Analysis of the community structure of yeasts associated with the decaying stems of cactus. I.Stenocereus gummosus

Yeast communities of decayingStenocereus gummosus were analyzed for spatial, temporal, and physiological characteristics. Analysis of random samples within plants, between plants, and between localities shows that the species proportions of the yeast community are relatively constant within plants and between localities, but that there is significant variability between rotting plants. It is suggested that the increased variability between plants represents sampling of different stages of succession. The physiological abilities of the yeast community also show a relatively constant pattern within plants and between localities yet more variability between plants.The variablity profiles of species proportions and community physiological characters are demonstrated to be correlated within and between plants. This observation is an extension of the Kluge-Kerfoot phenomenon to the level of the community. The correlation of within and between plant variability profiles is suggested to be a result of the temporal and spatial availability of resources during the stages of rotting plant succession. The community structure is thus postulated to result from a set of possible future resource states of the habitat.     

RAPD-marking of genomes of representative Hordeum species

Random amplification of polymorphic DNA (RAPD) was used to analyze six species, three populations, and seven regional cultivars of barley. A unique pattern of amplified DNA products was obtained for each species of the genus Hordeum. High polymorphism of barley species was revealed. Specific fragments were found in most RAPD patterns; the fragments can be used as molecular markers of corresponding species and subspecies. Several other DNA fragments were shown to serve as molecular markers of the H genome. Specific RAPD patterns were obtained for each population and each cultivar of H. vulgare sensu lato. In total, variation between the populations and between the cultivars was substantially lower than between species. Cluster analysis (UPGMA) was used to estimate genetic distances between the Hordeum species, between the H. spontaneum populations, and between regional H. vulgare cultivars and a dendrogram was constructed.     

Patterns of cranial sexual dimorphism in certain groups of extant hominoids

This paper presents a study of patterns of cranial variation within and between extant hominoids. Particular attention is paid to the relationship between sexual dimorphisms and size differences between sexes. It emerges that shape contrasts between sexes are closely linked to size differences whilst variance dimorphism appears to be relatively independent of size effects. This study demonstrates that there are differences between the hominoids in their magnitudes and patterns of sexual shape contrasts. These types of differences are also found to exist between subgroups of modern humans. It is suggested that the differences which occur between hominoid groups in their patterns of sexual dimorphism are probably the result of a mixture of time and rate hypermorphoses (in males relative to females) acting upon different ontogenetic trajectories. The findings of this study suggest the need for caution in extrapolating from the sexual dimorphisms found in living hominoids to hypothesized dimorphisms in fossils.     

Repeatability of hematocrits and body mass of Gray Catbirds

ABSTRACT.   Hematocrits may provide information about the physiological condition of birds, but, to be a useful measure, information is needed concerning how hematocrits vary among individuals and over time. We examined the repeatability of hematocrits in a population of Gray Catbirds ( Dumetella carolinensis ) in Pennsylvania at several time scales and also examined the repeatability of body mass, another measure commonly used as an indicator of condition. Both hematocrit ( r = 0.64) and mass ( r = 0.65) were repeatable ( P < 0.01) for first captures between years and between first and second captures within a year ( r = 0.41 and r = 0.50, respectively; P < 0.01), but not repeatable ( P > 0.05) between captures in different months within a year ( r = 0.11 for both). Repeatability of both measures differed by sex and age. Females exhibited repeatability of hematocrit and body mass only between years, while male hematocrits were repeatable between years and between first and second captures within a season. Male mass was repeatable for all time periods. Hematocrits of younger birds were repeatable between captures within a season and their body mass was repeatable between months and weeks while hematocrits of older birds were not repeatable and their body mass was repeatable only between captures in a season. Our results indicate that hematocrits and body mass had similar repeatability coefficients overall, but that hematocrits of Gray Catbirds were a consistent trait of individuals only across years. Because repeatability between captures and months depended on sex and age, we conclude that the hematocrit is a useful measure of individual performance only in limited circumstances.     

