Showing papers by "University of Georgia published in 1989"

Common amino acid sequence domains among the LEA proteins of higher plants.

Abstract: LEA proteins are late embryogenesis abundant in the seeds of many higher plants and are probably universal in occurrence in plant seeds. LEA mRNAs and proteins can be induced to appear at other stages in the plant's life by desiccation stress and/or treatment with the plant hormone abscisic acid (ABA). A role in protecting plant structures during water loss is likely for these proteins, with ABA functioning in the stress transduction process. Presented here are conserved tracts of amino acid sequence among LEA proteins from several species that may represent domains functionally important in desiccation protection. Curiously, an 11 amino acid sequence motif is found tandemly repeated in a group of LEA proteins of vastly different sizes. Analysis of this motif suggests that it exists as an amphiphilic α helix which may serve as the basis for higher order structure.

New method for generating deletions and gene replacements in Escherichia coli.

Abstract: We describe a method for generating gene replacements and deletions in Escherichia coli. The technique is simple and rapid and can be applied to most genes, even those that are essential. What makes this method unique and particularly effective is the use of a temperature-sensitive pSC101 replicon to facilitate the gene replacement. The method proceeds by homologous recombination between a gene on the chromosome and homologous sequences carried on a plasmid temperature sensitive for DNA replication. Thus, after transformation of the plasmid into an appropriate host, it is possible to select for integration of the plasmid into the chromosome at 44 degrees C. Subsequent growth of these cointegrates at 30 degrees C leads to a second recombination event, resulting in their resolution. Depending on where the second recombination event takes place, the chromosome will either have undergone a gene replacement or retain the original copy of the gene. The procedure can also be used to effect the transfer of an allele from a plasmid to the chromosome or to rescue a chromosomal allele onto a plasmid. Since the resolved plasmid can be maintained by selection, this technique can be used to generate deletions of essential genes.

Threat-sensitive predator avoidance in damselfish-trumpetfish interactions

Abstract: Predatory threat can vary during a predator-prey interaction as an attack escalates or among predators at different times A Threat-sensitivity hypothesis is presented which predicts that prey individuals will trade-off predator avoidance against other activities by altering their avoidance responses in a manner that reflects the magnitude of the predatory threat This hypothesis was tested in the field by presenting prey (threespot damselfish, Stegastes planifrons) with models of foraging predators (Atlantic trumpetfish, Aulostomus maculatus) During a presentation, damselfish displayed progressively stronger avoidance as predator models were brought nearer; response waned rapidly once predator models passed overhead Larger predator models and those oriented in a strike pose evoked stronger avoidance reactions than smaller and non-attacking models, intermediate responses were evoked by size and orientation combinations that were intermediate in threat, and habituation was more common to weakly-threatening presentations Smaller damselfish showed stronger avoidance of models than did larger damselfish Nonavoidance activities, such as feeding and territorial defense, were curtailed during presentations or were more common during weakly threatening presentations Approaches to the models, equated with mobbing, were more common among large damselfish, again reflecting degrees of vulnerability among different size prey individuals These initial results indicate that damselfish threatened by predators respond in a graded manner that reflects the degree of threat posed by the predator, in accordance with the Threat-sensitivity hypothesis

Lc, a member of the maize R gene family responsible for tissue-specific anthocyanin production, encodes a protein similar to transcriptional activators and contains the myc-homology region.

Abstract: Previous studies have suggested that the R locus of maize is responsible for determining the temporal and spatial pattern of anthocyanin pigmentation in the plant. In this report we demonstrate that three members of the R gene family, P, S, and Lc, encode homologous transcripts 2.5 kilobases in length. The structure of one R gene, Lc, was determined by sequencing cDNA and genomic clones. The putative Lc protein, deduced from the cDNA sequence, is composed of 610 amino acids and has homology to the helix-loop-helix DNA-binding/dimerization motif found in the L-myc gene product and other regulatory proteins. It also contains a large acidic domain that may be involved in transcriptional activation. Consistent with its proposed role as a transcriptional activator is our finding that a functional R gene is required for the accumulation of transcripts of at least two genes in the anthocyanin biosynthetic pathway. We discuss the possibility that the diverse patterns of anthocyanin pigmentation conditioned by different R genes reflect differences in the R gene promoters rather than their gene products.

