Showing papers by "University of Georgia published in 1991"

Case Study Research in Education : A Qualitative Approach

Abstract: Part 1 Foundations of qualitative case study research: the case study approach to research problems types and uses of case study research in education defining a research problem and selecting a case handling theory and literature reviews in case study research. Part 2 mastering qualitative data collection methods: conducting effective interviews being a careful observer mining data from documents. Part 3 Analyzing and reporting case study data: the components of data analysis using special techniques and computers to analyze qualitative data dealing with validity, reliability, and ethics in case study research writing the case study report.

Prevention of Apoptosis by a Baculovirus Gene During Infection of Insect Cells

Abstract: Programmed cell death is an active process of self destruction that is important in both the development and maintenance of multicellular animals. The molecular mechanisms controlling activation or suppression of programmed cell death are largely unknown. Apoptosis, a morphologically and biochemically defined type of programmed cell death commonly seen in vertebrates, was found to be initiated during baculovirus replication in insect cells. A specific viral gene product, p35, was identified as being responsible for blocking the apoptotic response. Identification of the function of this gene will allow further definition of the molecular pathways involved in the regulation of programmed cell death and may identify the role of apoptosis in invertebrate viral defense systems.

Measuring the Demand for Environmental Quality

Abstract: Part I: Theory and Methods. Introduction (J.B. Braden, C.D. Kolstad and D. Miltz). Environmental Demand Theory (C.D. Kolstad and J.B. Braden). Household Production Functions and Environmental Benefit Estimation (V.K. Smith). Hedonic Methods (R.B. Palmquist). Constructed Markets (R.T. Carson). Part II: Methods for Valuing Classes of Environmental Effects. Environmental Health Effects (M.L. Cropper and A.M. Freeman III). Aesthetics (P.E. Graves). Recreation (N.E. Bockstael, K.E. McConnell and I. Strand). Materials Damages (R.M. Adams and T.D. Crocker). Total and Nonuse Values (A. Randall). Summary and Conclusions (J.B. Braden and C.D. Kolstad). Bibliography. Author Index. Subject Index.

Critical behavior of the three-dimensional Ising model: A high-resolution Monte Carlo study.

Abstract: Using recently developed histogram techniques and an ultrafast multispin coding simulation algorithm, we have investigated the critical behavior of the d=3 simple-cubic Ising model We have studied lattice sizes ranging from L=8 to 96 using between 3\ifmmode\times\else\texttimes\fi{}${10}^{6}$ and 12\ifmmode\times\else\texttimes\fi{}${10}^{6}$ Monte Carlo steps (complete lattice updates) By accurately measuring the finite-size behavior of several different thermodynamic quantities, we are able to determine the critical properties with a precision comparable to that obtained with Monte Carlo renormalization-group and sophisticated series-expansion techniques The best estimate of the inverse critical temperature from our analysis is ${\mathit{K}}_{\mathit{c}}$=0221 659 5\ifmmode\pm\else\textpm\fi{}0000 002 6 The advantages of the histogram technique are discussed, as are the potential problems that can arise at this level of resolution

Mechanisms of exercise-induced muscle fibre injury

Abstract: Exercise for which a skeletal muscle is not adequately conditioned results in focal sites of injury distributed within and among the fibres. Exercise with eccentric contractions is particularly damaging. The injury process can be hypothesised to occur in several stages. First, an initial phase serves to inaugurate the sequence. Hypotheses for the initial event can be categorised as either physical or metabolic in nature. We argue that the initial event is physical, that stresses imposed on sarcolemma by sarcomere length inhomogeneities occurring during eccentric contractions cause disruption of the normal permeability barrier provided by the cell membrane and basal lamina. This structural disturbance allows Ca++ to enter the fibre down its electrochemical gradient, precipitating the Ca++ overload phase. If the breaks in the sarcolemma are relatively minor, the entering Ca++ may be adequately handled by ATPase pumps that sequester and extrude Ca++ from the cytoplasm ('reversible' injury). However, if the Ca++ influx overwhelms the Ca++ pumps and free cytosolic Ca++ concentration rises, the injury becomes 'irreversible'. Elevations in intracellular Ca++ levels activate a number of Ca(++)-dependent proteolytic and phospholipolytic pathways that are indigenous to the muscle fibres, which respectively degrade structural and contractile proteins and membrane phospholipids; for instance, it has been demonstrated that elevation of intracellular Ca++ levels with Ca++ ionophores results in loss of creatine kinase activity from the fibres through activation of phospholipase A2 and subsequent production of leukotrienes. This autogenetic phase occurs prior to arrival of phagocytic cells, and continues during the inflammatory period when macrophages and other phagocytic cells are active at the damage site. The phagocytic phase is in evidence by 2 to 6 hours after the injury, and proceeds for several days. The regenerative phase then restores the muscle fibre to its normal condition. Repair of the muscle fibres appears to be complete; the fibres adapt during this process so that future bouts of exercise of similar type, intensity, and duration cause less injury to the muscle.

