Opioid/adrenergic interactions were studied to evaluate two hypotheses: (1) naloxone potentiates the effect of epinephrine on cardiac contractility by increasing circulating epinephrine concentrations; and (2) endogenous and exogenous opioids alter left cardiac nerve stimulationinduced norepinephrine release and cardiac function. A canine isolated heart-lung preparation was used for the first study. Plasma epinephrine was determined and myocardial epinephrine uptake was calculated during intravenous epinephrine infusion. Naloxone (4 mg) was given and the epinephrine infusion was repeated. Naloxone increased cardiac contractility, coronary blood flow, and the coronary sinus epinephrine concentration. When coronary blood flow was subsequently held constant (100% above resting), naloxone increased only contractility. This result indicated that the previously observed increase in coronary sinus epinephrine was flow dependent. Corticosterone (an uptake II blocker) was employed as a positive control. Corticosterone increased the contractile response to epinephrine, but unlike naloxone, corticosterone was accompanied by a clear decrease in myocardial epinephrine uptake. The stereospecificity of the response to naloxone was investigated and (+) naloxone equaled or exceeded (-) naloxone in potentiating the inotropic effect of epinephrine. In the second study, the left cardiac nerve was isolated and electrically stimulated in intact dogs. Norepinephrine overflow gradually declined during successive control stimulations. Pretreatment with …

Serotonin (5-hydroxytryptamine, 5-HT) has been shown to activate carbohydrate metabolism in adult female Ascaris suum. Serotonin may be either absorbed directly from the environment or synthesized de novo from the absorbed L-tryptophan in adult female A. suum. The enzymes necessary for the synthesis of 5-HT have been identified in both intestine and muscle tissues. The serotonin absorbed from the environment is obtained either from the host's gastrointestinal contents or from the 5-HT producing bacteria in the intestine of A. suum. Numerous 5-HT producing bacteria were identified in the intestinal microflora. The physiological contributions of 5-HT producing bacteria to the 5-HT level, turnover and binding sites in the intestinal tissue of A. suum were investigated.

Wetland wastewater treatment offers low-cost, energy efficient alternatives to conventional wastewater technologies. In this study, an artificial wetland was constructed at the City of Denton, Texas Pecan Creek Water Reclamation Plant to facilitate diazinon removal from treated effluent.

Excessive nutrient loading of natural and artificial lakes has led, in some systems, to plethoric algal and aquatic macrophyte growth which can result in aesthetic degradation and undesirable tastes and odors. It would be advantageous to have some indication of the potential trophic status of a reservoir before it is filled. An objective of this study was to assess the water quality and nutrient loading potential of the tributaries entering Ray Roberts Lake, a large reservoir located in north central Texas. Samples from a maximum of thirteen sites were collected on the Elm Fork, Trinity River, Isle duBois Creek, and five additional tributaries. Data were also collected during six storms, from atmospheric deposition collectors, and from soil-water microcosms. The relationship between watershed landuse and mean water nutrient concentrations was evaluated. Significant differences will exist between the two major arms of Ray Roberts Lake: Elm Fork, Trinity River and Isle duBois Creek. While the majority of the annual phosphorus and nitrogen load entering both tributaries is coming from overland flow, the proportion is higher in Isle duBois Creek. Point sources in the Elm Fork contribute a larger percentage of the bioavailable phosphorus, which is significantly greater than in Isle duBois Creek. …

The feeding ecologies of leaf pack-associated systellognathan stoneflies were examined from 6 June 1980 21 May 1981. Species composition, seasonal abundance, nymphal growth, feeding habits and mouthpart morphology were determined for the eight dominant stonefly species. Prey preferences and predator-prey size relationships were also examined for omnivorous and carnivorous species. Foregut analysis from 2860 individuals indicated opportunistic feeding on the most abundant prey insects, usually in proportion to prey frequency. Feeding preference studies generally indicated random feeding on major prey groups. Prey and predator sizes were usually highly correlated (p<0.01), with predators expanding their prey size thresholds with growth. The potential for competition between sympatric stoneflies for prey is discussed.

