Analysis of the Accumulation, Toxic Effects, and Risk of Persistent Organic Pollutants in Pinnipeds (open access)

Analysis of the Accumulation, Toxic Effects, and Risk of Persistent Organic Pollutants in Pinnipeds

The present studies determine the accumulation of persistent organic pollutants (POPs) in three pinniped species, evaluate the relationship with relevant biomarkers of exposure, and calculate toxic effect thresholds. Stranded harp and hooded seals were found to be accumulating PBDEs at levels which could pose a based on threshold levels determined in this study. Northern fur seals are accumulating all three classes of POPs (PCBs, PBDEs, and OCPs) with significant relationships being seen with blubber percent lipid. Correlations between contaminant concentrations and expression levels of relevant biomarkers were seen potentially indicating an effect on multiple pathways. Overall risk can be hard to determine due to factors such as sex and age. Broad threshold response values and hazard quotients were calculated for toxic effect endpoints in pinnipeds. Overall these results suggest that certain populations of pinnipeds are at high risk of experiencing toxic effects due to POP exposure, but it is important to understand effects even at lower concentrations. The relationship between exposure, toxic effects, and other stressors, both environmental and physiological, can impact the overall fitness and survival of pinnipeds.
Date: August 2021
Creator: Soulen, Brianne K
System: The UNT Digital Library
Head Trauma Release of Histamine from Dural Mast Cells Alters Blood-Brain Barrier: Attenuation with Zolantidine (open access)

Head Trauma Release of Histamine from Dural Mast Cells Alters Blood-Brain Barrier: Attenuation with Zolantidine

This study employed a new model of mild-to-moderate head trauma to specifically identify the role of dural mast cell (MC) histamine in trauma-induced increased permeability in the blood-brain barrier (BBB). A single line was scored partially through the left dorsal parietal skull. Immediately following the trauma, degranulation was seen in 39% of the MCs on the left and in 2% on the right. After a 20 min survival period, left duras showed 55% with MC degranulation (fewer with complete degranulation) compared to 34% on the right. In the other experiments two parallel lines were scored following the injection of Evan's blue. Histamine assay showed histamine increased in the left cortex to 154% at 5 min, 174% at 10 min, and 151% at 20 min. Fluorescent quantitation of extravasated Evan's blue at 20 min following the trauma gave an increase of 1385% over the value measured for the right cortex. Zolantidine, a selective histamine H2 receptor antagonist, administered at 10- and 20- mg/kg 30 min before the trauma blocked 65% of the Evan's blue extravasation compared with the control and 2.5 mg group.
Date: December 2000
Creator: Laufer, Susan R.
System: The UNT Digital Library
Some Responses of Bacillus subtilis Spores to Glutaraldehyde (open access)

Some Responses of Bacillus subtilis Spores to Glutaraldehyde

Bacillus subtilis (ATCC 19659) were damaged by exposure to various concentrations of glutaraldehyde, as shown by decreased germination rates. The damage caused was repaired or otherwise obviated by the presence of sodium lactate in the holding medium. When two different salts of lactic acid were compared for ability to overcome the effect of glutaraldehyde, it was found that calcium salt of lactate was more effective than the sodium salt. The damage repair system involved l-alanine, lactate and either the sodium or calcium ions. The study involved in determining the difference in efficiency of spore repair was due to an organic or an amino acii snowed that the presence of two carboxylic functional groups did not effectively alter the reactivity.
Date: May 1985
Creator: Crum, Morris G. (Morris Glenn)
System: The UNT Digital Library
Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone (open access)

Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone

The goals of this dissertation work were to assess the bioaccumulation potential of carbamazepine and amiodarone, two widely used ionizable pharmaceutical compounds that possess mid-range and high LogD values, respectively, and to evaluate alternative methods to assess chemical accumulation in bluntnose minnows, catfish, and tilapia. Results indicated that carbamazepine does not appreciably bioaccumulate in fish tissue with BCFk and BAF carbamazepine values < 10. Amiodarone, however, with a log D of 5.87 at pH 7.4, accumulated in fish tissues with kinetic BCF values <2,400. Collectively, the data suggest that full and abbreviated laboratory-derived BCFs, BCFMs derived from S9 loss-of-parent assays, as well as field BAF values are similar for each of the two drugs. In summary, the results from this dissertation indicated: 1) The reduced design BCF test is a good estimate for the traditional OECD 305 test. 2) In vitro S9 metabolism assays provide comparable BCF estimates to the OECD 305 test. 3) Metabolism may play a large role in the accumulation of drugs in fish. 4) Reduced BCF tests and in vitro assays are cost effective and can reduce vertebrate testing.
Date: December 2013
Creator: García Martínez, Santos Noé
System: The UNT Digital Library
Maternal Transfer of Dietary Methylmercury and Implications for Embryotoxicity in Fathead Minnows (Pimephales promelas) (open access)

Maternal Transfer of Dietary Methylmercury and Implications for Embryotoxicity in Fathead Minnows (Pimephales promelas)

Mercury (Hg) is a ubiquitous environmental contaminant, which is capable of global atmospheric transport. As a result, even the most pristine aquatic ecosystems are affected by atmospheric Hg deposition, following which microbial transformation yield organic Hg forms, the most concerning of which is methylmercury (MeHg). Methylmercury is capable of bioaccumulation and biomagnification in food webs, resulting in potentially toxic body burdens due to regular dietary exposure in long-lived organisms at higher trophic levels. It is also a molecular mimic of some endogenous amino acids, providing a route of transfer from mother to offspring via large amino acid transporters. Exposure during neurodevelopment can lead to serious, irreversible neurological dysfunction, associated with a variety of cognitive and motor abnormalities across species. The present studies evaluate the effects of maternally-transferred dietary MeHg, at environmentally relevant concentrations on early life stage fathead minnows (Pimephales promelas). Embryos were collected from adult fatheads exposed to one of three diets with varying concentrations of MeHg for 30 days. Adult reproductive metrics were also monitored over the course of the study, with results indicating no effects on spawning frequency, clutch size, or total egg output. In embryos, Hg concentration was a function of female diet and the duration …
Date: December 2016
Creator: Bridges, Kristin N.
System: The UNT Digital Library
Identification of Glycine as the Factor in Peptone Which Induces Pleomorphism in Azotobacter Vinelandii (open access)

Identification of Glycine as the Factor in Peptone Which Induces Pleomorphism in Azotobacter Vinelandii

The rigid peptidoglycan layer of the cell wall is responsible for maintaining the structural integrity of bacteria. Antibiotics such as penicillin exert their anti-bacterial effect by inhibiting synthesis of peptodoglycan, and enzymes such as lysozyme destroy cell integrity by hydrolyzing specific bonds in the interior of this macromolecule. Defective cells can no longer withstand the high turgor pressure within the cell because they are no longer protected by a rigid wall and tend to become fragile and spherical or irregular in shape. While all bacteria are pleomorphic under certain conditions which do not normally affect other bacteria. This is exemplified by the pleomorphic growth of Azotobacter in nutrient agar or peptone-containing medium. The purpose of this investigation was to study the nature of peptone-induced pleomorphism of Azotobacter. The first phase of study dealt with the effects of poptone on the growth and morphology of A. vinelandii. Many diverse froms were observed in peptone-containing media, but it was shown that all cell types were related to the "fungoid" family of pleomorphic cells. Although Azotobacter failed to accumulate detectable levels of cell-wall precursors in response to glycine treatment, it was shown that glycine acted only on metabolically active cells. In addition, incorporation …
Date: December 1972
Creator: Rosenthal, Raoul Simon
System: The UNT Digital Library
The Physiology of Azotobacter Vinelandii Cysts (open access)

