Effects of a High-Fat Diet and Strain on Hypothalamic Gene Expression in Rats

Objective: This study was designed to investigate whether dietary fat and genetic background might differentially alter the expression of hypothalamic genes involved in food intake. Research Methods and Procedures: Three-month-old Osborne-Mendel (OM) and S5B/Pl rats were fed either a high-fat or a low-fat diet for 14 days. mRNA for neuropeptide Y (NPY), corticotrophin-releasing hormone, NPY Y-1 receptor and Y-5 receptor, and serotonin 2c (5-HT2c) receptors were measured using Northern blotting or ribonuclease protection assays. Results: OM rats showed an increased expression of NPY and corticotrophin-releasing hormone compared with S5B/Pl rats. The expression of NPY-Y1 and -Y5 receptor mRNA was significantly higher in the hypothalamus of OM rats compared with S5B/Pl rats. The expression of 5HT-2c receptor mRNA was significantly reduced in both strains of rats eating a high-fat diet when compared with the animals eating the low-fat diet. Discussion: These data suggest that over activity of the NPY system may contribute to the development of obesity in OM rats and that expression of the 5HT-2c receptor gene may be modulated by dietary fat.     

Hazing and movements of Canada geese near Elmendorf Air Force Base in Anchorage, Alaska

Bird strikes to aircraft are a serious economic and safety problem in the United States, annually causing millions of dollars in damage to civilian and military aircraft and the occasional loss of human life. We observed movements of 1236 neckbanded lesser Canada geese (Branta canadensis parvipes) to determine efficacy of hazing as a means to reduce goose presence at Elmendorf Air Force Base (EAFB), Anchorage, Alaska from August to October 1997. Emphasis was on movements of geese onto EAFB with additional data collected at the other two major airports in the area, Anchorage International Airport (AIA) and Merrill Field Airport (MFA). Daily observations indicated the presence of 208 individual neckbanded geese on EAFB, and 20% returned more than once after being hazed from EAFB. We identified three staging areas, geese utilized prior to entering EAFB, and three post-hazing dispersal sites. Collared geese began moving onto EAFB 30–40 days post-molt with the largest proportions moving onto EAFB 70–90 days post-molt. We observed 75 neckbanded geese on AIA from seven molting sites, and 23% returned more than once after being hazed from AIA. We observed 141 neckbanded geese on MFA from 14 molting sites, and 21% returned more than once after being hazed from MFA. Our data indicated that as long as local goose populations increase, large numbers of Anchorage area geese are likely to enter one of the airports creating a variety of management problems. Hazed geese returning to airports multiple times present a special hazard to aircraft safety because they appear to have become habituated to non-lethal scare tactics. We recommend an integrated management approach to limit the Anchorage area goose population utilizing various control techniques which are acceptable to Anchorage residents while continuing the hazing program at area airports.     

Long-Term Effects of Frequent Low-Intensity Burning on the Abundance of Litter-Dwelling Invertebrates in Coastal Blackbutt Forests of Southeastern Australia

Low-intensity fire is extensively used in Australian dry eucalypt forests to reduce fuel levels. The long-term impact of this management practice on terrestrial invertebrates is, however, unknown and is of concern given their contribution to ecosystem function and forest biodiversity. This study found that areas subjected to frequent low-intensity fire had significantly lower numbers of spiders, ticks and mites, pseudoscorpions, woodlice, springtails, bugs, beetles, ants and insect larvae in the leaf litter compared with adjacent unburnt areas. Taxa numbers were between 41 and 82% lower and these reductions in abundance have led to an overall decline in taxon richness. This decrease was attributed to a reduction in the amount of litter and associated moisture levels, and a simplification of habitat structure. The extent of local and regional extinctions will depend upon the scale of this disturbance, with future studies investigating the impact on individual species within these communities. A comparison of two sampling techniques, pitfall-trapping and litter extraction, highlighted important considerations for spatial components of invertebrate sampling designs.     

Megagametogenesis in Halophila johnsonii, a threatened seagrass with no known seeds,and the seed-producing Halophila decipiens (Hydrocharitaceae)

Megagametogenesis, the development of a megaspore into an embryo sac, has been identified in the seagrass Halophila johnsonii, a threatened species with no known sexual reproduction or seeds. Megagametogenesis in H. johnsonii was compared with megagametophyte development in Halophila decipiens, a related species known to readily produce viable seeds. In both species, ovules were structurally similar, megaspore mother cells were seen in premeiotic ovules, and linear tetrads and megagametophytes with two to eight nuclei were present in postmeiotic ovules. However, H. decipiens postmeiotic ovules had a chalazal pouch that was absent in the postmeiotic ovules of H. johnsonii. Late-stage H. decipiens ovules also contained embryos, indicating that they had been fertilized, whereas all late-stage H. johnsonii ovules were degrading and showed no signs of fertilization. These observations suggest that meiosis does occur in H. johnsonii megasporocytes, leading to the formation of viable megagametophytes and egg cells that could be fertilized if pollination occurred. Thus, the lack of seed set is due to a lack of pollination rather than any loss of capacity to produce seeds in this species.     

Nephrogenous cyclic adenosine monophosphate levels in normocalcemic cancer patients: its significance

We evaluated nephrogenous cyclic adenosine monophosphate ( NcAMP ) levels in 61 normocalcemic patients with documented cancer of various organs and cell types. NcAMP levels were elevated in 17 (28%) and decreased in 13 (21%) of the cancer patients. Both high and low NcAMP levels were seen within the various cancer groups. There was a significant correlation (r = 0.383, P less than 0.01) between NcAMP and serum parathyroid hormone (PTH) levels, suggesting that tumor-related factors affecting NcAMP , may be partially related to native PTH. Alternatively, these factors might be altering the effect of endogenous PTH on renal tubules. A significant negative correlation was also observed between NcAMP and tubular maximum for phosphate (r = -0.356, P less than 0.02) suggesting that either cAMP per se or factors affecting NcAMP alter phosphate excretion. Follow up serum calcium data was available on 48 of the 61 patients. Subsequent hypercalcemia developed independent of the initial nephrogenous cAMP levels. It therefore appears that NcAMP elevation and development of hypercalcemia are two separate paraneoplastic phenomena.