Adult stonefly emergence, nymphal growth, drift and microdistribution were examined in Battle Branch, a secondorder, spring-fed stream, from November, 1982 to May, 1984. Adults of 22 species emerged successionally, with specific adults present every month. Searching emergent objects and the stream margin was best for collection of winter and early spring emerging species. Sweeping the streamside and light trapping were most efficient for late spring and summer emerging species. Nymphal growth for nine abundant species generally fit double log or semilog models. Drift was low, but did show a post-sunset pulse. Generally, leaf material was found to be significantly related (p<O.001) to density, diversity and biomass of stoneflies in Battle Branch.

In this study, high-performance liquid chromatography (HPLC) was employed to detect and quantify pyrimidine salvage enzymes by monitoring the disappearance of substrates or formation of products.

In recent years there has been a great deal of scientific interest in processes that affect the fate of organic chemicals in the environment. one main reason for this increased interest is due to greater environmental concern over accidental or purposeful release of these chemicals into the environment by man. A major environmental concern is the increased use of pesticides over the last few years. In the thirty years prior to 1978 the use of pesticides has increased by a factor of forty (Ridgeway et al., 1978). Recently the use of herbicides has been increasing, but that of insecticides has stabilized (Willis, 1983). Detectable amounts of organic pesticides can be found in many areas of the biosphere. For toxic organic chemicals to be used safely, researchers must have a clear understanding of the fate and persistence of these chemicals when they are released into the environment. This understanding will also allow the development of new products that, when properly used, will not produce adverse effects to man or the environment (Weber, 1972). According to the Toxic Substance Control Act (TSCA) any new or expanded-use chemical that might be released into the environment must be tested for environmental hazard.

A comparative study was made of environmental variables and the density, biomass, diversity, and species composition of macroinvertebrates in areas downstream from a dam with a hypolimnetic release (Hungry Horse Dam on the Flathead River) and a dam with a selective withdrawal system (Libby Dam on the Kootenai River). A major objective of this study was to examine the response of macroinvertebrate communities to defined environmental gradients in temperature, flow, substrate, and food-related variables (periphyton, particulate organic carbon in the seston). In addition, the effects of experimental manipulations in discharge on macroinvertebrate drift and stranding were assessed, and the effects of temperature on the growth rates and emergence of five species of insects were measured.

Chronic ventricular sympathectomy elicits changes in the coronary circulation, myocardial oxygen consumption and size of infarction resulting fromcoronary occlusion. These changes indicate a change occurring in the basic metabolism of the heart in response to the removal of its sympathetic nervous input. This hypothesis was tested using two groups of dogs, a shamoperated control and a ventricular sympathectomized group. The sympathectomy procedure was an intrapericardial surgical technique which selectively removes ventricular sympathetic input. Four weeks after surgery, left ventricular tissue samples were obtained and rapidly frozen to -80°C. Selected metabolic variables were then compared between the two groups.

The clcD gene encoding dienelactone hydrolase (DLH) is part of the clc gene cluster for the utilization of the B-ketoadipate pathway intermediate chlorocatechol. The roles that individual amino acids residues play in catalysis and binding of the enzyme were investigated. Using PCR a 1.9 kbp clcD fragment was amplified and subcloned yielding a 821 bp BamHi to ZscoRI subclone in the plasmid pUC19.

