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Item Adenyl Cyclase and Its Relationship to Insect Diapause in the European Corn Borer, Ostrinia Nubilalis (Hubner)(1978) Gelman, Dale Berkman; Lockard, J. David; Hayes, Dora K.; Botany and Science Teaching; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)The purpose of this study was to determine if there is a link between adenyl cyclase activity and the diapause condition in the European corn borer, Ostrinia nubilalis. Insects inhabiting those latitudes where cold and warm seasons alternate with one another have evolved mechanisms which allow them to remain dormant (in a state of diapause) during the winter months of the year. Photoperiod, as well as temperature and humidity, has been shown to control the onset, maintenance and termination of insect diapause. In recent years, evidence supporting a role for the cyclic AMP system, including adenyl cyclase, as well as a role for one or more biogenic amines in the pathway between light reception and the neuroendocrine regulation of the insect life cycle and in the multitude of neuroendocrine pathways controlling insect growth and metamorphosis has been accumulating. In light of this evidence, it was decided to investigate the effects of two light regimens, short day (diapausing-inducing) and long day (pupation-inducing), on adenyl cyclase activity of various stages of fifth instar European corn borer larval heads, and to determine the effects of the biogenic amine neurotransmitters, norepinephrine, octopamine, and dopamine on this activity. Adenyl cyclase activity was measured by a modification of the method of Krishna, et al., (1968). A summary of the results follows. In head extracts of fifth instar European corn borer larvae reared under both long day and short day photoperiodic regimens, adenyl cyclase activity in the presence of sodium fluoride increased as the larvae progressed through early, middle and mature stages. In long day larval heads, activity decreased in late prepupae and reached a low in pharate pupae. In contrast, adenyl cyclase activity in short day larval heads peaked in early diapause and then returned to prediapause levels during late diapause. Norepinephrine significantly enhanced adenyl cyclase activity only in early diapause larval head extracts, while octopamine significantly enhanced adenyl cyclase activity in head extracts of late short day mature and early diapause larvae. Dopamine was ineffective as an activator. An analysis of the combined effect of neurotransmitter and developmental stage revealed that in general, a given neurotransmitter in combination with short day larval head extracts resulted in higher adenyl cyclase levels than that neurotransmitter in combination with long day head extracts.Item PLASMA CONCENTRATIONS OF LUTEINIZING HORMONE, FOLLICLE STIMULATING HORMONE AND PROLACTIN IN OVARIECTOMIZED, HYSTERECTOMIZED AND INTACT SWINE(1974) Wilfinger, William Walter Jr; Brinkley, Howard J.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)In order to critically evaluate the temporal patterns of plasma luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL); blood samples were collected daily at 0600, 1200, 1800 and 2400 hrs from intact, sham, ovariectomized and hysterectomized Yorkshire sows via indwelling vena caval cannulae. The maximum preovulatory plasma LH concentration in the intact and sham operated swine (mean ±l SD, 7.06±2.40 ng/ml) was reached between 2400 hrs on the first day of estrus (day 0) and 0600 hrs on day 1. Preovulatory LH peaks averaged 28.75±4.76 hrs duration from initial rise from, and return to, a baseline concentration of 1.19±.25 ng/ml plasma. In addition to the preovulatory LH peak, an average of 8.75 luteal phase peaks was observed during each estrous cycle . Approximately 69.5% ·of the luteal phase peaks had an average duration of 12.65±1.79 hrs, an average maximum plasma concentration of 2.29±.55 ng/ml and occurred during days 2 to 17. The remaining luteal phase peaks reached a maximum concentration of 2.86±1.04 ng/ml and occurred during days 2 to 13. The average duration of these luteal phase peaks was 18.61± 3.49 hrs. The largest and most consistent plasma FSH peak in the intact and sham operated swine occurred between days 2 and 3. This postovulatory peak had a duration of 58.17±16.25 hrs and reached an average maximum concentration of 13.14±9.42 ng/ml before returning to a baseline of 4.76± 1.56 ng/ml plasma. The initial rise of the postovulatory FSH peak coincided with the initial rise of the preovulatory LH peak, but did not reach maximum concentration until 2.66±.45 days after