Negative test for cloacal drinking in a semi-aquatic turtle (Trachemys scripta), with comments on the functions of cloacal bursae.

Many aquatic turtles possess paired evaginations of the cloaca called cloacal bursae. Despite more than two centuries of study, little consensus exists as to the function(s) of these organs. We tested a recent suggestion that bursae could function in water uptake ("cloacal drinking"). Turtles (Trachemys scripta) were dehydrated (68-86% of maximum body mass) and given the opportunity to drink orally or cloacally. Dehydration caused increases in hematocrit and osmolality of extracellular fluid (ECF), but only after loss of 10-12% of maximum body mass, suggesting that turtles osmoregulated by reabsorbing water from the urinary bladder. Turtles drank eagerly when they could submerge their heads, and drinking was accompanied by an increase in body mass and a decrease in ECF osmolality. However, dehydrated turtles with tail and anus submerged showed no changes in mass or osmolality, suggesting that water absorption is not a significant function of the cloacal bursae in this species. Evidence for other putative functions is reviewed, leading to a pluralistic view: in cryptodires, bursae apparently function primarily in buoyancy control and secondarily in ion transport and nesting, but several pleurodires have been shown recently to use them in aquatic respiration.

Factors predicting safe-sex talk and condom use in early sexual relationships.

This study explored some of the antecedents and consequences of young adults' beliefs about safe-sex communication in their early couple relationships. The sample consisted of 237 unmarried, heterosexual Australian university students, 16 to 19 years of age, approximately evenly divided between virgins and those with sexual experience. Drawing on a model of couple sexual communication as the product of prior experiences with communication, assertion, and conflict resolution in the family of origin, we examined links between these variables and respondents' attitudes and practices of safe-sex discussion and condom use with their dating partners. The results showed that women and nonvirgin men had more positive attitudes toward safe-sex communication than male virgins had. Difficulties with self-assertion outside of the sexual context and mothers' and fathers' use of avoidance as a conflict resolution strategy were negatively correlated with willingness to discuss safe sex, whereas mothers' more frequent safe-sex education was a positive predictor. The results of a hierarchical multiple regression analysis indicated that assertion, paternal conflict avoidance, and male gender were independent predictors of reluctance to negotiate for safer sex. At a behavioral level, positive attitudes to safe-sex discussion predicted having talked about AIDS and condoms with a dating partner as well as actual condom use by the subsample of daters who had experienced sexual intercourse. Implications for improving family and couple communication and for sex education were considered.

Grandfathers' and grandmothers' satisfaction with the grandparenting role: seeking new answers to old questions.

A total of 146 Australian grandparents rated their level of satisfaction with grandparenthood as an overall experience and ranked the satisfaction they gained from this role relative to other significant roles in adult life including parenthood, marriage and career. In contrast to the results of a seminal study conducted in the United States three decades ago (Neugarten & Weinstein, 1964), only a small minority (8%) were more dissatisfied than satisfied with the grandparenting role. On the other hand, in line with Neugarten and Weinstein's results, but in contrast to the results of two intervening studies of North American grandparents (Thomas 1986, 1989), there were no significant differences between grandfathers' and grandmothers' levels of satisfaction with grandparenting. Frequent contact with grandchildren predicted high levels of satisfaction in grandparents of both genders, whereas there were no effects of the grandparent's own age or marital status, or of the grandchildren's gender, age or number. In addition to the two main gratifications of biological renewal and emotional fulfillment reported by Neugarten and Weinstein, these older Australians frequently reported the opportunities to observe their grandchildren's development and share in their activities as the best features of grandparenthood, while lack of frequent enough contact was the worst feature.

Reference intervals and physiologic alterations in hematologic and biochemical values of free-ranging desert tortoises in the Mojave Desert.