Acclimation of Photosynthesis to Elevated CO2 in Five C3 Species

Abstract: The effect of long-term (weeks to months) CO(2) enhancement on (a) the gas-exchange characteristics, (b) the content and activation state of ribulose-1,5-bisphosphate carboxylase (rubisco), and (c) leaf nitrogen, chlorophyll, and dry weight per area were studied in five C(3) species (Chenopodium album, Phaseolus vulgaris, Solanum tuberosum, Solanum melongena, and Brassica oleracea) grown at CO(2) partial pressures of 300 or 900 to 1000 microbars. Long-term exposure to elevated CO(2) affected the CO(2) response of photosynthesis in one of three ways: (a) the initial slope of the CO(2) response was unaffected, but the photosynthetic rate at high CO(2) increased (S. tuberosum); (b) the initial slope decreased but the CO(2)-saturated rate of photosynthesis was little affected (C. album, P. vulgaris); (c) both the initial slope and the CO(2)-saturated rate of photosynthesis decreased (B. oleracea, S. melongena). In all five species, growth at high CO(2) increased the extent to which photosynthesis was stimulated following a decrease in the partial pressure of O(2) or an increase in measurement CO(2) above 600 microbars. This stimulation indicates that a limitation on photosynthesis by the capacity to regenerate orthophosphate was reduced or absent after acclimation to high CO(2). Leaf nitrogen per area either increased (S. tuberosum, S. melongena) or was little changed by CO(2) enhancement. The content of rubisco was lower in only two of the five species, yet its activation state was 19% to 48% lower in all five species following long-term exposure to high CO(2). These results indicate that during growth in CO(2)-enriched air, leaf rubisco content remains in excess of that required to support the observed photosynthetic rates.

Seasonal patterns of bacterivory by flagellates, ciliates, rotifers, and cladocerans in a freshwater planktonic community

Abstract: Bacterivory in eutrophic Lake Oglethorpe, Georgia, was determined by direct observation of tracer particle uptake by all members of the planktonic community. Heterotrophic flagellates dominated grazing at all times, accounting for 49-8 1% of grazing on an areal basis and up to 98% of grazing at some depths. Pigmented (mixotrophic) flagellates were major grazers during winter and spring blooms, when they contributed up to 45% of community grazing on an areal basis and 79% at depths of maximum abundance. In late spring to early summer, rotifers and ciliates were responsible for as much as 25 and 30% of bacterivory at some depths, but averaged 3 and 11% over the year, respectively. Grazing impact of cladoceran crustaceans was generally < 1% of the total. Bacterivory by copepods was not detected. Total bacterial mortality due to grazing ranged from 11 to 162% of bacterial cell production estimated from the incorporation of [3H]thymidine. Use of 0.57-pm microspheres as tracers gave similar estimates ofingestion to fluorescently labeled bacteria in this system. The use of 4% ice-cold glutaraldehyde mixed 1 : 1 with the water sample was found to be equally effective to an acrolein-tannic acid mixture for reducing egestion of particles by protists. We therefore consider our findings to be representative of bacterivory by the planktonic community in this eutrophic system.

Gene trees and organismal histories: a phylogenetic approach to population biology.

