Showing papers by "University of Georgia published in 1990"

Sampling, handling and analyzing plant tissue samples.

Abstract: Plant analysis (sometimes referred to as leaf analysis) is the determination of the total elemental content of a specified plant part. The emphasis in this chapter will be on the determination of those elements required for plant growth. Interpretation is normally based on the use of a "critical value" or "sufficiency range" (Smith, 1962) comparison between the elemental concentration found and a known norm (Goodall & Gregory, 1947; Chapman, 1966; Reuter & Robinson, 1986; Adriano, 1986; Martin-Prevel et al., 1987). An alternative method of interpretation is Diagnosis and Recommendation Integrated System (ORIS), which interprets the ratios of elements (N/P, K/Ca, and K/Mg) as indicators of elemental status (Beaufils, 1973; Sumner, 1977, 1982). Most growers primarily use a plant analysis for diagnosing suspected elemental insufficiencies, while its most significant, yet little used application, is for evaluating the soil/plant elemental status. This is partially reflected in the relatively few plant tissue samples assayed for growers, about 500 000, in the USA each year (Jones, 1985). Tissue testing, an elemental assay of extracted cell sap by means of quick chemical tests in the field, seems to be gaining an interest at levels equal to that observed several decades ago. A plant analysis is carried out in a series of steps as shown in Fig. 15-1. The results obtained are no better than the care taken in collecting, handling, preparing, and analyzing the collected tissue. An error made in one of these steps can result in an erroneous interpretation leading to recommendations that may be either unnecessary, costly, or even damaging to the crop. Therefore, it is important for those employing either a plant analysis or tissue test to follow the proper sampling, preparation, and analysis procedures. This chapter deals with the procedures required to successfully conduct a plant analysis or tissue test.

Theories of Creativity

Abstract: This article surveys the range of contemporary theories of creativity. These are heuristically divided into ten categories: developmental, psychometric, economic, stage and componential process, cognitive, problem solving and expertise-based, problem finding, evolutionary, typological, and systems. These perspectives span a range of subtopics, levels of analysis, and emphases within the study of creativity. Beyond the general overview, prospects for the future role and development of theories of creativity are discussed, offering a critical but hopefully constructive appraisal of current theories and their promise for a continued deeper understanding of the nature of creativity.

Pulmonary edema and hydrothorax in swine produced by fumonisin B1, a toxic metabolite of Fusarium moniliforme.

Abstract: Pulmonary edema and hydrothorax were observed in mature swine that died approximately 5 days after consuming corn screenings. These postmortem observations were reproduced in younger swine (16-24 kg) that died within 1 week when fed the corn screenings under experimental conditions. Additionally, pulmonary edema and hydrothorax occurred in a pig (7.1 kg) that died after receiving 4 daily intravenous injections of fumonisin B1. A fungus was isolated from the corn screenings that is identical to Fusarium moniliforme MRC-826 in colony morphology and under microscopic examination.

Psychiatric and Physical Morbidity Effects of Caregiving

Abstract: Existing empirical literature on the prolonged or cumulative consequences of exposure to the stresses of caregiving is reviewed. Specific goals are to identify psychiatric and physical morbidity effects, report the magnitude of those effects, evaluate research and analytic methods used to assess morbidity, and make recommendations for future research. Overall, the literature indicates increases in self-report psychiatric symptomatology and increases in psychiatric illness among most caregivers when compared to population norms or appropriate control groups. However, there is little information on the population prevalence or incidence of clinically significant psychiatric conditions attributable to caregiving. Studies of physical health effects as assessed by self-report, health care utilization, and immune function are less conclusive but, nevertheless, suggest increased vulnerability to physical illness among caregivers. We conclude with a discussion of why morbidity effects are difficult to obtain in caregiver studies and with recommendations for future research.

Brain morphology in developmental dyslexia and attention deficit disorder/hyperactivity.

Abstract: • This study examined the specificity of deviations in patterns of normal brain asymmetry on the magnetic resonance imaging scans of 10 dyslexic, 10 attention deficit disorder/hyperactivity (ADD/H), and 10 normal age- and sex-matched control children. Reliabilities of region of interest measurements for left and right anterior and posterior width and area, length of the bilateral insular region, and length of the bilateral planum temporale were excellent. Both the dyslexic and ADD/H children had significantly smaller right anterior-width measurements than did normal subjects. The dyslexics also had a bilaterally smaller insular region and significantly smaller left planum temporale than did the normal subjects. Seventy percent of the normal and ADD/H children had the expected left greater than right pattern of plana asymmetry, while only 10% of the dyslexic children did. The very significant increase in the incidence of plana symmetry or reversed asymmetry seems unique to dyslexia and may be related to deviations in normal patterns of corticogenesis. Although significantly more dyslexic children were left-handed than were the normal and ADD/H children, no significant relationship emerged between left-handedness, incidence of allergies or familial autoimmune disease, and variability in indexes of brain morphologic findings.

