Studies on the Mechanism of Protection by Carotenoids Against Photodynamic Killing in Curtobacterium Flaccumfaciens Pathover Poinsettiae (open access)

Studies on the Mechanism of Protection by Carotenoids Against Photodynamic Killing in Curtobacterium Flaccumfaciens Pathover Poinsettiae

The mechanism of protection by carotenoids against photodynamic killing in Curtobacterium flaccumfaciens pathover poinsettiae (C. poinsettiae) was studied using pigment mutants isolated by treatment with nitrosoguanidine and DNA gyrase inhibitors. Growth rates, pigment composition, pigment levels and the ultrastructure of the wild-type streptomycin resistant strain of G. poinsettiae (wt-str) and all mutants were compared. One mutant, NTG-1, lacked colored carotenoids, and another, NTG-2, was a slow growing mutant containing low levels (14%) of wild-type carotenoid pigments. Except for NTG-1, the other pigment mutants had different proportions of the same pigments found in the wild type as determined by high performance liquid chromatography (HPLC). Only NTG-2 was morphologically distinct at the ultrastructural level.
Date: August 1992
Creator: Abusada, Gabi M. (Gabi Michael)
System: The UNT Digital Library
Brain Activity in Rats Exposed to Short-Term External Electrical Fields (open access)

Brain Activity in Rats Exposed to Short-Term External Electrical Fields

The effects of external electric fields (EEF) on brain activity in anesthetized rats were studied. The field strengths used, 9 kV/m and 5 kV/m, both D.C. and A.C. (60Hz) were in the range of those measured beneath current overhead transmission lines. Brain activity was monitored from surface electrodes and from electrodes stereotaxically implanted in the posterior-lateral portion of the hypothalamus. It was found that 9 kV/m and 5 kV/m EEF's both D.C. and A.C. brought about statistically significant changes in hypothalamic activity, however, the effects were bi-directional, (i.e. increases and decreases). Only seven of the 60 animals exposed showed changes in the EEG recorded with surface electrodes. The data clearly indicate that (1) anesthetized animals do respond to a change in the external electric field around them, (2) the hypothalamus may contain special electro-receptors that, in turn, may alter various other physiological processes, and (3) the data indicates the need for further research to help government agencies to establish more adequate safety guidelines.
Date: May 1985
Creator: Hines, Gregory M. (Gregory Manuel)
System: The UNT Digital Library
The Effect of Long-Term Moderate Amounts of Ethanol on Paraventricular Nuclei Activity on Cold Stressed Adult Rats (open access)

The Effect of Long-Term Moderate Amounts of Ethanol on Paraventricular Nuclei Activity on Cold Stressed Adult Rats

The effects of moderate, long-term intake of ethanol on the hypothalamic response to cold stress were examined. The long-term experimental animals were given .25 ml of 28% ethanol or .25 ml of water orally once a day, five days a week for fourteen months. A stainless steel electrode was then surgically implanted into the paraventricular nucleus, after which the animal was subjected to cold stress (-150 C, 10 min.). Recordings were taken in the forms of frequency and activity. The data clearly indicate that: (1) alcohol fed rats exhibited a suppressed response to cold stress compared to sham-fed rats; (2) this suppression of activity occurred at the level of the hypothalamus, and (3) mortality was significantly lower in alcohol-fed males than it was in sham fed males. This study clearly points out the need for further work in the area of the beneficial effects of moderate doses of alcohol.
Date: December 1990
Creator: McKinnon, Mark S. (Mark Steven)
System: The UNT Digital Library
Environmental Correlates to Genetic Variation in the Coral Reef Fish, Thalassoma bifasciatum (open access)

Environmental Correlates to Genetic Variation in the Coral Reef Fish, Thalassoma bifasciatum

Genetic variation was examined in bluehead wrasse, Thalassoma bifasciatum, populations along the Florida Keys. Interpretion of mean heterozygosity (H), percent polymorphic loci per population (P), genetic similarity, and F and G statistics demonstrated a clear division of wrasse populations into "northern" and "southern" groups. Correlation and cluster analyses indicated the six reefs can be grouped in a similar fashion based on genetic and environmental data. The conclusion from this analysis of wrasse populations in the Florida Keys is that substantial population subdivision occurs in response to differing selective pressures created by heterogeneous environments.
Date: December 1988
Creator: Pirkle, Michelle S. (Michelle Serpas)
System: The UNT Digital Library
Use of ATP as a Planktonic Biomass Indicator in Reservoir Limnology (open access)

Use of ATP as a Planktonic Biomass Indicator in Reservoir Limnology

A series of laboratory experiments and a field investigation were conducted to closely define the application of the ATP assay and ATP as a planktonic biomass estimator for routine use in reservoir limnology. The laboratory experiments verified the published range of C:ATP ratios (i.e. 250:1) as a conversion factor for ATP to biomass in cultured selected genera of freshwater algae, except for the species of blue-green algae examined. The field investigation conducted at Moss Reservoir included organic carbon measurements with ATP biomass in size classes on a depth basis. The ATP biomass varied seasonally and with depth; the best significant mtltiple correlation was between organic carbon and the smallest size class (.45 to 10 um) and total net plankton biomass (.45 to 165 um). Daily monitoring of biomass in size classes demonstrated the sensitivity of the technique.
Date: August 1978
Creator: Perry, William B.
System: The UNT Digital Library
The Phospholipase B Response in Mice Infected With Fasciola Hepatica and Histochemical Demonstration of the Enzyme Source (open access)

The Phospholipase B Response in Mice Infected With Fasciola Hepatica and Histochemical Demonstration of the Enzyme Source

The phospholipase B activity was assayed in the small intestines, spleen and liver/bile duct of nonsensitized and sensitized mice infected with Fasciola hepatica. The primary infection resulted in a significant increase in phospholipase B activity in the small intestine, spleen and liver/bile duct over that of uninfected control animals. The response to the challenge infection was characterized by an earlier increase in enzyme activity with values significantly above those found for the primary infection in the same tissues. These data demonstrate that one response of mice to infection with F. hepatica is characterized by an increased phospholipase B activity. Thus, the enzyme response is not unique to cestode and nematode infections, but also is part of or associated with the inflammatory mechanisms against trematode infections. In addition, phospholipase B was demonstrated in leukocytes using electron microscopic histochemical techniques. Leukocytes were harvested from peritoneal exudates of mice. Cells were fixed in 4% calcium-forol fixative for 30 minutes at roan temperature for electron microscopy, after which they were incubated at 370C in medium at pH 6.6 containing 2 aM lysolecithin and Cal2 . The fatty acids released during the hydrolytic reaction were trapped as a calcium precipitate and were converted to a …
Date: December 1987
Creator: Pirkle, M. Scott (Michael Scott)
System: The UNT Digital Library