Abstract: A "gene tree" is the phylogeny of alleles or haplotypes for any specified stretch of DNA. Gene trees are components of population trees or species trees; their analysis entails a shift in perspective from many of the familiar models and concepts of population genetics, which typically deal with frequencies of phylogenetically unordered alleles. Molecular surveys of haplotype diversity in mitochondrial DNA (mtDNA) have provided the first extensive empirical data suitable for estimation of gene trees on a microevolutionary (intraspecific) scale. The relationship between phylogeny and geographic distribution constitutes the phylogeographic pattern for any species. Observed phylogeographic trees can be interpreted in terms of historical demography by comparison to predictions derived from models of gene lineage sorting, such as inbreeding theory and branching-process theory. Results of such analyses for more than 20 vertebrate species strongly suggest that the demographies of populations have been remarkably dynamic and unsettled over space and recent evolutionary time. This conclusion is consistent with ecological observations documenting dramatic population-size fluctuations and range shifts in many contemporary species. By adding an historical perspective to population biology, the gene-lineage approach can help forge links between the disciplines of phylogenetic systematics (and macroevolutionary study) and population genetics (microevolution). Preliminary extensions of the "gene tree" methodology to haplotypes of nuclear genes (such as Adh in Drosophila melanogaster) demonstrate that the phylogenetic perspective can also help to illuminate molecular-genetic processes (such as recombination or gene conversion), as well as contribute to knowledge of the origin, age, and molecular basis of particular adaptations.

Photochemical source of biological substrates in sea water: implications for carbon cycling

Abstract: DISSOLVED organic carbon (DOC) in sea water represents one of the largest reservoirs of carbon on the earth1. The main fraction of this DOC is generally believed to be composed of old2, biologi-cally refractory material3 such as humic substances, for which the removal mechanisms remain largely unknown. One potentially important removal process in the ocean that has not been investi-gated is the photochemical breakdown of this DOC in the photic zone to form biologically labile organic products. Here we show that biological uptake of pyruvate is highly correlated to its rate of photochemical production in sea water (r = 0.964), and that the photochemical precursor(s) of pyruvate is from the fraction of DOC having a nominal molecular weight of 500. This is the first evidence that photochemical breakdown of high-molecular-weight marine DOC, which is presumably biologically refractory, results in the production of a compound that is used by plankton as a substrate. Our results have important implications for the oceanic carbon cycle, particularly with respect to planktonic-food-web dynamics and the global carbon budget.

Accuracy of the AVHRR vegetation index as a predictor of biomass, primary productivity and net CO2 flux

Abstract: The Normalized Difference Vegetation Index (NDVI) or ‘greenness index’, based on the Advanced Very High Resolution Radiometer (AVHRR) aboard the NOAA-7 satellite, has been widely interpreted as a measure of regional to global vegetation patterns. This study provides the first rigorous, quantitative evaluation of global relationships between the NDVI and geographically representative vegetation data-bases, including field metabolic measurements and carbon-balance results from global simulation models. Geographic reliability of the NDVI is judged by comparing NDVI values for different surface types with a general global trend and by statistical analysis of relationships to biomass amounts, net and gross primary productivity, and actual evapotranspiration. NDVI data appear to be relatively reliable predictors of primary productivity except in areas of complex terrain, for seasonal values at high latitudes, and in extreme deserts. The strength of the NDVI-productivity relationship seems comparable to that of earlier climate-based productivity models. Little consistent relationship was found, across different vegetation types, between NDVI and biomass amounts or net biospheric CO2 flux.

Effect of the Tall Fescue Endophyte on Plant Response to Environmental Stress

Abstract: The objective of this study was to evaluate endophyte-free (EF) and endophyte-infected (EI) tall fescue plants from one clone for morphological and physiological responses to flooding, N rates (11, 73, and 220 mg N pot −1 ), and −0.03, −0.05 and −0.50 MPa drought stress in the greenhouse. Plants were grown in a synthetic mixture of the following by volume: Cecil sandy clay loam (clayey, kaolinitic, thermic Typic Hapludult) (33%), sand (16%), peat moss (17%), perlite (17%), and vermiculite (17%). There are positive benefits derived from association of an endophyte with tall fescue resulting in growth stimulation, improved survival, and drought tolerance to the host plant that could be important in plant competition

A baculovirus blocks insect molting by producing ecdysteroid UDP-glucosyl transferase

Abstract: The predicted amino acid sequence of a newly identified gene of the insect baculovirus Autographa californica nuclear polyhedrosis virus was similar to several uridine 5'-diphosphate (UDP)-glucuronosyl transferases and at least one UDP-glucosyl transferase. Genetic and biochemical studies confirmed that this gene encodes an ecdysteroid UDP-glucosyl transferase (egt). This enzyme catalyzes the transfer of glucose from UDP-glucose to ecdysteroids, which are insect molting hormones. Expression of the egt gene allowed the virus to interfere with normal insect development so that molting was blocked in infected larvae of fall armyworm (Spodoptera frugiperda).

