Hormonal growth-promotant effects on grain-fed cattle maintained under different environments

Six steers (3/4 Charolaisx1/4 Brahman) (mean body weight 314 +/- 27 kg) and six spayed heifers (3/5 Shorthornx2/5 Red Angus) (mean body weight 478 +/- 30 kg) were used to determine the effects of climatic conditions and hormone growth promotants (HGP) on respiration rate (RR; breaths/min), pulse rate (beats/min), rectal temperature (RT; degrees C), and heat production (HP; kJ). Cattle were exposed to the following climatic conditions prior to implantation with a HGP and then again 12 days after implantation: 2 days of thermoneutral conditions (TNL) [21.9 +/- 0.9 degrees C ambient temperature (T-A) and 61.7 +/- 22.1% relative humidity (RH)] then 2 days of hot conditions [HOT; 29.2 +/- 4 degrees C (T-A) and 78.3 +/- 13.2% (RH)], then TNL for 3 days and then 2 days of cold conditions [COLD; 17.6 +/- 0.9 degrees C (T-A) and 63.4 +/- 1.8% (RH); cattle were wet during this treatment]. The HGP implants used were: estrogenic implant (E), trenbolone acetate implant (TBA), or both (ET). Both prior to and following administration of HGP, RRs were lower (P < 0.05) on cold days and greater (P < 0.05) on hot days compared to TNL. On hot days, RTs, were 0.62 degrees C higher after compared to before implanting. Across all conditions, RTs were > 0.5 degrees C greater (P < 0.05) for E cattle than for TBA or ET cattle. On cold days, RTs of steers were > 0.8 degrees C higher than for the heifers, while under TNL and HOT, RTs of steers were 0.2-0.35 degrees C higher than those of heifers. Prior to implantation, HP per hour and per unit of metabolic body weight was higher (P < 0.05) for cattle exposed to hot conditions, when compared to HP on cold days. After implantation, HP was greater (P < 0.05) on hot days than on cold days. Under TNL, ET cattle had the lowest HP and greatest feed intake. On hot days, E cattle had the lowest HP, and the highest RT; therefore, if the potential exists for cattle death from heat episodes, the use of either TBA or ET may be preferred. Under cold conditions HP was similar among implant groups.

Behavioral determinants of healthy aging

With global trends in population aging, many nations are developing and implementing healthy aging policies to promote quality as well as years of healthy life. To broaden the evidence base for such policy development, a review of the literature was conducted to summarize the existing evidence regarding the behavioral determinants of health), aging. Such research is needed so that the efficacy of modes of intervention can be better understood. The Outcome of: healthy or successful aging was selected for this review since this nomenclature dominates the literature describing a global measure of multidimensional functioning at the positive end of the health continuum in older age. Studies published between 1985 and 2003 that reported statistical associations between baseline determinants and healthy aging Outcome were identified from a systematic search of medical, psychological, sociological, and gerontological databases. Eight studies satisfied the search criteria. Modifiable risk factors among the behavioral determinants included smoking status, physical activity level, body mass index, diet, alcohol use, and health practices. On the basis of these findings, effective healthy aging policies need to enhance opportunities across the life span for modification of lifestyle risk factors. Efforts to standardize concepts and terminology will facilitate further research activity in this important area. (Am J Prev Med 2005;28(3):298-304) (c) 2005 American Journal of Preventive Medicine.

Cytochrome P450-mediated metabolism of haloperidol and reduced haloperidol to pyridinium metabolites

