Comparative Biochemistry and Physiology a Comparative Physiology, 1997
Tissue distribution of "'I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the ... more Tissue distribution of "'I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the tissue content of the other were studied because previous work indicated that melatonin antagonized metamorphosis through peripheral, as well as thyroidal effects. Late pre-to prometamorphic Rana cat&e&o tadpoles on an 18 light: 6 dark cycle were used for injection of hormones in vioo or to supply tissues for in vitro hormone administration. Labeled melatonin uptake was highest in intestine, ventral skin and pituitary; lowest in thyroid and brain and intermediate in hindlimb, tail and gills. The tissue content of labeled T4 was distributed in nearly the same way, except that the thyroid level was relatively higher, and pituitary lower, than that of labeled melatonin. The pineal, studied only in the tracer T, experiments, had the highest content of labeled T4 of all tissues. Simultaneous injection of either 0.007 or 0.2 pg T, increased 'H-melatonin uptake into peripheral tissues that undergo major metamorphic changes but not into neural or endocrine organs. In contrast, 0.033, 3.75 or 15 pg melatonin had no significant influence on the content of '251-T4 in any tissue studied in viva. Results of in oitro labeling of selected tissues were generally in agreement with the in oivo work except that the '251,T4
The origin of circulating melatonin has been studied in Rana catesbeiana tadpoles and Rana pipien... more The origin of circulating melatonin has been studied in Rana catesbeiana tadpoles and Rana pipiens frogs on a 12L:12D cycle. Previous work had indicated that in tadpoles the eyes were a significant source of scotophase plasma melatonin, so we investigated the contribution of the pineal gland in tadpoles and the eyes and the pineal gland in frogs. The findings showed that in both larvae and adults the pineal gland and lateral eyes secrete nearly equal amounts of melatonin into the blood as determined by destruction of the pineal gland and eye extirpation. Pinealectomy and ophthalmectomy together reduce the mid-scotophase blood plasma level to that of photophase, so that the scotophase rise in melatonin is solely due to secretion of the pineal gland and the eyes. These procedures singly or in combination do not change the low mid-photophase level of plasma melatonin. The tadpole digestive tract was studied as a possible source of the photophase, and residual scotophase, plasma melatonin. The gut was found to contain a high level of melatonin, not changed by pineal and eye removal. However, gut extirpation did not change the plasma melatonin level in photophase or scotophase. The findings indicate
The objective of this study was to evaluate whether indicator microbes and physical-chemical para... more The objective of this study was to evaluate whether indicator microbes and physical-chemical parameters were correlated with pathogens within a tidally influenced estuary. Measurements included the analysis of physical-chemical parameters (pH, salinity, temperature, and turbidity), measurements of bacterial indicators (enterococci, fecal coliform, E. coli, and total coliform), viral indicators (somatic and MS2 coliphage), viral pathogens (enterovirus by culture), and protozoan pathogens (Cryptosporidium and Giardia). All pathogen results were negative with the exception of one sample which tested positive for culturable reovirus (8.5 MPN/100 L).. Notable physicalchemical parameters for this sample included low salinity (<1 ppt) and high water temperature (31°C ). Indicator bacteria and indicator virus levels for this sample were within average values typically measured within the study site and were low in comparison with levels observed in other freshwater environments. Overall results suggest that high levels of bacterial and viral indicators were associated with low salinity sites.
Since Rana pipiens tadpoles injected with thyroxine (TJ early in the dark develop more slowly tha... more Since Rana pipiens tadpoles injected with thyroxine (TJ early in the dark develop more slowly than those injected in the light, we studied the effect of giving a light pulse of 1 hr early in the dark. Tadpoles injected under a 7.5-W red light bulb in a darkened room with 0.2 pg T4 daily at 2200 h r went through metamorphosis faster on a 12L:3D:lL:8D cycle with a light pulse after injection than on a 12L:12D cycle without a light pulse, and even faster on a 12L:1.5D:lL:9.5D cycle with a light pulse before the injection. Thus a 1-hr light pulse counteracted the metamorphic delay resulting from administration of T4 in the dark, and set in motion the conditions that resulted in a more rapid response to an injection of T4. However, a 1-hr light pulse in the early dark had no effect on growth and development of older or younger untreated tadpoles or those constantly immersed in 30 pg/liter T4.
