20 Matching Results

Search Results

Advanced search parameters have been applied.

Physiological stress of acidification on fishes and its manifestation. Technical progress report, October 1, 1977--September 30, 1978

Description: The hypothesis was tested that the reproductive function would exhibit compensation to temperature if the organism was bred and reared at temperatures which produced less than optimal reproductive performance. Desert pupfish, Cyprinodon n. nevadensis, were bred and the eggs reared at the optimum temperature for reproduction, 28/sup 0/C, and at two marginal temperatures, 24/sup 0/ and 32/sup 0/C. Each brood was divided into three groups and reproductive performance was tested at the rearing temperature and at two alternate temperatures to which they had never before been exposed. The eggs laid per spawning and eggs laid per gram body weight per day showed no compensation to rearing temperature. Reproductive performance was optimal at 28/sup 0/C and was poor at both marginal temperatures, regardless of the previous thermal history of the fish. Lower hatchability at 32/sup 0/C was associated with a thin egg coat, small yolk diameter, and low gonosomatic index as compared with the same measurements at the lower temperatures.
Date: January 1, 1978
Creator: Gerking, S.D.
Partner: UNT Libraries Government Documents Department

Body shape differences in a pair of closely related Malawi cichlids and their hybrids: Effects of genetic variation, phenotypic plasticity, and transgressive segregation

Description: This article investigates the contributions of genetic and plastic components for differences in body shape in two species of Lake Malawi cichlids using wild-caught specimens and a common garden experiment.
Date: January 28, 2017
Creator: Husemann, Martin; Tobler, Michael; McCauley, Cagney; Ding, Baoqing & Danley, Patrick D.
Partner: UNT College of Arts and Sciences

Africa Adaptation Programme: An insight into AAP and Country project Profiles

Description: The Africa Adaptation Programme (AAP) has been designed to support the long-term efforts of targeted countries to further develop their capability to successfully identify, design and implement holistic adaptation and disaster risk reduction programmes that are aligned with national development priorities. This report provides insight into the Africa Adaptation Programme (AAP) and its related country project profiles. The AAP has shifted into implementation, with Namibia and Tunisia as the first countries to complete national inception workshops. Eighteen out of the total twenty programme countries will complete national inception processes and start full-fledged implementation in the coming months.
Date: January 2010
Creator: The Africa Adaptation Programme (AAP)
Partner: UNT Libraries

Transmutations across hierarchical levels. [Development of large-scale ecological models]

Description: The development of large-scale ecological models depends implicitly on a concept known as hierarchy theory which views biological systems in a series of hierarchical levels (i.e., organism, population, trophic level, ecosystem). The theory states that an explanation of a biological phenomenon is provided when it is shown to be the consequence of the activities of the system's components, which are themselves systems in the next lower level of the hierarchy. Thus, the behavior of a population is explained by the behavior of the organisms in the population. The initial step in any modeling project is, therefore, to identify the system components and the interactions between them. A series of examples of transmutations in aquatic and terrestrial ecosystems are presented to show how and why changes occur. The types of changes are summarized and possible implications of transmutation for hierarchy theory, for the modeler, and for the ecological theoretician are discussed.
Date: January 1, 1977
Creator: O'Neill, R. V.
Partner: UNT Libraries Government Documents Department

Dysbaric gas bubble disease in dogs. IV. Acclimatization to diving

Description: Acclimatization to diving was documented to occur in dogs. An increase in the number of repetitive dives which could be tolerated, as well as a decrease in the total number of pulmonary artery venous gas emboli resulting from individual dives were observed. The results from the experimental subject ''Jason'' indicate that acclimatization involves a reduction in the number of bubbles, and not an increase in the ability of the body to tolerate bubbles. Acclimatization is principally a physical rather than a physiological event. Bubbles forming in vivo must grow from nuclei of some sort. If these nuclei are stable, discrete structure that are destroyed when they grow into gross bubbles, then repetitive diving might markedly reduce by attrition the number of such bubble micronuclei. This would result in fewer bubbles being formed during subsequent dives, thus leading to the observed acclimatization effect. 7 refs., 3 figs., 4 tabs.
Date: January 1, 1986
Creator: Kunkle, T. D.; Morita, A. & Beckman, E. L.
Partner: UNT Libraries Government Documents Department