Haloperidol ( HP) has been reported to undergo cytochrome P450 (P450)-mediated metabolism to potentially neurotoxic pyridinium metabolites; however, the chemical pathways and specific enzymes involved in these reactions remain to be identified. The aims of the current study were to (i) fully identify the cytochrome P450 enzymes capable of metabolizing HP to the pyridinium metabolite, 4-(4-chlorophenyl)- 1-(4-fluorophenyl)-4-oxobutylpyridinium (HPP+), and reduced HP (RHP) to 4-(4-chlorophenyl)- 1-(4-fluorophenyl)-4-hydroxybutylpyridinium (RHPP+); and (ii) determine whether 4-(4-chlorophenyl)- 1-(4-fluorophenyl)-4-oxobutyl-1,2,3,6-tetrahydropyridine (HPTP) and 4-(4-chlorophenyl)1-( 4-fluorophenyl)-4-hydroxybutyl-1,2,3,6-tetrahydropyridine (RHPTP) were metabolic intermediates in these pathways. In vitro studies were conducted using human liver microsomal preparations and recombinant human cytochrome P450 enzymes (P450s 1A1, 1A2, 1B1, 2A6, 2B6, 2C9, 2C19 2D6, 2E1, 3A4, 3A5, and 3A7) expressed in bicistronic format with human NADPH cytochrome P450 reductase in Escherichia coli membranes. Pyridinium formation from HP and RHP was highly correlated across liver preparations, suggesting the same enzyme or enzymes were responsible for both reactions. Cytochrome P450s 3A4, 3A5, and 3A7 were the only recombinant enzymes which demonstrated significant catalytic activity under optimized conditions, although trace levels of activity could be catalyzed by NADPHP450 reductase alone. NADPH-P450 reductase-mediated activity was inhibited by reduced glutathione but not catalase or superoxide dismutase, suggesting O-2-dependent oxidation. No evidence was obtained to support the contention that HPTP and RHPTP are intermediates in these pathways. K-m values for HPP+ (34 +/- 5 mu M) and RHPP+ (64 +/- 4 mu M) formation by recombinant P450 3A4 agreed well with those obtained with human liver microsomes, consistent with P450 3A4 being the major catalyst of pyridinium metabolite formation in human liver.

The effect of different levels of dietary crude protein on urea metabolism of rusa deer (Cervus timorensis)

Two experiments were conducted to measure urea recycling and rumen flow dynamics in young rusa deer fed low (LP) or high (HP) protein diets. Pool size and flux rate of labelled urea. into and out of the blood pool were measured using single intravenous (i.v.) injection solutions containing [C-14] - and [N-15]-urea. A curve peeling technique was used to fit the enrichment of N-15 or specific radioactivity (SRA) of C-14 to exponential equations. Body urea-N pool size was significantly greater (P < 0.05) when a HP, compared to a LP diet, was fed. Urea space, expressed as a percent of live weight, total flux rate of urea through the blood pool and the irreversible loss of urea was similar for both diets. The mean (+/- S.E.M.) concentration of plasma urea-N was greater when animals were fed the HP diet compared to the LP diet (2 1.1 +/- 0.3 versus 14.4 +/- 1.4 mg/100 ml, respectively). Voluntary feed intake and digestibility of dietary components were also measured. Daily dry matter intakes were not affected by the crude protein (CP) content of the diet, although apparent DM digestibility was significantly greater for HP diet fed in both experiments. An intraruminal infusion of CrEDTA was used to determine rumen flow dynamics. Ruminal mean retention time, relative net outflow rate of water and passage rate constant (k(w)) were significantly greater (P < 0.05) when the HP diet was fed compared to the LP diet. The extent of urea metabolism and flux rates of urea between the blood and secondary pools appear similar to those previously reported for other ruminants fed diets contrasting in CP content. (c) 2005 Elsevier B.V. All rights reserved.

The corrosion performance of anodised magnesium alloys

The corrosion performance of anodised magnesium and its alloys, such as commercial purity magnesium (CP-Mg) and high-purity magnesium (HP-Mg) ingots, magnesium alloy ingots of MEZ, ZE41, AM60 and AZ91D and diecast AM60 (AM60-DC) and AZ91D (AZ91D-DC) plates, was evaluated by salt spray and salt immersion testing. The corrosion resistance was in the sequential order: AZ91D approximate to AM60 approximate to MEZ >= AZ91D-DC >= AM60-DC > HP-Mg > ZE41 > CP-Mg. It was concluded the corrosion resistance of an anodised magnesium alloy was determined by the corrosion performance of the substrate alloy due to the porous coating formed on the substrate alloy acting as a simple corrosion barrier. (c) 2006 Elsevier Ltd. All rights reserved.