Honey bee (Apis mellifera ligustica) acetylcholinesterase enzyme activity and aversive conditioning following aluminum trichloride exposure.

BACKGROUND: Aluminum is the third most prevalent element in the earth's crust. In most conditions, it is tightly bound to form inaccessible compounds, however in low soil pH, the ionized form of aluminum can be taken up by plant roots and distributed throughout the plant tissue. Following this uptake, nectar and pollen concentrations in low soil pH regions can reach nearly 300 mg/kg. Inhibition of acetylcholinesterase (AChE) has been demonstrated following aluminum exposure in mammal and aquatic invertebrate species. In honey bees, behaviors consistent with AChE inhibition have been previously recorded; however, the physiological mechanism has not been tested, nor has aversive conditioning. RESULTS: This article presents results of ingested aqueous aluminum chloride exposure on AChE as well as acute exposure effects on aversive conditioning in an Apis mellifera ligustica hive. Contrary to previous findings, AChE activity significantly increased as compared to controls following exposure to 300 mg/L Al3+. In aversive conditioning studies, using an automated shuttlebox, there were time and dose-dependent effects on learning and reduced movement following 75 and 300 mg/L exposures. CONCLUSIONS: These findings, in comparison to previous studies, suggest that aluminum toxicity in honey bees may depend on exposure period, subspecies, and study metrics. Further studies are encouraged at the moderate-high exposure concentrations as there may be multiple variables that affect toxicity which should be teased apart further.

Relationships among performance, residual feed intake, and temperament assessed in growing beef heifers and subsequently as 3-year-old, lactating beef cows.

Seventy-four beef heifers were used to evaluate relationships among performance, residual feed intake (RFI), and temperament measured as growing heifers (Phase 1) and subsequently as 3-yr-old lactating beef cows (Phase 2) in the same cohort. In both phases, females were housed in a covered facility and fed similar forage-based diets, and individual feed intakes, BW, BCS, chute scores (CS), exit velocities (EV), and pen scores (PS) were collected throughout the 70-d feeding trials. In Phase 2, cows were milked on trial d 14 (lactation d 28 ± 3.5) and trial d 70 (lactation d 84 ± 3.5) to determine energy-corrected milk (ECM) production. Ultrasonic backfat thickness (BF), and ribeye area (REA) were evaluated on d 0 and 70 of the trial in Phase 2. Heifers were ranked by RFI and placed into Low (<0.5 SD mean RFI; n = 27), Medium (within ± 0.5 SD; n = 23), and High (>0.5 SD mean RFI; n = 24) RFI groups. Body weight, BCS, and ADG were similar among all RFI groups; however, daily DMI differed for all groups (P < 0.01) and was greater (10.76 ± 0.24 kg/d) for High, intermediate (9.88 ± 0.25 kg/d) for Medium, and less (8.52 ± 0.23 kg/d) for Low RFI heifers. When cow performance was analyzed based on RFI rank as heifers, BW, BCS, ADG, RFI, d 14 and d 70 ECM, BF, and REA were similar among RFI groups; however, cows that were most efficient as heifers (Low) had decreased (P < 0.05) daily DMI values (10.30 ± 0.41 kg/d) compared with cows that ranked Medium (11.60 ± 0.44 kg/d) or High (11.50 ± 0.43 kg/d) as heifers. The Pearson rank correlation between Phase 1 and 2 RFI was r = 0.13 (P = 0.30), and Pearson rank correlations showed no relationship (P > 0.1) between RFI and temperament. Phase 1 CS was negatively associated with ADG in Phase 1 (r = -0.28; P = 0.02) and 2 (r = -0.32; P = 0.01), and positively associated with d 14 (r = 0.24; P = 0.04) and 70 (r = 0.25; P = 0.03) ECM. Phase 2 CS was negatively associated with Phase 2 ADG (r = -0.29; P = 0.01) and positively associated with d 14 (r = 0.46; P = 0.001) and 70 (r = 0.33; P = 0.004) ECM. Phase 2 PS also tended to be negatively associated with DMI in Phase 1 (r = -0.20; P = 0.096) and 2 (r = -0.20; P = 0.08). In this study, heifers that were most feed efficient subsequently consumed less feed as lactating cows and maintained similar performance. Feed efficiency was not associated with differences in temperament; however, more excitable females had poorer BW gains and tended to have reduced feed intakes but produced more ECM.

Effects of temporary calf removal before fixed-time artificial insemination on pregnancy rates and subsequent calf performance in suckled beef cows.

