Alzheimer's disease: a disorder of cortical cholinergic innervation

Great emphasis is being placed on identification of neurotransmitter systems involved in the symptomatic manifestations of neurological and psychiatric disorders. In the case of Alzheimer's disease, which now seems to be one of the most common causes of mental deterioration in the elderly, compelling evidence has been developed that acetylcholine-releasing neurons, whose cell bodies lie in the basal forebrain, selectively degenerate. These cholinergic neurons provide widespread innervation of the cerebral cortex and related structures and appear to play an important role in cognitive functions, especially memory. These advances reflect a close interaction between experimental and clinical neuroscientists in which information derived from basic neurobiology is rapidly utilized to analyze disorders of the human brain.     

Measurements of Ozone Deposition to Vegetation Quantifying the Flux,the Stomatal and Non-Stomatal Components

Water, Air, &; Soil Pollution - Ozone deposition to vegetation represents the major sink for boundary layer ozone and yet the underlying mechanism of reaction and uptake at the surface is poorly...     

Evaluation of growth, feed utilization, and economics of hybrid tilapia, Oreochromis niloticus×Oreochromis aureus, fed diets containing different protein sources in combination with distillers dried grains with solubles

A feeding trial was conducted in aquaria with juvenile hybrid tilapia (Oreochromis niloticus×Oreochromis aureus) to evaluate the use of different protein sources in combination with distillers dried grains with solubles (DDGS). Twelve 110‐L glass aquaria were stocked with 28 juvenile (2.7±0.5‐g) hybrid tilapia per aquarium. Three replicate aquaria were randomly assigned to each of the four dietary treatments. Diets were isonitrogenous and isocaloric. The control diet contained 12% fish meal and 41% soybean meal as the primary protein sources (Diet 1). Each experimental diet contained 30% DDGS by weight, in combination with 8% fish meal and 34% soybean meal (Diet 2), 26% meat and bone meal (MBM), and 16% soybean meal (Diet 3), or 46% soybean meal alone (Diet 4). Fish were fed to apparent satiation twice a day for 10 weeks. There were no significant differences (P>0.05) in average weight gain, specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) among tilapia fed Diets 1, 2, and 3. Fish fed Diet 4 had significantly lower (P<0.05) average weight gain, SGR, and PER than fish fed Diets 1 and 3. Relative cost per unit weight gain for Diets 1, 2, and 3 were statistically similar (P>0.05), while cost per unit weight gain for Diet 4 was significantly higher (P<0.05) than other diets. Diet 3 represented approximately a 20% cost savings compared with the control diet, with no reduction in growth. This study indicates that diets without fish meal containing 30% DDGS in combination with MBM and soybean meal provide good growth in tilapia. A diet without animal protein did not support acceptable growth.     

Characterizing tourism benefits associated with top‐predator conservation in coastal British Columbia

1. Facing public concern over costs related to top‐predator reintroductions and conservation, ecosystem services such as ecotourism are often used to evoke benefits that outweigh or offset those costs. Quantifying these benefits using rigorous scientific methods can provide confidence to policymakers and other stakeholders that predators can in fact deliver positive outcomes to people living alongside them. The evaluation of these benefits is often anecdotal or qualitative, however, and empirical quantifications are rare.
2. In coastal marine ecosystems, sea otter reintroduction is seen as a conservation success to some but a bane to others. The contribution of sea otters (Enyhdra lutris) to tourism revenue is touted as a crucial ecosystem service benefit to offset the loss of shellfish harvesting and associated revenue, but remains unquantified, weakening the favourable reception of conservation action.
3. The potential economic benefits of sea otters associated with tourism and the extent to which benefits are realized were evaluated based on: (i) choice‐experiment surveys of tourists; and (ii) interviews with tourism operators in British Columbia.
4. Sea otters were a strong factor in people's choices regarding wildlife viewing, and sea otters could have large benefits for local economies. Alongside socio‐economic characteristics, tourism experience influences tourists’ preferences. Tourism operators did not perceive sea otters as strongly influencing tourist choice, highlighting the gap that can occur between the perception and the reality of tourist preferences, leading to missed opportunities for the alignment of economic development with conservation actions.

     

Production Comparison of Three Genetic Strains of Freshwater Prawn,Macrobrachium rosenbergii,Raised Under Two Pond Management Technologies

Three genetic strains (Texas [cultured], Hawaii [cultured], and Myanmar [wild]) of freshwater prawn, Macrobrachium rosenbergii, were characterized and compared under two pond grow‐out management technologies using a 3 × 2 factorial design. Juvenile prawns (45 d nursed juveniles) from each strain were stocked at individual average weights of 0.4 ± 0.3 g (Texas), 0.3 ± 0.2 g (Hawaii), and 0.3 ± 0.2 g (Myanmar). The low input management technology prawns were stocked at 24,700 /ha with no added substrate. The high input management technology prawns were stocked at 74,100 /ha with the addition of artificial substrate. Each of the six treatment combinations were replicated in three, 0.04 ha earthen ponds (total of 18 ponds). Prawns were fed a sinking pellet (32% protein) once daily at a standardized rate. After 112 d, prawns were harvested, bulk weighed, and counted. Survival of Texas strain (95%) was significantly higher (P ≤ 0.05) than Myanmar strain (77–80%) under both management technologies with survival of Hawaii strain (86–91%) intermediate and not significantly different (P > 0.05) from other strains. Under both management technologies, average weight, total production, and marketable percentage (>20 g) was significantly better (P ≤ 0.05) in Texas and Hawaii strains in comparison to the Myanmar strain. These data appear to indicate that the cultured strains evaluated in this study demonstrate positive impacts of domestication and do not indicate inbreeding depression.     