The Physiology of Azotobacter Vinelandii Cysts

The value of the adenylate energy charge [(ATP)+1/2(ADP)/(ATP)+(ADP)+(AMP)] in Azotobacter vinelandii cells was monitored during growth and germination in flask cultures. The miximal value of 0.88 was attained during mid-log phase; this declined gradually to 0.50 by late stationary phase. When these cultures were transferred to encystment media, the adenylate energy charge decreased to an average value of 0.40 as the vegetative cells encysted and remained unchanged during the next 20 days. Encystment cultures wre composed of vegetative cells, encysting cells and mature cysts but the proportionate value of the energy charge could be assigned. Viability of the total population remained 95% or higher during the entire period studied. Azotobacter vinelandii cysts cultivated on phosphate-sufficient media. Although cell protein and nucleic acids were unaffected by phosphate deficiency, cell wall structures, oxygen uptake and sncystment were significantly affected. Phosphate-limited cysts contained much larger amounts of poly-beta-hydroxybutyric acid but had a lower adenylate energy charge than did control cysts. The ATP/ADP ratio was much lower in phosophate-deficient cysts than in the control cysts. The data indicate a "substrate saving" choice of three metabolic pathways available to cells of Azotobacter under different growth conditions.
Date: December 1980
Creator: Aladegbami, Solomon L.
System: The UNT Digital Library
The Acute Toxic Effects of the Synthetic Cannabinoid, JWH-018 on the Cardiovascular and Neuroendocrine Systems in Ictalurus punctatus (Channel Catfish) (open access)

The Acute Toxic Effects of the Synthetic Cannabinoid, JWH-018 on the Cardiovascular and Neuroendocrine Systems in Ictalurus punctatus (Channel Catfish)

Cannabinoid (CB) receptors have been found in most vertebrates that have been studied. The location of various CB receptors in the body and brain are known, but their physiological functions are not fully understood. The effects CBs have on the cardiovascular system have been of growing interest in recent years. Increasing reports from emergency departments and law enforcement agencies detail acute cardiovascular and psychological effects from synthetic CB intoxication, such as JWH-018. This major health concern is substantiated by governmental agencies like the CDC and NIDA. This pilot study investigates the acute toxic effects of the synthetic CB, JWH-018, on the cardiovascular and neuroendocrine systems in Ictalurus punctatus (channel catfish). Research in organisms besides the traditional mammal models can provide new insights into CB function and physiology. Ictalurus punctatus lend multiple benefits as a model organism that permits researchers to investigate in vivo effects of both cardiovascular and neuroendocrine systems without much influence from traditional sampling methods, and further more provide ample size and tissue to perform specific cardiovascular experiments. Multiple methods were used to assess cardiovascular function and sympathetic nervous system activation. Two different doses, low (500 µg/kg) and high 1,500 µg/kg, of JWH-018 were evaluated in the study. …
Date: August 2017
Creator: Taylor, Dedric Esmond
System: The UNT Digital Library

Traffic-Generated Air Pollution-Exposure Mediated Expression of Factors Associated with Progression of Multiple Sclerosis in a Female Polipoprotein E Knockout Mouse Model

Environmental air pollution is one risk factor associated with the onset and progression of multiple sclerosis (MS). In this project, we investigated the effects of ubiquitous traffic-generated pollutants, namely a mixture of gasoline and diesel vehicle exhaust (MVE), on signaling pathways associated with the pathophysiology of MS in the central nervous system (CNS) of either ovary intact (ov+) or ovariectomized (ov-) female Apolipoprotein (Apo) E-/-. Specifically, we investigated whether a subchronic inhalation exposure to MVE (200 PM μg/m3; 6 hr/d, 7d/wk, 30d) vs. filtered air (FA) controls altered myelination, T cell infiltration, blood-brain barrier (BBB) integrity, or production of reactive oxygen species (ROS) and expression of neuroinflammation markers in the CNS ov+ and ov- Apo E-/- mice. Our results revealed that inhalation exposure to MVE resulted in increased demyelination and CD4+ and CD8+ T cell infiltration, associated with alterations in BBB integrity. Disruption of the BBB was evidenced by decreased tight junction (TJ) protein expression, increased matrix metalloproteinase (MMPs) activity, and increased permeability of immunoglobin (Ig) G, which were more pronounced in the MVE ov- group. Moreover, MVE-exposure also promoted ROS and neuroinflammatory signaling in the CNS of ov+ and ov- mice, compared to FA groups. To analyze mechanisms that …
Date: December 2020
Creator: Adivi, Anna
System: The UNT Digital Library
Transgenerational Responses to Environmental Stressors in Vertebrates: From Organisms to Molecules (open access)

Transgenerational Responses to Environmental Stressors in Vertebrates: From Organisms to Molecules