Stock Trading Before the Announcement of Tender Offers: Insider Trading or Market Anticipation?

Abstract: Recent insider trading actions by the government against Dennis Levine, Ivan Boesky, Martin Siegel, and others have influenced the public's perception of mergers and acquisitions activity.' These well-publicized cases generally involve illegal insider trading based on nonpublic information about impending bids for takeover targets.2 Many regulators have interpreted public concern about illegal insider trading as political support for legislative proposals to restrict takeovers. These regulators argue that increased trading in stocks of tender offer targets before bid announcements indicates the pervasive nature of insider trading. Congressman Edward Markey (DMass.), chairman of the House Telecommunications and Finance Subcommittee, provides an example of how policymakers connect hostile takeovers

Isozymes and the Analysis of Genetic Structure in Plant Populations

Abstract: Ecologists and plant evolutionary biologists have long recognized that plants are not distributed at random within communities but, rather, are clustered in distinct patches. Environmental heterogeneity is usually cited as playing a critical role but colonization patterns and stochastic events affecting establishment and mortality are also important. More recently plant evolutionary biologists have demonstrated that genetic variation in plant populations is also distributed nonrandomly (Antonovics, 1971; Allard et al. 1972; Hamrick and Allard, 1972; Turkington and Harper, 1979). Rather, like the plants themselves, genes and genotypes tend to be clumped, with marked genetic differences occurring over short distances. This nonrandom distribution of genetic variation is often referred to as the genetic structure of a population (Loveless and Hamrick, 1984).

A role for molecular genetics in the recognition and conservation of endangered species.

Abstract: Taxonomies based on morphological traits alone sometimes provide inadequate or misleading guides to phylogenetic distinctions at the subspecies and species levels. Yet taxonomic assignments inevitably shape perceptions of biotic diversity, including recognition of endangered species. Case histories are discussed in which the data of molecular genetics revealed prior systematic errors of the two possible kinds: taxonomic recognition of groups showing little evolutionary differentiation, and lack of taxonomic recognition of phylogenetically distinct forms. In such cases, conservation efforts for 'endangered species' can be misdirected with respect to the goal of protecting biological diversity.

Resource partitioning by reef corals as determined from stable isotope composition

Abstract: The pattern of resource partitioning vs depth by corals collected in February 1983 from Jamaica and the Red Sea was determined from their stable carbon isotope composition. Observations were made on isolated zooxanthellae and corresponding algae-free animal tissue from eight species at four depths over a 50 m bathymetric range. Zooxanthellae δ13C was high in shallow water and became lower as depth increased. This trend correlated significantly with the anual integrated photosynthetic rate. The trend is interpreted according to a “depletion-diffusion” hypothesis; in shallow water, at high rates of photosynthesis, metabolic CO2 is nearly depleted and the supply of CO2 from seawater bicarbonate is limited by diffusion. Since most of the available CO2 is fixed, isotope fractionation is minimal. In deeper water, at lower rates of photosynthesis, metabolic CO2 is ample, and isotope fractionation is greater. Animal tissue δ13C was slightly lower than corresponding zooxanthellae values in shallow water. As depth increased the difference between zooxanthellae and animal tissue δ13C increased and the latter approached the δ13C of oceanic particulate organic carbon. These data suggest that carbon is translocated at all depths and that deep-water corals draw significantly on allocthonous sources of carbon.