The effect of ambient temperature on infrared thermographic images of joints in the distal forelimbs of healthy racehorses

The aim of the study was to describe the dependence on ambient temperature of distal joint temperature at the forelimbs of racehorses. The study also investigated the influence of differing ambient temperatures on the temperature difference between joints: this was measured ipsilaterally (i.e. between the carpal and fetlock joints along each forelimb) and contralaterally (i.e. between the same joints of the left and right forelimbs). Sixty-four healthy racehorses were monitored over 10 months. At each session, three thermographic images were taken of the dorsal, lateral and medial aspects of the distal forelimbs. Temperature measurements were made from regions of interest (ROIs) covering the carpal and fetlock joints. There was a strong correlation between ambient temperature and absolute joint temperature at all ROIs. The study also observed a moderate correlation between ambient temperature and the ipsilateral temperature differences between joints when measured from the medial and lateral aspects. No significant correlation was noted when measured dorsally. The mean contralateral temperature differences between joints were all close to 0 °C. The data support previous reports that the temperature distribution between the forelimbs of the healthy equine is generally symmetric, although some horses differ markedly from the average findings.     

Evaluation of linkage disequilibrium measures between multi-allelic markers as predictors of linkage disequilibrium between single nucleotide polymorphisms

Effectiveness of marker-assisted selection (MAS) and quantitative trait locus (QTL) mapping using population-wide linkage disequilibrium (LD) between markers and QTLs depends on the extent of LD and how it declines with distance between markers and QTLs in a population. Marker-QTL LD can be predicted from LD between markers. Our previous work evaluated LD measures between multi-allelic markers as predictors of usable LD of multi-allelic markers with QTLs. Since single nucleotide polymorphisms (SNPs) are the current marker of choice for high-density genotyping and LD-mapping of QTLs, the objective of this study was to use LD between multi-allelic markers to predict LD among biallelic SNPs or between SNPs and QTLs. Observable LD between multi-allelic markers was evaluated using nine measures. These included two pooled and standardized measures of LD between pairs of alleles at two markers based on Lewontin's LD measure, two pooled measures of squared correlations between alleles, one standardized measure using Hardy-Weinberg heterozygosities, and four measures based on the chi-square statistic for testing for association between alleles at two loci. The standardized chi-square measure that best predicted usable LD between multi-allelic markers and QTLs, based on our previous work, overestimated usable SNP-SNP or SNP-QTL LD. Instead, three other measures were found to be good predictors of usable SNP-SNP or SNP-QTL LD when LD is generated by drift. Therefore, the LD measure between multi-allelic markers that is best for predicting usable LD in a population depends on the type of markers (i.e. multi-allelic or biallelic) that will eventually be used for QTL mapping or MAS.     

Sex ratio of fetuses during the second trimester of gestation

The authors have investigated the sex ratio of fetuses between the thirteenth and twenty-fourth menstrual weeks. The study material, consisting of 749 fetuses, was obtained through induced second trimester abortions. The sex ratio of the 749 specimens was 109. The ratio was 129 between the thirteenth and sixteenth weeks, 105.8 between the seventeenth and twentieth weeks, and 94 between the twenty-first and twenty-fourth weeks of pregnancy. The overall ratio was 112 among Caucasian and 107 among both Black and Central American populations.     

Correspondences between classifications and between classes of entities in molecular genetics

Certain correspondences appear between the classifications and between the classes of various entities at molecular genetic level: types of fundamental correspondences between classifications and between classes of normal entities, on the one hand, and of mutant entities on the other hand; ranks of correspondences between classifications and between classes of entities. The concept of universality of the genetic code was reformulated on the basis of the above correspondences.     

Study on the Convergent Passages of Water Conducting Elements in Secondary Xylem of Fagaceae

Structural variations in the convergent passages of water conducting elements were described in secondary xylem of 70 species of Fagaceae. Two types of water conducting systems were recognized on the ground of water-flow directions. The convergent passages of the longitudinal system mainly exhibited in the forms as perforations between the ends of Vessel elements, lateral wall pitting between the lateral walls of vessel elements, pitting be-tween vessel elements and imperforate tracheary elements, and pitting between imperforate tracheary elements. The convergent passages in the transverse system consisted of pitting between vessel elements and ray cells, pitting between imperforated tracheary elements and ray cells and simple pitting between ray cells. In addition, the roles of vasicentric tracheids and broad rays played in terms of conducting effectiveness and efficiency as proposed by Zimmermann were discussed.     

Thermally reversible hydration of beta-chitin

Thermally induced transition between anhydrous and hydrated forms of highly crystalline beta-chitin was studied by differential thermal calorimetry (DSC) and X-ray diffraction. DSC of wet beta-chitin in a sealed pan gave two well-defined endothermic peaks at 85.2 and 104.7 degrees C on heating and one broad exothermic peak at between 60 and 0 degrees C on cooling. These peaks were highly reproducible and became more distinct after repeated heating-cooling cycles. The X-ray diffraction pattern of wet beta-chitin at elevated temperature showed corresponding changes in d-spacing between the sheets formed by stacking of chitin molecules. These phenomena clearly show that water is reversibly incorporated into the beta-chitin crystal and that the temperature change induces transitions between anhydrous, monohydrate, and dihydrate forms. The DSC behavior in heating-cooling cycles, including reversion between the two endothermic peaks, indicated that the transition between monohydrate and dihydrate was a fast and narrow-temperature process, whereas the one between the anhydrous and the monohydrate form was a slow and wide-temperature process.     

