The taste of polycose in hamsters

Hamsters show a preference for Polycose, a mixture of starch-derived glucose polymers, that is as strong as their preference for sucrose. However, in the hamster, taste aversions to Polycose may be less easily acquired than taste aversions to sucrose and the qualitative aspects of Polycose are unknown in this species. In order to examine the taste of Polycose in the hamster, we utilized a taste-aversion protocol with two conditioning trials. Animals were trained to avoid one of three different conditioning stimuli: 50 mM sucrose, 100 mM Polycose and a mixture of 50 mM sucrose with 100 mM Polycose. Control animals were conditioned with deionized water. After the second conditioning trial, generalization testing began for the three conditioning stimuli plus 3 mM citric acid, 300 mM KCI and 30 mM NaCl. The results showed that aversions to Polycose, sucrose or the Polycose/sucrose mixture cross- generalized, demonstrating that Polycose and sucrose share a common taste percept in the hamster. None of the aversions generalized to NaCl, citric acid or KCI. In addition, comparisons among the patterns of taste generalizations indicated that the tastes of Polycose and sucrose also had distinct qualitative components. Finally, although the taste of 100 mM Polycose was more salient than the taste of 50 mM sucrose, the taste of sucrose could still be detected in a mixture with Polycose.      

Increased carbon monoxide excretion in Bolivian squirrel monkeys with fasting hyperbilirubinemia

Pulmonary carbon monoxide (CO) excretion rates (VeCO) were 50% greater, on average, in Bolivian squirrel monkeys (BoSMs) which exhibit a unique fasting hyperbilirubinemia (FH), than in fasted control Brazilian squirrel monkeys (BrSMs). Since the catabolism of heme produces equimolar amounts of CO and bilirubin, the increased VeCOs are consistent with concurrent increases in endogenous bilirubin production rates. Tin-protoporphyrin, a competitive inhibitor of heme oxygenase, significantly decreased both the VeCO and serum bilirubin level in fasted BoSMs. Overproduction of bilirubin may be responsible in part for the marked FH in BoSMs.     

Isolation of zoosporogenous actinomycetes from desert soils

We have undertaken a study to estimate the species diversity of zoosporogenous actinomycetes that can be isolated from an arid environment. The study site encompassed an area of approximately 22 000 square kilometers of the Mojave Desert along the California-Nevada border. A series of 29 soil samples was collected along two intersecting transects of approximately 190 and 240 km which traversed a number of distinct ecosystems. A₀ horizon soils were collected from the rhizosphere of the predominant vegetation at each sampling site and screened for the target genera using selective isolation techniques: chemoattraction (xylose and -collidine) and baiting with hair. Following incubation of primary isolation plates for 28 days at 28°C, all colonies that exhibited filamentous growth, presence of sporangia and/or motile spores upon direct microscopic observation (450 and 1000×) were further characterized by fatty acid analysis (FAME). Most of the isolates fell into three broad clusters that roughly correlated with presumptive genus assignments. Individual isolates could be assigned to 226 FAME biotypes based on chromatographic similarity (85%). The dominant species (514/826 isolates) belong to a previously undescribed taxon that morphologically resemblesGeodermatophilus but possesses unique FAME profiles that include at least three novel lipids. The remainder of the isolates were species ofActinoplanes, indeterminate species or vagrant isolates ofStreptomyces.     

Choline acetyltransferase activity of spinal cord cell cultures increased by co-culture with muscle and by muscle-conditioned medium

Activity of the enzyme choline acetyltransferase (CAT), which mediates the synthesis of the neurotransmitter, acetylcholine, was increased up to 20- fold in spinal cord (SC) cells grown in culture with muscle cells for 2 wk. This increase was directly related to the duration of co-culture as well as to the cell density of both the SC and muscle involved and was not affected by the presence of the acetylcholine receptor blocking agent, α-bungarotoxin. Glutamic acid decarboxylase (GAD) activity was often markedly decreased in SC-muscle cultures while the activities of acetylcholinesterase and several other enzymes were little changed. Increased CAT activity was also observed when SC cultures were maintained in medium which had been conditioned by muscle cells or by undifferentiated cells from embryonic muscle. Muscle-conditioned medium (CM) did not affect the activities of SC cell GAD or acetylcholinesterase. Dilution or concentration of the CM directly affected its ability to increase SC CAT activity , as did the duration and timing of exposure of the SC cells to the CM. The medium could be conditioned by muscle cells in the presence or absence of serum, and remained effective after dialysis or heating to 58 degrees C. Membrane filtration data were consistent with the conclusion that the active material(s) in CM had a molecular weight in excess of 50,000 daltons. We conclude that large molecular weight material that is released by muscle cells is capable of producing a specific increase in CAT activity of SC cells.     