Geographical perspectives of space, time, and scale

Abstract: This article reviews space and time scales from a geographer's point of view. Because spatial phenomena come in incredibly different size classes, geographers have conducted analyses across many orders of spatial magnitude. Geographers seem adept at moving from one scale to another, but they are not prone to explicitly state these scales a priori. Moreover, in spite of many appeals for multiscaler research (e.g., Abler 1987; Miller 1970; Stone 1968; Kirkby 1985), this is seldom done, although higher-level information is often used to predict lower levels. Good multiscale work apparently meets data-handling thresholds rather quickly. Most geographic research is now conducted with a relativistic view of space rather than a view of space as a ‘container.’ Spatial scales for relative space are more difficult to define, however, than those for the absolute space of cartography and remote sensing. The relevant, important, and useful variables from a modeling standpoint change with spatial scale. By reviewing the literature on a topic in a systematic way, as was done here for physical climatology and orographie precipitation, this scale change in variables can be seen. We do not as yet have models of the changes in models caused by changes in scale. Spatial data violate nearly every requirement for parametric statistical analysis (Meentemeyer and Box 1987), which is partially responsible for fallacies and erroneous inference. Many of these problems are scale dependent. Based on the work of Harvey (1969), we see that there are three primary methodological problems in spatial analyses. There are first of all the differences in inference and relevant variables caused by different scales or hierarchical levels. This has been called the ‘scale problem’ in geographic literature. Secondly, the description and modeling of spatial patterns, as noted above, may defy easy solutions, and finally the relationships between spatial patterns and process remain a challenge. The geographic literature contains many examples of extrapolations to lower levels from higher levels. Often the higher levels have been more widely sampled geographically (e.g., weather and climate, topography) and may be data rich. Models which predict spatial patterns and process often use the data-rich higher levels as driving variables for lower levels. Young (1978) argues that central place theory in geography should be a component of hierarchy theory. Indeed it can be argued here that space is inherently hierarchical and needs to be more fully incorporated into hierarchy theory. As the various disciplines under the umbrella of the environmental sciences more fully incorporate the spatial dimension into their research agendas, problems associated with spatial scale will be encountered. Many of these problems have in varying degrees been recognized if not solved. Nevertheless it is worth noting Clark's (1985) warning, ‘No simple rules can automatically select the “proper” scale for attention.’ Good geographic models require good geographic coverage, but this may mean that lower-level details are simply not needed. As mentioned earlier, the question of whether one is working at a ‘fundamental’ level is never discussed in geography. The Long-Term Ecological Reserve (LTER) sites are a step in the right direction, but a geographer would prefer much more intensive spatial sampling, even if that means a sacrifice in accuracy or detail. Otherwise a spatial analysis may not be possible. It remains to be seen to what degree the reductionist sciences can contribute to IGBP. More work with explicitly stated scales is needed, as well as across-scales research. Scale has been treated philosophically in this essay. But I am reminded of Couclelis's caution, ‘Philosophizing in an empirical discipline is a sure sign of trouble’ (cited in Abler 1987).

Optimal informants on childhood disruptive behaviors

Abstract: The question of which informant on childhood behavior disorders is the most useful an'd valid for which disorders influences diagnostic accuracy and research findings. The present study focuses on 177 boys, most of whom had been referred to outpatient services because they were displaying disruptive behavior. The boys, their mothers, and their teachers responded to a psychiatric interview concerning the boys' behavior. Analyses of conditional agreements between informants show that children, as compared with mothers and teachers, were less adequate informants on their own hyperactivity and inattentiveness. The same applied to children's reports of their own oppositional behavior. In contrast, children's reports of their conduct problems tended to complement the reports by adults. Although informants agreed significantly on the presence of many disruptive child behaviors, there were several on which they did not agree, particularly in the realm of hyperactivity/inattentiveness. There were few age differences between older and younger boys in this sample of 7- to 12-year-olds. The implications of the findings for research and clinical practice are discussed.

