Transgenic organisms in evolutionary ecology

Evolutionary ecology aims to understand how phenotypes are designed for reproductive success and survival. Perhaps the most powerful approach towards this goal is to alter a character genetically and observe the resulting change in reproduction, survival, growth, defense or competitive ability. Until recently, this strategy was not practical. Transgenic manipulation now offers a solution - novel genes are introduced into the germ line and are then expressed in the developing organism. This technique is already available in model and agricultural organisms. The challenge for molecular evolutionary ecologists is to find ways to adopt these powerful systems to understand the mechanisms underlying adaptive traits and their evolution.

Secondary school pupils' perceptions of burnout among teachers

BACKGROUND

Numerous studies examined teachers' self-reports concerning their occupational burnout. Given that pupils are in a prime position to assess teachers' burnout, due to their intensive daily contact with their teachers and because some of pupils' behaviours can induce stress, the present study focuses on a relatively unexplored topic, namely the meanings that adolescents attach to burnout among their teachers.

AIMS

This study was aimed at examining pupils' perceptions regarding burnout among their teachers, and to investigate the possible recommendations that the pupils would suggest to different constituents of the educational system for coping with burnout among teachers.

SAMPLE

A total of 297 Israeli secondary school pupils (approximately 57% girls and 43% boys) studying in 12 tenth grade classes (mean age 15 years 8 months, SD = 0.42 years) participated in this study.

METHODS

A questionnaire dealing with pupils' perceptions of burnout among teachers was administered. It included four sections. The first part asked for background of the pupils (sex and age). Next, pupils were asked an open-ended question in which they need to describe the most salient behaviour of a burned-out teacher in the classroom and to indicate the proportion of burned-out teachers among those teaching them. The third section consisted of a list of 14 items describing potential characteristics of burned-out teachers. The respondents were asked to indicate the extent to which, in their opinion, each of the descriptors characterized burned-out teachers. In addition, pupils were asked three open-ended questions in which they were required to describe the most salient way for (a) the students, (b) the teachers themselves and (c) the school principal to cope with teachers' burnout.

RESULTS

Findings showed that the most frequently mentioned characteristics of burned-out teachers were: teachers who 'feel that working with pupils for a full day is an oppressive effort', 'feel wiped out at the end of a teaching day', 'feel that teaching is turning them into impatient persons' and 'feel that teaching frustrates them'. No differences were found between girls' and boys' perceptions of burned-out teachers: both emphasize the psychological exhaustion of teachers as the most salient characteristic of burnout among teachers. Pupils suggest that the better ways for coping with this phenomenon include a more positive behaviour of the pupils themselves towards teachers, that burned-out teachers quit their jobs and that better work conditions be offered to them by the educational authorities.

CONCLUSIONS

Our findings allude to the importance of analyzing interactional phenomena like burnout among teachers from the perspectives of different actors in the school arena and allow us to broaden our understanding of pupils' perceptions of teachers. Suggestions for further research and for the development of methodological refinements are discussed.

Toward reconciling inferences concerning genetic variation in senescence in Drosophila melanogaster

Standard models for senescence predict an increase in the additive genetic variance for log mortality rate late in the life cycle. Variance component analysis of age-specific mortality rates of related cohorts is problematic. The actual mortality rates are not observable and can be estimated only crudely at early ages when few individuals are dying and at late ages when most are dead. Therefore, standard quantitative genetic analysis techniques cannot be applied with confidence. We present a novel and rigorous analysis that treats the mortality rates as missing data following two different parametric senescence models. Two recent studies of Drosophila melanogaster, the original analyses of which reached different conclusions, are reanalyzed here. The two-parameter Gompertz model assumes that mortality rates increase exponentially with age. A related but more complex three-parameter logistic model allows for subsequent leveling off in mortality rates at late ages. We find that while additive variance for mortality rates increases for late ages under the Gompertz model, it declines under the logistic model. The results from the two studies are similar, with differences attributable to differences between the experiments.