Palatability and efficacy to possums and rats of pest control baits containing bird repellents

Repellents used to reduce by-kill of birds during pest control must not compromise acceptance by target species. Two repellents combined, anthraquinone (AQ; 0.4 g kg^?1) and d-pulegone (DP; 1.0) did not reduce the palatability of blue-coloured carrot baits to laboratory rats (Rattus norvegicus); nor did DP (2.0). Green-coloured carrot baits coated with AQ, DP or AQ + DP were taken from bait stations by wild possums (Trichosurus vulpecula) and rats. Toxic (1080) bait coated with AQ (0.4) and peanut oil (0.1) had reduced palatability but was accepted by laboratory rats. However, laboratory rats did not consume enough baits coated with AQ and bacon, peanut butter, cinnamon or DP to be killed. Anthraquinone (0.4 or 0.8) plus cinnamon and DP (0.5) did not affect palatability or lethality to captive ship rats (R. rattus) or possums. Anthraquinone and DP as surface coatings on baits are therefore acceptable to possums and possibly rats, at concentrations that deter some bird species.     

Critical temperatures for xylogenesis in conifers of cold climates

Aim To identify temperatures at which cell division and differentiation are active in order to verify the existence of a common critical temperature determining growth in conifers of cold climates. Location Ten European and Canadian sites at different latitudes and altitudes. Methods The periods of cambial activity and cell differentiation were assessed on a weekly time‐scale on histological sections of cambium and wood tissue collected over 2 to 5 years per site from 1998 to 2005 from the stems of seven conifer species. All data were compared with daily air temperatures recorded from weather stations located close to the sites. Logistic regressions were used to calculate the probability of xylogenesis and of cambium being active at a given temperature. Results Xylogenesis lasted from May to October, with a growing period varying from 3 to 5 months depending on location and elevation. Despite the wide geographical range of the monitored sites, temperatures for onset and ending of xylogenesis converged towards narrow ranges with average values around 4–5, 8–9 and 13–14 °C for daily minimum, mean and maximum temperature, respectively. On the contrary, cell division in the cambium stopped in July?August, when temperatures were still high. Main conclusions Wood formation in conifers occurred when specific critical temperatures were reached. Although the timing and duration of xylogenesis varied among species, sites and years, the estimated temperatures were stable for all trees studied. These results provide biologically based evidence that temperature is a critical factor limiting production and differentiation of xylem cells in cold climates. Although daily temperatures below 4?5 °C are still favourable for photosynthesis, thermal conditions below these values could inhibit the allocation of assimilated carbon to structural investment, i.e. xylem growth.     

Effects of ozone exposure on the lungs and the erythrocytes of rats and monkeys: relative biochemical changes.

Ozone exposure (0.5 p.p.m., 8 hours daily for 7 days) resulted in a 20-26% (P less than 0.05) increase in the level of reduced glutathione (GSH), and the activities of the GSH peroxidase system in rat lungs. The increases were of smaller magnitude (10-15%) in the lungs of ozone-exposed monkeys. No significant changes were observed in these parameters in the erythrocytes of ozone-exposed and control animals of the two species. The results suggest that rats may be more sensitive to ozone than monkeys in terms of biochemical lesions in the lung, and that ozone effects are manifested primarily in the lung.     

Examining the influence of sport program staff and parent/caregiver support on youth outcomes

Abstract

Youth participation in sport is associated with positive developmental outcomes. The development of life skills is especially important for urban youth of color who are often underserved and face poor long-term outcomes. To service the needs of underserved youth, community youth sport programs have begun to utilize sport-based positive youth development (PYD). Through this approach, key adult figures such as sport program staff and parents/caregivers have been identified as important mechanisms for life skill development and the transfer of learning. The aim of the current study sought to better understand how key adult figures influence life skill outcomes of urban youth of color involved in a community sport-based PYD program. Hierarchical linear regression analyses were used to examine the independent and interactive effects of staff support and parent/caregiver support on youth life skill and transfer of learning outcomes. Results indicated that staff support and parent/caregiver support predicted youth life skill and transfer of learning outcomes, both independently and, in some cases, interactively.