Effect of Culture Temperature on Growth, Survival, and Biochemical Composition of Yellow Perch Perca fiavescens

Juvenile yellow perch Perca fiavescens were evaluated under controlled conditions in tanks for 13 wk to determine the effect of temperature on growth to advanced sizes under intensive culture conditions. Yellow perch weighing 6.6 ± 1.5 g were stocked into nine 4,755-L tanks at 131 fish/m³ (625 perch/tank). There were three replicate tanks per temperature (20, 24, and 28 C). Perch were fed to apparent satiation twice daily using a 45% crude protein diet with 16% crude fat. After 93 d the perch in the 24 C treatment were significantly larger ( P < 0.05) than those in the 20 C and 28 C treatments, which were not significantly different (P < 0.05) from each other. Yellow perch raised at 28 C had significantly higher ( P < 0.05) feed conversion ratios and significantly lower ( P < 0.05) survival and net protein utilization than perch raised at 20 C or 24 C. Whole body moisture was significantly higher in ( P < 0.05) yellow perch raised at 20 C which also had significantly higher levels of arachidonic acid (20:4 n-6) and docosohexaenoic acid (22:6 n-3). The ratio of palmitic acid (16:0) and palmitoleic acid (16:1 n-6) had a positive correlation ( P < 0.05) with culture temperature. These data indicate that 24 C may be an optimum temperature for yellow perch. At 20 C survival and feed conversion are good but growth rates are reduced. Temperatures near 28 C appear sufficient to represent chronic stress conditions.     

Effect of Stocking Density on Growth and Water Quality for Largemouth Bass Micropterus salmoides Growout in Ponds

Juvenile largemouth bass Micropterus salmoides , trained to accept artificial diets, were stocked into six 0.04-ha ponds at stocking densities of either 6,175 or 12,350 fish/ha. Fish were fed a floating custom-formulated diet, containing 44% protein, once daily to satiation for 12 mo (May 1994–May 1995). At final harvest, the total yield of fish was significantly greater (P < 0.05) and feed conversion ratio (FCR) was significantly lower, for bass stocked at the higher density (4,598 kg/ha and 2.3, respectively) than when stocked at the lower density (2,354 kg/ha and 3.3, respectively). There was no significant difference (P > 0.05) in average weight, length, or survival of bass stocked at the two densities. Averaged over the study period, there were no significant differences (P > 0.05) in total ammonia-nitrogen (TAN), nitrite-nitrogen, or un-ionized ammonia concentrations in ponds in which bass were stocked at the two densities. These data indicate that largemouth bass of the size used in this study are amenable to pond culture at densities of at least 12,350 fish/ha and that higher stocking densities may be possible.     

Production Response of Freshwater Prawns Macrobrachium rosenbergii to Increasing Amounts of Artificial Substrate in Ponds

Abstract.— The response of freshwater prawns Macrobrachium rosenbergii to increasing amounts of artificial substrate was evaluated in ponds. Juvenile prawns (0.24 ± 0.13 g) were stocked into nine 0.04-ha ponds at 74,000/ha. Three control ponds received no artificial substrate while artificial substrate in the form of horizontal strips of polyethylene construction fence was added to the six treatment ponds to produce 40% or 80% increases in available surface area. Increasing availability of surface area produced a direct linear increase ( P < 0.05, r ²= 0.89) in total production with no significant change in average weight ( P > 0.05). There was an inverse linear relationship between available surface area and feed conversion ratios ( P < 0.01, r ² = 0.66) likely indicating increased availability of natural foods or reduced stress among animals. There was a direct linear increase in the percentage of females which achieved sexual maturity ( P < 0.01, r ²= 0.71) as the amount of added substrate was increased. Size and number of other sexual morphotypes were not significantly affected. These responses are consistent with those that would be expected if stocking densities were decreased. These data indicate that prawn production increases in direct relation to the amount of added substrate while utilizing feed more efficiently. The effect of substrate orientation on its functionality should be evaluated to allow further increases in substrate inclusion amounts for additional production intensification.     

Quantitative and qualitative properties of host polymorphonuclear cells during experimentally induced Staphylococcus aureus mastitis in cows

Polymorphonuclear cells have a critical role in the pathogenesis of bovine mastitis. We have documented that experimentally induced Staphylococcus aureus mastitis is associated with cyclic increase and decrease in the quantity of viable bacteria shed in the milk. Concomitant with this cycling of bacteria is an inverse cycling of the hosts cells within the milk. Such somatic cells were determined to be greater than or equal to 95% polymorphonuclear cells. The quality of these cells was evaluated by measuring their relative efficiency of bacterial killing and phagocytosis at various times during an infection. Host polymorphonuclear cells had as much as 10,000-fold variation in the bactericidal failure rate for staphylococci during cell cycling. The most efficient bactericidal effect was observed at or near the peak of the somatic cell count (SCC). The ability of these cycling cells to ingest fluorescent beads was also quantitated by use of flow cytometry. The percentage of phagocytic polymorphonuclear cells that ingested fluorescent latex beads ranged from 15 to 80% of the total cell population during cell cycling, and tended to be optimal at or near peak SCC. In addition, the average number of beads ingested varied between 1 and 2 particles/polymorphonuclear cell, with as many as 17% of the phagocytic cells ingesting 4 or more beads at maximal efficiency. Polymorphonuclear cells from quarters infected with S aureus varied quantitatively (total SCC) and qualitatively (bactericidal activity and phagocytic ability) during the course of an infection. Not only is the quantity of host's phagocytic cells in the mammary gland central to the defense mechanism against infection, but the biological activation state appears to be equally important. The role of these cells in the pathogenesis of a cycling infection is presented in a model to explain the cyclic nature of mastitis.