Desert tortoise (Gopherus agassizii) populations have experienced precipitous declines resulting from the cumulative impact of habitat loss, and human and disease-related mortality. Evaluation of hematologic and biochemical responses of desert tortoises to physiologic and environmental factors can facilitate the assessment of stress and disease in tortoises and contribute to management decisions and population recovery. The goal of this study was to obtain and analyze clinical laboratory data from free-ranging desert tortoises at three sites in the Mojave Desert (California, USA) between October 1990 and October 1995, to establish reference intervals, and to develop guidelines for the interpretation of laboratory data under a variety of environmental and physiologic conditions. Body weight, carapace length, and venous blood samples for a complete blood count and clinical chemistry profile were obtained from 98 clinically healthy adult desert tortoises of both sexes at the Desert Tortoise Research Natural area (western Mojave), Goffs (eastern Mojave) and Ivanpah Valley (northeastern Mojave). Samples were obtained four times per year, in winter (February/March), spring (May/June), summer (July/August), and fall (October). Years of near-, above- and below-average rainfall were represented in the 5 yr period. Minimum, maximum and median values, and central 95 percentiles were used as reference intervals and measures of central tendency for tortoises at each site and/or season. Data were analyzed using repeated measures analysis of variance for significant (P < 0.01) variation on the basis of sex, site, season, and interactions between these variables. Significant sex differences were observed for packed cell volume, hemoglobin concentration, aspartate transaminase activity, and cholesterol, triglyceride, calcium, and phosphorus concentrations. Marked seasonal variation was observed in most parameters in conjunction with reproductive cycle, hibernation, or seasonal rainfall. Year-to-year differences and long-term alterations primarily reflected winter rainfall amounts. Site differences were minimal, and largely reflected geographic differences in precipitation patterns, such that results from these studies can be applied to other tortoise populations in environments with known rainfall and forage availability patterns.

Intrapopulation variation in ecological energetics of the garter snake Thamnophis sirtalis, with analysis of the precision of doubly labeled water measurements.

The evolution of energetics must begin with variation within populations in ecologically realized rates of energy acquisition and expenditure. We measured aspects of field energy budgets (including metabolic rates, feeding rates, and growth rates) in a large sample of free-living garter snakes (Thamnophis sirtalis) from a single temperate/mesic population in northwestern California during their summer active season. We then analyzed interindividual variation for correlations among variables and patterns attributable to body size and sex. Field metabolic rates (measured with use of doubly labeled water) scaled in direct proportion to body mass. These rates of field energy expenditure were higher (both in absolute terms and in relation to resting metabolic rates) than those previously measured in snakes and iguanian lizards and were similar to those reported for highly active, widely foraging scincomorphan lizards. Feeding rates (as indexed by water influx rates) and growth rates were correspondingly high compared to those of other squamate reptiles. We found considerable residual variation in all measured variables not attributable to body size. Effects of sex were detected for water influx and growth rates (females > males), but not for field metabolic rate. Individual field metabolic rate was apparently consistent (repeatable) over time, water influx rate was not, and individual growth rates were strongly negatively correlated over two sequential time periods. We were unable to detect convincing correlations between any individual measures of field energetics and any commonly measured, standard laboratory measurements of oxygen consumption (standard metabolic rate at two body temperatures and maximal oxygen consumption for exercise) made on the same individuals. However, body-size-independent field rates of energy expenditure, energy intake, and growth were strongly and positively intercorrelated among individuals. We attribute these patterns to an overriding effect of costs associated with digestion and growth on field energetics, such that individual snakes that were effective foragers achieved high feeding rates and, hence, high growth rates, but also incurred high costs of growth and digestion that largely determined field metabolic rate.

Preschoolers' understanding of lies and innocent and negligent mistakes.

