Showing papers by "Louisiana State University published in 1988"

Nuclease hypersensitive sites in chromatin

Abstract: PERSPECTIVES AND SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 160 EXPERIME:�TAL DETECTION OF HYPERSENSITIVE SITES . . . . . . . . . . . . . . . .. . . . . . . . . . 161 DNA Cleavage and Base Modification Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 161 Mapping the Positions of Hypersensitive Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . 163 Mapping the Fine Structure of Hypersensitive Sites . . . . . . . . . . . . . . . ... . . . . . . . . . . .. . . . . . . . . . 163 MORPHOLOGICAL FEATURES OF HYPERSENSITIVE SITES . . . . . . . . . . . . .. . . . . . . . . . . . 166 BIOLOGY OF HYPERSENSITIVE SITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . 168 Constitutive, Inducible, Developmental, and Tissue-Specific. . . . . . . . . . . . . . . .. . . . . . . . . . . . . 168 FUNCTIONAL SEQUENCES ASSOCIATED WITH HYPERSENSITIVE SITES . . . . . . 169 Enhancers, Silencers, Upstream Activation Sequences, Promoters, Terminators, Replication Origins, Topoisomerase Sites, Recombination Loci, Centromeres, and Telomeres . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 PROTEINS ASSOCIATED WITH HYPERSENSITIVE SITES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 Histones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 Topoisomerases I and II . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . , .. . . . 174 RNA Polymerase II 175 Transcription Factors and Other Proteins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 MECHANISMS OF ESTABLISHMENT OF HYPERSENSITIVE SITES . . . . . . . . . . . . . . . . 176 cis-Acting DNA Sequence Determinants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176 trans-Acting Protein Factors .. . . ... . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177 DNA Conformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180 MAINTENANCE AND PROPAGATION OF HYPERSENSITIVE SITES . . . . . . . . . . . . . . . 181 ROLE OF DNA METHYLATION . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . 182 NUCLEOSOME POSITIONING AND HYPERSENSITIVE SITES . . . . . . . . . . . . . . . . . . . . . . . . 184 CONCLUDING REMARKS AND PROSPECTS . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

Role of xanthine oxidase and granulocytes in ischemia-reperfusion injury

Abstract: In this lecture, evidence is presented to support the following hypothesis regarding the roles of xanthine oxidase-derived oxidants and granulocytes in ischemia-reperfusion-induced microvascular injury. During the ischemic period, ATP is catabolized to yield hypoxanthine. The hypoxic stress also triggers the conversion of NAD-reducing xanthine dehydrogenase to the oxygen radical-producing xanthine oxidase. During reperfusion, molecular oxygen is reintroduced into the tissue where it reacts with hypoxanthine and xanthine oxidase to produce a burst of superoxide anion and hydrogen peroxide. In the presence of iron, superoxide anion and hydrogen peroxide react via the Haber-Weiss reaction to form hydroxyl radicals. This highly reactive and cytotoxic radical then initiates lipid peroxidation of cell membrane components and the subsequent release of substances that attract, activate, and promote the adherence of granulocytes to microvascular endothelium. The adherent granulocytes then cause further endothelial cell injury via the release of superoxide and various proteases.

Cultural Constraints on Transfer of Technology Across Nations: Implications for Research in International and Comparative Management

Abstract: Cultural variations across nations and organizational culture-based differences between organizations that are involved in the transfer of various kinds of technologies are considered two major factors that influence the success of transfer. Relevant contributions from cross-cultural studies on management and organizations are integrated into the literature on organizational culture and diffusion of innovations, and a conceptual model is developed. Implications for research in international and comparative management are discussed.

Quantum Langevin equation.

Abstract: The macroscopic description of a quantum particle with passive dissipation and moving in an arbitrary external potential is formulated in terms of the generalized Langevin equation. The coupling with the heat bath corresponds to two terms: a mean force characterized by a memory function \ensuremath{\mu}(t) and an operator-valued random force. Explicit expressions are given for the correlation and commutator of the random force. The random force is never Markovian. It is shown that \ensuremath{\mu}\ifmmode \tilde{}\else \~{}\fi{}(z), the Fourier transform of the memory function, must be a positive real function, analytic in the upper half-plane and with Re[\ensuremath{\mu}\ifmmode \tilde{}\else \~{}\fi{}(\ensuremath{\omega}+i${0}^{+}$)] a positive distribution on the real axis. This form is then derived for the independent-oscillator model of a heat bath. It is shown that the most general quantum Langevin equation can be realized by this simple model. A critical comparison is made with a number of other models that have appeared in the literature.