Sources of uncertainty in assessment of marine phytoplankton communities

Characterisation of phytoplankton communities is important for classification of the ecological status of marine waters. In order to design a monitoring programme, it is important to know what degree of variation in the measurements occur at each level (water body, station and sample), so that resources can be spent in a way that maximise the precision of the measured parameters. Seven European water bodies were sampled to assess the variation in pigment concentrations and population densities attributed to water body, station and sample levels. It was found that the main proportion of the variation between pigment measurements was explained by the variation between stations (12–91% of variation) followed by the variation between water bodies (0–89% of variation). For measurements of population density, the main proportion of the variation between densities of cells recorded was explained by the variation between the taxonomists counting the samples (61%), whilst the main proportion of the variation between numbers of taxa recorded was explained by the variation between water bodies (83%). When the cell density of the nine dominant classes were analysed separately, the main proportion of variation was explained at the water body level for all but two class.     

Relation of genetic distance between cattle breeds and heterosis of resulting crosses

The relationship was investigated between performance differences, and genetic distance between parental breeds, and heterosis increment in milk and fat yield. Heterosis increments were positively correlated with both yield difference and genetic distance but only the relation between heterosis of fat yield and genetic distance between parental breeds was statistically significant. It appears that measures of genetic distance could provide a useful tool in selecting breeds for crossbreeding.     

A neutral model of transcriptome evolution

Microarray technologies allow the identification of large numbers of expression differences within and between species. Although environmental and physiological stimuli are clearly responsible for changes in the expression levels of many genes, it is not known whether the majority of changes of gene expression fixed during evolution between species and between various tissues within a species are caused by Darwinian selection or by stochastic processes. We find the following: (1) expression differences between species accumulate approximately linearly with time; (2) gene expression variation among individuals within a species correlates positively with expression divergence between species; (3) rates of expression divergence between species do not differ significantly between intact genes and expressed pseudogenes; (4) expression differences between brain regions within a species have accumulated approximately linearly with time since these regions emerged during evolution. These results suggest that the majority of expression differences observed between species are selectively neutral or nearly neutral and likely to be of little or no functional significance. Therefore, the identification of gene expression differences between species fixed by selection should be based on null hypotheses assuming functional neutrality. Furthermore, it may be possible to apply a molecular clock based on expression differences to infer the evolutionary history of tissues.     

The effects of temperature and humidity on the nocturnal activity of different shell colour morphs of the land snail Arianta arbustorum

The noctural activities of the phenotypic shell colour morphy and age classes (adults and juveniles) of Arianta arbustorum were recorded 1 day week^-1 for 4 weeks in several laboratory microclimatic conditions. Six constant temperatures between 3 and 18C and four levels of relative humidities between 34 and 98% were maintained. A light regime of 16 h light: 8 h dark was used. There are highly significant differences in activity at different levels of adaptation temperature and relative humidity. The interaction between these factors is significant. There are no significant differences in nocturnal activity between the two phenotypic shell colours nor between the two age classes, but the interaction between morph and relative humidity is significant. The interaction between age classes and relative humidity is also significant. Yellows are more active than browns at high humidities, but less active at low. They are therefore likely to be behaviourally more responsive than browns in an environment of fluctuating humidities. This result is discussed in relation to the maintenance of the polymorphism.     

Effect of provenance on free amino acid and chemical composition of Scots pine needles

Free amino acid (16 amino acids) and chemical composition (N, P, K, Mg, Ca, S, Fe, Mn, Cu, Zn) of Scots pine (Pinus sylvestris L.) needles were compared between six provenances in three different experimental areas. The main free amino acids in the needles were in the sequence of quantity; glutamic acid, glutamine, arginine and γ-aminobutyric acid. There were no significant differences in the concentrations of phenylalanine, γ-aminobutyric acid, methionine, proline and threonine in pine needles between the sites or between the provenances. Significant differences in the foliar concentrations of alanine and leucine were found between the sites and in the foliar concentrations of isoleucine, glutamine, glycine and tyrosine between the provenances. The concentrations of aspartic acid, glutamic acid, arginine and lysine were significantly affected by the sites and the provenances. The foliar nutrients, except copper, had statistically significant differences, both between the sites and between the provenances. Calcium did not differ between the provenances. This revised version was published online in June 2006 with corrections to the Cover Date.     