Baculovirus expression vectors

Abstract: A method and composition for improving the level of expression of a gene or collection of genes by providing a novel baculovirus promoter to which a heterologous gene is attached. The novel promoter may contain a modification of a natural viral promoter or may be totally synthetic. The novel baculovirus promoter may also comprise a combination promoter such as a promoter with a double start site or a combination of two different promoters. Foreign gene placement in a novel location or genomic orientation is also included.

Climate change and the evolution of C4 photosynthesis

Abstract: Plants assimilate carbon by one of three photosynthetic pathways, commonly called the C 3 , C 4 , and CAM pathways The C 4 photosynthetic pathway, found only among the angiosperms, represents a modification of C 3 metabolism that is most effective at low concentrations of CO 2 Today, C 4 plants are most common in hot, open ecosystems, and it is commonly felt that they evolved under these conditions However, high light and high temperature, by themselves, are not sufficient to favor the evolution of C 4 photosynthesis at atmospheric CO 2 levels significantly above the current ambient values A review of evidence suggests that C 4 plants evolved in response to a reduction in atmospheric CO 2 levels that began during the Cretaceous and continued until the Miocene

Isolation and expression of a cDNA encoding Renilla reniformis luciferase.

Abstract: Renilla reniformis is an anthozoan coelenterate capable of exhibiting bioluminescence. Bioluminescence in Renilla results from the oxidation of coelenterate luciferin (coelenterazine) by luciferase [Renilla-luciferin:oxygen 2-oxidoreductase (decarboxylating), EC 1.13.12.5]. In vivo, the excited state luciferin-luciferase complex undergoes the process of nonradiative energy transfer to an accessory protein, green fluorescent protein, which results in green bioluminescence. In vitro, Renilla luciferase emits blue light in the absence of any green fluorescent protein. A Renilla cDNA library has been constructed in lambda gt11 and screened by plaque hybridization with two oligonucleotide probes. We report here the isolation and characterization of a luciferase cDNA and its gene product. The recombinant luciferase expressed in Escherichia coli is identical to native luciferase as determined by SDS/PAGE, immunoblot analysis, and bioluminescence emission characteristics.

Corpus Callosum Morphology in Attention Deficit-Hyperactivity Disorder: Morphometric Analysis of MRI

Abstract: Although behavioral evidence provides support for the notion that attention deficit-hyperactivity disorder (ADHD) is related to central nervous system dysfunction, there is little direct evidence to reveal which neurometabolic systems or brain structures are involved. Recent magnetic resonance imaging (MRI) studies suggest that, compared to nondisabled controls, ADHD children may have a smaller right frontal region. Morphometric analysis of MRI scans was used in this exploratory study to determine whether correlated regional variation might exist in the corpus callosum of children with ADHD. While all MRI scans were judged to be clinically normal, morphometric analysis revealed that, compared to nondisabled controls, ADHD children had a smaller corpus callosum, particularly in the region of the genu and splenium, and in the area just anterior to the splenium. Interhemispheric fibers in these regions interconnect the left and right frontal, occipital, parietal, and posterior temporal regions. These results...

A calcium-dependent protein kinase with a regulatory domain similar to calmodulin.

Abstract: Calcium can function as a second messenger through stimulation of calcium-dependent protein kinases. A protein kinase that requires calcium but not calmodulin or phospholipids for activity has been purified from soybean. The kinase itself binds calcium with high affinity. A complementary DNA clone for this kinase has been identified; it encodes a protein with a predicted molecular mass of 57,175 daltons. This protein contains a catalytic domain similar to that of calmodulin-dependent kinases and a calmodulin-like region with four calcium binding domains (EF hands). The predicted structure of this kinase explains its direct regulation via calcium binding and establishes it as a prototype for a new family of calcium-regulated protein kinases.

The 2.3 angstrom X-ray structure of nitrite reductase from Achromobacter cycloclastes

Abstract: The three-dimensional crystal structure of the copper-containing nitrite reductase (NIR) from Achromobacter cycloclastes has been determined to 2.3 angstrom (A) resolution by isomorphous replacement. The monomer has two Greek key beta-barrel domains similar to that of plastocyanin and contains two copper sites. The enzyme is a trimer both in the crystal and in solution. The two copper atoms in the monomer comprise one type I copper site (Cu-I; two His, one Cys, and one Met ligands) and one putative type II copper site (Cu-II; three His and one solvent ligands). Although ligated by adjacent amino acids Cu-I and Cu-II are approximately 12.5 A apart. Cu-II is bound with nearly perfect tetrahedral geometry by residues not within a single monomer, but from each of two monomers of the trimer. The Cu-II site is at the bottom of a 12 A deep solvent channel and is the site to which the substrate (NO2-) binds, as evidenced by difference density maps of substrate-soaked and native crystals.