Phylogenetic trees support the coevolution of parasites and their hosts

Abstract: The close correspondence often observed between the taxonomy of parasites and their hosts has led to Fahrenholz's rule, which postulates that parasites and their hosts speciate in synchrony. This leads to the prediction that phylogenetic trees of parasites and their hosts should be topologically identical. We report here a test of this prediction which involves the construction of phylogenetic trees for rodents and their ectoparasites using protein electrophoretic data. We find a high degree of concordance in the branching patterns of the trees which suggests that there is a history of cospeciation in this host-parasite assemblage. In several cases where the branching patterns were identical in the host and parasite phylogenies, the branch lengths were also very similar which, given the assumptions of molecular clock theory, strongly suggests that the speciation of these hosts and ectoparasites was roughly contemporaneous and causally related.

The impact of divorce on children.

Abstract: With the acceleration of the divorce rate from the mid- 1960s to the early 1980s, the number of nontraditional families (such as single-parent families and reconstituted families) have increased relative to intact, first-time nuclear families, This article reviews empirical evidence addressing the relationship between divorce, family composition, and children's well-being. Although not entirely consistent, the pattern of empirical findings suggests that children's emotional adjustment, gender-role orientation, and antisocial behavior are affected by family structure, whereas other dimensions of well-being are unaffected. But the review indicates that these findings should be interpreted with caution because of the methodological deficiencies of many of the studies on which these findings are based. Several variables, including the level of family conflict, may be central variables mediating the effect of family structure on children.

Hemorrhagic shock induces bacterial translocation from the gut.

Abstract: Sepsis and multiple organ failure are common after hemorrhagic shock. The goal of the current experiments was to determine whether hemorrhagic shock would promote the translocation of bacteria from the gut to visceral organs. Twenty-four hours after being subjected to sham shock, or 30, 60, or 90 minutes of shock (30 mm Hg), rats were sacrificed and their organs quantitatively cultured for translocating bacteria. There was a direct relationship between the duration of hemorrhagic shock and the 24-hour mortality rate (p = 0.02). Bacteria did not translocate from the gut in the sham-shock rats, but did translocate to the mesenteric lymph nodes, livers, and spleens of the rats subjected to hemorrhagic shock (p less than 0.01). Rats subjected to 90 minutes of shock shock exhibited a greater degree of bacterial translocation than rats receiving 30 or 60 minutes of shock (p less than 0.05). The most common translocating bacteria were Escherichia coli and Enterococcus. Hemorrhagic shock injured the gut mucosa and caused subepithelial edema and focal areas of necrosis. Thus hemorrhagic shock followed by reinfusion of shed blood disrupts the gut barrier and allows indigenous bacteria normally contained within the gut to cause systemic infections.

Host range of avian influenza virus in free-living birds

Abstract: Isolation of avian influenza virus (AIV) has been reported from 12 orders and 88 species of free-living birds. Most isolations are reported from species in the orders Anseriformes and Charadriiformes and it is recognized that species in Anseriformes represent important reservoirs of AIV. Morbidity and mortality among free-living birds attributable to AIV infection are rare, but differences in prevalence of AIV occur within and between avian species. Seasonal variation has been reported from free-living and sentinel ducks with peak AIV infection occurring in late summer and early fall. Prevalence of AIV is age-related, with highest isolation rates reported from juvenile birds. Differences in susceptibility to AIV infection among species have been demonstrated under experimental conditions. The dynamics and epidemiology of species-related variation in populations of free-living birds require further study.

Oral zinc in macular degeneration.

Abstract: Macular degeneration associated with age and drusen, an important cause of severe visual loss in older persons, is of unknown cause. The sensory retina and retinal pigment epithelium, which are cell layers in zinc, appear to be prominently involved in the disease process. Because zinc plays a role in the metabolic function of several important enzymes in the chorioretinal complex, we undertook a prospective, randomized, double-masked, placebo-controlled investigation of the effects of oral zinc administration on the visual acuity outcome in 151 subjects with drusen or macular degeneration. Although some eyes in the zinc-treated group lost vision, this group had significantly less visual loss than the placebo group after a follow-up of 12 to 24 months. This is the first controlled oral intervention study to show a positive, if limited, treatment effect in macular degeneration, a major public health problem. Because of the pilot nature of the study and the possible toxic effects and complications of oral zinc administration, widespread use of zinc in macular degeneration is not now warranted.