Osmoregulation in methanogens. Progress report, May 15, 1991--January 15, 1993

Description: Our major goal of our work has been to develop and use NMR techniques to study how methanogenic archaebacteria deal with osmotic stress with the hope of providing insights into increasing the salt tolerance of other cells. The project has three main sections: (i) in vivo studies of methanogens; (ii) use of {sup l3}C- and {sup l5}N- labeled potential precursors and in vitro analyses of specific label uptake for elucidation of osmolyte dynamics and biosynthetic pathways of osmolytes in these organisms, and isolation of key biosynthetic enzymes; and (iii) collaborative studies on identification of organic solutes in other methanogens.
Date: January 1993
Creator: Roberts, Mary F.
Partner: UNT Libraries Government Documents Department

(Carbon and hydrogen metabolism of green algae in light and dark)

Description: The focus of this project was the elucidation of anaerobic metabolism in ecuaryotic green algae, chlamydomonas reinhardii. Chlamydomonas is a versatile organism that can grow under disparate conditions such as fresh water lakes and sewage ponds. The cell an photoassimilate CO{sub 2} aerobically and anaerobically, the latter after adaptation'' to a hydrogen metabolism. It can recall the knallgas or oxyhydrogen reaction and utilize hydrogen the simplest of all reducing agents for the dark assimilation of CO{sub 2} by the photosynthetic carbon reduction cycle. The dark reduction with hydrogen lies on the border line between autotrophic and heterotrophic carbon assimilation. Both autotrophic and heterotrophic bacteria are known in which molecular hydrogen can replace either inorganic or organic hydrogen donors. Here the dark reduction of CO{sub 2} acquires a particular importance since it occurs in the same cell that carries on photoreduction and photosynthesis. We will demonstrate here that the alga chloroplast possesses a respiratory capacity. It seems likely that Chlamydomonas may have retained the chloroplastic respiratory pathway because of the selective advantage provided to the algae under a wide range of environmental conditions that the cells experience in nature. The ability to cycle electrons and poise the reduction level of the photosynthetic apparatus under aerobic and microaerobic conditions could allow more efficient CO{sub 2} fixation and enhanced growth under unfavorable conditions or survival under more severe conditions.
Date: January 1, 1990
Partner: UNT Libraries Government Documents Department

Biosynthesis of metal-binding polypeptides and their precursors in response to cadmium in Datura innoxia

Description: Metal-tolerant Datura innoxia cells synthesize large amounts of a class of metal-binding polypeptides, poly({gamma}-glutamylcysteinyl) glycines (({gamma}-EC){sub n}G, n=2-5), when exposed to Cd. These polypeptides have a high affinity for Cd (2) and certain other metal ions and are thought to play a role in metal tolerance in higher plants. ({gamma}-EC){sub n}G is biosynthetically derived from glutathione. Therefore, the response of Datura cells to Cd must include an increase in production of glutathione and its precursors, since cells rapidly accumulate very high concentrations of these metal-binding polypeptides. The biosynthesis of ({gamma}-EC){sub n}Gs, glutathione, and cysteine in response to Cd exposure is described. The physiological significance of the synthesis of these polypeptides and their precursors and its relevance to Cd tolerance and metal homeostasis are discussed. 34 refs., 6 figs., 1 tab.
Date: January 1, 1991
Creator: Jackson, P.J.; Delhaize, E. & Kuske, C.R.
Partner: UNT Libraries Government Documents Department

Molecular biology in studies of oceanic primary production

Description: Remote sensing and the use of moored in situ instrumentation has greatly improved our ability to measure phytoplankton chlorophyll and photosynthesis on global scales with high temporal resolution. However, the interpretation of these measurements and their significance with respect to the biogeochemical cycling of carbon relies on their relationship with physiological and biochemical processes in phytoplankton. For example, the use of satellite images of surface chlorophyll to estimate primary production is often based on the functional relationship between photosynthesis and irradiance. A variety of environmental factors such as light, temperature, nutrient availability affect the photosynthesis/irradiance (P vs I) relationship in phytoplankton. We present three examples showing how molecular biology can be used to provide basic insight into the factors controlling primary productivity at three different levels of complexity: 1. Studies of light intensity regulation in unicellular alga show how molecular biology can help understand the processing of environmental cues leading to the regulation of photosynthetic gene expression. 2. Probing of the photosynthetic apparatus using molecular techniques can be used to test existing mechanistic models derived from the interpretation of physiological and biophysical measurements. 3. Exploratory work on the expression of specific proteins during nutrient-limited growth of phytoplankton may lead to the identification and production of molecular probes for field studies.
Date: January 1, 1992
Creator: LaRoche, J.; Falkowski, P.G. (Brookhaven National Lab., Upton, NY (United States)) & Geider, R. (Delaware Univ., Lewes, DE (United States). Coll. of Marine Studies)
Partner: UNT Libraries Government Documents Department

