The ability to traverse barriers of high water velocity limits the distributions of many diadromous and other migratory fish species, and is central to effective fishway design. This dissertation provides a detailed analysis of volitional sprinting behavior of six migratory fish species (American shad Alosa sapidissima, alewife A. pseudoharengus, blueback herring A. aestivalis, striped bass Morone saxatilis , walleye Stizostedion vitreum, and white sucker Catostomus commersoni), against controlled water velocities of 1.5–4.5 m · s−1 in a large, open-channel flume. In Chapter 1, I develop models of maximum distance traversed ( Dmax) by fish ascending these flows, accounting for water velocity and other covariate effects. I then demonstrate the application of these models, using them to predict proportions of active migrants capable of traversing a range of distances and flow velocities. Chapter 2 focuses on behavior and swimming performance of American shad, analyzing covariate effects on attempt rate as well as Dmax, and formalizing how rate and distance jointly affect overall rates of passage. Models describe a complex pattern of varying responses of attempt rate and Dmax to hydraulics, temperature, effort expended on and recovery time since the previous attempt. In Chapter 3, I use the effect of swimming speed on fatigue time to calculate an optimal swimming speed that maximizes the over-ground distance fish can traverse, and hence defines their maximum ability to traverse velocity barriers. This speed reduces to a constant groundspeed within a given gait, regardless of the speed of flow. Data from all six species support this view, although only American shad exhibit a clear shift from the optimum prolonged speed to the optimum sprint speed at the predicted critical flow velocity. Throughout this dissertation I make extensive and novel use of statistical techniques developed for survival analysis to analyze and model behavioral data, both with respect to attempt rate and to D max. Chapter 4 provides an overview of these methods and demonstrates their application to a fish passage study of downstream-migrating Atlantic salmon (Salmo salar) smolts. An understanding of the principles described here will help the reader to better understand the findings of the previous three chapters.

This study was designed to assess the energetic cost of upstream migration in American shad (Alosa sapidissima) and to examine physiological changes during migration that relate to swimming performance or energetic efficiency. Overall total stored energy expenditure ranged from 35-60% during upstream migration. Migrating American shad preferentially use energy stores (lipid and protein) in some tissues, such as the skin and its sub-dermal fat layer (depleted by 63%), while sparing other tissue stores such as red muscle protein. American shad generally increased the activity of aerobic and energy mobilization enzymes as much as 60%, while decreasing the activity of anaerobic enzymes as much as 80% during upstream migration. There was a generalized reversal of these enzyme changes seen during migration at the most upriver site sampled. It is suggested that American shad may be able to metabolically prepare for migration prior to its onset and cessation. The data demonstrate that fish migrating in the middle of the migratory period possessed higher (5-42%) total stored energy content than fish migrating early or late in the season, primarily due to elevated lipid in the white muscle and the sub-dermal fat layer. American shad demonstrate a spleen-controlled increase in available blood hemoglobin (22%) and hematocrit likely resulting in increased oxygen carrying capacity during upstream migration. Active and standard metabolic rates of American shad, determined by respirometry, were intermediate between salmonids and fast-swimming perciforms. Active metabolic rate was logarithmically related to swimming speed (r$\sp2$ = 0.26; slope = 0.2) and tailbeat frequency (r$\sp2$ = 0.36; slope = 0.002). Directly determined standard metabolic rate was 71-198 $\rm mgO\sb2kg\sp{-1}h\sp{-1}.$ The energetically optimal swimming speed was 1.45 $\pm$ 0.51 body lengths per second. Using the data from the swimming respirometer, an empirical model of the Cabot Station fish ladder in Turners Falls, MA was constructed which suggests that the impact of the fish ladder on migration is highly dependent on passage time. This study demonstrates that American shad are equipped with a variety of mechanisms for increasing energetic efficiency during upstream migration and highlights the importance of short-term physiological adaption to migration and the ultimate success of an iteroparous, anadromous fish.