Reexamination of pore water sulfide concentrations and redox potentials near the aerial roots of Rhizophora mangle and Avicennia germinans

Abstract: Soil redox potentials and pore water sulfide concentrations on a mangrove island in the Belizean barrier reef system were significantly correlated with the presence of the aerial roots of mangrove trees. Sulfide concentrations were three to five times lower near the prop roots of Rhizophora mangle (red mangrove) and the pneumatophores of Avicennia germinans (black mangrove) than in adjacent (? 1 meter away) unvegetated sediment. Soil redox potentials were also significantly higher near the aerial roots. A comparison of the two species revealed that sulfide concentrations in the rhizosphere of R. mangle were as low as that of A. germinans. However, sulfide concentrations in areas occupied by the black mangrove were variable and a function of pneumatophore density. The occurrence of an oxidized rhizosphere around the roots of both species suggests that the adult trees are equally capable of exploiting reduced sediments as long as their respective pathways for root aeration are functional. RHIZOPHORA MANGLE L. and Avicennia germinans (L.) L. are dominant mangrove species of neotropical intertidal regions where they sometimes occur in monospecific zones. In the Caribbean region, R. mangle is typically found in regularly flooded intertidal areas and A. germinans in areas farther inland at higher elevations (Davis, 1940; Chapman, 1976). A number of hypotheses have been forwarded to explain mangrove species distribution. These explanations include 1) succession due to land building (Davis, 1940), 2) dispersal properties of propagules (Rabinowitz, 1978), 3) interspecific competition (Ball, 1980), 4) changes in abiotic factors along elevational gradients (Thom, 1967; Macnae, 1968), 5) physiological tolerance to flooding or salinity (Lugo and Snedaker, 1974; Walsh, 1974), and 6) predation of propagules (Smith, 1987). Nickerson and Thibodeau (1985) and Thibodeau and Nickerson (1986) proposed that the distribution ofR. mangle and A. germinans may be related to patterns of soil H2S concentrations and the differential abilities of these two mangrove species to oxidize the anaerobic substrate. They found that the oxidized rhiI Received for publication 31 August 1987; revision accepted 28 December 1987. Contribution No. 232, Caribbean Coral Reef Ecosystems (CCRE) Program, Smithsonian Institution, partially supported by a grant from Exxon Corporation. We appreciate the comments of two anonymous reviewers. zospheres associated with the extensive network of negatively geotropic pneumatophores of A. germinans reduced pore water H2S concentrations to much lower levels than that measured in adjacent unvegetated soil. In contrast, the oxidation state of the soil and pore water H2S concentrations did not appear to be influenced by proximity to R. mangle prop roots. They further speculated that high concentrations of H2S excluded R. mangle, but did not inhibit colonization by A. germinans. The apparent differential effect reported by these investigators (Nickerson and Thibodeau, 1985; Thibodeau and Nickerson, 1986) contradicts previous work conducted with R. mangle and A. germinans which demonstrated the presence of a well-developed gas space system which provides an effective pathway for gas movement within the roots of both species, independent of the anaerobic substrate (Scholander, van Dam, and Scholander, 1955; Gill and Tomlinson, 1977). Scholander et al. ( 195 5) demonstrated that oxygen enters the lenticels on the pneumatophores of A. germinans and moves by mass or bulk flow (driven by pressure changes resulting from the rise and fall of the tides) to the roots growing in the anaerobic sediment. A similar mechanism was demonstrated for R. mangle by which oxygen tensions in the roots were maintained by gas movement through the aerenchyma tissue in the prop (aerial) roots (Scholander et al., 1955). Oxygen

Dynamic changes and processes in the Mississippi River delta

Abstract: Research in the modern delta of the Mississippi River has revealed short-term changes and processes that are of significant magnitude. Deltaic lobes, each lobe covering an area of 30,000 sq km and having an average thickness of 35 km, switch sites of deposition on an average of every 1,500 yr. Through short periods of geologic time, this process results in a relatively thick accumulation of stacked deltaic cycles covering extremely large areas. Within a single delta lobe, and operating on an even higher frequency, are bay fills and overbank splays. Bay fills, having areas of 250 sq km and thickness of 15 m, require only 150 yr to accumulate. Four major events have taken place in the modern Balize delta since 1838. Overbank splays are much smaller, covering areas of less than 2 sq km and having thicknesses of 3 m, but are associated with high floods on the river. At the river mouth, continued progradation of the distributary channel can form distributary mouth sand bodies that have dimensions of 17 km long, 8 km wide, and a thickness of 80 m in a period of only 200 yr. Differential sedimentary loading at the river mouth results in formation of diapirs that display vertical movements in excess of 100 m in a period of 20 yr. On the subaqueous delta platform, sediment instabilities operate nearly continuously, mass-moving large quantities of shallow-water deposits to deeper-water environments via arcuate rotational slides and mudflow gullies and depositional lobes. All of these changes and processes operate at differing spatial and temporal scales, but all result in deposition of large volumes of sediment over extremely short periods of time.

