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open access

Biological and Toxicological Responses Resulting from Dechlorination of a Major Municipal Wastewater Treatment Plant Discharge to the Trinity River

Description: Federal regulations such as the Clean Water Act (P.L. 92-500), and its amendments, direct the Environment Protection Agency (EPA) to implement programs to control the releases of conventional pollutants and toxics into the waterways of the United States. The EPA began requiring treatment plants to conduct toxicity tests (biomonitoring) of their effluent discharges. To control toxicity caused by chlorination of wastewater discharges, the EPA also began requiring some treatment facilities to dech… more
Date: August 1995
Creator: Guinn, Richard J. (Richard Joe)
open access

Effects of External Electric Fields on Light Transmittance in Isolated Crayfish Nerves

Description: Acute effects of a pulsed external electric field (PEEF) at 20 V/cm and a d.c. EEF at 90 V/cm on light transmittance in an isolated compound crayfish nerve was measured. In a third series, the nerve was pre-treated with the Na+ channel blocker tetrodotoxin (TTX). A PEEF produced an irreversible increase in the variation of light transmittance in normal nerves but a reversible increase in TTX treated nerves. This data was statistically insignificant. The d.c. EEFs produced a reversible and stati… more
Date: December 1995
Creator: Northcutt, Brian S. W.
open access

GABAᴀ Receptors in Rat Whisker Barrel Cortex: Effects of Sensory Deprivation

Description: The GABAergic system in adult sensory cortex is affected by sensory deprivation, but little is known about how this predominant inhibitory system is affected during ontogeny. The present study investigates developmental effects of whisker trimming on GABAa receptors in rat barrel cortex. Rats trimmed for 6 wk beginning at birth and adulthood showed similar decreases in [3H]muscimol binding in deprived relative to non-deprived barrels, suggesting absence of a critical period.
Date: August 1995
Creator: Salazar, Eduardo, 1962-
open access

Heat Shock Proteins in Ascaris suum

Description: Ascaris suum were exposed to a number of stressors, including heavy metals and both high (40°C) and low (18°C) temperatures. The 70kD and 90kD heat shock proteins (HSPs) in the different A. suum tissues were analyzed by Western blot and quantitated by Macintosh Image Program.
Date: August 1995
Creator: Chao, Sheng-Hao
open access

The Life History and Ecology of Camelobaetidius Mexicanus (Ephemeroptera: Baetidae) from Honey Creek, Oklahoma

Description: The primary objective of this study is to describe the life history of Camelobaetidius mexicanus living in Honey Creek in south central Oklahoma. Specific objectives were to determine emergence phenology and behavior, describe nupital flight and female oviposition, measure subimaginal and imaginal life spans, examine egg morphology and time to hatching, describe larval microdistribution, analyze gut contents and to determine voltinism from nymphal head capsule widths and adult emergence.
Date: August 1995
Creator: Wagner, Paul F.
open access

Pyrimidine Salvage Enzymes in Microorganisms: Labyrinths of Enzymatic Diversity

Description: Pyrimidine salvage pathways are essential to all cells. They provide a balance of RNA synthesis with the biosynthetic pathway in pyrimidine prototrophs and supply all the pyrimidine requirements in auxotrophs. While the pyrimidine biosynthetic pathway is found in almost all organisms and is nearly identical throughout nature, the salvage pathway often differs from species to species, with aspects of salvage seen in every organism. Thus significant taxonomic value may be ascribed to the salvage … more
Date: December 1995
Creator: Beck, Debrah A. (Debrah Ann)
open access

Quantitative Analysis of the Gabaergic System in Cat Primary Somatosensory Cortex and Its Relation to Receptive Field Properties

Description: Sensory neocortex contains a significant number of inhibitory neurons that use gamma-aminobutyric acid (GABA) as their neurotransmitter. Functional roles for these neurons have been identified in physiological studies. For example, in primary somatosensory cortex (SI), blockade of GABAa receptors with bicuculline leads to expansion of receptive fields (RFs). The magnitude of RF enlargement varies between SIpopulations of GABAergic neurons were identified by labeling specific calcium binding pro… more
Date: May 1995
Creator: Li, Jianying
open access

Regulation of Escherichia coli pyrBI Gene Expression in Pseudomonas fluorescens

Description: Pseudomonas fluorescens does not appear to regulate the enzymes of de novo pyrimidine biosynthesis at the level of gene expression. Little or no apparent repression of pyr gene expression is observed upon addition of exogenous pyrimidines to the growth medium. The Escherichia coli pyrBI genes for aspartate transcarbamoylase (ATCase) were sized down and cloned into the broad host range plasmid, pKT230. Upon introduction into a P.fluorescenspyrB mutant strain, ATCase showed repression in response… more
Date: May 1995
Creator: Shen, Weiping
open access

A Two Semester Life Science Syllabus for Use in Texas Public Schools with Seventh Grade Students

Description: The problem of using a state adopted textbook written to apply to a large body of students with varying interests and needs was overcome by using a detailed syllabus that arranged course content in a meaningful sequence that appealed to student interest. The outlined syllabus prepared a two semester life science curriculum to be used by the teacher to guide lesson planning. Both semesters were divided into three units each. Materials included in the syllabus were given to actual student groups … more
Date: May 1995
Creator: Edwards, Gail G. (Gail Graham)
open access

Upper and Lower Temperature Tolerances of Three Freshwater Game-Fish Species Exposed to Cycling Temperatures

Description: A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values genera… more
Date: August 1995
Creator: Currie, Rebecca J. (Rebecca Jean)
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