Does vocal learning accelerate acoustic diversification? Evolution of contact calls in Neotropical parrots.

Learning has been traditionally thought to accelerate the evolutionary change of behavioural traits. We evaluated the evolutionary rate of learned vocalizations and the interplay of morphology and ecology in the evolution of these signals. We examined contact calls of 51 species of Neotropical parrots from the tribe Arini. Parrots are ideal subjects due to their wide range of body sizes and habitats, and their open-ended vocal learning that allows them to modify their calls throughout life. We estimated the evolutionary rate of acoustic parameters of parrot contact calls and compared them to those of morphological traits and habitat. We also evaluated the effect of body mass, bill length, vegetation density and species interactions on acoustic parameters of contact calls while controlling for phylogeny. Evolutionary rates of acoustic parameters did not differ from those of our predictor variables except for spectral entropy, which had a significantly slower rate of evolution. We found support for correlated evolution of call duration, and fundamental and peak frequencies with body mass, and of fundamental frequency with bill length. The degree of sympatry between species did not have a significant effect on acoustic parameters. Our results suggest that parrot contact calls, which are learned acoustic signals, show evolutionary rates similar to those of morphological traits. This is the first study to our knowledge to provide evidence that change through cultural evolution does not necessarily accelerate the evolutionary rate of traits acquired through life-long vocal learning.

Isolation and characterization of dinucleotide microsatellite loci in the Asian elephant (Elephas maximus).

The endangered Asian elephant is found today primarily in protected areas. We characterized 18 dinucleotide microsatellite loci in this species. Allelic diversity ranged from three to eight per locus, and observed heterozygosity ranged from 0.200 to 0.842 in a wild population. All loci were in Hardy-Weinberg equilibrium, but linkage disequilibrium was detected between two loci in the wild, but not in the zoo elephants. These loci will be useful for the population-level studies of this species.

Duplication and concerted evolution of the mitochondrial control region in the parrot genus Amazona.

We report a duplication and rearrangement of the mitochondrial genome involving the control region of parrots in the genus Amazona. This rearrangement results in a gene order of cytochrome b/tRNA(Thr)/pND6/pGlu/CR1/tRNA(Pro)/NADH dehydrogenase 6/tRNA(Glu)/CR2/tRNA(Phe)/12s rRNA, where CR1 and CR2 refer to duplicate control regions, and pND6 and pGlu indicate presumed pseudogenes. In contrast to previous reports of duplications involving the control regions of birds, neither copy of the parrot control region shows any indications of degeneration. Rather, both copies contain many of the conserved sequence features typically found in avian control regions, including the goose hairpin, TASs, the F, C, and D boxes, conserved sequence box 1 (CSB1), and an apparent homolog to the mammalian CSB3. We conducted a phylogenetic analysis of homologous portions of the duplicate control regions from 21 individuals representing four species of Amazona (A. ochrocephala, A. autumnalis, A. farinosa, and A. amazonica) and Pionus chalcopterus. This analysis revealed that an individual's two control region copies (i.e., the paralogous copies) were typically more closely related to one another than to corresponding segments of other individuals (i.e., the orthologous copies). The average sequence divergence of the paralogous control region copies within an individual was 1.4%, versus a mean value of 4.1% between control region orthologs representing nearest phylogenetic neighbors. No differences were found between the paralogous copies in either the rate or the pattern in which the two copies accumulated base pair changes. This pattern suggests concerted evolution of the two control regions, perhaps through occasional gene conversion events. We estimated that gene conversion events occurred on average every 34,670 +/- 18,400 years based on pairwise distances between the paralogous control region sequences of each individual. Our results add to the growing body of work indicating that under some circumstances duplicated mitochondrial control regions are retained through evolutionary time rather than degenerating and being lost, presumably due to selection for a small mitochondrial genome.

Population genetic structure and vocal dialects in an amazon parrot.

The relationship between cultural and genetic evolution was examined in the yellow-naped amazon Amazona auropalliata. This species has previously been shown to have regional dialects defined by large shifts in the acoustic structure of its learned contact call. Mitochondrial DNA sequence variation from a 680 base pair segment of the first domain of the control region was assayed in 41 samples collected from two neighbouring dialects in Costa Rica. The relationship of genetic variation to vocal variation was examined using haplotype analysis, genetic distance analysis, a maximum-likelihood estimator of migration rates and phylogenetic reconstructions. All analyses indicated a high degree of gene flow and, thus, individual dispersal across dialect boundaries. Calls sampled from sound libraries suggested that temporally stable contact call dialects occur throughout the range of the yellow-naped amazon, while the presence of similar dialects in the sister species Amazona ochrocephala suggests that the propensity to form dialects is ancestral in this clade. These results indicate that genes and culture are not closely associated in the yellow-naped amazon. Rather, they suggest that regional diversity in vocalizations is maintained by selective pressures that promote social learning and allow individual repertoires to conform to local call types.

Laparoscopic versus open appendectomy.

This prospective clinical study was done because our initial retrospective review suggested that laparoscopic appendectomy (LA) offers no significant advantages over open appendectomy (OA) yet is significantly more expensive. From July 1992 to August 1993, 57 patients were approached preoperatively for randomization to either LA (n = 19) or OA (n = 18). There were no statistically significant differences between the LA and OA groups in operative risk: mean age, 28 +/- 2 vs 26 +/- 2 years; percent female, 26% vs 22%; body mass index, 24 +/- 0.8 vs 26 +/- 1.2 kg/m2. All patients were either ASA class I or class II, 78% in each group being class II. The differences between the LA and OA groups in mean operating time required (93 +/- 12 vs 87 +/- 8 minutes), postoperative intramuscular narcotic analgesic usage (24 +/- 6 vs 26 +/- 6 hours), postoperative hospital stay (57 +/- 12 vs 66 +/- 10 hours), and return to normal activity (20 +/- 6 vs 14 +/- 3 days) were also not significant. However, LA was much more expensive because of higher operating room charges. The mean total hospital bill was $4,600 +/- $160 for the LA group and $1,700 +/- $70 for the OA group. This prospective study corroborated our previous analysis. Laparoscopic appendectomy is safe, effective, and expensive and overall has no greatly significant advantages over open appendectomy.