the preovulatory LH peak had reached maximum concentration. In some animals, a luteal phase FSH peak occurred between days 8 to 14. The luteal phase FSH peaks had a duration of 18.09±5.36 hrs and an average maximum concentration of 9.76± 3.78 ng/ml plasma. An average of 2.58±1.08 plasma PRL peaks was observed between day 0 and day 2 of the estrous cycle in the intact and sham operated swine. These peaks averaged 20.54±4.02 hrs in duration and reached maximum concentrations of 11.49±2.97 ng/ml before returning to a baseline of 6.54± 1.29 ng/ml plasma. They reached their maximum concentration approximately 9.12±9.84 hrs after the maximum concentration of the preovulatory LH peak had been reached. Larger prolactin peaks occurred during the follicular phase of the estrous cycle. An average of 3.09±1.38 peaks occurred between days 14 and 19.· These peaks had an average duration of 18.98±3.30 hrs and reached a maximum concentration of 14.28±4.27 ng/ml plasma. Shortly after removal of the ovaries (6 to 8 hrs), baseline LH (2.2± .14 ng/ml) and FSH (12.20±2.90 ng/ml) plasma concentrations in the ovariectomized swine were significantly greater (P<.05) than those found in the intact and sham operated animals, but baseline prolactin concentrations (6.70±2.10 ng/ml) were not significantly different (P>.05) from the controls. The temporal patterns of maximum plasma concentrations associated with LH (3.47±.21 ng/ml), FSH (21.43±.82 ng/ml) and PRL (9.32±2.00 ng/ml) peaks were not similar among the ovariectomized animals. Baseline LH (1.12±.34 ng/ml), FSH (5.30±2.09 ng/ml) and PRL (6.05± 1.89 ng/ml) concentrations in the hysterectomized swine were not significantly different (P>.05) from the baseline concentrations in the intact and sham operated animals. Numerous plasma LH peaks (14.30±4.59) were observed during the 20-day collection period. These peaks averaged 19.50 ±1.49 hrs in duration and reached maximum concentrations of 2.63±.23 ng/ ml before returning to baseline. Plasma FSH and PRL peaks averaged 21.00 ±4.51 and 17,69±3.50 hrs in duration and reached maximum concentrations of 8.12±1.95 and 10.18±2.95 ng/ml before returning to baseline. Mean plasma LH concentrations in the intact, sham, ovariectomized and hysterectomized swine were significantly greater at the 2400 hr collections than at the 1800 hr collections. A critical assessment of plasma hormone concentrations is an essential prerequisite to a basic understanding of the physiological mechanisms governing the reproductive process. The descriptive data provided by this study will enable future investigators to design critical experiments to evaluate the physiological importance of these hormone fluctuations, thereby broadening our basic understanding of the mechanisms which govern the reproductive cycle.Item Differences facilitating the coexistence of two sympatric, orb-web spiders, Argiope aurantia Lucas and Argiope trifasciata (Forskal) (Araneidae, Araneae)(1977) Taub, Marilyn Lorraine; Morse, Douglass H.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Two closely-related, sympatric, orb-web spiders, Argiope aurantia and Argiope trifasciata, take prey which differ in size. In accordance with the often-assumed direct relationship between the size of predators and their prey, A. aurantia is larger than A. trifasciata at any single point in time, largely a result of their asynchronous reproductive cycles. The ratio of their sizes exceeds the 1.28 proposed by Hutchinson (1959) for coexistence. Vertical and horizontal differences in their use of the microhabitat also occur and may further reduce the overlap in their use of food or reduce the frequency of interspecific interactions. In this study, vertical stratification of webs occurred only late in the season, with A. aurantia higher than A. trifasciata. These results contrast with those of Enders (1974), probably due to different densities of the two species in our study areas. Experiments show that the differences in the size of prey taken by these Argiope spiders were due, in part, to dissimilarities in the filtering properties of their webs and to differences in the ability of the two species to capture prey of the same relative size. However, the differences were mainly due to the spiders' rejection of a large and different portion of the available prey.Item The Significance of Cytological Characteristics as Revealed by Protargol Silver Staining in Evaluating the Systematics of the Ciliate Suborder Tintinnina(1977) Brownlee, David Carl; Small, Eugene B.; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)The present systematics of the tintinnid ciliates is