The diel fluctuations in plasma thyroxine (T4) and plasma and ocular melatonin entrain to the lig... more The diel fluctuations in plasma thyroxine (T4) and plasma and ocular melatonin entrain to the light/dark (LD) cycle in the bullfrog tadpole, although the phase of the rhythms changes during development. Previous studies on the rhythmicity of these hormones were conducted under various LD cycles, but with a constant temperature, raising the question of the role of the natural thermocycle in determining the phase of the rhythms, and the changes that occur in the hormone levels and rhythms during late metamorphosis. To study this question, tadpoles were acclimated to simulated natural conditions of 14.5L:9.5D with a corresponding thermocycle in which the thermophase was 28 °C and the cryophase was 18 °C, or to the same thermocycle under constant light (24L). On both photoregimens, the diel fluctuations changed between prometamorphosis and metamorphic climax. However, more statistically significant rhythms, as indicated by the cosinor, occurred on 14.5L:9.5D than on 24L. At climax on the LD cycle, all hormones peaked around the same time in the late scotocryophase, whereas on 24L, plasma T4 peaked in the thermophase and plasma and ocular melatonin peaks occurred some distance from each other early in the cryophase. The earlier peaks of plasma and ocular melatonin on 24L were due to a transient rise in these hormones at the onset of the cryophase, which was not sustained in the absence of an LD cycle. On 14.5L:9.5D with a corresponding thermocycle, the hormone rhythms had nearly the same phases as was found in previous work on 12L:12D at a constant temperature of 22 °C, allowing for minor phase shifting due to the photocycle differences, indicating that in this species laboratory studies on constant temperature give valid results even in the absence of a thermocycle. The findings show that the phases of the hormone rhythms are determined by the LD cycle although the onset of the cryophase, in the absence of a photocycle, may exert some influence on the nighttime rise in melatonin. The developmental rise in plasma T4, and drop in plasma melatonin, occurred on both 14.5L:9.5D and 24L, indicating, taken together with previous work, that these climactic changes were independent of temperature and light cycling.
Results Encouragingly, the vast majority of students reported that their plans to major in scienc... more Results Encouragingly, the vast majority of students reported that their plans to major in science actually became more likely over the course of the term. Less than 12% of students reported a decreased interest in their decisions to be science majors (Table 1 ). In regression ...
We present two models for assessment of a large and diverse quantitative reasoning (QR) requireme... more We present two models for assessment of a large and diverse quantitative reasoning (QR) requirement at the University of Michigan. These approaches address two key challenges in assessment: (1) dissemination of findings for curricular improvement and (2) resource constraints associated with measurement of large programs. Approaches we present for data collection include convergent validation of self-report surveys, as well as use of mixed methods and learning analytics. Strategies we present for dissemination of findings include meetings with instructors to share data and best practices, sharing of results through social media, and use of easily accessible dashboards. These assessment approaches may be of particular interest to universities with large numbers of students engaging in a QR experience, projects that involve multiple courses with diverse instructional goals, or those who wish to promote evidence-based curricular improvement.
discontinued systemic anti-CMV therapy while receiving highly active antiretroviral therapy (HAAR... more discontinued systemic anti-CMV therapy while receiving highly active antiretroviral therapy (HAART) were prospectively observed. Fifteen patients developed immune recovery uveitis (IRU); 3 of the patients developed extensive retinal neovascularization, 1 of whom required vitrectomy for recurrent vitreous hemorrhages. These late complications indicate a need for continued ophthalmologic follow-up of HIV-infected patients who have a history of CMV retinitis, even for individuals who have not required anti-CMV therapy for 14 years.