Brachymeria intermedia is a primary parasitoid of pupae of the gypsy moth, Lymantria dispar (Lepidoptera: Lymantriidae). Previous studies established how females determine the acceptability of potential hosts through contact with their cuticular kairomones. This work investigates how olfactory cues initially may lead females to their hosts. Inexperienced females were less likely to walk toward the host than females with oviposition experience; however, a single antennal contact with the host was sufficient to increase the probability of walking to the host suggesting that females learned the odor of their host on the first encounter (Chapter 1). Olfactory conditioning was then demonstrated using a novel odor (Chapter 2). Through a single oviposition experience on their natural host in presence of vanilla odor, wasps were induced to drum and drill in a vanilla-scented paper roll. Although some wasps were conditioned when exposure to odor coincided with pre-oviposition drumming on the host, conditioning was most successful when odor exposure coincided with oviposition. Evidently, conditioning occurred through the formation of an association between the odor and the 'aroused' state underlying host acceptance. Results support the hypothesis that conditioning occurs through a stimulus-arousal association rather than, as is generally assumed, through a stimulus-stimulus association. Wasps were also conditioned to fly toward a source of vanilla odor in a wind tunnel (Chapter 3). Then, upon approaching vanilla-scented paper rolls hung on a vertical cylinder, conditioned wasps landed on them readily, whereas few wasps landed on real pupae. However, more wasps reached pupae or pupal cases than white scented paper rolls. Thus, visual and olfactory cues appeared to mediate the foraging behavior of wasps in conflicting ways. Conditioned wasps flying upwind, along a plume of vanilla odor flew shallow zigzag tracks (Chapter 4). Contrary to male moths flying to sex pheromone, wasps flew similar zigzag tracks along ribbon and turbulent plumes of vanilla odor. When the plume was removed while wasps were flying upwind, wasps either maintained an upwind course, or drifted sideways, flying alternately upwind and downwind before turning around and flying downwind. No wasp casted upon plume loss, as is typical of male moths.

The osmoregulatory physiology of American shad, Alosa sapidissima, was investigated. Tolerance to full strength seawater developed at the larval-juvenile transition (45 d post-hatch) three months prior to seaward migration. Increased seawater tolerance was associated with gill development, proliferation of chloride cells and increased gill Na$\sp+$,K$\sp+$-ATPase activity. Shad lose the ability to osmoregulate in fresh water during autumnal migration (a possible cue) evidenced by declines in plasma chloride (20%) observed in wild juveniles. Gill Na$\sp+$,K$\sp+$-ATPase activity increases during this period. These changes were observed in the laboratory under natural conditions. Plasma chloride dropped 68% and gill Na$\sp+$,K$\sp+$-ATPase activity increased three-fold. Decreased plasma chloride was associated with increased mortality. Chloride cells (on both the primary filament and secondary lamellae in fresh water) increased during autumn as temperature declined. Changes in physiology and chloride cells are delayed and of a lower magnitude when shad in fresh water were held at constant (24$\sp\circ$C) temperature. In seawater, chloride cells on the secondary lamellae (likely ion uptake cells) declined to less than 2% of fresh water levels. Chloride cells (in both fresh and seawater acclimated shad) were shown to be rich in mitochondria and Na$\sp+$,K$\sp+$-ATPase by developing a technique for using specific fluorescent dyes in fixed tissue. In order to differentiate between the mechanisms of branchial ion uptake and excretion, radioligand binding methods were used to quantify Na$\sp+$,K$\sp+$,2Cl$\sp-$ cotransporters in the gill tissue of Atlantic salmon (Salmo salar). However, no high affinity binding was measured. The Na$\sp+$,K$\sp+$,2Cl$\sp-$ cotransporter was immuno-histochemically colocalized with Na$\sp+$,K$\sp+$-ATPase to chloride cells in fresh water and seawater acclimated shad. Western blot analysis was used to characterize a 170-190 kDa protein (Na$\sp+$,K$\sp+$,2Cl$\sp-$ cotransporter) present in greater quantities in seawater acclimated shad and Atlantic salmon than in fresh water acclimated fish. The presence of the cotransporter in the chloride cells of seawater acclimated shad supports the accepted model of ion excretion but the immunolocalization of the cotransporter in chloride cells of fresh water acclimated American shad is unexpected and remains poorly understood.

Prior research has indicated that students of all ages show little understanding of respiration beyond breathing in and out and the need for air to survive. This occurs even after instruction with alternative conceptions persisting into adulthood. Whether this is due to specific educational strategies or to the level of difficulty in understanding a complex system is an important question. The purpose of this study was to obtain a deeper understanding of middle school students' development of mental models of human respiration. The study was composed of two major parts, one concerned with documenting and analyzing how students learn, and one concerned with measuring the effect of teaching strategies. This was carried out through a pre-test, "learning aloud" case studies in which students engaged in one-on-one tutoring interviews with the researcher, and a post-test. Transcript data from the intervention and post-test indicates that all students in this study were successful in constructing mental models of a complex concept, respiration, and in successfully applying these mental models to transfer problems. Differences in the pretest and posttest means were on the order of two standard deviations in size. While findings were uncovered in the use of a variety of strategies, possibly most interesting are the new views of analogies as an instructional strategy. Some analogies appear to be effective in supporting construction of visual/spatial features. Providing multiple, simple analogies that allow the student to construct new models in small steps, using student generated analogies, and using analogies to determine prior knowledge may also increase the effectiveness of analogies. Evidence suggested that students were able to extend the dynamic properties of certain analogies to the dynamics of the target conception and that this, in turn, allowed students to use the new models to explain causal relationships and give new function to models. This suggests that construction of causal, dynamic mental models is supported by the use of analogies containing dynamic and causal relationships.