A Mediational Model of the Impact of Marital Conflict on Adolescent Adjustment in Intact and Divorced Families: The Role of Disrupted Parenting.

Abstract: The present study was concerned with the development and testing of a structural equation model wherein the relation of interparental conflict to the adjustment problems of young adolescents is mediated through its impact on 3 aspects of parenting behavior: lax control, psychological control, and parental rejection/withdrawal. The model was tested separately on a sample of 46 young adolescents from intact families and a group of 51 adolescents from recently divorced families. The hypothesis that most of the relation between martial conflict and adolescent adjustment problems could be explained through perturbations in the parent-child relationship received considerable support; the only direct effect of conflict was on externalizing problems in the intact sample. The results also suggested that the mediational patterns were somewhat different for the 2 samples, and that the model accounts for a greater proportion of the variance in the adjustment problems of adolescents from intact homes than of those from recently divorced families.

Initial events in exercise-induced muscular injury.

Abstract: Immediately following unaccustomed exercise, particularly that with eccentric contractions, there is evidence of injury to skeletal muscle fibers: a) disruption of the normal myofilament structures in some sarcomeres, observable with both light and electron microscope and b) loss of intramuscular proteins (e.g., creatine kinase enzymes) into the plasma, indicating damage to sarcolemma. This pathology is probably responsible for the temporary reductions in muscle force and delayed-onset soreness that can occur following eccentric exercise. The mechanisms underlying this injury are not known, although loss of intracellular Ca2+ homeostasis could play a primary role. In other experimental muscle injury models, elevated [Ca2+]i appears to cause release of muscle enzymes through activation of phospholipase A2, which in turn could induce injury to sarcolemma through production of leukotrienes and prostaglandins, through free O2 radical formation (in the subsequent lipoxygenase and cyclooxygenase reactions), and/or through release of detergent lysophospholipids. On the other hand, the mechanism responsible for the rapid damage to myofibrils caused by increased [Ca2+]i is unknown. Regardless of the cause(s), the initial and early events in the injury process are autogenetic; i.e., they are indigenous to the muscle cells and occur before phagocytic cells enter the injury site.

A simple rheological method for the in vitro assessment of mucin-polymer bioadhesive bond strength.

Abstract: A simple viscometric method was used to quantify mucin-polymer bioadhesive bond strength. Viscosities of 15% (w/v) porcine gastric mucin dispersions in 0.1 N HC1 (pH 1) or 0.1 N acetate buffer (pH 5.5) were measured with a Brookfield viscometer in the absence (ηm) or presence (ηt) of selected neutral, anionic, and cationic polymers (0.1–2.5%, w/v). Viscosity components of bioadhesion (1%) were calculated from the equation, ηt = ηm + ηp + ηb, where ηp is the viscosity of corresponding pure polymer solution as measured by an Ostwald viscometer. The forces of bioadhesion (F) were calculated from the equation, F = ηbσ, where σ is the rate of shear/sec. ηb's and F's for polyelectrolytes, e.g., polyacrylic acid, cationic gelatin, and chitosan were always higher in acetate buffer than in HC1. Validity of the technique and the effect of ionic charge, polymer conformation, and rate of shear on ηb and F are discussed, as is a comparison of this method to other methods for evaluating bioadhesive materials.

Biological removal of dimethyl sulphide from sea water

Abstract: DIMETHYL sulphide (DMS) is an important sulphur-containing trace gas in the atmosphere. It is present in oceanic surface waters at concentrations sufficient to sustain a considerable net flux of DMS from the oceans to the atmosphere, estimated to comprise nearly half of the global biogenic input of sulphur to the atmosphere1. DMS emitted from the oceans may be a precursor of tropospheric aerosols and of cloud condensation nuclei in the remote marine atmosphere, thereby affecting the Earth's radiative balance and thus its climate2–4. Relatively little is known, however, about the biogeochemical and physical processes that control the concentration of DMS in sea water. Here we present data from incubation experiments, carried out at sea, which show that DMS is removed by microbial activity. In the eastern, tropical Pacific Ocean, DMS turnover is dominated by biological processes, with turnover times for biological DMS removal generally more than ten (3–430) times faster than turnover by ventilation to the atmosphere. Thus biological consumption of DMS seems to be a more important factor than atmospheric exchange in controlling DMS concentrations in the ocean, and hence its flux to the atmosphere. These results have significant implications for climate feedback models involving DMS emissions3, and highlight the importance of the microbial food web in oceanic DMS cycling.