Beach advisories are issued at recreational beaches when the water quality exceeds regulatory lim... more Beach advisories are issued at recreational beaches when the water quality exceeds regulatory limits for the indicator organism, enterococci. Elevated levels of enterococci have been observed at Hobie Cat Beach, the study marine beach site, located on Virginia Key, Florida. The study site represents a classic non-point source sub/tropical marine recreational beach area with high human and animal use, representative
Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-... more Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-hr intervals over a 36-hr span in order to see if the cell cycle in the tadpole hindlimb epidermis varied with time or showed rhythmicity. There was a pattern of two long cell cycles followed by a shorter one. Total cell cycle length (Tc) and the length of the G1 phase plus one-half of the mitotic time (TG1 + 1/2M) fluctuated the most, although only TG1 + 1/2M varied significantly with the Chi-square test. The proportion of TC spent in each phase was also calculated. Only TG1 + 1/2M/TC had statistically significant fluctuations with time. Rhythmicity was analyzed by a computer program using the method of least squares for cosine curve fitting. Statistically significant ultradian rhythms of 18.4 hr in TC, 18.5 hr in TG1 + 1/2M and 18.6 hr in TG1 + 1/2M/TC and the length of the DNA synthetic phase/total cell cycle length (TS/TC) were found. Circadian rhythmicity was not observed. The acrophases of the ultradian rhythms of TC and TG1 + 1/2M coincided, suggesting that the rhythm of TC was due mainly to variation in TG1 + 1/2M. In the absence of significant variation in TS, the longest phase of the cell cycle, whenever G1 + 1/2M was short, TS/TC increased, so that the 18.6 hr rhythm in TS/TC was also a result of the periodicity in TG1 + 1/2M.
International Journal of Environmental Health Research, Jul 1, 2004
Climate change has received recent extensive media attention (e.g., Kyoto Protocol) and is curren... more Climate change has received recent extensive media attention (e.g., Kyoto Protocol) and is currently on the international public health agenda. The purpose of this study was to survey knowledge, attitudes and behaviours related to climate change in the province of Alberta, Canada. A random sample of 600 Alberta households, using proportional quotas based on the Canada Census of the Alberta population, was surveyed on knowledge, attitudes and behaviours related to climate change using a computer-assisted telephone interviewing protocol. Albertans are highly concerned, particularly about health problems related to the environment and air pollution; yet are only moderately informed about a variety of environmental issues. While the great majority of Albertans appear to be engaged in environmental behaviours at home, fewer consider energy efficiency when purchasing consumer goods. An even smaller percentage makes environmentally conscious transportation decisions. To encourage the population to make recommended environmental behaviours, mass media approaches may do well to target the specific beliefs that were deemed salient (e.g., promote the association between environment issues and health). The public health sector has a major role in working with inter-sectoral groups to address this significant public health issue.
The goal of this study was to quantify the microbial load (enterococci) contributed by the differ... more The goal of this study was to quantify the microbial load (enterococci) contributed by the different animals that frequent a beach site. The highest enterococci concentrations were observed in dog feces with average levels of 3.9 Â 10 7 CFU/g; the next highest enterococci levels were observed in birds averaging 3.3 Â 10 5 CFU/g. The lowest measured levels of enterococci were observed in material collected from shrimp fecal mounds (2.0 CFU/g). A comparison of the microbial loads showed that 1 dog fecal event was equivalent to 6940 bird fecal events or 3.2 Â 10 8 shrimp fecal mounds. Comparing animal contributions to previously published numbers for human bather shedding indicates that one adult human swimmer contributes approximately the same microbial load as one bird fecal event. Given the abundance of animals observed on the beach, this study suggests that dogs are the largest contributing animal source of enterococci to the beach site.
Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology, 1999
Bullfrog (Rana catesbeiana) tadpoles are of value to amphibian researchers because of their large... more Bullfrog (Rana catesbeiana) tadpoles are of value to amphibian researchers because of their large size, and year-round availability due to overwintering in many latitudes. Concern over a possible difference in hormonal parameters in tadpoles obtained at different times of the year prompted us to investigate thyroid gland secretion in vitro, plasma and ocular melatonin, and plasma corticosteroids in late pre- to early prometamorphic larvae on 12L:12D. Winter tadpoles exposed to 22 degrees C for 3 weeks of acclimation (winter group) were compared to summer tadpoles kept at 22 degrees C (summer group), as well as to summer tadpoles exposed to cold (12 degrees C) for the 3 weeks (cold group), or kept at 22 degrees C and starved for the last week of acclimation (starved group). Thyroids from the summer group had a significantly higher response to 0.2 microg/ml ovine thyrotropin (TSH) than the other groups, indicating that cold and starvation inhibited subsequent in vitro thyroid sensitiv...
Comparative biochemistry and physiology. Part A, Physiology, 1997
Tissue distribution of 125I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the... more Tissue distribution of 125I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the tissue content of the other were studied because previous work indicated that melatonin antagonized metamorphosis through peripheral, as well as thyroidal effects. Late pre- to prometamorphic Rana catesbeiana tadpoles on an 18 light:6 dark cycle were used for injection of hormones in vivo or to supply tissues for in vitro hormone administration. Labeled melatonin uptake was highest in intestine, ventral skin and pituitary; lowest in thyroid and brain and intermediate in hindlimb, tail and gills. The tissue content of labeled T4 was distributed in nearly the same way, except that the thyroid level was relatively higher, and pituitary lower, than that of labeled melatonin. The pineal, studied only in the tracer T4 experiments, had the highest content of labeled T4 of all tissues. Simultaneous injection of either 0.007 or 0.2 microgram T4 increased 3H-melatonin uptake into peripheral tissu...
Comparative Biochemistry and Physiology a Comparative Physiology, 1997
Tissue distribution of "'I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the ... more Tissue distribution of "'I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the tissue content of the other were studied because previous work indicated that melatonin antagonized metamorphosis through peripheral, as well as thyroidal effects. Late pre-to prometamorphic Rana cat&e&o tadpoles on an 18 light: 6 dark cycle were used for injection of hormones in vioo or to supply tissues for in vitro hormone administration. Labeled melatonin uptake was highest in intestine, ventral skin and pituitary; lowest in thyroid and brain and intermediate in hindlimb, tail and gills. The tissue content of labeled T4 was distributed in nearly the same way, except that the thyroid level was relatively higher, and pituitary lower, than that of labeled melatonin. The pineal, studied only in the tracer T, experiments, had the highest content of labeled T4 of all tissues. Simultaneous injection of either 0.007 or 0.2 pg T, increased 'H-melatonin uptake into peripheral tissues that undergo major metamorphic changes but not into neural or endocrine organs. In contrast, 0.033, 3.75 or 15 pg melatonin had no significant influence on the content of '251-T4 in any tissue studied in viva. Results of in oitro labeling of selected tissues were generally in agreement with the in oivo work except that the '251,T4
The origin of circulating melatonin has been studied in Rana catesbeiana tadpoles and Rana pipien... more The origin of circulating melatonin has been studied in Rana catesbeiana tadpoles and Rana pipiens frogs on a 12L:12D cycle. Previous work had indicated that in tadpoles the eyes were a significant source of scotophase plasma melatonin, so we investigated the contribution of the pineal gland in tadpoles and the eyes and the pineal gland in frogs. The findings showed that in both larvae and adults the pineal gland and lateral eyes secrete nearly equal amounts of melatonin into the blood as determined by destruction of the pineal gland and eye extirpation. Pinealectomy and ophthalmectomy together reduce the mid-scotophase blood plasma level to that of photophase, so that the scotophase rise in melatonin is solely due to secretion of the pineal gland and the eyes. These procedures singly or in combination do not change the low mid-photophase level of plasma melatonin. The tadpole digestive tract was studied as a possible source of the photophase, and residual scotophase, plasma melatonin. The gut was found to contain a high level of melatonin, not changed by pineal and eye removal. However, gut extirpation did not change the plasma melatonin level in photophase or scotophase. The findings indicate