Genomic modifications occur slowly across generations, whereas short-term epigenetic transgenerational inheritance of adaptive phenotypes may be immediately beneficial to large numbers of individuals, acting as a bridge for survival when adverse environments occur. In this study we used dietary exposure to crude oil as an example of an environmental stressor to assess its effects from the molecular to the organismal levels in piscine and avian animal models. In addition, we assessed the role of the parental exposures on their offspring F1 generation. The research developed in this dissertation has contributed to several areas of investigation including molecular biology, animal physiology, and evolutionary biology. The quantitative information from these studies may be utilized to supplement information regarding the proximate and ultimate effects of environmental stressors on fish and bird populations. Furthermore, this information may be used as additional support for understanding the conservation of the responses from the molecular to the whole organismal levels across the vertebrate taxa, as well as their implications for population survival and maintenance. Additionally, the zebrafish (Danio rerio), the Siamese fighting fish (Betta splendens) and the king quail (Coturnix chinensis) have proven to be excellent models to start building a strong basis for understanding the effects …
Date: December 2019
Creator: Martinez Bautista, Naim
System: The UNT Digital Library
Cellular Biomarkers for Measuring Toxicity of Xenobiotics: Effects of PCBs on Earthworm Lumbricus Terrestris Coelomocytes (open access)

Cellular Biomarkers for Measuring Toxicity of Xenobiotics: Effects of PCBs on Earthworm Lumbricus Terrestris Coelomocytes

The research presented herein provides information on coelomocyte (leukocyte) collection, function and immunotoxicity from polychlorinated biphenyls (PCB) in the earthworm Lumbricus terrestris. Research was undertaken as part of an overall goal to develop a well-documented and scientifically valid non-mammalian surrogate immunoassay with the earthworm Lumbricus terrestris to assess immunotoxic potential of xenobiotics. The principal objectives were to: (1) Develop an extrusion model for analyzing immunotoxicity of xenobiotics; (2) determine if coelomocytes can be collected repeatedly without obvious harm to the earthworm or change in immune response of the coelomocytes harvested and (3) validate the response sensitivity profiles of a panel of biomarkers {differential and total cell counts, erythrocyte rosette (ER) and secretory rosette (SR) formation with, and phagocytosis of antigenic rabbit red blood cells} in earthworms after acute exposure to a known mammalian and L. terrestris immunotoxin, the PCB Aroclor 1254.
Date: May 1991
Creator: Eyambe, George Sona
System: The UNT Digital Library
The Effect of Curcumin Supplementation on Physical and Biological Indices of Delayed Onset Muscle Soreness and Inflammation Following Muscle Injury (open access)

The Effect of Curcumin Supplementation on Physical and Biological Indices of Delayed Onset Muscle Soreness and Inflammation Following Muscle Injury

In this project, the effects of dietary polyphenols on exercise-induced muscle damage and vascular health are examined. Dietary polyphenols exert well-known anti-inflammatory effects; however, how these effects are realized with respect to vascular health and EIMD is relatively unknown. I begin by reviewing the available literature surrounding the impact of three dietary polyphenols (curcumin, catechins, and quercetin) on inflammation associated with EIMD. It is well established that their primary means of anti-inflammation is through alterations of NF-κB and AP-1 transcription activities. Given this, their inclusion into training strategies seems reasonable. Consistent evidence is presented making a case for the anti-inflammatory effects of dietary polyphenols following EIMD. I follow this review up by completing an in-depth study on the consumption of curcumin prior to EIMD. I found curcumin (1000 mg/day) can reduce subjective soreness and decrease inflammation compared to placebo controls. To further understand the effects of dietary polyphenols on health, I investigate the effects of a four-week supplementation period of cocoa (catechins) on vascular. I concluded that atherogenic risk in obese women is reduced after consumption of cocoa. In addition to these experimental projects, I developed two novel methods that can be used to investigate vascular health (EMP concentration) and …
Date: May 2015
Creator: Venable, Adam Steven
System: The UNT Digital Library
Effects of Trichinella Soluble Antigens on Macrophage Subpopulations (open access)

