated that amino acids, alone and in combination, can markedly stimulate or inhibit hamster embryo development in vitro up to the blastocyst stage. Embryo transfer experiments showed that HECM-5 and ?6 (chemically defined, protein-free culture media) supported normal preimplantation embryo development in vitro. This study also indicates that empirically designed embryo culture media formulations can be as effective as those obtained by application of statistical methodologies. © 1995 wiley-Liss, Inc.     

Cloning and Expression of a 5-Hydroxytryptamine7 Receptor Positively Coupled to Adenylyl Cyclase

Abstract: In a number of different cell types, phosphorylation of a 63-kDa protein has been shown to increase rapidly in response to stimuli that lead to an increase in intracellular calcium. Here, a stimulus-sensitive protein at this molecular weight is identified in PC12 cells and rat cortical synaptosomes as phosphoglucomutase. In addition, the added phosphate is shown to be in an oligosaccharide terminating in phosphodiester-linked glucose. In synaptosomes, incorporated radioactivity, following incubation with [¹⁴C]glucose or the [β-³⁵S]phosphorothioate analogue of UDP-glucose, was found to increase within 5 s of stimulation and return to baseline within 25 s. Despite the many pathways utilizing glucose, this was the only detectable protein glycosylation observed in synaptosomes. These results indicate that cytoplasmic glycosylation is reversible and rapidly regulated, and suggest that phosphoglucomutase undergoes an alteration in function and/or topography in response to increases in intracellular calcium.     

Cell cycle checkpoints

Checkpoints help ensure that cell cycle events occur in the correct order. Studies on mammalian cells identified inhibitors of complexes of cyclins and cyclin-dependent kinases as components of cell cycle checkpoints and provide the first glimpse of the molecular pathways that prevent cells with damaged DNA from replicating their DNA. In embryos, the extent to which checkpoints arrest the cell cycle reflects the relative strength of inhibitory checkpoints and the machinery driving the cell cycle forward.