Lipovitellin, the predominant yolk protein of vertebrate eggs, is a mixture of heat-stable and heat-labile molecules in mature winter flounder eggs. The heat-stable lipovitellin fraction, purified from extracts of unfertilized eggs by brief heat treatment and gel permeation chromatography, contains a single 94 kDa polypeptide. Native lipovitellin also possesses several smaller polypeptides, suggesting that heat-labile lipovitellin contains proteolytic cleavages of the 94 kDa polypeptide which destabilize its structure. The Stokes radii of native, heat-stable and heat-labile lipovitellin are 4.50 nm, 4.26 nm and 5.17 nm, respectively. A polyclonal antiserum raised against heat-stable lipovitellin binds a 175 kDa polypeptide in vitellogenic female winter founder serum, but does not bind any component of male serum. An ELISA constructed from this antiserum identifies serum vitellogenin as a single gel permeation peak with a Stokes radius of 6.70 nm and confirms that vitellogenin is a dimer, while lipovitellin from mature eggs is a monomer. During embryogenesis, lipovitellin is cleaved from a 94 kDa polypeptide to 67 kDa and 26 kDa polypeptides. Proteolytic processing is initially slow, but becomes more rapid between days eight and 12 post fertilization in embryos reared at 4°C–5°C, approaching 50% completion at day ten (tail-bud stage). Processing is essentially complete three days before hatching; nevertheless, major degradation of the lipovitellin polypeptides only occurs in larvae. The Stokes radius of lipovitellin decreases from 4.50 nm in unfertilized eggs to 4.19 nm in late embryos and newly hatched larvae, while processed lipovitellin retains its heat stability relative to other yolk polypeptides. However, 49.2% of the lipid moiety is released from lipovitellin concomitant with cleavage of the 94 kDa polypeptide. Lipovitellin processing may thus render a portion of its stored lipids more accessible to the embryo; alternately, removal of lipid may heighten proteolytic vulnerability of the polypeptide. In either case, only a portion of the lipovitellin particle plays a significant nutritive role for the embryo, while most of the molecule, including its protein component, is reserved for larval use.

Lipids of minced or comminuted muscle foods are particularly susceptible to oxidative deterioration. As a result, antioxidants are added to these products to retard the undesirable changes accompanying oxidation. The efficiency of an added antioxidant is related to its particular location within the product. Thus, directing the added antioxidant to the site where oxidation is initiated and/or propagated is of significant importance. The partitioning of δ-tocopherol between the neutraland the polar lipids of chicken leg muscles was investigated. The two lipid fractions were separated using differential ultracentrifugation techniques. Neutral lipids were obtained after high speed centrifugation of the minced muscle at 130,000 g for 30 min. The polar membrane lipids were collected from a muscle-buffer homogenate (pH 7.5) between 10,000 g for 20 min and 130,000 g for 30 min. The neutral oil collected represented from 11 to 90% of the to triacylglycerols of the minced muscle. The polar membrane lipids represented from 25 to 35% of the total membrane lipids of the muscle. The partitioning of δ-tocopherol between the two lipid fractions depended on the amount of tocopherol added. At low total lipid contents the added δ-tocopherol was present in approximately the same concentration in both muscle lipid fractions. At higher total lipid contents the δ-tocopherol concentration in the membrane lipids increased relative to the neutral lipids. The δ-tocopherol uptake by the lipids of the membranes suspended in buffer increased linearly with tocopherol concentration added in the range of 4 to 4,000 ppm δ-tocopherol on a lipid basis. The membrane lipids contained up to 50% of the added tocopherol. This indicates a high capacity of the membranes for tocopherol incorporation or binding. Studies with model systems consisting of suspended membrane lipids and chicken oil suggested an insignificant exchange of δ-tocopherol between the two lipid fractions when the tocopherol was initially residing in either fraction. This may be due to strong hydrophobic interactions between the antioxidant and the lipids in which it resides. An insignificant uptake of δ-tocopherol by the membrane lipids was also observed when the tocopherol was added in corn oil to a model membrane lipid-chicken oil system. In contrast, when δ-tocopherol was added to the model system dissolved in ethanol the uptake of the membrane lipids increased dramatically. It is proposed that the partitioning of tocopherol between the different lipids of a minced muscle is governed mainly by the relative surface areas of the lipids and the tocopherol concentration in the aqueous phase immediately after its addition. For this purpose the polarity of the tocopherol carrier (solvent) is of particular importance.