It has often been proposed that young children are not capable of distinguishing mistakes from lies and that they do not discriminate between the reactions that are generated by innocent and negligent mistakes. In our investigation, children aged 3 to 5 years were asked to choose whether a perpetrator had made a mistake or had lied about a food's contact with contaminants and were required to indicate whether this choice would produce a neutral or a negative reaction in the facial expression of a bystander. In this context, many children distinguished mistakes from lies and displayed an incipient ability to discriminate between lies and negligent mistakes that often generate negative reactions and innocent mistakes that do not.

The ticking of the social clock: adults' beliefs about the timing of transition events.

In two studies, beliefs about descriptive and prescriptive age norms for adult developmental transitions were examined in a sample of 214 Australian university students aged seventeen to fifty years. The results of Study 1 revealed a belief by the vast majority that descriptive age norms still exist for both family transitions (marriage, parenthood, grandparenthood) and career transitions (leaving school, retirement). While these results were in keeping with those of Neugarten et al.'s original study of age norms in the United States, the actual "best" normative ages recommended by this sample of contemporary Australian adults differed in every case from the U.S. age norms of three decades ago. Matching contemporary demographic trends, the present Australian young-adult sample advocated later ages for marriage and grandparenthood, a younger norm for leaving school, and a broader normative age range for retiring from work. Study 2 tested Neugarten's hypothesis that age norms today lack some of the prescriptive overtones implicit in original "social clock" concept. The results supported this suggestion. In fact, only a minority of contemporary Australian adults believed that there were prescriptive upper age boundaries for first marriage or university study. Furthermore, their prescriptive lower age limits for every transition except retirement fell at or below the onset of adulthood itself (18 years), in keeping with biological constraints on procreation and maturational constraints on social and cognitive development. The mean ranges of acceptability prescribed by this Australian sample for each key adult transition were likewise very wide, stretching from an average of twenty-four years (for motherhood) to forty-nine years (for a man's first marriage). This result also contrasts sharply with the ranges of no more than five years prescribed for the same transitions by the vast majority of Neugarten et al.'s sample three decade ago. The probable consequences for self-esteem, mental health and life planning of this heightened variability and reduced prescriptiveness in the timing of life events for contemporary men and women were discussed.

Confidentiality issues in psychological research.

There has been increased attention in recent years to the importance of individual privacy and professional confidentiality both in Australia and overseas. At the same time, psychologists' growing research interests in areas such as AIDS, child sexual abuse, and domestic violence have led to new ethical dilemmas over the contract of confidentiality between researchers and their research participants. The present paper discusses a number of issues regarding the ethics of confidentiality in psychological research. Following Bok (1989), the issues are highlighted within the context of four ethical principles that underlie researchers' obligations to preserve confidentiality. These principles are derived from considerations of privacy, loyalty, the pledge of silence, and professional codes of ethical standards. Each of these principles is illustrated with examples taken from recent research. We devote special attention to instances that appear to provide a clash between moral principles.

Deafness, conversation and theory of mind.

The child's developing theory of the mind as an interconnected network of beliefs, desires and feelings that govern behaviour provides a cornerstone for social and intellectual life. Recent research has suggested that autistic children have difficulty acquiring such a theory. Although it is speculated that a specific neurological deficit may be responsible for autistic children's difficulties on false belief tasks devised to test a theory of mind, these may also be due to a lack of exposure to conversation about mental states. In this study we explored the development of a theory of mind in a group of 26 signing, prelingually-deaf Australian children of normal intelligence, aged 8-13 years. Results revealed that 65% of these deaf children failed a simple test of false belief which normal preschoolers, mentally retarded children, and other handicapped groups--apart from children with autism--routinely pass at a mental age of 4-5 years. No significant difference emerged between deaf children's performance and that of autistic children tested on the same task in previous research. We discuss the results in terms of a conversational account of the development of a theory of mind in deaf children, and the extent to which this account is applicable to children with autism.

The accuracy of older and younger Australians' understanding of mental health and aging.

