Showing papers by "University of Georgia published in 1974"

Elemental mercury evolution mediated by humic Acid.

Abstract: Elemental mercury is formed in aqueous solution by the chemical reduction of mercuric ion in the presence of humic acid. The reduction proceeds via first order kinetics (rate constant, 0.009 hour-1) and is depndent on pH. The reaction mechanism involves interaction of the ionic metal species with the free radical electrons of the humic acid.

Serum Levels of Luteinizing Hormone and Progesterone During the Estrous Cycle, Pseudopregnancy and Pregnancy in the Dog

Abstract: Serum levels of LH and proges-terone were measured by radioimmunoassay and competitive protein binding techniques respectively in nonmated, sterile-mated (to a vasectomized male) and fertile-mated female beagles. There were no differences in the pattern of LH secretion in the non-pregnant and pregnant animals. The levels of LH were elevated for approximately 4 days, with the peak concentration (27 ± 5.2 ng/ml) occurring on the day prior t o the first day of standing estrus. At all other times, LH remained between 2–4 ng/ml. Ovulation was observed late on the first day of standing estrus or nearly 24 hr after the LH peak. By 10 days after the LH peak, the concentration of progesterone had increased to 20–30 ng/ml in the nonpregnant and pregnant dogs. In all nonpreg-nant animals, the pattern of progesterone secretion after day 10 was similar: decreasing from day 10 and subsequently waning to nondetectable levels (<0.5 ng/ml) by 80 days after the LH peak. On the other hand, in the pregnant dogs, progesterone...

Adaptive coloration in Peromyscus polionotus experimental selection by owls

Abstract: Predation experiments were conducted in field enclosures using two naturally occurring phenotypes of the old-field mouse ( Peromyscus polionotus ) as prey, with barn owls and screech owls as predators. Two mice, one light brown and one dark brown, were released into enclosures each containing one owl. The phenotype of the first mouse captured was recorded. Effectiveness of selection against the conspicuous prey by owls under the experimental conditions was estimated using the selection index from Dice (1947). Owls captured more of the conspicuous than the matching phenotype on both dark and light soils. Changes in intensity of illumination altered the intensity of selection and this effect differed on light and dark soils.

Evidence for the Periplasmic Location of Hydrogenase in Desulfovibrio gigas

Abstract: Hydrogenase has been found to be located in the periplasmic space of Desulfovibrio gigas, and it is proposed that hydrogenase plays an important and specific role in interspecies hydrogen transfer.

Ultrastructural and chemical alteration of the cell envelope of Pseudomonas aeruginosa, associated with resistance to ethylenediaminetetraacetate resulting from growth in a Mg2+-deficient medium.

Abstract: Cells of Pseudomonas aeruginosa became resistant to the lytic effect of ethylenediametetraacetate (EDTA) when grown in a Mg(2+)-deficient medium. To correlate ultrastructural changes in the cell wall associated with the shift to EDTA-resistance, a freeze-etch study was performed. Upon fracturing, the outer cell wall membrane split down the hydrophobic center to reveal the outer (concave) and inner (convex) layers. The concave cell wall layer of EDTA-sensitive cells grown in Mg(2+)-sufficient medium contained spherical units resting on an underlying smooth support layer. Upon EDTA treatment, approximately one-half of these spherical units were extracted. Cells grown in Mg(2+)-deficient medium were resistant to EDTA. The concave cell wall layer of EDTA-resistant cells had increased numbers of highly compacted spherical units, giving this layer a disorganized appearance. The highly compacted appearance of this layer was unaltered by EDTA treatment. Thus, growth in Mg(2+)-deficient medium resulted in cells which were resistant to EDTA and which possessed an ultrastructurally altered outer layer of the outer cell wall membrane. Cell envelopes from EDTA-resistant cells were found to possess 18% less phosphorus, 16.4% more total carbohydrate, and 13.3% more 2-keto-3-deoxyoctonate than cell envelopes from EDTA-sensitive cells. There were also qualitative, but not quantitative, differences in the protein content of cell envelopes from EDTA-resistant and EDTA-sensitive cells.