Turkish hospital management at a crossroads: prospects for the year 2000

The Turkish health system has been undergoing a radical reform process since the early 1990s. Reform proposals, based on purchaser/provider split, self-governing hospitals (ultimately leading to full privatization), compulsory health insurance etc., are expected to have a profound effect on hospital management. In such an environment, hospital administrators' views on the domains and issues that will come to the fore in the year 2000 gain importance. In this paper, results of a study undertaken among hospital administrators are presented. The study aimed to find the views of hospital administrators on issues likely to gain prominence in the year 2000 and the skills, knowledge, and abilities required to tackle these issues. It was concluded the autonomous status of hospitals, privatization, competition, and health trusts will become the central domains in the year 2000 in hospital administration. Innovation and following technological developments were considered most critical.

Genetic analysis of extended life span in Drosophila melanogaster. II. Replication of the backcross test and molecular characterization of the N14 locus

We are interested in localizing chromosomal regions that extend life span in Drosophila. Using stocks artificially selected for long life by Luckinbill and his colleagues, we have identified marker loci that are highly divergent in allelic frequencies between replicated long-lived lines and controls (Curtsinger et al., 1998). Several of the most divergent loci have been found to be associated with effects on life span in segregating backcross populations. Here we report an independent replication of the backcross test for the N14 marker locus, previously reported to extend male life spans by 12 days. The life span effect successfully replicates in males. N14 accounts for 30% of the total selection response in males. Life span extension occurs by a decrease in age-specific mortality rates at all ages, and is not attributable to modification of the slope of the age-specific mortality curve. The effect in females is small or nonexistent. Sequencing of the N14 locus shows that it is non-coding and not obviously regulatory, suggesting that the phenotypic effect arises from linkage disequilibrium with another locus or loci that directly affect life span. N14 DNA hybridizes to 63F/64A on the left arm of chromosome 3. The location is consistent with previous whole-chromosome substitution studies, and suggests new candidate genes for life span extension in Drosophila, including ras2.

Significant individuals in adolescence: adolescent and adult perspectives

This study examines the ways in which 360 Israeli adolescents, and 395 midlife adults looking retrospectively perceive significant individuals from their adolescence. Following the methodology developed by Hendry et al. (Journal of Adolescence 1992, 15, 255-270), participants were asked to chose the most significant family and non-family individuals in their adolescent lives, and to indicate which of a number of characteristics applied or did not apply to their chosen significant persons. Our results indicate that most of the adults and the adolescents chose a parent as the most significant relative in their adolescence and that females in both samples chose their mothers more than did males. Compared with adolescents, adults attributed, retrospectively, more negative characteristics to their parents (e.g. as being mollycoddlers and rejectors). Adults were more likely to mention their teachers as significant non-family individuals in their lives and to characterize them in terms of their future impact as teachers and role models. Adolescents referred more positively to their parents, they also chose more friends of the same or opposite sex as significant others, and characterized them in terms of present-oriented features as being supporters and challengers.

Mutation and senescence: where genetics and demography meet

Two evolutionary genetic models-mutation accumulation and antagonistic pleiotropy-have been proposed to explain the origin and maintenance of senescence. In this paper, we focus our attention on the mutation accumulation model. We re-examine previous evidence for mutation accumulation in light of new information from large-scale demographic experiments. After discussing evidence for the predictions that have been put forth from models of mutation accumulation, we discuss two critical issues at length. First, we discuss the possibility that classical fruit fly stock maintenance regimes may give rise to spurious results in selection studies of aging. Second, we consider evidence for the assumptions underlying evolutionary models of aging. These models assume that mutations act additively on age-specific survival rate, that there exist mutations whose effects are confined to late age-classes, and that all mutations have equal effects. Recent empirical evidence suggests that each of these three assumptions is unlikely to be true. On the basis of these results, we do not conclude that mutation accumulation is no longer a valid explanation for the evolution of aging. Rather, we suggest that we now need to begin developing more biologically realistic genetic models for the evolution of aging.

Teachers as significant others: gender differences in secondary school pupils' perceptions

BACKGROUND

Numerous studies refer to the impact of parents and friends as significant others for adolescents. Given the unique nature of the relationships between teachers and their pupils and their intensive everyday interactions, the present study focuses on a not yet covered topic, namely the meanings that adolescents attach to the significance of their teachers.

AIMS

This study was aimed at examining gender differences in secondary school pupils' perceptions regarding positive and negative aspects of the significance of their teachers, and to investigate the possible different domains in which teachers as compared with parents and friends might be significant for the adolescents.