Inadequacies in contemporary mental health care for elderly individuals may come about partly through ignorance of both positive aspects of mental health in old age (e.g., the responsiveness of older clients to psychotherapy) and the negative aspects (e.g., elderly men's unusually high suicide risk). A quiz measuring knowledge of both kinds was administered to a total of 250 Australian men and women aged seventeen to eighty-one years who were either retired, employed, housewives, or university students. As hypothesized, the retired group scored lowest on the quiz, with no significant differences among younger students versus non-students. Age was found to be a more important mediator of the retired group's low scores than gender, living with an older person, or self-definition as retired versus employed or a housewife. A previous finding of higher scores by Australians than by U.S. undergraduates in an aging course was also replicated and extended to older nonstudent groups. Implications of these findings for mental health services for elderly individuals and for educational interventions to improve understanding of mental health in older age groups were considered.

Sustained metabolic scope.

Sustained metabolic rates (SusMR) are time-averaged metabolic rates that are measured in free-ranging animals maintaining constant body mass over periods long enough that metabolism is fueled by food intake rather than by transient depletion of energy reserves. Many authors have suggested that SusMR of various wild animal species are only a few times resting (basal or standard) metabolic rates (RMR). We test this conclusion by analyzing all 37 species (humans, 31 other endothermic vertebrates, and 5 ectothermic vertebrates) for which SusMR and RMR had both been measured. For all species, the ratio of SusMR to RMR, which we term sustained metabolic scope, is less than 7; most values fall between 1.5 and 5. Some of these values, such as those for Tour de France cyclists and breeding birds, are surely close to sustainable metabolic ceilings for the species studied. That is, metabolic rates higher than 7 times RMR apparently cannot be sustained indefinitely. These observations pose several questions: whether the proximate physiological causes of metabolic ceilings reside in the digestive tract's ability to process food or in each tissue's metabolic capacity; whether ceiling values are independent of the mode of energy expenditure; whether ceilings are set by single limiting physiological capacities or by coadjusted clusters of capacities (symmorphosis); what the ultimate evolutionary causes of metabolic ceilings are; and how metabolic ceilings may limit animals' reproductive effort, foraging behavior, and geographic distribution.

Husbands' and wives' perceptions of marital fairness across the family life cycle.

Marital fairness, or the subjective balance between two spouses' gains and losses, was evaluated by a cross-sectional sample of 134 married Australian men and women representing five phases in the family life cycle: preparental, childbearing, the full house, launching, and the empty nest. Husbands' perceptions of their own marital equity described a U-shaped curve across these phases, with significantly more men feeling equitably treated both initially and after children's departure than during any of the three phases with children in the home. Wives' perceptions, by contrast, showed little variation with life cycle phase. Overall, a slight majority (52 percent) of husbands and wives perceived their marriages as equitable. Both sexes were inclined to agree, however, that whenever deviations from strict marital equity arose during family life, these were most likely to overbenefit husbands and to underbenefit wives. Results are discussed in relation to 1) equity theory, 2) marital satisfaction research, and 3) Bernard's model of the intrinsic sexual inequality of marriage as an institution [1].

Positive justice reasoning in deaf and hearing children before and after exposure to cognitive conflict.

The development of positive justice reasoning in profoundly deaf, signing Australian 7- to 12-year-olds and hearing children was compared. Reactions to cognitive conflict were also assessed. The performance of those deaf children whose signed English skills were adequate to give detailed justifications for reward allocation was examined separately. The deaf children were delayed relative to hearing children in number and liquid conservation, but equally mature in justice reasoning. Spontaneous conflicts with signing peers over sharing possessions conceivably could be responsible for the fluently signing deaf children's development of positive justice reasoning on pace with their normally-hearing counterparts. Experimentally-induced conflict resulted in progress for the hearing but not the deaf children. Results are discussed in relation to factors that promote deaf children's tolerance for ambiguity (Brice, 1985) and impede their resolution of cognitive conflict (Liben, 1978).

Light-harvesting pigment-proteins of photosystem I in maize. Subunit composition and biogenesis.

