Adrenocorticotropic hormone and corticosterone responses to acute hypoxia in the neonatal rat: effects of body temperature maintenance

The corticosterone response to acute hypoxia in neonatal rats develops in the 1st wk of life, with a shift from ACTH independence to ACTH dependence. Acute hypoxia also leads to hypothermia, which may be protective. There is little information about the endocrine effects of body temperature maintenance during periods of neonatal hypoxia. We hypothesized that prevention of hypothermia during neonatal hypoxia would augment the adrenocortical stress response. Rat pups separated from their dams were studied at postnatal days 2 and 8 (PD2 and PD8). In one group of pups, body temperature was allowed to spontaneously decrease during a 30-min prehypoxia period. Pups were then exposed to 8% O(2) for 3 h and allowed to become spontaneously hypothermic or externally warmed (via servo-controlled heat) to maintain isothermia. In another group, external warming was used to maintain isothermia during the prehypoxia period, and then hypoxia with or without isothermia was applied. Plasma ACTH and corticosterone and mRNA expression of genes for upstream proteins involved in the steroidogenic pathway were measured. Maintenance of isothermia during the prehypoxia period increased baseline plasma ACTH at both ages. Hypothermic hypoxia caused an increase in plasma corticosterone; this response was augmented by isothermia at PD2, when the response was ACTH-independent, and at PD8, when the response was ACTH-dependent. In PD8 rats, isothermia also augmented the plasma ACTH response to hypoxia. We conclude that maintenance of isothermia augments the adrenocortical response to acute hypoxia in the neonate. Prevention of hypothermia may increase the stress response during neonatal hypoxia, becoming more pronounced with increased age.     

A magnesium-induced conformational transition in the loop of a DNA analog of the yeast tRNA(Phe) anticodon is dependent on RNA-like modifications of the bases of the stem.

Two single-stranded DNA heptadecamers corresponding to the yeast tRNA(Phe) anticodon stem-loop were synthesized, and the solution structures of the oligonucleotides, d(CCAGACTGAAGATCTGG) and d(CCAGACTGAAGAU-m5C-UGG), were investigated using spectroscopic methods. The second, or modified, base sequence differs from that of DNA by RNA-like modifications at three positions; dT residues were replaced at positions 13 and 15 with dU, and the dC at position 14 with d(m5C), corresponding to positions where these nucleosides occur in tRNA(Phe). Both oligonucleotides form intramolecular structures at pH 7 in the absence of Mg2+ and undergo monophasic thermal denaturation transitions (Tm = 47 degrees C). However, in the presence of 10 mM Mg2+, the modified DNa adopted a structure that exhibited a biphasic "melting" transition (Tm values of 23 and 52 degrees C) whereas the unmodified DNA structure exhibited a monophasic denaturation (Tm = 52 degrees C). The low-temperature, Mg(2+)-dependent structural transition of the modified DNA was also detected using circular dichroism (CD) spectroscopy. No such transition was exhibited by the unmodified DNA. This transition, unique to the modified DNA, was dependent on divalent cations and occurred most efficiently with Mg2+; however, Ca2+ also stabilized the alternative conformation at low temperature. NMR studies showed that the predominant structure of the modified DNA in sodium phosphate (pH 7) buffer in the absence of Mg2+ was a hairpin containing a 7-nucleotide loop and a stem composed of 3 stable base pairs. In the Mg(2+)-stabilized conformation, the loop became a two-base turn due to the formation of two additional base pairs across the loop.(ABSTRACT TRUNCATED AT 250 WORDS)     

Animal Housing and Welfare: Effects of Housing Conditions on Body Weight and Cortisol in a Medium-Sized Rodent (Cavia aperea)

Rodents are the most abundant experimental nonhuman animals and are commonly studied under standard laboratory housing conditions. As housing conditions affect animals' physiology and behavior, this study investigated the effects of indoor and outdoor housing conditions on body weight and cortisol level of wild cavies, Cavia aperea. The changing housing condition strongly influenced both parameters, which are commonly used as indicators for animal welfare. The transfer from outdoor to indoor enclosures resulted in a body-weight loss of about 8%. In contrast, animals kept indoors showed a substantial weight gain of about 12% when they were transferred outdoors. These effects were reversible. To substantiate a connection between body-weight changes and the health states of the animals, blood basal cortisol concentrations were measured. Animals kept outdoors had significantly lower cortisol levels than did animals kept indoors. These results imply that indoor conditions have a direct effect on the animals' states. The physiological and metabolic consequences as well as potential welfare aspects should be taken into account when planning experimental work, especially on nondomestic animals.     