RFLP variability in peanut (Arachis hypogaea L.) cultivars and wild species.

Abstract: RFLP variability was studied in eight U.S. peanut cultivars, representing the four market types, and in 14 wild Arachis species accessions, using random genomic clones from a PstI library. Very low levels of RFLP variability were found among the allotetraploids, which included the U.S. cultivars and Arachis monticola, a wild species. The diploid wild species were very diverse, however. RFLP patterns of the allotetraploids were more complex than the diploids, and the two constituent genomes could usually be distinguished. On the basis of RFLP band sharing, A. ipaensis, A. duranensis, and A. spegazzinii appeared most closely related to the diploid progenitor species of the allotetraploids. A dendrogram of relationships among the diploid wild species was constructed based on band sharing.

Pollen-mediated introgression and hybrid speciation in Louisiana irises.

Abstract: Populations of the "Louisiana iris" species Iris fulva, I. hexagona, and I. nelsonii were examined genetically to test for interspecific gene flow between I. fulva and I. hexagona, for pollen- versus seed-mediated introgression between these species, and for the presumed hybrid origin of I. nelsonii. Genetic markers were identified by using both a polymerase chain reaction-like method that allows the identification of random, nuclear markers and standard polymerase chain reaction experiments involving specific chloroplast DNA (cpDNA) oligonucleotides. Restriction endonuclease digestions of the cpDNA amplification products resolved diagnostic restriction site differences for I. fulva and I. hexagona. The distribution of the species-specific nuclear markers supports a hypothesis of bidirectional introgression between I. fulva and I. hexagona. Thus, individuals analyzed from a contemporary hybrid population demonstrate multilocus genotypes that are indicative of advanced-generation hybrid individuals. Furthermore, several markers from the alternate species were present in low frequency in one allopatric population each of I. fulva and I. hexagona. Data from the nuclear analysis also support the hypothesized hybrid origin of I. nelsonii from the interaction of I. fulva and I. hexagona. Finally, cpDNA data support the hypothesis that the localized and the dispersed introgression are largely due to pollen transfer. In addition to the biological implications, this study demonstrates the power of the polymerase chain reaction methodology for the rapid identification of random and specific genetic markers for testing evolutionary genetic hypotheses.

Insect paralysis by baculovirus-mediated expression of a mite neurotoxin gene.

Abstract: FEMALE mites of the species Pyemotes tritici inject an extremely potent venom into their insect prey that causes muscle-contraction and paralysis1–4. These mites are able to paralyse insects 150,000 times their size5 and their venom is effective in a broad range of insect species4. A toxin (TxP-I) associated with the mite venom apparatus causes immediate muscle-contractive paralysis when injected into insects but not mice6. In this report, we describe the cloning, sequencing and expression of a complementary DNA (Tox-34) encoding TxP-I. Insect cells infected with a recombinant baculovirus (vEV–Tox34) expressing Tox-34 secrete three polypep-tides related to TxP-I which cause paralysis on injection. Larvae infected with vEV–Tox34 become paralysed during infection, thus reflecting the potential application of this toxin gene in insect biocontrol methods. The toxin gene expression system will also allow further exploration of the neurophysiological basis of its insect-specific effects.

Rodletless, a new Aspergillus developmental mutant induced by directed gene inactivation.

Abstract: The Aspergillus nidulans CAN41 transcription unit is activated by the brlA regulatory gene early during development of the asexual reproductive apparatus, the conidiophore. Disruption of CAN41 results in a novel mutant phenotype in which conidiophore cells and spores lack an external wall layer, the rodlet layer, making them less hydrophobic than in the wild type and leading to inefficient spore dispersal. The rodletless mutation defines a new locus on chromosome III, rodA. rodA encodes a small, moderately hydrophobic polypeptide containing 8 cysteines arranged in a pattern similar to that observed in three hydrophobic cell wall proteins from the Holobasidiomycete Schizophyllum commune. We propose that the Aspergillus and Schizophyllum 8-cysteine polypeptides define a class of secreted, hydrophobic, fungal cell wall proteins that are important in the formation and function of aerial structures such as conidiophores and mushrooms.

The effect of the density of flowering individuals on the mating systems of nine tropical tree species

Abstract: The effect of the density of flowering individuals on the mating systems of nine tropical tree species

Context and Rationality In Mezirow's Theory of Transformational Learning

Abstract: Transformational learning is fundamentally concerned with construing meaning from experience as a guide to action. In his theory of perspective transformation, Mezirow presents a significant concep...