Respiratory and metabolic patterns in response to variations in exercise workload (WL) and pedal frequency (RPM) were examined in 10 healthy males. Each subject performed WLs of low (L), moderate (M) and high (H) intensity, equivalent to 25%, 50% and 75% V02 m a x at 7 pedal frequencies (40, 50, 60, 70, 80, 90 and 100 RPM). ANOVA ( 3 X 7 design) indicated that WL and RPM had independent and significant effects on all respiratory and metabolic measures; i.e., the greater the WL and RPM, the higher the HR, V02, VC02, Ve, Fb, Vt, Vt/Ti, Vt/Te and Ti/TtQt and the lower the Ti and Te. However, analysis of the interaction effect revealed different response patterns for Fb, Vt, Ti, Vt/Ti, Vt/Te and Ve among the WLs. During L-WL, increases in RPM produced increases in Ve which were due to progressive increases in both Fb and Vt. However, during M-WL and H-WL, increases in RPM produced increases in Ve which were accomplished by a constant Vt and a progressive increase in Fb. My findings suggest that during low WLs, the signal for Vt is dependent on rate of contraction, while during M-WL and H-WL, the signal for Vt appears …

Aspartate transcarbamoylase (ATCase) of Streptomyces was characterized and its interaction with other pyrimidine enzymes explored.

Simultaneous size fractionation of plankton populations associated with NaH^14CO_3 and ^3H-glucose uptake was employed in eutrophic Lake Texoma (Texas and Oklahoma) and oligotrophic Flathead Lake (Montana). Autoradiography was utilized to determine the role of specific microorganisms in community metabolism. Ultraplankton (0.45-10 μm) dominated plankton numbers and metabolic activity in both aquatic systems. Many of the most abundant species were not the most productive, in terms of inorganic C fixation. Rates of heterotrophic uptake of ^3H-glucose were small in comparison to photolithotrophic uptake in both lakes, Photoheterotrophy was more extensive in Flathead Lake, Autoradiographs indicated that bacteria were responsible for observed photoheterotrophy. Oscillatoria sp. exhibited. mixotrophy in Lake Texoma,

Aspartate transcarbamoylase (ATCase; encoded by pyrBI genes) is one of the most studied regulatory enzymes in bacteria. It is feedback inhibited by cytidine triphosphate (CTP) and activated by adenosine triphosphate (ATP). Much is known about the catalytic site of the enzyme, not nearly as much about the regulatory site, to which CTP binds. Until now a positive selection for feedback-modified mutants was not available. The selection we have developed involves the use of a pyrA deletion in S. typhimurium. This strain lacks carbamoylphosphate and requires both a pyrimidine and arginine for growth. In this strain citrulline is used to satisfy the pyrimidine and arginine requirements. The minimal flow through the pyrimidine pathway from the citrulline-produced carbamoylphosphate is exquisitely sensitive to feedback control of ATCase by CTP. By elevating the CTP pool, via exogenous cytidine, in a strain that also contains a cytidine deaminase mutant (cdd) growth can be stopped completely, indicating 100% inhibition. It was therefore possible to measure in vivo feedback inhibition of ATCase among the citrulline users and to isolate a family of ATCase regulatory mutants with either modified or no response to effectors.

The physiological characteristics and organization of cat primary somatosensory cortex (SI) were studied in electrophysiological and anatomical experiments. In single cell recording experiments, quantitatively controlled mechanical stimuli were used to examine the responses of SI cortical neurons to the velocity component of skin or hair displacement. The firing frequency of most rapidly adapting neurons increased as stimulus velocity was increased. Rapidly adapting neurons were classified based on their response patterns to constant-velocity ramp stimuli. Neurons in these classes differed significantly in sensitivity to stimulus velocity and amplitude, adaptation rate, and spontaneous firing rate. The results suggest that frequency coding of stimulus displacement velocity could be performed by individual SI rapidly adapting neurons, and that the classes of rapidly adapting neurons may play different roles in sensation of tactile stimuli. Tract-tracing experiments were used to investigate the ipsilateral corticocortical connections of areas 3b and 2 in SI. Different patterns of connections were found for these areas: area 2 projects to areas 3b, 1, 3a, 5a, 4 and second somatosensory cortex (SII), and area 3b projects to areas 2, 1, 3a and SII. To further compare the organization of these areas, the thalamic input to the forepaw representation within each area was …