Virulent Bacteriophage for Efficient Biocontrol of Listeria monocytogenes in Ready-To-Eat Foods

Food-borne Listeria monocytogenes is a serious threat to human health, and new strategies to combat this opportunistic pathogen in foods are needed. Bacteriophages are natural enemies of bacteria and are suitable candidates for the environmentally friendly biocontrol of these pathogens. In a comprehensive set of experiments, we have evaluated the virulent, broad-host-range phages A511 and P100 for control of L. monocytogenes strains Scott A (serovar 4b) and WSLC 1001 (serovar 1/2a) in different ready-to-eat (RTE) foods known to frequently carry the pathogen. Food samples were spiked with bacteria (1 × 10³ CFU/g), phage added thereafter (3 × 10⁶ to 3 × 10⁸ PFU/g), and samples stored at 6°C for 6 days. In liquid foods, such as chocolate milk and mozzarella cheese brine, bacterial counts rapidly dropped below the level of direct detection. On solid foods (hot dogs, sliced turkey meat, smoked salmon, seafood, sliced cabbage, and lettuce leaves), phages could reduce bacterial counts by up to 5 log units. Variation of the experimental conditions (extended storage over 13 days or storage at 20°C) yielded similar results. In general, the application of more phage particles (3 × 10⁸ PFU/g) was more effective than lower doses. The added phages retained most of their infectivity during storage in foods of animal origin, whereas plant material caused inactivation by more than 1 log₁₀. In conclusion, our data demonstrate that virulent broad-host-range phages, such as A511 and P100, can be very effective for specific biocontrol of L. monocytogenes in contamination-sensitive RTE foods.     

Comparison of gonadorelin products in lactating dairy cows: Efficacy based on induction of ovulation of an accessory follicle and circulating luteinizing hormone profiles

This study evaluated whether the four gonadorelin products that are commercially available in the United States produce comparable ovulation responses in lactating cows. Dairy cows at 7 d after last gonadotropin-releasing hormone (GnRH) treatment of Ovsynch (Day 7), with a corpus luteum (CL) ≥15 mm and at least one follicle ≥10 mm, were evaluated for response to GnRH treatment. Selected cows were randomized to receive (100 μg; im): (1) Cystorelin (n = 146); (2) Factrel (n = 132); (3) Fertagyl (n = 140); or (4) Ovacyst (n = 140). On Day 14, cows were examined for ovulation by detection of an accessory CL. Circulating luteinizing hormone (LH) concentrations were also evaluated in some cows after treatment with 100 μg (n = 10 per group) or 50 μg (n = 5 per group) GnRH. Statistical analyses were performed with the procedures MIXED and GLIMMIX of the SAS program. Percentage of cows ovulating differed (P < 0.01) among groups, with that for Factrel being lower (55.3%) than that for Cystorelin (76.7%), Fertagyl (73.6%), or Ovacyst (85.0%). There was no effect of batch, parity, or follicle size on ovulation response, but increasing body condition score decreased ovulation response. There was a much greater LH release in cows treated with 100 μg than in those treated with 50 μg, but there were no detectable differences among products in time to LH peak, peak LH concentration, or area under the LH curve and no treatment effects nor treatment by time interactions on circulating LH profile. Thus, ovulation response to Factrel on Day 7 of the cycle was lower than that for other commercial GnRH products, although a definitive mechanism for this difference between products was not demonstrated.     

Recent developments in essential oil production

The 29 essential oils described in this article are the backbone of the cosmetics industry and are of great importance also to other industries. Their sources are almost exclusively outside the United States, many of them being in the Old World. To develop more New World sources is of utmost importance.     