Proteomic Insights: Cryoadaption of Permafrost Bacteria

Description: The permafrost microbial community has been described as 'a community of survivors' (Friedman 1994). Because of the permanently cold condition and the long term isolation of the permafrost sediments, the permafrost microorganisms have acquired various adaptive features in the membrane, enzymes, and macromolecular synthesis. This chapter reviews the different adaptive mechanisms used by permafrost microorganisms with a focus on the proteomic level of cryoadaptation that have recently been identified during the low temperature growth in permafrost bacteria.
Date: January 1, 2009
Creator: Qiu, Yinghua; Vishnivetskaya, Tatiana A. & Lubman, David M.
Partner: UNT Libraries Government Documents Department

Osmoregulation in methanogens

Description: Our major goal of our work has been to develop and use NMR techniques to study how methanogenic archaebacteria deal with osmotic stress with the hope of providing insights into increasing the salt tolerance of other cells. The project has three main sections: (i) in vivo studies of methanogens; (ii) use of [sup l3]C- and [sup l5]N- labeled potential precursors and in vitro analyses of specific label uptake for elucidation of osmolyte dynamics and biosynthetic pathways of osmolytes in these organisms, and isolation of key biosynthetic enzymes; and (iii) collaborative studies on identification of organic solutes in other methanogens.
Date: January 1, 1993
Creator: Roberts, M.F.
Partner: UNT Libraries Government Documents Department

(Plant growth with limited water)

Description: When water is in short supply, soybean stem growth is inhibited by a physical limitation followed in a few hours by metabolic changes that reduce the extensibility of the cell walls. The extensibility then becomes the main limitation. With time, there is a modest recovery in extensibility along with an accumulation of a 28kD protein in the walls of the growth-affected cells. A 3lkD protein that was 80% similar in amino acid sequence also was present but did not accumulate in the walls of the stem cells. In the stem, growth was inhibited and the mRNA for the 28kD protein increased in response to water deprivation but the mRNA for the 3 1 kD protein did not. The roots continued to grow and the mRNA for the 28kD protein did not accumulate but the mRNA for the 3lkD protein did. Thus, there was a tissuespecific response of gene expression that correlated with the contrasting growth response to low water potential in the same seedlings. Further work using immunogold labeling, fluorescence labeling, and western blotting gave evidence that the 28kD protein is located in the cell wall as well as several compartments in the cytoplasm. Preliminary experiments indicate that the 28kD protein is a phosphatase.
Date: January 1, 1992
Partner: UNT Libraries Government Documents Department

Effects of freezing and cold acclimation on the plasma membrane of isolated protoplasts

Description: Our goal is to provide a mechanistic understanding of the cellular and molecular aspects of freezing injury and cold acclimation from a perspective of the structural and functional integrity of the plasma membrane -- the primary site of freezing injury in winter cereals. We have utilized protoplasts isolated from leaves of winter rye (Secale cereale L. cv Puma) to study the cryobehavior of the plasma membrane during a freeze/thaw cycle. The focus of our current studies is on lesions in the plasma membrane that result from severe freeze-induced dehydration and result in the alteration of the semipermeable characteristics of the plasma membrane so that the protoplasts are osmotically unresponsive. In protoplasts isolated from non-acclimated rye leaves (NA protoplasts), injury is associated with the formation of aparticulate domains in the plasma membrane, aparticulate lamellae subtending the plasma membrane, and lamellar-to-hexagonal II phase transitions in the plasma membrane and the subtending lamellae. However, lamellar-to-hexagonal II phase transitions are not observed following severe dehydration of protoplasts isolated from cold-acclimated rye leaves (ACC protoplasts). Rather, injury is associated with the fracture-jump lesion,'' which, in freeze-fracture electron microscopy studies, is manifested as localized deviations in the fracture face of the plasma membrane. The fracture plane jumps'' from the plasma membrane to either subtending aparticulate lamellae or aparticulate regions of various endomembranes (predominantly chloroplast envelopes) that are in close apposition with the plasma membrane.
Date: January 1, 1993
Creator: Steponkus, P.L.
Partner: UNT Libraries Government Documents Department