The biosynthesis of pyrimidines in Pseudomonas putida was investigated. In this study, pyrimidine requiring mutants were isolated by conventional mutagenesis and enrichment. The strains required exogenously supplied pyrimidines for growth and were found by enzyme assays to be deficient for the product of the pyrB gene encoding the enzyme aspartate transcarbamoylase. None of the intermediates of the pathway could supply the auxotrophic requirement of the strain; only preformed pyrimidines, metabolized via salvage pathways could suffice. Pyrimidine limitation in the mutant caused a slight but significant fifty per cent increase in expression of all the de novo biosynthetic enzymes. Pyrimidine starvation's effect on nucleotide pool levels was examined in the mutant and caused a marked swelling of the purine nucleotide pools.

Several biomarkers (cell viability and phagocytosis) based on earthworm (Lumbricus terrestris) immune cells (coelomocytes), together with whole-worm mortality (LC/LD50's), were used to assess a bioremediation attempt to reduce pentachlorophenol (PCP) toxicity in a former wood processing hazardous waste site (HWS).

In translational research, disease models in preclinical studies are used as media for discovery of drugs or novel therapeutics. Development of in vitro models for various neurological diseases that enable efficient pharmacological or toxicological screening has been ongoing but challenging. Recognizing the potential benefit of in vitro disease models, dysfunctions in the cortical neuronal networks were induced to mimic the functional pathology of neurological symptoms using microelectrode arrays. Two different disease states – tinnitusand excitotoxicity – were investigated and discussed. In this model, pentylenetetrazol-induced increase in spontaneous firing rate and synchrony in the auditory cortical networks was used as correlate of tinnitus. Potential tinnitus treatment drugs from several different classes – including the novel class of potassium channel openers – were screened and quantified. The potentialtherapeutic values of these drugs were also discussed as the basis for drug repurposing. Functional excitotoxicity was induced by cisplatin (a cancer drug that causes neurological sideeffects) and glutamate (the major excitatory neurotransmitter). As proof-of-principle that the model may contribute to expediting the development of therapeutics, cisplatin excitotoxicity wasprevented by the antioxidant D-methionine, while glutamate excitotoxicity was prevented by ceftriaxone (a modulator of a glutamate reuptake transporter). In the latter part of the study, with …

This investigation studied the physiological means by which myocardium can survive and function properly when oxygen supply is limited and cannot initially match oxygen demand. The effects of isoproterenol (ISO) stimulations during low coronary perfusion pressure or hypoxemia on myocardial oxygen demand, work, and oxygen utilization efficiency were investigated.

The lumbar motor activity in isolated spinal cords of 72 postnatal Balb/C mice aged 2, 5, 10 and 21 days (PN2-21) was electroneurographically recorded (ENG) via bilateral ventral roots following treatment with three different concentrations (25, 100 and 200 pM) of the neurotransmitter, 5-hydroxytryptamine (5-HT), i.e., serotonin, to determine its effects on spinal pattern generation.

General objectives of my study were to describe the reproductive ecology of gray gulls in the large Lealtad colony, with emphasis on demographic parameters and physiological adaptations of eggs and chicks, which would complete some original objectives established in the early 1980's by Guerra and Fitzpatrick. Specifically, my study focused on describing, then comparing with other desert and non-desert nesting larids, interactive effects of ambient physical conditions and nest-site predation on eggs and chicks.

The objective of this research was to determine if physical and microbial sediment characterizations could be used to explain benthic macroinvertebrate distribution in two branches of Lake Ray Roberts, Texas.

Twenty-two natural populations of the red shiner minnow, Notropis lutrensis were examined for morphological and genetic variation. This research was aimed at testing the hypothesis that morphological and genetic variation was primarily influenced by the degree of gene flow between populations. Ten linear measurements were taken from each of 1320 specimens. Morphological characters were adjusted for differential growth by least squares linear regression techniques. Genetic variability was estimated for each individual red shiner through the methods of starch gel electrophoresis. Twenty presumtive gene loci were resolved.