based on the shape, size, and composition of the lorica as established by Kofoid and Campbell. Construction of a classification based on a restricted set of characteristics, such as those pertaining only to the lorica in the tintinnid ciliates, may lead to an artificial or unnatural scheme. This lorica based classification also prohibits phylogenetic comparisons of the tintinnids to other ciliate groups whose taxonomy is based on cytological characteristics. In an attempt to demonstrate the value and necessity of employing cytological characteristics in constructing the taxonomy of the tintinnid ciliates, the cytology of representative species was examined using the protargol silver-impregnation technique. Specimens were collected from a wide range of environments, including marine, brackish, and fresh water habitats which ranged from tropical to temperate latitudes. Eleven species comprising ten genera and representing seven families were chosen to represent the suborder in this preliminary analysis. The examination of the stained species provided the first precise description of somatic ciliation patterns, a more complete understanding of the buccal organization, and insight into the biological processes of these ciliates. Using these observations,comparisons are made to other ciliate groups and a preliminary analysis of evolutionary trends in the tintinnid ciliates is supported. It is suggested that a revision of the placement of certain genera within the families of tintinnids is necessary and that such changes should be based on both cytology and morphology of the lorica.Item Resource Partitioning in a Neotropical Necrophagous Scarab Guild(1978) Young, Orrey P.; Morse, Douglass H.; Zoology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md)Data collected from naturally occurring and artificially placed vertebrate carcasses were examined for the purpose of revealing mechanisms permitting the coexistence of carrion feeders in tropical forests. Studies concentrated on the necrophagous scarab guild and were conducted at three sites in the Panama Canal Zone during the periods January-June 1974, January-May 1975, and September-December 1975. Only mammalian carcasses were discovered at the principal study site, Barre Colorado Island (BCI). The seven species represented were among the 15 largest mammalian species known to occur on the island. Naturally occurring carcasses were most abundant late in the wet season, but the rate of utilization of carcasses was greatest in the dry season. Vertebrate scavengers appeared to be the most important consumers of carrion on BCI, and were the primary cause of high carcass utilization rates in the dry season. Invertebrate carrion consumers were rare in the dry season, but in the wet season probably consumed as much as 50% of the available vertebrate carrion. Field experiments demonstrated that mammalian carcasses were consumed by arthropods faster than bird carcasses, and that lizard carcasses were consumed very slowly, if at all. Consumption time by arthropods was directly proportional to carcass size, and fresh carcasses attracted many more species of arthropods than did older carcasses. Larval dipterans dominated carrion during the wet season. They could render a typical large (2 kg) vertebrate carcass unsuitable for other consumers in three days and consume 80% of the carcass in nine days. Larval dipterans also provided the food of a large group of predators. Potential competitors of larval dipterans (vertebrates, scarab beetles) were only successful if they arrived at the carcass quickly and removed portions of the carcass before larval dipteran populations rendered the food unsuitable. The necrophagous scarab guild on BCI contained 25 species and partitioned food along several dimensions. Differences in the techniques of removing food from a carcass for subsequent consumption or egg-laying appeared to be the most important in achieving species separation within this guild. Along temporal dimensions, both wet vs. dry season and day vs. night were important in species separation, Also of importance was the ability of species to consume a variety of foods, both carrion and other resources. Body size and trophic apparati were also of some importance. A linear dominance hierarchy, based on fighting ability, exists in the necrophagous scarab guild and is directly correlated with the type of food removal. Species biomass was also directly correlated with the dominance hierarchy. Ball-rolling species, for example, were always capable of taking food away from other species and represented the largest portion of the guild biomass.