The bioenergetics of salt tolerance

Description: The aim of this project was to try to understand the adaptive mechanisms that organisms develop in order to respond to a sudden transformation in their environment to a salt shock.'' To study this problem we used a fresh water oxygenic photosynthetic cyanobacterium known as Synecoccus 6311. This organism suffers injury after this sudden exposure to high concentrations of sodium chloride equivalent to or even higher than that in sea water. Yet they are able to re-establish their photosynthetic activity which is partially injured and return to virtually normal growth rates. Identification of the temporal sequence of changes involved in adaptation to this stress was the rationale. Indeed this project employed a wide variety of biochemical and biophysical methods, including electron spin resonance techniques and nuclear magnetic resonance to study the bioenergetics and transport mechanisms, growth and energy changes in these organisms and how the structural components of the cells changed in response to adaptation to growth at high salinity. The problem has relevance for higher plants because most of the arable farmland in the work is already under use and that which is not used is usually in salite environments. Hence, understanding basic mechanisms of salt tolerance is a fundamental biological problem with great applications for bioproductivity and agriculture. 18 refs.
Date: January 1, 1991
Creator: Packer, L.
Partner: UNT Libraries Government Documents Department

[Tonoplast transport and salt tolerance in plants]

Description: We have showed that the tonoplast V-ATPase could be specifically inhibited by antisense DNA to the catalytic (A) subunit; that cell expansion was inhibited in carrot transformants deficient in the enzyme and have provided evidence for at least two different isoforms of the A subunit which are Golgi- and tonoplast-specific. These findings prompted a search for sequences of the isoforms of the A subunit in carrot. We have cloned and sequenced 1.0--1.5 kb fragments of three different genes for the catalytic subunit, the fragments differ greatly in their introns, but have nearly identical exons. We are using PCR to amplify and subclone carrot seedling cDNA. Thus far two bands have been amplified and are currently being subcloned for sequencing.
Date: January 1, 1993
Creator: Taiz, L.
Partner: UNT Libraries Government Documents Department

Predicting the response of a temperate forest ecosystem to atmospheric CO sub 2 increase

Description: All research goals for the current year have been met. We have prepared eight manuscripts reporting these discoveries. Individual projects have determined: Soil volume is not critical to the decline of photosynthetic rates under elevated CO{sub 2}. However, the shape, as well as the size, exerts a strong influence on growth in response to elevated CO{sub 2}, but this response is variable dependent on the species. Elevated CO{sub 2} may increase the growth of shade-tolerant trees to a greater extent than shade-intolerant trees. All birch trees examined responded in a similar positive way to a doubling of CO{sub 2}, but only yellow birch showed an increase in survival. Seedling regeneration in a New England deciduous forest may be altered by future CO{sub 2} levels. Plants grown in a high CO{sub 2} atmosphere altered their physiological functions, growth rates, biomass, and allometric growth patterns, probably influencing individual survival and plant/plant interactions within a community. The changes in photosynthetic rate (Ps) in response to elevated CO{sub 2} may involve alteration of multiple physiological characteristics. Growth enhancement in elevated CO{sub 2} is contingent on soil moisture conditions. Model simulations show increases in plant survival under elevated CO{sub 2} can have unexpected results on population dynamics. Finally, CO{sub 2} levels do not affect the heat shock response. Future experiments are described. 21 refs., 1 tab. (MHB)
Date: January 1, 1991
Creator: Bazzaz, F.A.
Partner: UNT Libraries Government Documents Department