Three different pigment-binding proteins of the light-harvesting complex (LHC I) of maize photosystem I (PS I) have been isolated. Absorption and fluorescence excitation spectral analyses showed that each pigment-protein can transfer absorbed energy from its carotenoid and/or chlorophyll b components to chlorophyll alpha. Their apoproteins with apparent sizes of 24 (LHC Ia), 21 (LHC Ib), and 17 (LHC Ic) kDa have been purified to homogeneity. Differences in their pigment and amino acid compositions and in their reactions with antibodies demonstrate that the two smaller pigment-proteins are not proteolytically derived from the largest one. LHC Ib's apoprotein is particularly enriched in cysteine residues. None of the three apoproteins cross-reacted with antibodies raised against the major light-harvesting chlorophyll a/b-protein of photosystem II (LHC IIb) or against the PS I core complex (CC I) subunits. Studies of the biogenesis of PS I during greening of etiolated plants showed that all of the CC I subunits accumulated to a detectable level prior to the appearance of the 17-kDa subunit of LHC I, the accumulation of which preceded those of the 24- and 21-kDa subunits of LHC I. In addition, subunit VI of CC I is shown to be differentially expressed in mesophyll and bundle sheath cells; a slightly larger form of it accumulates in mesophyll than in bundle sheath thylakoids during plastid development.

Expression of the Major Light-Harvesting Chlorophyll a/b-Protein and Its Import into Thylakoids of Mesophyll and Bundle Sheath Chloroplasts of Maize.

Distribution of the major light-harvesting chlorophyll a/b-protein (LHCII) and its mRNA within bundle sheath and mesophyll cells of maize (Zea mays L.) was studied using in situ immunolocalization and hybridization, respectively. In situ hybridization with specific LHCII RNA probes from maize and Lemna gibba definitively shows the presence of high levels of mRNA for LHCII in both bundle sheath cells and mesophyll cells. In situ immuno-localization studies, using an LHCII monoclonal antibody, demonstrate the presence of LHCII polypeptides in chloroplasts of both cell types. The polypeptide composition of LHCII and the amount of LHCII in bundle sheath cells are different from those in mesophyll cells. Both mesophyll and bundle sheath chloroplasts can take up, import and process the in vitro transcribed and translated LHCII precursor protein from L. gibba. Although bundle sheath chloroplasts incorporate LHCII into the pigmented light-harvesting complex, the efficiency is lower than that in mesophyll chloroplasts.

Age, sex, and contact with elderly adults as predictors of knowledge about psychological aging.

Using an instrument developed in the United States to assess students' knowledge of mental health in old age, the present study tested 179 Australian undergraduates who varied in age, sex, and the frequency of their contact with aged people at home, at work, and in the neighborhood. As predicted, women scored higher than men and scores rose with age and with contact when age was partialed out. Unexpectedly, Australian students averaged two more items correct than the American students for whom the test was developed. Implications for teaching are considered.

Older men's and women's relationships with adult kin: how equitable are they?

Recent research has shown that satisfying casual relationships and short-term intimacies among young adults tend to be characterized by mutual perceptions of global equity or a proportional subjective balance between each partner's overall inputs and gains. The present study extended the measurement of global equity perceptions to sixty-two elderly men's and women's relationships with their frequently-contacted spouses, adult children, and aged parents. A comparison group of forty younger adults likewise rated the equity of their marriages and relationships with elderly parents and grandparents. Results showed that the majority of both generations' involvements with all categories of immediate adult kin were seen as globally equitable. In addition, most departures from strict equity involved respondents feeling subjectively overbenefited rather than underbenefited. Theories of kinship exchange in longstanding and elderly relationships were considered. The possibilities either of subjective biases in longstanding intimates' perceptions and/or of a link between social disengagement and underbenefit during old age enabled reconciliation of the present findings with theoretical predictions.