A review of the decomposition method and some recent results for nonlinear equations

Abstract: The decomposition method can be an effective procedure for solution of nonlinear and/or stochastic continous-time dynamical systems without usual restrictive assumptions. This paper is intended as a convenient tutorial review of the method. 1

Influence of gene flow and breeding tactics on gene diversity within populations.

Abstract: Expressions describing the accumulation of gene correlations within and among lineages and individuals of a population are derived. The model permits different migration rates by males and females and accounts for various breeding tactics within lineages. The resultant equations enable calculation of the probabilistic quantities for the fixation indices, rates of loss of genetic variation, accumulation of inbreeding, and coefficients of relationship for the population at any generation. All fixation indices were found to attain asymptotic values rapidly despite the consistent loss of genetic variation and accumulation of inbreeding within the population. The time required to attain asymptotic values, however, was prolonged when gene flow among lineages was relatively low (less than 20%). The degree of genetic differentiation among breeding groups, inbreeding coefficients, and gene correlations within lineages were found to be primarily functions of breeding tactics within groups rather than gene flow among groups. Thus, the asymptotic value of S. Wright's island model is not appropriate for describing genetic differences among groups within populations. An alternative solution is provided that under limited conditions will reduce to the original island model. The evolution of polygynous breeding tactics appears to be more favorable for promoting intragroup gene correlations than modification of migration rates. Inbreeding and variance effective sizes are derived for populations that are structured by different migration and breeding tactics. Processes that reduce the inbreeding effective population size result in a concomitant increase in variance effective population size.

Background concentrations of elements in soils of China

Abstract: Mean concentrations of 62 elements, pH, organic matter and grain size have been computed for soil samples from 4,095 locations throughout mainland China The compositions of geochemical data between mainland China and the conterminous United States and between Tibet and Alaska show a close correspondence for most elements determined. These geochemical data may reveal evidence of regional variations in the abundance of elements in soils. In general, the sequence for metal content in samples of soil orders was: Lithosol>Cold-highland soils>Inceptisol> Aridisol = Mollisol>Ultisol>Alfisol>Oxisol. This trend was apparently a result of climatic influence on soil genesis, with the Oxisols (high rainfall areas with highly weathered and highly leached soils) yielding the lowest elemental mean values. However, the highest mean values of most trace elements in the Lithosols were a result of its relatively high indigenous elemental contents as well as chemical properties of the bedrock from which the soils were formed.

Information technology for negotiating groups: generating options for mutual gain

Abstract: The study of negotiating groups, whether distributive between competing parties i.e., "win-lose" or integrative between essentially friendly parties from the same organization i.e., "win-win", remains important. While much previous research in this area has focused on key analytical issues such as evaluating proposed options, much less research has addressed the equally important initial stage of negotiation: generating options for mutual gain. In general, groups do this poorly, as there are many obstacles that inhibit successful option generation. Recent advances in computer technology provide additional approaches that can be used to support option generation as one component in an overall Negotiation Support System. This paper presents an integrated series of laboratory and field studies that investigated various aspects of computer-supported option generation for groups that meet at the same place and time. The use of anonymity to separate personalities from the issues and promote more objective evaluation was found to improve option generation in some circumstances, particularly those with increased criticalness and/or power differences among the participants. Larger groups were found to be more effective than smaller groups, several smaller groups combined, and nominal groups. We present several implications for theory development and system design and use, as well as a tentative model for computer-supported group option generation.

Stability of self-esteem as a moderator of the relation between level of self-esteem and depression.

Abstract: The hypothesis that stability of self-esteem would moderate the predictive relationship between level of self-esteem and depression was tested. Specifically, level of self-esteem was hypothesized to relate more strongly to subsequent depression for individuals with stable self-esteem than for individuals with unstable self-esteem. Results strongly supported this hypothesis. Implications for the relation between level of self-esteem and depression, and for the moderator variable approach to personality and prediction, are discussed.

The Ams (altered mRNA stability) protein and ribonuclease E are encoded by the same structural gene of Escherichia coli

Abstract: The in vitro and in vivo analysis of the ribonuclease E-deficient (rne-) and the altered mRNA stability protein-deficient (ams-) strains of Escherichia coli has demonstrated that they carry mutations in the same structural gene. Strains encoding either thermolabile RNase E (rne-3071) or Ams protein (ams-1) are defective in both rRNA processing and mRNA turnover. Immediately after a shift to the nonpermissive temperature, the chemical decay rate of bulk mRNA is slowed 2- to 3-fold, and within 70 min, precursors to 5S rRNA begin to accumulate. In addition, all of the phenotypes associated with either the rne-3071 or the ams-1 alleles were complemented by a recombinant plasmid carrying ams+. When taken together with previous genetic studies, these results suggest that the role of ribonuclease E in mRNA turnover involves endonucleolytic cleavages at the proposed ACAG(A/U)AUUUG consensus sequence.