Role of x-ray-induced transcripts in adaptive responses following x-rays

Description: Potentially lethal damage repair (PLDR) and sublethal damage repair, may be the same manifestations of a series of common enzymatic steps. PLDR, has two distinct phases based upon DNA lesion repair and survival recovery studies. The first phase of PLDR occurs very quickly (t{sub {1/2}}:2--20 mins) to increase the survival of X-irradiated cells by mending the vast array of DNA lesions created by ionizing radiation. The second slower phase of PLDR proceeds much later (i.e., >1--2 hrs) following X-irradiation, during which the remaining double-stranded DNA breaks are completely repaired. This second phase of repair closely corresponds to the restructuring of gross chromosomal damage, and can be partially blocked in some human cells by inhibiting protein synthesis. This slower phase of PLDR correlated with a rapid decline in X-ray-induced transformation of normal cells. The fast component of PLDR may be due to constitutively synthesized DNA ligases, topoisomerases, or polymerases, which act immediately to repair damaged, DNA. In contrast, the slow phase of PLDR in human cells may require the induction of specific genes and gene product's involved in the repair of potentially lethal or carcinogenic DNA lesions. Induced gene products (i.e., proteins) specifically synthesized in response to physiological doses of ionizing radiation in radioresistant human melanoma (U1-Mel) cells, and in a variety of other human normal and cancer-prone cells, were identified using two-dimensional gel electrophoresis. We identified and partially characterized ten proteins synthesized by U1-Mel cells. The synthesis of eight of these proteins were specifically induced by ionizing radiation and two proteins were repressed Neither heat shock, UV-irradiation, nor bifunctional alkylating agent treatments resulted in the induction of these proteins. The expression of one protein, XIP269, correlated very well with PLDR capacity.
Date: January 1, 1992
Creator: Boothman, D. A.
Partner: UNT Libraries Government Documents Department

Effects of freezing and cold acclimation on the plasma membrane of isolated protoplasts

Description: This project focuses on lesions in the plasma membrane of protoplasts that occur during freezing to temperatures below {minus}5{degrees} which result in changes in the semipermeablity of the plasma membrane. This injury, referred to as loss of osmotic responsiveness, is associated with the formation of large, aparticulate domains in the plasma membrane, aparticulate lamellae subtending the plasma membrane, and lamellar-to-hexagonal{sub II} phase transitions in the plasma membrane and subtending lamellar. The goals of this project are to provide a mechanistic understanding of the mechanism by which freeze-induced dehydration effects the formation of aparticulate domains and lamellar-to-hexagonal{sub II} phase transitions and to determine the mechanisms by which cold acclimation and cryoprotectants preclude or diminish these ultrastructural changes. Our working hypothesis is the formation of aparticulate domains and lamellar-to-hexagon{sub II} phase transitions in the plasma membrane and subtending lamellae are manifestations of hydration-dependent bilayer-bilayer interactions.
Date: January 1, 1991
Creator: Steponkus, P. L.
Partner: UNT Libraries Government Documents Department

Genetics of thermophilic bacteria. [Bacillus stearothermophilus:a2]

Description: Organisms adapted to high temperature have evolved a variety of unique solutions to the biochemical problems imposed by this environment. Adaptation is commonly used to describe the biochemical properties of organisms which have become adapted to their environment (genetic adaptation). It can also mean the direct response-at the cellular level-of an organism to changes in temperature (physiological adaptation). Thermophilic bacilli (strains of Bacillus stearothermophilus) can exhibit a variety of biochemical adaptations in response to changes in temperature. These include changes in the composition and stability of the membrane, metabolic potential, the transport of amino acids, regulatory mechanisms, ribose methylation of tRNA, protein thermostability, and nutritional requirements. The objectives of the research were to develop efficient and reliable genetic systems to analyze and manipulate B. Stearothermophilus, and to use these systems initiate a biochemical, molecular, and genetic investigations of genes that are required for growth at high temperature.
Date: January 1, 1991
Creator: Welker, N.E.
Partner: UNT Libraries Government Documents Department

Effects of electronic identification, temperature monitoring, and ELA on the meat industry. [Electronic monitoring of cattle herds and serological testing for diseases]

Description: Electronic identification of CaHl/sub e/ and temperature monitoring of tolerance to environmental changes are technically feasible for the management of breeder herds and dairy cattle. Some commercial organizations are already manfacturing simple forms of electronic identification. A nearly ideal system can become a reality if the various potential user groups work together with the developers, manufacturers, and regulatory agencies. Widespread use of electronic identification and temperature monitoring in the livestock industry would improve the cost/benefit ratios to all portions of the industry by enhancing efficiency of production and management of records. The enzyme-labeled antibody (ELA) serological test of cattle in the slaughter plant makes it possible to screen for many diseases in a simple, fast inexpensive way.
Date: January 1, 1977
Creator: Holm, D. M.
Partner: UNT Libraries Government Documents Department