The objective of this study was to evaluate whether indicator microbes and physical-chemical para... more The objective of this study was to evaluate whether indicator microbes and physical-chemical parameters were correlated with pathogens within a tidally influenced estuary. Measurements included the analysis of physical-chemical parameters (pH, salinity, temperature, and turbidity), measurements of bacterial indicators (enterococci, fecal coliform, E. coli, and total coliform), viral indicators (somatic and MS2 coliphage), viral pathogens (enterovirus by culture), and protozoan pathogens (Cryptosporidium and Giardia). All pathogen results were negative with the exception of one sample which tested positive for culturable reovirus (8.5 MPN/100 L).. Notable physicalchemical parameters for this sample included low salinity (<1 ppt) and high water temperature (31°C ). Indicator bacteria and indicator virus levels for this sample were within average values typically measured within the study site and were low in comparison with levels observed in other freshwater environments. Overall results suggest that high levels of bacterial and viral indicators were associated with low salinity sites.
Since Rana pipiens tadpoles injected with thyroxine (TJ early in the dark develop more slowly tha... more Since Rana pipiens tadpoles injected with thyroxine (TJ early in the dark develop more slowly than those injected in the light, we studied the effect of giving a light pulse of 1 hr early in the dark. Tadpoles injected under a 7.5-W red light bulb in a darkened room with 0.2 pg T4 daily at 2200 h r went through metamorphosis faster on a 12L:3D:lL:8D cycle with a light pulse after injection than on a 12L:12D cycle without a light pulse, and even faster on a 12L:1.5D:lL:9.5D cycle with a light pulse before the injection. Thus a 1-hr light pulse counteracted the metamorphic delay resulting from administration of T4 in the dark, and set in motion the conditions that resulted in a more rapid response to an injection of T4. However, a 1-hr light pulse in the early dark had no effect on growth and development of older or younger untreated tadpoles or those constantly immersed in 30 pg/liter T4.
The diel fluctuations in plasma thyroxine (T4) and plasma and ocular melatonin entrain to the lig... more The diel fluctuations in plasma thyroxine (T4) and plasma and ocular melatonin entrain to the light/dark (LD) cycle in the bullfrog tadpole, although the phase of the rhythms changes during development. Previous studies on the rhythmicity of these hormones were conducted under various LD cycles, but with a constant temperature, raising the question of the role of the natural thermocycle in determining the phase of the rhythms, and the changes that occur in the hormone levels and rhythms during late metamorphosis. To study this question, tadpoles were acclimated to simulated natural conditions of 14.5L:9.5D with a corresponding thermocycle in which the thermophase was 28 °C and the cryophase was 18 °C, or to the same thermocycle under constant light (24L). On both photoregimens, the diel fluctuations changed between prometamorphosis and metamorphic climax. However, more statistically significant rhythms, as indicated by the cosinor, occurred on 14.5L:9.5D than on 24L. At climax on the LD cycle, all hormones peaked around the same time in the late scotocryophase, whereas on 24L, plasma T4 peaked in the thermophase and plasma and ocular melatonin peaks occurred some distance from each other early in the cryophase. The earlier peaks of plasma and ocular melatonin on 24L were due to a transient rise in these hormones at the onset of the cryophase, which was not sustained in the absence of an LD cycle. On 14.5L:9.5D with a corresponding thermocycle, the hormone rhythms had nearly the same phases as was found in previous work on 12L:12D at a constant temperature of 22 °C, allowing for minor phase shifting due to the photocycle differences, indicating that in this species laboratory studies on constant temperature give valid results even in the absence of a thermocycle. The findings show that the phases of the hormone rhythms are determined by the LD cycle although the onset of the cryophase, in the absence of a photocycle, may exert some influence on the nighttime rise in melatonin. The developmental rise in plasma T4, and drop in plasma melatonin, occurred on both 14.5L:9.5D and 24L, indicating, taken together with previous work, that these climactic changes were independent of temperature and light cycling.