Effects of Trichinella Soluble Antigens on Macrophage Subpopulations

The immunomodulatory effects of Trichinella spiralis or Trichinella pseudospiralis soluble antigen extracts were examined in an effort to characterize the differences in immune responses seen during these Trichinella infections. The newborn larvae extracts of either parasite exhibited similar potency for stimulating macrophage PGE production; however, the muscle larvae extracts of T. pseudospiralis stimulated greater levels of PGE than did the muscle larvae extracts of T. spiralis. These data clearly indicate that Trichinella antigens possess immunomodulatory capabilities.
Date: August 1992
Creator: Dixon, Guy Cameron, 1960-
System: The UNT Digital Library

Investigating the Effects of Inhaled Diesel Exhaust Particles on Gut Microbiome, Intestinal Integrity, Systemic Inflammation, and Biomarkers of Cardiovascular Disease in Wildtype Mice

We investigated the hypothesis that exposure to inhaled diesel exhaust PM can alter the gut microbiome and intestinal integrity, thereby promoting systemic inflammatory response and early CVD risk, which are exacerbated by HF diet. Furthermore, we investigated whether the observed exposure and diet-mediated outcomes could be mitigated through probiotic treatment. We performed an exposure study on C57Bl/6 male mice, placed on either a low fat (LF) diet or a high-fat (HF) diet, and exposed via oropharyngeal aspiration to 35 μg diesel exhaust particles (DEP) suspended in 35 μl of sterile saline or sterile saline controls (CON) twice a week for four weeks. A subset of mice on HF diet were dosed with 0.3 g/day (PRO, ~7.5x108 CFU/day) of probiotic Ecologic® Barrier 849 (Winclove Probiotics) in drinking water during the course of the study. For our first aim, we investigated the alterations in the gut microbiome, measured circulating cytokines and lipopolysaccharide (LPS), and measured CVD biomarkers in the heart. Our results revealed that exposure to inhaled DEP results in gut dysbiosis characterized by expansion of the phyla Verrucomicrobia and Proteobacteria and reduction in Actinobacteria, which was exacerbated by HF diet. Probiotics mitigated the DEP-mediated expansion of Proteobacteria and re-established Actinobacteria in …
Date: December 2021
Creator: Phillippi, Danielle T.
System: The UNT Digital Library
Physiological Responses of Myriophyllum spicatum to Time Varying Exposures of Diquat, 2,4-D and Copper (open access)

Physiological Responses of Myriophyllum spicatum to Time Varying Exposures of Diquat, 2,4-D and Copper

The physiological responses of Myriophyllum spicatum to 2,4-D, diquat and copper were quantified using a plant tissue viability assay, and daily measures of dissolved oxygen and pH. Correlations of herbicide tissue residues to physiological response measures were determined and the relationship was used to develop exposure-response models. Diquat and copper had a greater effect on plant tissue viability than was observed for 2,4-D. Diquat produced greater reductions in dissolved oxygen concentrations and pH values than 2,4-D or copper. Copper exposure had the least effect on these parameters. Exposure-response models developed for 2,4-D predicted effective control at plant tissue residues ranging from 4000 to 4700 mg/kg. Aqueous exposure concentrations necessary to produce effective control plant tissue residues ranged from 0.20 to 0.40 mg/L. Exposure-response models developed for diquat predicted effective control at plant tissue residues ranging from 225 to 280 mg/kg. Aqueous exposure concentrations necessary to produce effective control plant tissue residues ranged from 0.113 to 0.169 mg/L. Exposure-response models developed for copper predicted effective control at plant tissue residues ranging from 680 to 790 mg/kg. Aqueous exposure concentrations necessary to produce effective control plant tissue residues ranged from 0.32 to 0.64 mg/L. Model predictions for 2,4-D, diquat and copper were …
Date: May 1988
Creator: Rocchio, Patricia Mary
System: The UNT Digital Library
Systematics of Coccidian Parasites (Apicomplexa) from Amphibians and Reptiles in Northcentral Texas (open access)

Systematics of Coccidian Parasites (Apicomplexa) from Amphibians and Reptiles in Northcentral Texas