Two experiments were conducted to determine the effect of calf removal (CR) on pregnancy rate (PR) and calf performance in suckled beef cows. Cows in both experiments were synchronized with the 7-d CO-Synch + CIDR protocol [i.e., 100-µg injection of GnRH at controlled internal drug release (CIDR) device insertion (d -7) with 25-mg injection of PGF2α at CIDR removal (d 0), followed by injection of GnRH and timed AI (TAI) on d 3]. Cows were blocked by location (6 locations), stratified by days postpartum (DPP) and parity, and assigned to 1 of 2 treatments in Exp. 1: 1) control (Control; n = 156); 2) calves were separated from their dams between d 0 and 3 (CR72; n = 168); and 1 of 4 treatments in Exp. 2: 1) Control (n = 103); 2) CR72 (n = 104); 3) calves were separated from their dams between d 0 and 2 (CR48A; n = 95); and 4) similar to CR48A but CR between d 1 and 3 (CR48B; n = 53). Transrectal ultrasonography of ovarian structures was performed on d 0, 1, 2, 3, 4, and 10 (in a subset of cows) to determine pregnancy status on d 33. Blood samples were collected on d -14, -7, 0, 3, and 10 (in a subset of cows) to determine concentrations of progesterone (P4) and estradiol (E2). Calves were blocked by age as young (25 to 59 d), medium (60 to 79 d), and old (≥80 d), and were weighed on d 0, 3, 33, and 63. Overall PR did not differ among treatments and averaged 50%. Follicle growth rate from d 0 to 3 tended (P = 0.06) to be greater for CR72 (0.42 ± 0.15 mm/d) compared with Control (0.02 ± 0.15 mm/d). Young (-3.9 ± 0.3%) and old (-3.1 ± 0.4%) calves lost a greater (P < 0.001) percent of BW (PBW) during CR than medium-age (-1.6 ± 0.3%) calves exposed to CR72. In Exp. 2, PR were similar among all 3 locations (49%; P = 0.15). Young (-4.8 ± 0.6%) and medium (-3.0 ± 0.5%) calves lost greater (P < 0.01) percent body weight (PBW) during CR than old (-1.4 ± 0.6%) calves within the CR72 treatment. Calves exposed to CR48 (-2.2 ± 0.6%, -1.1 ± 0.6%, and -2.4 ± 0.6% PBW change for young, medium, and old, respectively) lost more BW than calves in the Control group (-3.7 ± 0.4%, -1.7 ± 0.5%, and -2.1 ± 0.5% PBW change for young, medium, and old, respectively). Subsequent calf weights on d 33 and 63 were greater (P < 0.05) in Controls than cows exposed to CR48 or CR72 treatments. We conclude that CR stimulated follicle growth but failed to enhance PR to TAI. However, CR had a negative impact on subsequent calf performance, which differed, depending on the duration and age of the calf when exposed to CR.

Neuromuscular block: atracurium and vecuronium compared and combined.

The neuromuscular blocking action of atracurium and vecuronium acting separately and in combination have been compared using the evoked EMG of the adductor pollicis muscle. Dose response curves have been drawn for the drugs given separately and found to be nonparallel (P less than 0.05). Atracurium was calculated to be 5.25 and 4.1 times less potent than vecuronium, ED50 and ED95 respectively. The effect on neuromuscular transmission of a combined medication using equipotent doses of atracurium and vecuronium, determined from the dose response plots, was found to be greater than would be expected by addition of their separate actions. The combination of small doses resulted in significant neuromuscular blockade.

Reducing the haemodynamic responses to laryngoscopy and intubation. A comparison of alfentanil with fentanyl.

The effects of alfentanil and fentanyl on controlling the haemodynamic responses to laryngoscopy and intubation have been compared. Five groups of ten patients were studied. Induction was with thiopentone 4 mg/kg. Thirty seconds later group 1 received 1 ml/20 kg saline, group 2 received 15 micrograms/kg alfentanil, group 3 received 30 micrograms/kg alfentanil and group 4 received 5 micrograms/kg fentanyl one minute before induction. Suxamethonium was given 60 seconds after induction and intubation of the trachea was performed 150 seconds after the start of induction. Heart rate and mean arterial pressure were recorded every minute throughout and compared with pre-induction control values. Control patients (group 1) showed significant increases associated with tracheal intubation in all haemodynamic variables. No increases were noted in groups receiving 30 micrograms/kg alfentanil or 5 micrograms/kg fentanyl. The heart rate, but not blood pressure, increased with intubation after 15 micrograms/kg alfentanil. The mean time to movement in 50% of the control patients was 7 minutes. In those given 15 and 30 micrograms/kg alfentanil it was 11 and 12 minutes respectively. In those given 5 micrograms/kg fentanyl it was greater than 15 minutes. Alfentanil is shown to reduce the cardiovascular responses to laryngoscopy and intubation and the effect appears to have a shorter duration than that of fentanyl.

The analgesic effect of a low dose of alfentanil.

The effect of a single small dose of alfentanil (6 micrograms/kg) on postoperative pain was compared with saline using a double blind study. Pain was assessed using a linear analogue scale and shown to decrease at 2, 5 and 10 minutes after injection of alfentanil (p less than 0.01). The PE'CO2 was increased at 2 and 15 minutes (p less than 0.05) and 5 and 10 minutes (p less than 0.01) after injection of alfentanil. There were no changes in pain or PE'CO2 in the control group throughout the study. Intravenous alfentanil given to patients in pain provides quick effective analgesia for a short period of time, but respiratory depression may occur.