Interstitial cells of Cajal: mediators of communication between circular and longitudinal muscle layers of canine colon

The network of interstitial cells of Cajal associated with Auerbach’s (myenteric) plexus in the canine colon was investigated to determine its role in facilitating communication between circular and longitudinal muscle layers. Electrical coupling between the muscle layers was demonstrated by propagating extracellularly evoked electrotonic pulses from circular muscle cells to nearby longitudinal muscle cells. The likelihood of cytoplasmic continuity across Auerbach’s plexus was further demonstrated by the ability of neurobiotin to spread between the interstitial cells and the circular and longitudinal muscle cells. Importantly, direct neurobiotin spread between circular and longitudinal muscle cells was not observed even when they were in close proximity as determined by confocal microscopy. When neurobiotin did spread across the two muscle layers, the intervening interstitial cells were always neurobiotin-positive. In regions where circular and longitudinal muscle cells approach each other closely, electron microscopy revealed the presence of close appositions between interstitial cells and smooth muscle cells. Gap junctions between interstitial cells and smooth muscle cells of both layers, as judged by electron microscopy, were extremely rare. Neither gap junctions nor close appositions were observed between longitudinal and circular muscle cells. The special arrangement for electrotonic coupling across Auerbach’s plexus through interstitial cells of Cajal suggests controlled coupling between the two muscle layers, explaining the preservation of their distinct electrical activities. Received: 21 July 1995 / Accepted: 22 April 1998     

Syntheses of depsipeptide analogues of the insect neuropeptide proctolin

Four depsipeptide analogues of the insect neuropeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) have been prepared, containing a single ester linkage between Arg(1) and Tyr(2), Tyr(2) and Leu(3), and between Pro(4) and Thr(5), respectively. A didepsipentapeptide containing an ester linkage between Tyr(2) and Leu(3) and between Pro(4) and Thr(5), has also been prepared. The depsipeptide 4 is the first example of a backbone-modified proctolin analogue which shows full myotropic activity.     

Influence of predator density on nonindependent effects of multiple predator species

Interactions between multiple predator species are frequent in natural communities and can have important implications for shared prey survival. Predator density may be an important component of these interactions between predator species, as the frequency of interactions between species is largely determined by species density. Here we experimentally examine the importance of predator density for interactions between predator species and subsequent impacts on prey. We show that aggressive interactions between the predatory shore crabs Carcinus maenas and Hemigrapsus sanguineus increased with predator density, yet did not increase as fast as negative interactions between conspecifics. At low density, interactions between conspecific and heterospecific predators had similar inhibitory impacts on predator function, whereas conspecific interference was greater than interference from heterospecifics at high predator density. Thus the impact of conspecific interference at high predator density was sufficient in itself that interactions with a second predator species had no additional impact on per capita predation. Spatial and temporal variability in predator density is a ubiquitous characteristic of natural systems that should be considered in studies of multiple predator species.     

The specificity of purified porcine pancreatic elastase

An electrophoretically homogeneous elastase preparation free from tryptic and chymotryptic activities was obtained by chromatography on DEAE-Sephadex and CM-cellulose. This preparation exhibits a narrower specificity towards peptide bonds than that observed by Naughton & Sanger (1961). With oxidized insulin B chain as substrate, the fastest breaks occur between alanine-14 and leucine-15 and between valine-18 and cysteic acid-19. The bond between glycine-23 and phenylalanine-24 is also efficiently hydrolysed. Other bonds hydrolysed are that between valine-12 and glutamic acid-13 and that between serine-9 and histidine-10. Oxidized insulin A chain is hydrolysed only at one of two points, between alanine-8 and serine-9 or between serine-12 and leucine-13, and the rate of hydrolysis is very low.     

Obtaining chimeric embryos of groundling for study of the role of cellular interactions in early development]

A methos of production of chimaeric embryos of the loach by parabiosis of whole embryos and a whole embryo and an isolated blastodisc is proposed. The parabiosis was shown to be possible between the embryos of both the same and different ages during cleavage and blastulation. The relation between the frequency of parabiosis and the age of embryos and temperature was studied. An electric coupling is established between the cells of parabionts, similar by its value to that between the cells of each parabiont. The interrelations of cells of chimaeric embryos are considered as a model for studying the role of cell interactions during embryogenesis.