Tubuloglomerular feedback (TGF) is a delayed negative feedback mechanism that stabilizes the glomerular filtration rate (renal blood flow) and salt concentration in a single nephron, the basic filtering unit of the kidney. Fluid flow through the nephron exhibits three distinct patterns. It may flow at a constant rate, or it may oscillate in one of two ways: regularly or chaotically. Earlier models indicate that the TGF mechanism plays a role in the mediation of both a constant flow rate and limit cycle oscillations. However, these models do not incorporate the influence of backleak (diffusion) in coupled nephrons (those that are linked anatomically by their vasculature). This dissertation examines the effects of backleak on coupled nephrons. The main result is that backleak stabilizes the system: coupled nephrons with backleak exhibit steady flow rates at higher feedback gains than do those without backleak. This same stabilizing effect was observed in a model of a single nephron with backleak. The model describing the TGF mechanism in two coupled nephrons is also extended in a model of three coupled nephrons. The results suggest that the addition of a nephron to the system may have a destabilizing effect: limit cycle oscillations are exacerbated when a third nephron is added to the system. Numerical methods are developed and implemented to study the predictions given by the bifurcation analysis.

A reduction in the availability of oxidizable metabolic fuels inhibits reproduction. When ovariectomized, steroid-primed hamsters are food deprived for 48 hours, estrous behavior is suppressed. However, the specific neuroendocrine alterations that mediate the suppression or restoration of estrous behavior are unknown. In the following set of experiments, I investigated various possible neuroendocrine alterations associated with nutritional infertility and I found the following. Increasing circulating levels of estradiol can increase lordosis durations in fasted animals, but the suppression of estrous behavior occurs despite increased circulating estradiol levels in ovariectomized, steroid-treated animals. Next, I found that it takes more than 24 h of metabolic inhibitor administration to inhibit lordosis, whereas only 6 h of refeeding is sufficient to restore sexual receptivity. Furthermore, neither plasma insulin nor leptin levels parallel the changes in estrous behavior, suggesting that changes in circulating leptin and insulin probably do not play a critical role in these behavioral changes. Finally, several conditions that inhibit female sexual behavior are thought to be associated with altered corticotropin-releasing hormone (CRH) activity in the brain. Intracerebroventricular (ICV) infusion of CRH or urocortin inhibited estrous behavior in ovariectomized steroid-primed hamsters. Conversely, ICV infusion of the potent CRH receptor antagonist, astressin, prevented the suppression of estrous behavior by food deprivation. Furthermore, astressin blocked the inhibition of estrous behavior by ICV administration of neuropeptide Y and CRH but did not enhance estrous behavior in animals given an inadequate dose of progesterone. Astressin treatment also induced sexual receptivity in nonresponders, animals that do not normally come into heat when treated with hormones. This effect persisted in subsequent weekly tests in the absence of any further astressin treatment. Manipulations that altered sexual behavior did so without affecting food intake and, in most cases, without affecting circulating corticosteroid levels, indicating that the animals were neither ill nor stressed. These results support the hypothesis that endogenous CRH receptor signaling mediates the inhibition of estrous behavior by undernutrition and in other instances of sexual dysfunction suggesting that CRH receptor signaling may be a final common pathway by which a number of distinct conditions inhibit female sexual behavior.

The onset and termination of female rat sexual receptivity are regulated by the activation of steroid hormone receptors. In addition, the onset and termination of sexual receptivity are influenced by mating stimulation. For example, repeated mating stimulation increases sexual behavior in previously unreceptive estradiol-primed female rats. Apparently, sensory cues from the male rat lead to changes in female sexual behavior. The current studies investigated the exact sensory cues responsible for these changes and the mechanisms by which they influence sexual behavior. Mating-induced increases in sexual behavior appear to result largely from vaginal-cervical stimulation (VCS) received from intromissions and ejaculations. Furthermore, it is likely that the effects of VCS are mediated by ligand-independent activation of progestin receptors. Likewise, odors from male rats are necessary for maximal increases in sexual behavior following repeated mating; however, unlike VCS, odors do not seem to influence sexual behavior via a progestin receptor-dependent mechanism. Mating stimulation also accelerates estrous termination. The mechanisms mediating the acceleration of estrous termination following mating were also investigated. It has been hypothesized that mating-induced estrous abbreviation results from down-regulation of progestin receptors; however, several immunocytochemical studies found no evidence supporting this hypothesis. Instead, it appears that the effects of mating stimulation on estrous termination are more complex than previously appreciated. It appears that, while VCS decreases levels of sexual behavior, other sensory cues (e.g. flank stimulation and odors) maintain high levels of sexual receptivity. Thus, the results suggest that estrous duration is the result of a complex interplay between those factors that promote the expression of sexual receptivity and those that inhibit it.