Between February 1986 and October 1988, 863 amphibians and reptiles were collected in northcentral Texas and examined for coccidial parasites. Thirteen percent of amphibians <26% salamanders, 11% frogs and toads) and 28% of reptiles (54% turtles, 25% snakes) harbored 20 previously described and 16 new species of coccidia; overall prevalence of infection was 176/863 < 20%). Sixteen Ambvstoma texanum were infected with Eimeria ambystomae which represents new host and geographic locality records for the coccidium. Forty anurans were found to be passing coccidia, including Pseudacris streckeri. Bufo valliceos and Gastrophryne olivacea. Four new species of coccidia were described from anurans and include Eimeria flexuosa. E. streckeri. Isospora dellcatus and I_. fraaosum. However, oocysts found in B. v.. valliceps were determined experimentally to represent pseudoparasites. Sixty-eight turtles were infected with coccidia, including Chelvdra serpentina, Kinoeternon flavescens. Pseudemvs texana. Terrapeng ornata and Trachemvs scripta eleoans. Fourteen eimerians (5 of which are described as new species) were found in turtles. The new species from turtles include Eimeria cooteri, E. ornata, E. Btvlosa. E. texana and E. trachemvdis. Interestingly, all 96 lizards examined were negative for coccidia. Fifty-three snakes including 11 colubrids and 1 viperld harbored coccidia of the genera Caryospora. Cryptosporidium. Eimeria and …
Date: December 1989
Creator: McAllister, Chris Thomas
System: The UNT Digital Library
Understanding Microbial Biodegradation of Environmental Contaminants (open access)

Understanding Microbial Biodegradation of Environmental Contaminants

The accumulation of industrial contaminants in the natural environments have rapidly become a serious threat for human and animal life. Fortunately, there are microorganisms capable of degrading or transforming environmental contaminants. The present dissertation work aimed to understand the genomic basis of microbial degradation and resistance. The focus was the genomic study of the following bacteria: a) Pseudomonas fluorescens NCIMB 11764, a unique bacterium with specific enzymes that allow cyanide adaptation features. Potential cyanide degradation mechanisms found in this strain included nit1C cluster, and CNO complex. Potential cyanide tolerance genes found included cyanide insensitive oxidases, nitric oxide producing gene, and iron metabolism genes. b) Cupriavidus sp. strain SK-3 and strain SK-4. The genome of both bacteria presented the bph operon for polychlorinated biphenyl (PCB) degradation, but we found differences in the sequences of the genes. Those differences might indicate their preferences for different PCB substrates. c) Arsenic resistant bacterial communities observed in the Atacama Desert. Specific bacteria were found to thrive depending on the arsenic concentration. Examples were Bacteroidetes and Spirochaetes phyla whose proportions increased in the river with high arsenic concentrations. Also, DNA repair and replication metabolic functions seem to be necessary for resistance to arsenic contaminated environments. Our …
Date: May 2015
Creator: Vilo Muñoz, Claudia Andrea
System: The UNT Digital Library

Regulation of Receptors in Neuronal Cilia with Development, Seizures, and Knockouts: Implications for Excitability

Neurons commonly have a primary cilium, which is a non-motile organelle extending from the centrosome into the extracellular space. In most brain regions, neuronal cilia are enriched in either somatostatin receptor type 3 (SstR3) or melanin concentrating hormone receptor type 1 (MCHR1), or both. The present immunohistochemical study provides novel evidence that primary cilia regulate neuronal excitability via G-protein coupled receptors (GPCRs), and that their identity is governed by brain region and by competition, both in adulthood and in postnatal development. The hippocampus, which is particularly vulnerable to seizures, has opposing gradients of SstR3(+) and MCHR1(+) ciliary GPCRs. We hypothesized that there is a competition between these two ciliary GPCRs, which might take place on any level from gene expression to presence in the cilium. We examined whether receptor colocalization occurs transiently in development before ciliary GPCR dominance is established in neurons in the CNS. In postnatal CA1 and CA3, the first GPCR to appear in cilia was the one that will dominate in adults: MCHR1 in CA1 and SstR3 in CA3. Some days later, the second GPCR was expressed along with the first; dual-receptor cilia were the exclusive type until single-receptor cilia emerged again around P14. Single-receptor cilia then …
Date: August 2022
Creator: Shrestha, Jessica
System: The UNT Digital Library
Cardiovascular Fetal Programming in Quail (Colinus virginianus), An Avian Comparative Model (open access)