Variation in potential for isoprene emissions among Neotropical forest sites

As part of the Large Scale Biosphere–Atmosphere Experiment in Amazônia (LBA), we have developed a bottom‐up approach for estimating canopy‐scale fluxes of isoprene. Estimating isoprene fluxes for a given forest ecosystem requires knowledge of foliar biomass, segregated by species, and the isoprene emission characteristics of the individual tree species comprising the forest. In this study, approximately 38% of 125 tree species examined at six sites in the Brazilian Amazon emitted isoprene. Given logistical difficulties and extremely high species diversity, it was possible to screen only a small percentage of tree species, and we propose a protocol for estimating the emission capacity of unmeasured taxa using a taxonomic approach, in which we assign to an unmeasured genus a value based on the percentage of genera within its plant family which have been shown to emit isoprene. Combining this information with data obtained from 14 tree censuses at four Neotropical forest sites, we have estimated the percentage of isoprene‐emitting biomass at each site. The relative contribution of each genus of tree is estimated as the basal area of all trees of that genus divided by the total basal area of the plot. Using this technique, the percentage of isoprene‐emitting biomass varied from 20% to 42% (mean=31%; SD=8%). Responses of isoprene emission to varying light and temperature, measured on a sun‐adapted leaf of mango (Mangifera indica L.), suggest that existing algorithms developed for temperate species are adequate for tropical species as well. Incorporating these algorithms, estimates of isoprene‐emitting biomass, isoprene emission capacity, and site foliar biomass into a canopy flux model, canopy‐scale fluxes of isoprene were predicted and compared with the above‐canopy fluxes measured at two sites. Our bottom‐up approach overestimates fluxes by about 50%, but variations in measured fluxes between the two sites are largely explained by observed variation in the amount of isoprene‐emitting biomass.     

Amazonian biogenic volatile organic compounds under global change

Biogenic volatile organic compounds (BVOCs) play important roles at cellular, foliar, ecosystem and atmospheric levels. The Amazonian rainforest represents one of the major global sources of BVOCs, so its study is essential for understanding BVOC dynamics. It also provides insights into the role of such large and biodiverse forest ecosystem in regional and global atmospheric chemistry and climate. We review the current information on Amazonian BVOCs and identify future research priorities exploring biogenic emissions and drivers, ecological interactions, atmospheric impacts, depositional processes and modifications to BVOC dynamics due to changes in climate and land cover. A feedback loop between Amazonian BVOCs and the trends of climate and land‐use changes in Amazonia is then constructed. Satellite observations and model simulation time series demonstrate the validity of the proposed loop showing a combined effect of climate change and deforestation on BVOC emission in Amazonia. A decreasing trend of isoprene during the wet season, most likely due to forest biomass loss, and an increasing trend of the sesquiterpene to isoprene ratio during the dry season suggest increasing temperature stress‐induced emissions due to climate change.     

Mitiglinide treatment may decreases plasma fibroblast growth factor-21 levels in individuals with new-onset T2DM

Fibroblast growth factor 21 (FGF-21) has been identified as a potent metabolic regulator. Despite the importance of FGF-21 in the regulation of glucose, lipid and energy homeostasis, much less is known about the effect of common anti-diabetic treatment on the plasma levels of FGF-21. The aim of our study was to measure its plasma levels in patients with new-onset type 2 diabetes mellitus (nT2DM) and healthy subjects, and to assess the changes of its circulating levels after pharmacological interventions. One hundred and eleven patients with nT2DM, and 87 gender-, age- and body mass index (BMI)-matched normal glucose tolerance (NGT) controls participated in the study. The patients with nT2DM were treated with mitiglinide for 16 weeks. Biochemical parameters, plasma FGF-21 and insulin levels were measured by commercial ELISA or RIA kits pre- and post-treatment with mitiglinide. Fasting plasma FGF-21 levels were higher in the nT2DM group than in controls (3.21 ± 1.37 vs. 1.52 ± 0.36 μg/L, P<0.01). In nT2DM patients, fasting plasma FGF-21 concentrations were significantly decreased after mitiglinide treatment for 16 weeks (3.21 ± 1.37 vs. 2.79 ± 1.14μg/L, P<0.05), accompanied by significant amelioration of glucose metabolism. Our study showed that mitiglinide treatment decreased plasma FGF-21 levels, and this decrease might be associated with the amelioration of glucose metabolism.