Parasitism of fungi on Vascular Plants

Abstract: I have had one piece of advice in the preparation of the presidential address: make it short. Colleagues such as mine help keep events in perspective. I am a plant pathologist-not a mycologist who happens to be stationed in a plant pathology department, not an applied mycologist, but a professional, certifiable plant pathologist. A few mycologists are beginning to recognize that plant pathology is not applied mycology; fewer appreciate that it never was. True, the foundations for modern plant pathology were laid by de Bary in the years 1853 to 1886. In the same era Koch laid the foundations for modern medicine. Bacteriology has made important contributions to medicine, and its association with medicine has been the basis for its progress. Yet, there is no suggestion that medicine is, or ever was, applied bacteriology. If there were no viruses, no bacteria, no algae, no protozoa, no nematodes, no arthropods, no genetic abnormalities, no environmental deficiencies, no smogif all plant diseases were caused by fungi, plant pathology still would be a distinct science. Although pathologists and mycologists often range the same fields, they occupy different niches. The pathologist's

Backward Profiling of Male Innovators

Abstract: Male innovative behavior is examined from the perspective of a multidimensional conceptualization of the innovator. The analysis suggests that the simultaneous study of innovative behavior for seve...

Rumen bacterial interrelationships with plant tissue during degradation revealed by transmission electron microscopy.

Abstract: The mode of rumen bacterial degradation of cell walls in coastal bermudagrass [Cynodon dactylon (L) Pers.] differed with the plant tissue type. Bacteria degraded thin, primary cell walls of mesophyll and phloem apparently by extracellular enzymes and without prior attachment; thick-walled bundle sheath and epidermal cells apparently were degraded after bacterial attachment, in some types by an extracellular substance, to the plant cell walls. Rumen bacteria split the nondegraded cuticle from the epidermis by preferentially attacking the cell just underneath the cuticle. The propensity for bacterial attachment to lignified cells of the vascular tissue was low, and bacterial degradation of these cells did not occur after 72 h of incubation.

Pyrrhotite Isograd in Southeastern Tennessee and Southwestern North Carolina

Abstract: The first appearance of pyrrhotite in the Barrovian-type metamorphic succession of the Blue Ridge province of southeastern Tennessee and southwestern North Carolina is interpreted to represent a metamorphic isograd located in the upper chlorite zone slightly west of the biotite isograd. At lower grades of metamorphism, pyrite is the only recognizable iron sulfide, and it is characterized by textures indicating an arrested state of growth. Concentrations of pyrite are commonly aligned parallel to bedding planes. Pyrrhotite appears as streaks along slaty cleavage and is preferentially developed in pyrite-bearing zones. Hexagonal pyrrhotite is dominant, but monoclinic and monoclinic + hexagonal intergrowths also occur. Where pyrrhotite is present, coexisting pyrite is typically replaced by quartz, chlorite, and biotite. The sulfur and some of the iron contained in pyrrhotite is interpreted to have been derived locally from the replaced pyrite simultaneously with the development of metamorphic minerals.

Nicotinamide Adenine Dinucleotide Phosphate-Dependent Formate Dehydrogenase from Clostridium thermoaceticum: Purification and Properties

Abstract: The nicotinamide adenine dinucleotide phosphate (NADP)-dependent formate dehydrogenase in Clostridium thermoaceticum used, in addition to its natural electron acceptor, methyl and benzyl viologen. The enzyme was purified to a specific activity of 34 (micromoles per minute per milligram of protein) with NADP as electron acceptor. Disc gel electrophoresis of the purified enzyme yielded two major and two minor protein bands, and during centrifugation in sucrose gradients two components of apparent molecular weights of 270,000 and 320,000 were obtained, both having formate dehydrogenase activity. The enzyme preparation catalyzed the reduction of riboflavine 5′-phosphate flavine adenine dinucleotide and methyl viologen by using reduced NADP as a source of electrons. It also had reduced NADP oxidase activity. The enzyme was strongly inhibited by cyanide and ethylenediaminetetraacetic acid. It was also inhibited by hypophosphite, an inhibition that was reversed by formate. Sulfite inhibited the activity with NADP but not with methyl viologen as acceptor. The apparent Km at 55 C and pH 7.5 for formate was 2.27 × 10−4 M with NADP and 0.83 × 10−4 with methyl viologen as acceptor. The apparent Km for NADP was 1.09 × 10−4 M and for methyl viologen was 2.35 × 10−3 M. NADP showed substrate inhibition at 5 × 10−3 M and higher concentrations. With NADP as electron acceptor, the enzyme had a broad pH optimum between 7 and 9.5. The apparent temperature optimum was 85 C. In the absence of substrates, the enzyme was stable at 70 C but was rapidly inactivated at temperatures above 73 C. The enzyme was very sensitive to oxygen but was stabilized by thiol-iron complexes and formate.