Results Encouragingly, the vast majority of students reported that their plans to major in scienc... more Results Encouragingly, the vast majority of students reported that their plans to major in science actually became more likely over the course of the term. Less than 12% of students reported a decreased interest in their decisions to be science majors (Table 1 ). In regression ...
We present two models for assessment of a large and diverse quantitative reasoning (QR) requireme... more We present two models for assessment of a large and diverse quantitative reasoning (QR) requirement at the University of Michigan. These approaches address two key challenges in assessment: (1) dissemination of findings for curricular improvement and (2) resource constraints associated with measurement of large programs. Approaches we present for data collection include convergent validation of self-report surveys, as well as use of mixed methods and learning analytics. Strategies we present for dissemination of findings include meetings with instructors to share data and best practices, sharing of results through social media, and use of easily accessible dashboards. These assessment approaches may be of particular interest to universities with large numbers of students engaging in a QR experience, projects that involve multiple courses with diverse instructional goals, or those who wish to promote evidence-based curricular improvement.
discontinued systemic anti-CMV therapy while receiving highly active antiretroviral therapy (HAAR... more discontinued systemic anti-CMV therapy while receiving highly active antiretroviral therapy (HAART) were prospectively observed. Fifteen patients developed immune recovery uveitis (IRU); 3 of the patients developed extensive retinal neovascularization, 1 of whom required vitrectomy for recurrent vitreous hemorrhages. These late complications indicate a need for continued ophthalmologic follow-up of HIV-infected patients who have a history of CMV retinitis, even for individuals who have not required anti-CMV therapy for 14 years.
Beach advisories are issued at recreational beaches when the water quality exceeds regulatory lim... more Beach advisories are issued at recreational beaches when the water quality exceeds regulatory limits for the indicator organism, enterococci. Elevated levels of enterococci have been observed at Hobie Cat Beach, the study marine beach site, located on Virginia Key, Florida. The study site represents a classic non-point source sub/tropical marine recreational beach area with high human and animal use, representative
Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-... more Using the percentage labeled mitoses method, seven cell cycle determinations were initiated at 6-hr intervals over a 36-hr span in order to see if the cell cycle in the tadpole hindlimb epidermis varied with time or showed rhythmicity. There was a pattern of two long cell cycles followed by a shorter one. Total cell cycle length (Tc) and the length of the G1 phase plus one-half of the mitotic time (TG1 + 1/2M) fluctuated the most, although only TG1 + 1/2M varied significantly with the Chi-square test. The proportion of TC spent in each phase was also calculated. Only TG1 + 1/2M/TC had statistically significant fluctuations with time. Rhythmicity was analyzed by a computer program using the method of least squares for cosine curve fitting. Statistically significant ultradian rhythms of 18.4 hr in TC, 18.5 hr in TG1 + 1/2M and 18.6 hr in TG1 + 1/2M/TC and the length of the DNA synthetic phase/total cell cycle length (TS/TC) were found. Circadian rhythmicity was not observed. The acrophases of the ultradian rhythms of TC and TG1 + 1/2M coincided, suggesting that the rhythm of TC was due mainly to variation in TG1 + 1/2M. In the absence of significant variation in TS, the longest phase of the cell cycle, whenever G1 + 1/2M was short, TS/TC increased, so that the 18.6 hr rhythm in TS/TC was also a result of the periodicity in TG1 + 1/2M.