Cardiovascular Fetal Programming in Quail (Colinus virginianus), An Avian Comparative Model

The consequences of early embryonic insults and how they affect subsequent life reflects the emerging concept of "fetal programming". The aim of this project is to study the effects of embryonic insults as they subsequently manifest themselves in adults, with emphasis on the heart and vasculature. My experiments establish that fetal programming operates on the bobwhite quail inducing similar changes as those observed in mammalians and other birds. The quail's fast development provides reliable data in a short period of time than other avian models (e.g. domestic chicken). Data on quail showed a correlation between egg mass and hatchling mass; where small eggs produce small hatchlings but a high mortality made it impractical as a stressor for this study. Hypoxia was used as a stressor during embryonic incubation, where it induced a low hatching weight in quail that was not observable in adult birds. Morphological measurements demonstrated an increased ventricular collagen content and reduced ventricular lumen in birds in adults incubated in hypoxia consistent with hypertension. The hematological analyzes showed few differences indicating organ remodeling instead of hematopoietic compensation. The assessment of vascular reactivity pointed out an impaired endothelium dependent relaxation commonly associated to hypertension in birds and mammals. Fetal …
Date: December 2016
Creator: Flores Santin, Josele R.
System: The UNT Digital Library
Key Factors Influencing Retention Rates among Historically Underrepresented Student Groups in STEM Fields (open access)

Key Factors Influencing Retention Rates among Historically Underrepresented Student Groups in STEM Fields

The aim of the study was to identify the factors that have an influence on the completion rates of undergraduate students in the fields of science, technology, engineering and mathematics (STEM). Using Tinto's retention rate theory as the theoretical foundation, data were collected from freshman who were enrolled in the years 2005 to 2008. Results showed gender and first-generation status were significant predictors of STEM completion and time taken to complete the degree. Institutional bias played a role in race/ethnicity not being a factor affecting completion rates, as this study was conducted at a Predominantly White Institution. SAT scores and first and second-year college GPA showed to have the most prominent influence on both STEM completion rate and time taken to complete the degree. Females with higher first-year college GPA and higher high school rank finished faster. Similar results were found with first-generation students as well. Students belonging to ethnic minority groups with higher SAT scores and college GPA had greater success in STEM fields as well. The study results can be used to increase completion rates of underrepresented students in the STEM fields, given what we know about the interactions between underrepresented student groups and the most important predictors.
Date: December 2018
Creator: Premraj, Divya
System: The UNT Digital Library

The Developmental Physiology of the Zebrafish: Influence of Environment and Cardiovascular Attributes

Access: Use of this item is restricted to the UNT Community
Temperature effects on the development of the zebrafish embryos and larvae and adults were examined. It was found that the earlier in development a temperature change was performed on an embryo, the more significant the change in survival and/or subsequent development. Thus, viable temperature ranges for zebrafish widened significantly as development proceeded. Adults reared and bred at 25oC produced embryos that were significantly more successful at the lower range of rearing temperatures compared to embryos produced from adults reared at 28oC. The majority of this study focused on the physiological effects of swim training during development in the zebrafish. The earlier in development the zebrafish larvae were trained, the greater the mortality. Trained free swimming larvae had a significantly higher routine oxygen consumption after 11 days of training, and a higher mass specific routine metabolic rate after 8 and 11 days of training. Trained free swimming larvae consumed significantly less oxygen during swimming and were more efficient at locomotion, compared to control larvae. Training enhanced survival during exposure to extreme hypoxia in all age groups. Performance aspects of training were investigated in attempt to quantify training effects and in most cases, trained fish performed significantly better than controls. As blood …
Date: August 2001
Creator: Bagatto, Brian
System: The UNT Digital Library
Benthic Macroinvertebrates of Temperate, Sub-Antarctic Streams: The Effects of Altitudinal Zoning and Temperature on the Phenology of Aquatic Insects Associated to the Robalo River, Navarino Island (55°S), Chile (open access)

Benthic Macroinvertebrates of Temperate, Sub-Antarctic Streams: The Effects of Altitudinal Zoning and Temperature on the Phenology of Aquatic Insects Associated to the Robalo River, Navarino Island (55°S), Chile