Suspended‐load fallout rate as an independent variable in the analysis of current structures

Abstract: The dynamic interpretation of most current-structure sequences derives directly from experiments on the succession of bedforms produced by flows in flumes. The results of these and related studies have been used to construct stability field diagrams in which the fields of individual bedforms are usually expressed as a function of flow intensity (power, velocity, bed shear stress, etc.) and grain size. The data underlying existing stability-field diagrams were collected largely from the study of flows carrying coarse-grained sediment entrained through particle-by-particle bed erosion. Many flows, however, do not entrain sediment through simple bed erosion. Most turbidity currents originate by the development of turbulence in slumps, slides, and other slope failures. Such flows generally form with highly concentrated suspended loads and their bed-load layers derive sediment from the collapsing suspended-sediment clouds. Because the collapse properties of such clouds may be related as much to suspended particle concentration, size distribution, particle interactions, and other factors as to flow intensity, the stability fields of bedforms developed beneath such flows may differ in flow intensity-grain-size relationships from those beneath flows deriving sediment from bed erosion alone. Useful stability-field diagrams for turbidity currents must include suspended-load fallout rate as a third variable, independent of flow intensity and mean grain size. A preliminary stability-field diagram of this type indicates that Bouma Tabc sequences may theoretically form with essentially no velocity variation of the attendant flow. This type of analysis may have considerable relevance to the interpretation not only of turbidites but also of other deposits formed where bed-load layers are fed from above rather than below. These include shallow-shelf storm units deposited from highly concentrated flows and volcaniclastic layers formed where pyroclastic debris falls directly into moving water.

Life-style risk factors for pancreatic cancer in louisiana: a case-control study

Abstract: A hospital-based, incident case-control study of pancreatic cancer was conducted between 1979 and 1983 in parallel with similarly designed studies of lung and stomach cancers in high-risk areas of Louisiana. To evaluate life-style practices, including diet, the authors pooled controls from the three studies, and then excluded subjects with diet-altering chronic diseases. When the 363 cases were compared with the 1,234 identified controls, significantly elevated risks were found among persons with Cajun ancestry, especially in rural areas. Among current smokers, a significant twofold risk was associated with moderate (16-25 cigarettes per day) and heavy (greater than or equal to 26 cigarettes per day) consumption, while ex-smokers showed no consistent pattern of risk. After adjustment for potential confounding by smoking, diet, and demographic factors, the risk of pancreatic cancer was unrelated to use of alcoholic beverages or coffee. Pork products and rice were conspicuous as dietary risk factors, each showing a positive dose-response effect, whereas fruit consumption exerted a protective influence.

Menstrual irregularity and stress fractures in collegiate female distance runners

Abstract: From 240 questionnaires, we investigated the prevalence of stress fractures in competitive collegiate female long distance runners and its relationship to menstrual history. The runners were divided into three groups according to their menstrual history: very irregular 69/240 (0 to 5 menses/year), irregular 51/240 (6 to 9 menses/year), and regular 120/240 (10 to 13 menses/year). Stress fractures occurred in 49% of the very irregular runners, 39% of the irregular runners, and 29% of the regular runners. The majority of the stress fractures occurred in the tibia. Runners who had never used oral contraceptives were over twice as likely to have had a stress fracture when compared with runners who had used oral contraceptives for more than 1 year. These data suggest that female distance runners who have a history of irregular or absent menses and who have never used oral contraceptives may be at an increased risk for developing a stress fracture. When amenorrheal runners were separated from the very irregular group, an alarming trend was noted in eating behavior disorders. Forty-seven percent of the amenorrheal group, 20% of the one to five menses/year group, 10% of the irregular group, and 7% of the regular group admitted to an eating behavior disorder.