Influence of wetland hydroperiod on diversity and abundance of metamorphosing juvenile amphibians

Abstract: Numbers of successfully metamorphosing juvenile amphibians were tabulated at three wetlands in South Carolina, U.S.A. using terrestrial drift fences with pitfall traps. A relatively undisturbed Carolina bay was studied for eight years, a partially drained Carolina bay for four years, and a man-made borrow pit for three years. Annual production of juveniles at the undisturbed Carolina bay ranged from zero to 75,644 individuals of 15 species. Fewer individuals of fewer species typically metamorphosed at the borrow pit than at the undisturbed bay, with the least numbers at the partially drained Carolina bay. Both total number and species diversity of metamorphosing juveniles at each site each year showed a strong positive correlation with hydroperiod, i.e., the number of days a site contained standing water that year. Data for one common anuran species and the most common salamander species were analyzed separately by multiple regression, in addition to the community analyses. For the mole salamander, Ambystoma talpoideum, hydroperiod was a significant predictor of the number of metamorphosing juveniles, but the number of breeding females was not. For the ornate chorus frog, Pseudacris ornata, the number of breeding females was a significant predictor of the number of metamorphosing juveniles, but hydroperiod was not. Variation in the dates of wetland filling and drying interacts with other factors to determine amphibian community structure and diversity. Either increasing or decreasing the number of days a wetland holds water could increase or decrease the number and species diversity of amphibians in and around a wetland.

Theoretical investigations of molecules composed only of fluorine, oxygen and nitrogen: determination of the equilibrium structures of FOOF, (NO)2 and FNNF and the transition state structure for FNNF cis-trans isomerization

Abstract: The deficiencies of common ab initio methods for the reliable prediction of the equilibrium structures of compounds composed of only the fluorine, oxygen and nitrogen atoms are investigated. Specifically, the importance of using large one-particle basis sets with multiple sets of polarization functions has been studied. Additionally, the need for a set of f basis functions was investigated. Several different single reference electron correlation methods have been tested in order to determine whether it is possible for a single reference based method to be routinely used on such chemical systems. These electron correlation methods include second order Moller-Plesset perturbation theory (MP2), singles and doubles configuration interaction (CISD), the coupled pair functional (CPF) approach and singles and doubles coupled cluster (CCSD) theory. The molecular systems studied include difluoroperoxide (FOOF), the cis form of the NO dimer, cis and trans difluorodiazene (FNNF) and the transition state to interconversion of the cis and trans isomers of FNNF. To the best of our knowledge, this is the first time that the cis-trans isomerization transition state has been reported. At the highest level of theory employed, the equilibrium structures of cis and trans FNNF agree very well with the experimental structures. However, the barrier to interconversion is predicted to be 65 kcal/mole, which is substantially higher than the experimental activation energy of 32 kcal/mole. Potential sources of error are discussed. A new diagnostic method for determining a priori the reliability of single reference based electron correlation methods is suggested and discussed.

Host-Pathogen Interactions: XXXIII. A Plant Protein Converts a Fungal Pathogenesis Factor into an Elicitor of Plant Defense Responses

Abstract: This paper describes the effect of a plant-derived polygalacturonase-inhibiting protein (PGIP) on the activity of endopolygalacturonases isolated from fungi. PGIP9s effect on endopolygalacturonases is to enhance the production of oligogalacturonides that are active as elicitors of phytoalexin (antibiotic) accumulation and other defense reactions in plants. Only oligogalacturonides with a degree of polymerization higher than nine are able to elicit phytoalexin synthesis in soybean cotyledons. In the absence of PGIP, a 1-minute exposure of polygalacturonic acid to endopolygalacturonase resulted in the production of elicitor-active oligogalacturonides. However, the enzyme depolymerized essentially all of the polygalacturonic acid substrate to elicitor-inactive oligogalacturonides within 15 minutes. When the digestion of polygalacturonic acid was carried out with the same amount of enzyme but in the presence of excess PGIP, the rate of production of elicitor-active oligogalacturonides was dramatically altered. The amount of elicitor-active oligogalacturonide steadily increased for 24 hours. It was only after about 48 hours that the enzyme converted the polygalacturonic acid into short, elicitor-inactive oligomers. PGIP is a specific, reversible, saturable, high-affinity receptor for endopolygalacturonase. Formation of the PGIP-endopolygalacturonase complex results in increased concentrations of oligogalacturonides that activate plant defense responses. The interaction of the plant-derived PGIP with fungal endopolygalacturonases may be a mechanism by which plants convert endopolygalacturonase, a factor important for the virulence of pathogens, into a factor that elicits plant defense mechanisms.