The Cape Horn Biosphere Reserve, within the remote Sub-Antarctic ecoregion is a reservoir of expressions of biological and cultural diversity. Although it is considered one of 24 wilderness areas remaining in the world, it is not free from local and global threats, such as invasive species, and climate change. Field biologists and philosophers associated to the Sub-Antarctic Biocultural Conservation Program and the Omora Ethnobotanical Park, have worked to describe the region’s biocultural diversity, linking ecological and philosophical research into education, ecotourism, and conservation, through a methodology called field environmental philosophy (FEP), which integrates ecological sciences and environmental ethics through a 4-step cycle consisting of: 1) interdisciplinary research; 2) composition of metaphors; 3) design of field activities with an ecological and ethical orientation; and 4) implementation of in situ conservation areas. In this context, the purposes of this dissertation were to: 1) provide a comprehensive review of publications regarding the conservation status of aquatic and terrestrial insects at a global scale and with an emphasis in southern South America; 2) study the distribution of benthic macroinvertebrates through the sharp altitudinal gradient of the Róbalo River watershed; 3) describe the life histories of Gigantodax sp (Simuliidae: Diptera) and Meridialaris chiloeense (Leptophlebiidae: Ephemeroptera) …
Date: December 2011
Creator: Contador Mejías, Tamara Andrea
System: The UNT Digital Library
Toxicological Characterization of Trinity River Sediments (open access)

Toxicological Characterization of Trinity River Sediments

Sediments in the Trinity River were chemically, physically and biologically characterized and assessed for toxicity. Laboratory bioassays were conducted to identify sediments which induced toxic responses in test organisms and to document these responses through time. Metal and organic contaminant concentrations in bottom sediments were measured. Relationships between these concentrations and biological responses observed in laboratory bioassays were determined. Toxicity identification / reduction methods were used to characterize sediment toxicants. Sediment oxygen demand was also measured in resuspended and undisturbed bottom sediments through time. The Background Sediment Chemistry Approach and the Sediment Bioassay Approach were used to assess sediment quality. Sediment toxicity was observed in whole sediment bioassays using Chironomus tentans as the test species. A relationship between sediment contaminant concentration and toxicity was observed in approximately sixty percent of the sediments. Oxygen demand of resuspended sediments was elevated in sediments at two locations on the river. Oxygen demand of undisturbed sediments was elevated at one location on the river. Characterization of sediment toxicants was conducted using EDTA, pH, and carbon treatments and manipulations of the sediments. Aeration tests were also used to evaluate the contribution of volatile organic contaminants to observed toxicity.
Date: December 1989
Creator: Hall, Jerry F. (Jerry Fowler)
System: The UNT Digital Library
Reproduction and Metabolic Responses to Acute and Chronic Hypoxia in Ovoviviparous Blaberid Cockroaches, with a Focus on Blaptica dubia (open access)

Reproduction and Metabolic Responses to Acute and Chronic Hypoxia in Ovoviviparous Blaberid Cockroaches, with a Focus on Blaptica dubia

The major components of the tracheal system of insects are an extension of the exoskeleton, and the size of the exoskeleton is fixed in the adult stage, so any increase in metabolic demand that may accompany reproduction must be met by a relatively unaltered tracheal system that the female set in place at ecdysis, when entering adulthood. Acute hypoxia tends to elicit an increase in ventilation in insects, and here, I observe increased interburst VCO2 release, and a tendency towards a more continuous gas exchange pattern being preferred over discontinuous gas exchange when Blaptica dubia and Eublaberus posticus are exposed to a descending regime of hypoxia. Additionally, higher temperatures appear to increase sensitivity to hypoxia in these species, an expected result because both species, like most ectothermic animals, display a Q10 effect, increasing metabolic rates as temperature increases. The reproductive mode of B. dubia is considered to be lecithotrophic pseudoviviparity (or type A ovoviviparity), and by the time the embryos are born, they have more than doubles in volume from the time of oviposition. This gain is apparent in the wet mass of the embryo, with no change occurring in dry mass. The egg mass that can be attributed to …
Date: August 2017
Creator: Mallery, Christopher Sean
System: The UNT Digital Library