The relationship of smooth cordgrass ( Spartina alterniflora ) to tidal datums: A review

Abstract: An analysis of data relatingSpartina alterniflora Loisel. to tidal elevations along the Atlantic and Gulf coasts demonstrated that although this species is primarily confined to the intertidal zone, its elevational limits. of occurrence do not correspond to a consistent elevation relative to a tidal datum in all marsh locations. The variation in the vertical distribution of this species reported among marsh studies was attributed primarily to differences in mean tide range (MTR). A positive correlation between MTR and elevational growth range (r=0.91) demonstrated that theSpartina alterniflora zone expands with increasing tidal amplitude. Differences in MTR among marsh locations accounted for 70 and 68% of the statistical variation in the upper and lower limits, respectively, ofS. alterniflora growth. Among marshes of similar tidal amplitudes, the upper limit of occurrence ofS. alterniflora in northern marshes was significantly lower than that in marshes at lower latitudes. These results, in combination with regional differences in plant species distribution across the upper intertidal zone, suggested that some of the variation in the upper limit was due to latitudinal differences in growth conditions and/or differences in interspecific competition. Local and regional differences in other factors such as salinity, nutrients, or physical disturbance may have also contributed to the variation in the limits of growth relative to a tidal plane within and among marshes.

Marine dispersal and deposition of Yellow River silts by gravity-driven underflows

Abstract: Field measurements of the processes of dispersion of concentrated suspended silts over the active delta front of the Yellow River (China) show that cross-isobath sediment dispersal into the shallow Bohai Gulf is dominated by gravity-driven underflows. These underflows descend the rapidly programing delta front as hyperpyc-nal plumes 1–4 m thick. The widespread, dilute plumes observed during the summer flood season deposited most of their sediment and experienced extinction between the 5-m and 10-m depth con-tours. High-frequency internal waves on the upper interface of the underflows may have contributed to the rapid deceleration. Muds resuspended by an intense autumn storm caused denser, but short-lived, plumes which extended downslope to depths of over 13 m.

The Siable-Law Model of Stock Returns

Abstract: This study investigates the tail shapes of empirical distributions of returns on an extensive group of common stocks. The tails of the return distributions are found to be thinner than those of infinite variance stable distributions. Therefore, although homogeneity is evident in general, economic and statistical inferences drawn from stable-law parameters estimated from samples of stock returns may be misleading. This is in spite of the apparent overall similarity (in shape) between empirical and stable distributions.

Molecular Fluorescence, Phosphorescence, and Chemiluminescence Spectrometry

Abstract: As you may have already noted, this year introduces a new set of authors for this fundamental review. As new authors, they hope that they can do as accurate a job as did their predecessor, Professor Earl Wehry, of the University of Tennessee. The format for this review follows the basic outline used by Professor Wehry, with some modifications. They have condensed several sections and eliminated the section on gas-phase chemiluminescence. The primary areas of emphasis including advances in experimental techniques, developments in instrumentation, and applications for chemical analysis, remain the same. To keep the review at a reasonable length, they have not included articles that are only peripherally related to analytical chemistry or those that represent straightforward extensions or demonstrations of previously published research. In this first issue, it is likely that they have made some errors of omission, and they request your assistance in identifying any obvious errors. They have tried to be conscientious in surveying the literature and have also surveyed individual researchers in the field. This review covers literature indexed by Chemical Abstracts from January, 1985, Vol. 102, issue 1, through October 1987, Vol. 107, issue 16. Accordingly, there will be some overlap between this reviewmore » and Professor Wehry's last review.« less

The decline in the suspended load of the Lower Mississippi River and its influence on adjacent wetlands

Abstract: Since 1850, there has been an overall decrease in excess of 70 percent in the suspended load transported by the Lower Mississippi River. A decrease of 25 percent between the earliest measurements and 1950 may be partly the result of a decline in discharge and partly the result of a change in land use practices. The largest decrease occurred in 1952–53 following construction of major main-stem reservoirs on the Missouri River. Similar construction on the Arkansas River has resulted in a further decrease in 1962–63. The decrease in suspended load, combined with the artificial levee construction program and the overall enhancement of the river channel for navigation has been accompanied by an accelerating decline in land area of the Louisiana coastal zone from 17 km2/yr in 1913 to 102 km2/yr in 1980.

Bioassays for allelopathy: Measuring treatment responses with independent controls

Abstract: In bioassays for allelopathy, where responses to treatments are determined in conjunction with responses to independent controls, statistical comparisons among treatments require an index which measures each treatment response (T) in relation to its control response (C). The most commonly used index, the treatment-control ratio (T/C), exhibits two analytical problems. First, means ofT/C values are distorted upward when any of the individual values is greater than one, i.e., when stimulation occurs. Second, the distribution ofT/C values may not be normal and homoscedastic. We provide two alternative indices of response whose means do not exhibit the upward distortion ofT/C means. Then, the two indices are compared toT/C values in an empirical test for normality and homoscedasticity on a large bioassay data set. Results indicate that for this data set, one of the alternatives,RI, is clearly superior.RI is defined as 1 — (C/T) ifT≥C and asT/C — 1 ifT