The effects of native LDL and oxidized LDL on EDRF bioactivity and nitric oxide production in vascular endothelium.

Low-density lipoprotein (LDL) and oxidized low-density lipoprotein (OxyLDL) have previously been shown to inhibit vasorelaxation caused by endothelium-derived relaxing factor (EDRF). The purpose of the present study was to directly determine the effects of LDL and OxyLDL on EDRF bioactivity and nitric oxide (NO) production in vascular endothelium to further understand the mechanism whereby lipoprotein alters vascular reactivity. Cultured bovine aortic endothelial cells were incubated with either LDL or OxyLDL for 1 hour. After washing the cells free of lipoprotein, agonist-stimulated (bradykinin; BK) EDRF bioactivity and NO content of the effluent were quantitated. These results were compared with control cells not exposed to lipoprotein. In a second series of experiments, the effects of LDL and OxyLDL on EDRF-mediated increases in cyclic guanosine monophosphate (cGMP) in a reporter fibroblast cell line were determined. Last, the direct effects of LDL on NO-induced vasodilation of isolated coronary artery rings were determined by using standard in vitro isometric recording methods. LDL and OxyLDL significantly decreased EDRF bioactivity but not NO production by endothelial cells. When expressed as percent relaxation of the biodetector per mole of NO produced, both LDL and OxyLDL resulted in the release of a significantly less-potent vasodilator than that derived from control cells. In the reporter fibroblast experiments, there was no significant difference in the amount of cGMP generated by fibroblasts in response to medium from control and lipoprotein-treated cells. In isolated ring experiments, LDL did not directly alter NO vasorelaxation. We conclude that both LDL and OxyLDL inhibit EDRF-induced vasorelaxation by complex mechanisms other than the direct inhibition of NO synthesis by endothelial cells or extracellular inactivation of EDRF. LDL and OxyLDL may result in the release of a less potent NO-containing relaxing factor by altering the metabolism of an endogenous nitrosovasodilator.

Hardiness, stress, and burnout among intensive care nurses.

The purposes of this study were to determine whether hardiness is a predictor of burnout and whether it can buffer the effect of stress on burnout. Thirty-one registered nurses who work in intensive care units completed the Hardiness test, the Nursing Stress scale, and the Tedium scale. Descriptive statistics, correlational statistics, t tests, analysis of variance, and hierarchical multiple regressions were used to analyze the data. Results indicated that hardiness and burnout had a significant inverse relationship (r = 0.66). Stress and the stress-hardiness interaction term accounted for 29% of the variance in burnout scores. This study found hardiness to be a predictor of burnout and a buffer in the stress-burnout relationship. Furthermore, the relationship between hardiness and stress was found to be stronger than that between stress and burnout. Further study is needed to verify that hardiness is a stress mediator in nursing and to determine how to best promote hardiness in nurses.

EDRF and nitric oxide production in cultured endothelial cells: direct inhibition by E. coli endotoxin.

Recent studies have yielded contradictory interpretations about the influence of gram-negative endotoxin on endothelium-derived relaxing factor (EDRF). We tested the hypothesis that Escherichia coli endotoxin exerts primary facilitatory or, alternatively, inhibitory actions on EDRF release and the synthesis of either nitric oxide or a nitroso compound in cultured endothelial cells. Bovine aortic endothelial cells were grown on microcarrier beads and either exposed acutely (30 min) to E. coli endotoxin or incubated with endotoxin for 1 h followed by a 1-h wash (prolonged exposure). EDRF bioactivity was measured under basal, bradykinin-stimulated, and A23187-stimulated conditions using standard isometric tension recordings. EDRF-derived nitric oxide was quantitated using a specific chemiluminescence technique. Endotoxin (0.005-5 micrograms/ml) decreased EDRF bioactivity and nitric oxide production under both basal and bradykinin-stimulated conditions after prolonged, but not acute, exposure. A23187-stimulated EDRF bioactivity and nitric oxide production were minimally, albeit significantly, reduced after endotoxin. The present results demonstrate that EDRF activity and nitric oxide production are decreased in vascular endothelial cells exposed to endotoxin. Endotoxin itself failed to directly stimulate EDRF release from endothelium. Alternative sources of nitrovasodilators, endothelium-independent effects, or release of other vasoactive mediators by endotoxin may be responsible for systemic hypotension during in vivo endotoxemia.

A comparison of epidural and non-epidural anesthesia and analgesia in total hip or knee arthroplasty patients.

This retrospective study explores a number of variables encountered with the use of either epidural or non-epidural anesthesia and analgesia. Postoperative mobility, amount of narcotic used, incidence of blood transfusion, length of stay, and presence of urinary retention, pruritus, nausea and vomiting, or respiratory depression were compared in a group of 101 consecutive patients scheduled for total hip or knee arthroplasty. Fifty-two patients received epidural anesthesia and analgesia; the remaining 49 received non-epidural anesthesia, followed by standard IM/IV postoperative analgesia. Epidural patients required significantly less narcotic than the non-epidural group. There were significantly fewer blood transfusions in the epidural group; however, epidural patients had significantly increased incidence of urinary retention and pruritus. The use of epidural anesthesia and analgesia for total hip and knee arthroplasty patients has definite merit, but is most safely administered in a monitored, skilled nursing unit.