Isolation, sequencing, and disruption of the yeast CKA2 gene: casein kinase II is essential for viability in Saccharomyces cerevisiae.

Abstract: Casein kinase II of Saccharomyces cerevisiae contains two distinct catalytic subunits, alpha and alpha', which are encoded by the CKA1 and CKA2 genes, respectively. Null mutations in the CKA1 gene do not confer a detectable phenotype (J. L.-P. Chen-Wu, R. Padmanabha, and C. V. C. Glover, Mol. Cell. Biol. 8:4981-4990, 1988), presumably because of the presence of the CKA2 gene. We report here the cloning, sequencing, and disruption of the CKA2 gene. The alpha' subunit encoded by the CKA2 gene is 60% identical to the CKA1-encoded alpha subunit and 55% identical to the Drosophila alpha subunit (A. Saxena, R. Padmanabha, and C. V. C. Glover, Mol. Cell. Biol. 7:3409-3417, 1987). Deletions of the CKA2 gene were constructed by gene replacement techniques. Haploid cells in which the CKA2 gene alone is disrupted show no detectable phenotype, but haploid cells carrying disruptions in both the CKA1 and CKA2 genes are inviable. Cells in which casein kinase II activity is depleted increase substantially in size prior to growth arrest, and a significant fraction of the arrested cells exhibit a pseudomycelial morphology. Disruption of the activity also results in flocculation. Yeast strains lacking both endogenous catalytic subunit genes can be rescued by expression of the alpha and beta subunits of Drosophila casein kinase II or by expression of the Drosophila alpha subunit alone, suggesting that casein kinase II function has been conserved through evolution.

Biotechnology in the pulp and paper industry

Abstract: Biotechnology implies the technical exploitation of biological processes. One of nature's most important biological processes is the degradation of wood and other lignocellulosic materials to carbon dioxide, water, and humic substances. Consequently, there should be possibilities to apply biotechnology to wood conversion. This article summarizes briefly the knowledge relating to the enzymic degradation of cellulose, hemicelluloses, and lignin. However, it is mainly focused upon biotechnological processes in commercial use or in various stages of development for the pulp and paper industry. Areas covered are ethanol and protein production, water purification, development of new bleaching techniques, microbial delignification (biopulping), and development of “biosensors” for analysis of pulp fiber surfaces.

A genetic discontinuity in a continuously distributed species: mitochondrial DNA in the American oyster, Crassostrea virginica.

Abstract: Restriction site variation in mitochondrial DNA (mtDNA) of the American oyster (Crassostrea virginica) was surveyed in continuously distributed populations sampled from the Gulf of St. Lawrence, Canada, to Brownsville, Texas. mtDNA clonal diversity was high, with 82 different haplotypes revealed among 212 oysters with 13 endonucleases. The mtDNA clones grouped into two distinct genetic arrays (estimated to differ by about 2.6% in nucleotide sequence) that characterized oysters collected north vs. south of a region on the Atlantic mid-coast of Florida. The population genetic "break" in mtDNA contrasts with previous reports of near uniformity of nuclear (allozyme) allele frequencies throughout the range of the species, but agrees closely with the magnitude and pattern of mtDNA differentiation reported in other estuarine species in the southeastern United States. This concordance of mtDNA phylogenetic pattern across independently evolving species provides strong evidence for vicariant biogeographic processes in initiating intraspecific population structure. The post-Miocene ecological history of the region suggests that reduced precipitation levels in an enlarged Floridian peninsula may have created discontinuities in suitable estuarine habitat for oysters during glacial periods, and that today such population separations are maintained by the combined influence of ecological gradients and oceanic currents on larval dispersal. The results are consistent with the hypothesis that historical vicariant events, in conjunction with contemporary environmental influences on gene flow, can result in genetic discontinuities in continuously distributed species with high dispersal capability.

Chloroplast DNA sequence from a Miocene Magnolia species

Abstract: DNA has been successfully extracted from several samples of preserved tissue, the oldest so far reported originating from a 13,000-year-old ground sloth1.But severe damage to the preserved DNA, primarily due to oxidation of the pyrimidines1, has prevented the acquisition of sequence data from ancient samples except in a few cases2–4. We report here the extraction of DNA from fossil leaf samples from the Miocene Clarkia deposit (17-20 My r old), the amplification of an 820-base pair (bp) DNA fragment from the chloroplast gene rbcL from a fossil of the genus Magnolia, and its subsequent sequencing. The sequence was verified by comparison with published and unpublished rbcL sequences. These results extend our ability to analyse ancient DNA and may open new avenues into problems in palaeobotany, biogeography, and in the calibration of mutation rates.