International Journal of Environmental Health Research, Jul 1, 2004
Climate change has received recent extensive media attention (e.g., Kyoto Protocol) and is curren... more Climate change has received recent extensive media attention (e.g., Kyoto Protocol) and is currently on the international public health agenda. The purpose of this study was to survey knowledge, attitudes and behaviours related to climate change in the province of Alberta, Canada. A random sample of 600 Alberta households, using proportional quotas based on the Canada Census of the Alberta population, was surveyed on knowledge, attitudes and behaviours related to climate change using a computer-assisted telephone interviewing protocol. Albertans are highly concerned, particularly about health problems related to the environment and air pollution; yet are only moderately informed about a variety of environmental issues. While the great majority of Albertans appear to be engaged in environmental behaviours at home, fewer consider energy efficiency when purchasing consumer goods. An even smaller percentage makes environmentally conscious transportation decisions. To encourage the population to make recommended environmental behaviours, mass media approaches may do well to target the specific beliefs that were deemed salient (e.g., promote the association between environment issues and health). The public health sector has a major role in working with inter-sectoral groups to address this significant public health issue.
The goal of this study was to quantify the microbial load (enterococci) contributed by the differ... more The goal of this study was to quantify the microbial load (enterococci) contributed by the different animals that frequent a beach site. The highest enterococci concentrations were observed in dog feces with average levels of 3.9 Â 10 7 CFU/g; the next highest enterococci levels were observed in birds averaging 3.3 Â 10 5 CFU/g. The lowest measured levels of enterococci were observed in material collected from shrimp fecal mounds (2.0 CFU/g). A comparison of the microbial loads showed that 1 dog fecal event was equivalent to 6940 bird fecal events or 3.2 Â 10 8 shrimp fecal mounds. Comparing animal contributions to previously published numbers for human bather shedding indicates that one adult human swimmer contributes approximately the same microbial load as one bird fecal event. Given the abundance of animals observed on the beach, this study suggests that dogs are the largest contributing animal source of enterococci to the beach site.
Comparative biochemistry and physiology. Part C, Pharmacology, toxicology & endocrinology, 1999
Bullfrog (Rana catesbeiana) tadpoles are of value to amphibian researchers because of their large... more Bullfrog (Rana catesbeiana) tadpoles are of value to amphibian researchers because of their large size, and year-round availability due to overwintering in many latitudes. Concern over a possible difference in hormonal parameters in tadpoles obtained at different times of the year prompted us to investigate thyroid gland secretion in vitro, plasma and ocular melatonin, and plasma corticosteroids in late pre- to early prometamorphic larvae on 12L:12D. Winter tadpoles exposed to 22 degrees C for 3 weeks of acclimation (winter group) were compared to summer tadpoles kept at 22 degrees C (summer group), as well as to summer tadpoles exposed to cold (12 degrees C) for the 3 weeks (cold group), or kept at 22 degrees C and starved for the last week of acclimation (starved group). Thyroids from the summer group had a significantly higher response to 0.2 microg/ml ovine thyrotropin (TSH) than the other groups, indicating that cold and starvation inhibited subsequent in vitro thyroid sensitiv...
Comparative biochemistry and physiology. Part A, Physiology, 1997
Tissue distribution of 125I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the... more Tissue distribution of 125I-thyroxine (T4) and 3H-melatonin and the effect of each hormone on the tissue content of the other were studied because previous work indicated that melatonin antagonized metamorphosis through peripheral, as well as thyroidal effects. Late pre- to prometamorphic Rana catesbeiana tadpoles on an 18 light:6 dark cycle were used for injection of hormones in vivo or to supply tissues for in vitro hormone administration. Labeled melatonin uptake was highest in intestine, ventral skin and pituitary; lowest in thyroid and brain and intermediate in hindlimb, tail and gills. The tissue content of labeled T4 was distributed in nearly the same way, except that the thyroid level was relatively higher, and pituitary lower, than that of labeled melatonin. The pineal, studied only in the tracer T4 experiments, had the highest content of labeled T4 of all tissues. Simultaneous injection of either 0.007 or 0.2 microgram T4 increased 3H-melatonin uptake into peripheral tissu...
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