SAMPLES

A total of 297 Israeli secondary school pupils (approximately 57 per cent girls and 43 per cent boys) studying in 12 tenth grade classes (age modal 16) participated in this study.

METHODS

A questionnaire dealing with pupils' perceptions of significant teachers was administered. Pupils were asked to indicate the extent to which significant teachers are characterised by various descriptors (it was defined for the pupils that a significant teacher is one whom the pupil perceives as having an important influence on her/him). In addition pupils were asked to answer two open-ended questions regarding the domains in which teachers, as compared to their parents and their friends, might be significant for them.

RESULTS

Findings showed that the most frequently mentioned characteristics of significant teachers were: teachers who 'take pupils seriously', 'have confidence in them', 'make it easier for them to understand things' and 'push them to do well'. It was also found that girls, more than boys, characterise significant teachers as facilitating learning and relationships; and that boys, more than girls, perceive significant teachers as obstructing their personal development.

CONCLUSIONS

Our findings allude to the high potential that teachers may have for impact on their pupils, beyond the domain of learning alone, and provide support for the existence of differential perceptions of significant teachers among boys and girls. These gender differences were explained in terms of the different character of teachers' interaction with the two sexes, and the fact that in the Israeli educational system more than 80 per cent of the teaching staff are women.

Reproductive cessation in female mammals

In female mammals, fertility declines abruptly at an advanced age. The human menopause is one example, but reproductive cessation has also been documented in non-human primates, rodents, whales, dogs, rabbits, elephants and domestic livestock. The human menopause has been considered an evolutionary adaptation, assuming that elderly women avoid the increasing complications of continued childbirth to better nurture their current children and grandchildren. But an abrupt reproductive decline might be only a non-adaptive by-product of life-history patterns. Because so many individuals die from starvation, disease and predation, detrimental genetic traits can persist (or even be favoured) as long as their deleterious effects are delayed until an advanced age is reached, and, for a given pattern of mortality, there should be an age by which selection would be too weak to prevent the onset of reproductive senescence. We provide a systematic test of these alternatives using field data from two species in which grandmothers frequently engage in kin-directed behaviour. Both species show abrupt age-specific changes in reproductive performance that are characteristic of menopause. But elderly females do not suffer increased mortality costs of reproduction, nor do post-reproductive females enhance the fitness of grandchildren or older children. Instead, reproductive cessation appears to result from senescence.

Friendship expectations among immigrant adolescents and their host peers

This study investigated differences in friendship expectations between immigrants in early and middle adolescence and their Israeli-born peers. Israeli newcomers from the former Soviet Union and their non-immigrant classmates were asked to rate behavioural characteristics of peers according to the extent of their importance for friendship, and also to assess the importance of these characteristics as friendship expectations of members of the other group. Results indicate that immigrants assign greater importance than their host counterparts to all aspects of friendship expectations (help and assistance, status, similarity, and avoidance of harm). Immigrants also tend to view their host peers as expecting more of their friendship in terms of status and similarity, whereas host adolescents perceive the help and avoidance functions of friendship to be a strong factor in the friendship expectations of their immigrant counterparts. Immigrants' friendship expectations were found to be correlated with social distress, especially among early adolescent girls. The results are discussed in terms of the functions of friendships and friendship expectations in the immigrants' adaptation process, and of institutional differences in allocation of immigrants to integrated or segregated classrooms.

Primary health care in Turkey: a passing fashion?

The Alma-Ata Declaration has long been regarded as a watershed in the health policy arena. The global goal of the World Health Organization, 'Health for All by the Year 2000' through primary health care, has attracted many countries both in the developed and the developing world and commitments to this end have been made at every level. However, albeit this consensus on the paper, a common and explicit definition of the concept has not been reached yet. This paper aims at discussing various definitions of primary health care that emerged after the Declaration and also presenting a case study from Turkey, a country that advocates primary health care in her recent health policy reform attempts. After setting the conceptual framework for discussion the Turkish case is presented by using research carried out among Turkish policy-makers at different levels of the State apparatus. It has been concluded that application of primary health care principles as defined in the broad definition of the concept requires major changes or rather shake-ups in Turkey. These areas are outlined briefly at the end of the paper.