A Regulatory Gene as a Novel Visible Marker for Maize Transformation

Abstract: The temporal and spatial patterns of anthocyanin pigmentation in the maize plant are determined by the presence or absence of the R protein product, a presumed transcriptional activator. At least 50 unique patterns of pigmentation, conditioned by members of the R gene family, have been described. In this study, microprojectiles were used to introduce into maize cells a vector containing the transcription unit from one of these genes (Lc) fused to a constitutive promoter. This chimeric gene induces cell autonomous pigmentation in tissues that are not normally pigmented by the Lc gene. As a reporter for gene expression studies in maize, R is unique because it can be quantified in living tissue simply by counting the number of pigmented cells following bombardment. R may also be useful as a visible marker for selecting stably transformed cell lineages that can give rise to transgenic plants.

Ecological versus phylogenetic determinants of helminth parasite community richness

Abstract: We examine patterns of community richness among intestinal parasitic helminth communities in fishes, herptiles, birds and mammals with respect to the comparative number of component species in a host population. We show that terrestrial hosts have, on average, fewer component species than aquatic hosts. We also show that the mean number of component species in aquatic hosts increases from fishes through herptiles to birds before declining slightly in mammals. For terrestrial hosts, the mean number of component species increases from herptiles, through birds, reaching a maximum in mammals. We conclude that: (i) habitat of the host is more important in determining community richness than is host phylogeny; (ii) the phenomenon of ‘host capture’ may be largely responsible for increased species richness in some host groups; (iii) aquatic birds harbour the richest intestinal helminth communities; and (iv) as we interpret them, our data refute the time hypothesis, which would predict that fishes as the oldest lifestyle should have the richest helminth communities.

Bacterial production on humic and nonhumic components of dissolved organic carbon

Abstract: Dissolved humic substances make up - 50% or more of the dissolved organic carbon (DOC) in freshwater ecosystems, yet their trophodynamic roles remain unresolved. We separated DOC from two freshwater environments, a lake and a blackwater marsh, into two fractions, humic DOC and nonhumic DOC, using an XAD-8 resin to selectively adsorb the humic substances. Results of microcosm studies revealed that the humic fraction of DOC was used by natural bacterial assemblages from the lake and marsh as a C and energy source, as indicated both by increases in bacterial biovolume and rates of bacterial incorporation of [3H]thymidine. Humic substances supported fourfold less bacterial secondary production per unit of initial C, however, than did nonhumic substances from the same environment. Bacterial utilization of humic compounds accounted for a significant fraction of the total bacterial production on DOC, measured as increases in bacterial biovolume; humic substances supported an average of 22% of total growth on DOC from the lake and 53% of the total growth on DOC from the marsh. The relative bioavailability of both the humic and nonhumic fractions of DOC differed between the lake and blackwater marsh, with less bacterial production per unit of initial C occurring on marsh-derived dissolved compounds. In aquatic ecosystems, turnover of dissolved organic carbon (DOC) is almost exclusively the domain of bacteria as a result of their high numbers, large surface-to-volume ratios, and transport systems efficient at low substrate concentrations. Studies of bacterial utilization of DOC have indicated the existence of two distinct pools of dissolved compounds, one labile and one refractory, in most aquatic systems (Ogura 1975). Although the labile pool generally accounts for < 20% of the total DOC (Ogura 1975; Allen 1976), it turns over rapidly, on the order of hours to days, and is thought to support the bulk of DOC-based bacterial secondary production (Wright and Hobbie 1966; Allen 1976). The refractory pool is larger but turns over more slowly, on the order of weeks to months (Geller 1986) and therefore may be relatively unimportant as a substrate for bacterial growth. Neither of these two fractions of the DOC pool has been well characterized with respect to

Survival and Growth of Listeria monocytogenes on Lettuce as Influenced by Shredding, Chlorine Treatment, Modified Atmosphere Packaging and Temperature

Abstract: The effects of shredding, chlorine treatment and modified atmosphere packaging on survival and growth of Listeria monocytogenes, mesophilic aerobes, psychrotrophs and yeasts and molds on lettuce stored at 5°C and 10°C were determined. With the exception of shredded lettuce which had not been chlorine treated, no significant changes in populations of L. monocytogenes were detected during the first 8 days of incubation at 5°C; significant increases occurred between 8 and 15 days. Significant increases occurred within 3 days when lettuce was stored at 10°C; after 10 days, populations reached 108-109 CFU/g. Chlorine treatment, modified atmosphere (3% O2, 97% N2) and shredding did not influence growth of L. monocytogenes. It was concluded that L. monocytogenes is capable of growing on lettuce subjected to commonly used packaging and distribution procedures used in the food industry.