Molecular Genetic Relationships of the Extinct Dusky Seaside Sparrow

Abstract: Mitochondrial DNA from the extinct dusky seaside sparrow (Ammodramus maritimus nigrescens) was compared in terms of nucleotide sequence divergence to mitochondrial DNAs from extant populations of seaside sparrows. Analyses of restriction sites revealed a close phylogenetic affinity of A. m. nigrescens to other sparrow populations along the Atlantic coast of the United States but considerable genetic distance from Gulf coast birds. Concerns and applied management strategies for the seaside sparrow have been based on a morphological taxonomy that does not adequately reflect evolutionary relationships within the complex.

Influence of serum and hormones on bovine oocyte maturation and fertilization in vitro.

Abstract: Three approaches were investigated for improvement of in vitro maturation (IVM), in vitro fertilization (IVF), and early embryonic development in cattle. These were: 1) Selection of oocytes, 2) medium supplementation with fetal calf serum (FCS) and cow sera (DO, Dl, D10, and D20 to correspond with estrus, metestrus, diestrus, and proestrus, respectively), and 3) addition of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol-17β (E2)during maturation. Greater proportions (percentage) of oocytes initially selected for their compact cumulus cells completed IVM and IVF when compared to unselected oocytes (P < .05). Proportions (percentage) of selected oocytes that matured and cleaved after in vitro insemination according to serum type used for IVM were: FCS: 110/175 (62.9%) and 37/110 (33.6%) and DO: 130/145 (89.7%) and 52/130 (40.0%); D1 127/130 (97.7%) and 41/127 (32.3%); D10 95/98 (96.9%) and 35/95 (36.8%); D20:113/116 (97.4%) and 49/113 (43.4%). A higher proportion (P < .05) of embryos resulting from the D20 group reached four- and eight-cell stages. In FCS-supplemented maturation media with no hormones added during maturation (control), results of IVM and IVF were 157/265 (59.2%) and 39/157 (24.8%), respectively. With E2 (1 μg/ml) and FSH (5 μg/ml), comparable results were 189/215 (87.9%) and 71/189 (37.6%); with E2 (1 μg/ml) plus LH (10 μml), 280/327 (85.6%) and 111/280 (39.6%). Added hormones improved IVM results (P < .05) and, when FSH or LH was added with E2, in vitro development to four- and eight-cell stages was markedly enhanced (P < .05). Selection of oocytes, D20 serum, and added E2 and FSH or LH for IVM improved in vitro development of bovine embryos after IVF.

Bleaching in reef corals: Physiological and stable isotopic responses

Abstract: During the late summer to fall of 1987, Caribbean reef corals experienced an intense and widespread discoloration event described as bleaching. Contrary to initial predictions, most bleached corals did not die. However, energy input from zooxanthellae decreased, as estimated from: (i) δ13C values, a measure of the discrimination against 13C in 12C/13C assimilation, of skeletal aragonite; (ii) in situ photosynthesis-irradiance measurements; (iii) and tissue biomass parameters of Montastraea annularis and Agaricia lamarcki. The δ18O signal, a measure of the discrimination against 18O in 16O/18O assimilation, from M. annularis skeletons demonstrated that this event coincided with abnormally elevated water temperatures.

Identification of Actively Filling Sucrose Sinks

Abstract: Certain actively filling plant sucrose sinks such as a seed, a tuber, or a root can be identified by measuring the uridine diphosphate and pyrophosphate-dependent metabolism of sucrose. Sucrolysis in both active and quiescent sucrose sinks was tested and sucrose synthase was found to be the predominant sucrose breakdown activity. Sucrolysis via invertases was low and secondary in both types of sinks. Sucrose synthase activity dropped markedly, greater than fivefold, in quiescent sinks. The tests are consistent with the hypothesis that the sucrose filling activity, i.e. the sink strength, of these plant sinks can be measured by testing the uridine diphosphate and pyrophosphate-dependent breakdown of sucrose. Measuring the initial reactions of sucrolysis shows much promise for use in agriculture crop and tree improvement research as a biochemical test for sink strength.