Heat-induced longevity extension in Drosophila. I. Heat treatment, mortality, and thermotolerance

Survival data were collected on a total of 28,000 Drosophila melanogaster adults in order to investigate mortality patterns and induced physiological responses after a mild thermal stress. A brief, nonlethal heat treatment extends adult life span at normal temperatures by an average of 2 days (64), compared to nontreated controls of the same genotypes. Life expectancy is extended as a demographic consequence of reduced age-specific mortality over a period of up to several weeks after the heat treatment. Heat treatment also increases tolerance to subsequent, more severe thermal stress. Observations on single-sex populations suggest that heat-induced longevity extension is independent of the suppression of reproductive activity.

Age-specific patterns of genetic variance in Drosophila melanogaster. II. Fecundity and its genetic covariance with age-specific mortality

Under the mutation accumulation model of senescence, it was predicted that the additive genetic variance (VA) for fitness traits will increase with age. We measured age-specific mortality and fecundity from 65,134 Drosophila melanogaster and estimated genetic variance components, based on reciprocal crosses of extracted second chromosome lines. Elsewhere we report the results for mortality. Here, for fecundity, we report a bimodal pattern for VA with peaks at 3 days and at 17-31 days. Under the antagonistic pleiotropy model of senescence, it was predicted that negative correlations will exist between early and late life history traits. For fecundity itself we find positive genetic correlations among age classes > 3 days but negative nonsignificant correlations between fecundity at 3 days and at older age classes. For fecundity vs. age-specific mortality, we find positive fitness correlations (negative genetic correlations) among the traits at all ages > 3 days but a negative fitness correlation between fecundity at 3 days and mortality at the oldest ages (positive genetic correlations). For age-specific mortality itself we find overwhelmingly positive genetic correlations among all age classes. The data suggest that mutation accumulation may be a major source of standing genetic variance for senescence.

Age-specific patterns of genetic variance in Drosophila melanogaster. I. Mortality

PETER MEDAWAR proposed that senescence arises from an age-related decline in the force of selection, which allows late-acting deleterious mutations to accumulate. Subsequent workers have suggested that mutation accumulation could produce an age-related increase in additive genetic variance (VA) for fitness traits, as recently found in Drosophila melanogaster. Here we report results from a genetic analysis of mortality in 65,134 D. melanogaster. Additive genetic variance for female mortality rates increases from 0.007 in the first week of life to 0.325 by the third week, and then declines to 0.002 by the seventh week. Males show a similar pattern, though total variance is lower than in females. In contrast to a predicted divergence in mortality curves, mortality curves of different genotypes are roughly parallel. Using a three-parameter model, we find significant VA for the slope and constant term of the curve describing age-specific mortality rates, and also for the rate at which mortality decelerates late in life. These results fail to support a prediction derived from MEDAWAR's "mutation accumulation" theory for the evolution of senescence. However, our results could be consistent with alternative interpretations of evolutionary models of aging.

Community participation in health care: the Turkish case

World Health Organization's global goal of Health for All by the Year 2000 (HFA) and achievement of this laudable goal through the Primary Health Care (PHC) approach has been accepted unanimously by participant countries of the Alma-Ata Conference in 1978. Turkey is also among the countries that showed their approval to the concept. However, that approval of the policy did not generate particular attention among the policy-makers until the 1990s. The year 1990 can be regarded as a watershed in the Turkish health policy-making environment as attempts at producing a National Health Policy document that centred around the global goal of HFA and PHC commenced. This paper aims at discussing the commitment of Turkey to one of the prerequisites of the approach, or heart of the PHC as regarded by some: community participation. After a brief presentation of community participation the Turkish commitment to the concept is analyzed based on a research carried out among Turkish health policy-makers. It is concluded that the prospect for community participation in Turkey does not look good mainly because of the medical approach adopted by the policy-makers. The need for more discussion of the topic among the academic circles has been emphasized.

Genetic variation and aging

Life span is subject to genetic modification in yeasts, nematodes, fruit flies, mice, humans, and other vertebrates and invertebrates. There are a few single-gene mutants known that extend life span in yeast and nematodes; in other experimental systems the character is treated quantitatively, and generally has a low to moderate heritability. Life span responds to artificial selection in Drosophila and Caenorhabditis. There are many candidate genes presently under investigation, including the anti-oxidizing enzymes and heat-shock proteins. The main evolutionary models of senescence are antagonistic pleiotropy and mutation accumulation, neither of which has substantial experimental support. The incorporation of analytical techniques from demography is playing an increasing role in research on aging.