Social Class and Social Time Perspective

Abstract: The present research introduces and provisionally tests an improved methodological procedure (the Social Time Perspective Scale) for determining class-linked differences in the way persons anticipate the future and orient their behavior to it. Data for this analysis are drawn from a sample of freshmen in college who come largely, but not entirely, from middle-class backgrounds and from a sample of Job Corpsmen who come primarily from lower-class backgrounds. The findings reveal that: (1) lowerclass youth in the Job Corps have a more circumscribed notion of future time than youth from the middle class and their outlook on the future is less systematically ordered; (2) upwardly mobile lower-class youth in college have succeeded in incorporating some features of the middle-class pattern of future orientation in their temporal outlook, but residues of their lower-class backgrounds are still present; and (3) in both the lowerand middle-class samples, the length of temporal perspectives is a factor mediating effective role performance. The effects of social class upon the development of future time perspectives have been the object of much speculation and inquiry. Various theories have been advanced to explain social class differences in temporal perspectives (see O'Rand, 1969:1-38). Yet our state of knowledge is still in its formative stage. Those studies providing the most consistent evidence of class-linked differences in temporal perspectives tend to be rich in substantive detail but lacking in methodological rigor (Davis and Dollard, 1940; Horton, 1967; Liebow, 1967). Those studies attempting to offer more precise evidence often turn up inconsistent results, partially because the methodology employed is inadequate for the task at hand (cf. Doob, 1971; Lessing, 1968; O'Rand,

Chromatoid bodies in somatic cells of the planarian : observations on their behavior during mitosis

Abstract: The behavior of somatic cell chromatoid bodies in the planarian Dugesia dorotocephala during mitosis has been studied by electron microscopy. The relatively undifferentiated beta (progenitor) cells are the only somatic cells containing chromatoid bodies and also are the only dividing somatic cells. Somatic cell chromatoid bodies are known to disappear as differentiation takes place and reappear when dedifferentiation occurs. Interphase and prophase beta cells have juxtanuclear and peripheral cytoplasmic chromatoid bodies. There is no ultrastructural evidence to suggest they are derived from formed nuclear material. During metaphase and anaphase, the chromatoid bodies are segregated from the chromosomes and adjacent cytoplasm by cups of double membranes. By the completion of telophase, the chromatoid body size and number immediately adjacent to the nucleus is markedly decreased and extremely large chromatoid bodies may be found further out in the cytoplasm. These findings are compared to the behavior of germ cell chromatoid bodies and discussed in terms of their possible significance and function.

Differential Absorption, Translocation and Metabolism of Metribuzin [4‐amino‐6‐tert‐butyl‐3‐(methylthio)‐as‐triazine‐5(4H)one] by Soybean Cultivars

Abstract: Soybean (Glycine max (L.) Merr.) cultivars have been reported to range in tolerance to injury by 4-amino-6-tert-butyl-3-(methylthio)-as-triazine-5(4H)one (metribuzin), from tolerant (e.g.‘Bragg’) to susceptible (e.g.‘Coker 102’ and ‘Semmes’). ‘Bragg,’‘Coker 102’, and ‘Semmes’ soybeans were grown in sand subirrigated with nutrient solution containing labelled (14C-carbonyl metribuzin) and nonlabelled metribuzin to determine cultivar variability in absorption, translocation, and metabolism of metribuzin. Plants were periodically harvested, autoradiographed, and radioactivity in tissue extracts quantified. Data indicated that all 3 cultivars readily absorbed and translocated metribuzin. However, ‘Bragg’ tissues accumulated greater quantities of metribuzin metabolites than the other two cultivars. The major 14C-containing metabolite in ‘Semmes’ and ‘Coker’ roots and stems was 6-tert-butyl-as-triazine-3-5-(2H,4H)-dione, whereas the major 14C-metabolite isolated from‘Bragg’ roots and stems was a glucose conjugate. Results indicated that differential-intraspecific responses to metribuzin may result from differential capacities for herbicide detoxification by conjugation.

Purification and properties of acetate kinase from Clostridium thermoaceticum.

Abstract: Acetate kinase (ATP: acetate phosphotransferase EC 2.7.2.1) has been purified from Clostridium thermoaceticum. The enzyme of a specific activity of 282 μmoles min-1 mg-1 appeared homogeneous as judged from Sephadex chromatography and sedimentation velocity. Polyacrylamide gel electrophoretic patterns at pH 9.0 and 9.5 showed heterogeneity. Velocity curves obtained with varying amount of acetate were of the Michaelis-Menten type with an apparent K m of 0.135 M. With varying amounts of ATP sigmoidal kinetic was observed (S0.5=1.64 mM), suggesting cooperative binding of this substrate. The enzyme had only moderate thermal stability with a temperature optimum of about 60°C and exhibited a broken line in an Arrhenius graph. From gel filtration a molecular weight of about 60 000 daltons was estimated for the enzyme. The S20w value was 6.0 S.