Laryngeal and tracheobronchial cough in anesthetized dogs

Tussigenic sensitivity of laryngeal and tracheobronchial regions to mechanical and chemical stimuli was compared in 22 urethan-alpha-chloralose-anesthetized dogs. In addition, the contribution of myelinated and unmyelinated vagal fibers in mediating laryngeal and tracheobronchial cough was investigated. The intensity of cough was evaluated from changes in esophageal pressure. Whereas all mechanical stimulations and citric acid inhalations into tracheobronchial region elicited cough, only 56.7% of mechanical stimulation and 33.3% of citric acid challenges to larynx were effective. The intensity of tracheobronchial cough was significantly higher than that of laryngeal cough. When mechanical stimulation was conducted under visual control (bronchofiberscope), cough elicitability was found to be higher from tracheal bifurcation and main stem bronchi (62.5-87.5%) than from any laryngeal structure (0-42.9%). During partial block of vagal conduction (cooling to 6 degrees C), mechanical and citric acid tracheobronchial stimulations failed to elicit cough and mechanical laryngeal stimulation was effective only in 1 of 10 dogs. Intensity of cough was strongly decreased when mechanical stimulation followed capsaicin administration into trachea (0.3 ml; 100 micrograms/ml) or intravenously (10 micrograms/kg). We conclude that, in anesthetized dogs, stimulation of tracheobronchial region is more effective and prompt in eliciting cough than stimulation of larynx, myelinated vagal afferent fibers play an important role in mediating mechanically and citric acid-induced tracheobronchial cough and mechanically induced laryngeal cough, and stimulation of tracheobronchial and pulmonary capsaicin-sensitive receptors strongly inhibits mechanically induced cough.

Veratrine-induced reflexes and cough

With cats anaesthetized with sodium pentobarbital we studied how veratrine-induced reflexes interact with cough. Cough was elicited by mechanical stimulation of tracheobronchial mucosa and its intensity was evaluated from the changes in oesophageal pressure. Veratrine injected intravenously produced apnoea, bradycardia and long-lasting hypotension. With each dose the intensity of cough was significantly decreased during the apnoea. When the mechanical stimulus was repeated during the breathing following apnoea with remaining hypotension, cough intensity parameters were not changed from control. Veratrine injected intracardially caused bradycardia, hypotension, and decreases in respiratory rate and tidal volume. The intensity of cough elicited just after injection of veratrine was also significantly decreased. We suggest that veratrine-induced reflexes depress the cough reflex mainly by inhibitory reflexes arising from cardiac receptors. The inhibition of cough is probably mediated indirectly via the inhibition of medullary respiratory neurons.

Lung C-fibre receptor activation and defensive reflexes in anaesthetized cats

1. With pentobarbitone-anaesthetized cats we have elicited cough reflexes from the tracheobronchial tree and the larynx, and the aspiration and sneeze reflexes from the nasopharynx and the nose respectively. The reflexes were induced by mechanical stimulation of the mucosa, before and during activation of pulmonary C-fibre receptors by intravenous injections of capsaicin or phenylbiguanide. 2. During the 20-30 s apnoea due to C-fibre stimulation, the cough reflex from both sites and the sneeze reflex were completely abolished, whereas the aspiration reflex response was approximately halved. Reflex contractions of genioglossus muscle still occurred at this time, but were far weaker than in the control state. 3. During the rapid shallow breathing that immediately followed apnoea due to C-fibre receptor stimulation, the defensive reflexes recovered: the aspiration and sneeze reflexes fully and the cough reflexes to about half of the control response. 4. Acute hypotension due to haemorrhage, of a size considerably greater than that due to stimulation of the pulmonary C-fibre receptors, caused no significant inhibition of the cough reflex from the tracheobronchial tree. 5. We conclude that the pulmonary C-fibre reflex powerfully inhibits airway defensive reflexes, and that its activation is unlikely to contribute positively to coughing induced by aerosols of capsaicin and similar agents.