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Belief systems are individual-level phenomena that describe the interrelationships of the political attitudes of a person. However, the modal study of the structure of political ideologies and beliefs uses cross-sectional survey data to estimate what is central to the belief system or the dimensionality of the belief system, aggregating across many people. Cross-sectional data, however, are ill-suited to the task of studying individual-level phenomena because they contain an unobservable mixture of within-person and between-person variation. In this project, we use longitudinal datasets from the Netherlands (representative) and the United States (convenience), spanning between 6 months and 10 years, to we ask whether between-subjects methods can help us understand the within-person structure of belief systems. First, we use Bayesian STARTS models (Lüdtke et al., 2018) to assess what type of variance cross-sectional studies are likely tapping into. We find that variability in measures of ideology and political beliefs is primarily due to stable between-person differences, with relatively smaller amounts of variation due to within-person differences. Second, we estimate between-person, within-person, and cross-sectional correlations between all items in our study and find that between-person correlations are larger and in some cases differ in their direction from within-person correlations. Furthermore, cross-sectional correlations are most similar to between-person correlations. Taken together, these findings indicate that the modal study may help describe differences between people, but is ill-suited to tell us about the structure of individuals' belief systems. New methods are necessary for a complete understanding of political belief systems that clarify both between- and within-person processes. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

This paper presents advancements in tracking features in high-speed videos of Caribbean steelpans illuminated by electronic speckle pattern interferometry, made possible by incorporating robust computer vision libraries for object detection and image segmentation, and cleaning of the training dataset. Besides increasing the accuracy of fringe counts by 10% or more compared to previous work, this paper introduces a segmentation-regression map for the entire drum surface yielding interference fringe counts comparable to those obtained via object detection. Once trained, this model can count fringes for musical instruments not part of the training set, including those with non-elliptical antinode shapes.

This review covers theory and research on the psychological characteristics and consequences of attitudes that are experienced as moral convictions, that is, attitudes that people perceive as grounded in a fundamental distinction between right and wrong. Morally convicted attitudes represent something psychologically distinct from other constructs (e.g., strong but nonmoral attitudes or religious beliefs), are perceived as universally and objectively true, and are comparatively immune to authority or peer influence. Variance in moral conviction also predicts important social and political consequences. Stronger moral conviction about a given attitude object, for example, is associated with greater intolerance of attitude dissimilarity, resistance to procedural solutions for conflict about that issue, and increased political engagement and volunteerism in that attitude domain. Finally, we review recent research that explores the processes that lead to attitude moralization; we integrate these efforts and conclude with a new domain theory of attitude moralization.

What causes people to see their political attitudes in a moral light? One answer is that attitude moralization results from associating one's attitude stance with feelings of disgust. To test the possibility that disgust moralizes, the current study used a high-powered preregistered design looking at within-person change in moral conviction paired with an experimental manipulation of disgust or anger (versus control). Results from the preregistered analyses found that we successfully induced anger but not disgust; however, our manipulation had no effect on moral conviction. Additional exploratory analyses investigating whether emotion and harm predicted increases in moral conviction over time found that neither disgust, anger, nor sadness had an effect on moralization, whereas perceptions of harm did predict moralization. Our findings are discussed in terms of their implications for current theory and research into attitude moralization.

Quaternary paleontological and archaeological evidence often is crucial for uncovering the historical mechanisms shaping modern diversity and distributions. We take an interdisciplinary approach using multiple lines of evidence to understand how past human activity has shaped long-term animal diversity in an island system. Islands afford unique opportunities for such studies given their robust fossil and archaeological records. Herein, we examine the only non-volant terrestrial mammal endemic to the Bahamian Archipelago, the hutia Geocapromys ingrahami. This capromyine rodent once inhabited many islands but is now restricted to several small cays. Radiocarbon dated fossils indicate that hutias were present on the Great Bahama Bank islands before humans arrived at AD ~800-1000; all dates from other islands post-date human arrival. Using ancient DNA from a subset of these fossils, along with modern representatives of Bahamian hutia and related taxa, we develop a fossil-calibrated phylogeny. We found little genetic divergence among individuals from within either the northern or southern Bahamas but discovered a relatively deep North-South divergence (~750 ka). This result, combined with radiocarbon dating and archaeological evidence, reveals a pre-human biogeographic divergence, and an unexpected human role in shaping Bahamian hutia diversity and biogeography across islands.

Background: Previous studies linking social activity and disability have been limited by focussing on self-reported physical performance in older adults (>65). We examined whether social participation in mid-life is associated with objective and subjective measures of physical performance in older age., Methods: Participants of the Medical Research Council National Survey of Health and Development reported their involvement in social activities at ages 43 and 60-64 years; frequency of such involvement was classified into thirds. Physical performance was measured at age 60-64 using: grip strength; standing balance; chair rises; timed get-up-and-go; self-reported physical function from the Short Form-36. Multivariable regression was used to examine longitudinal associations between social participation and each physical performance measure. We also investigated whether change in social participation between 43 and 60-64 was associated with each outcome., Results: In fully adjusted models, higher frequency of social participation at 43 was associated with faster chair rise (1.42 repetitions/min, 95% CI 0.45-2.39) and timed get-up-and-go speed (2.47 cm/s, 95% CI 0.27-4.67) and lower likelihood of self-report limitations (OR of low physical function 0.67, 95% CI 0.50-0.91) at 60-64 compared with low frequency. Better performance in objectively measured outcomes was observed only if higher social participation persisted over time whereas lower odds of self-reported limitations were found in all groups when compared to those with persistently low participation (ORs 0.43-0.56, all P≤0.02)., Conclusion: Our findings suggest that associations between higher levels of social participation in mid-life and better physical performance exist only if this social participation persists through to older age., (© The Author(s) 2019. Published by Oxford University Press on behalf of the European Public Health Association. All rights reserved.)

Background: Increasing physical activity in older adults remains a key public health priority in countries with a high burden of non-communicable disease, yet current interventions have failed to substantially increase population uptake with UK data suggesting that only half of 65-74 year olds report meeting recommended levels. The aim of this study was to conduct a systematic and inductive qualitative synthesis of the large body of qualitative research describing what influences physical activity at this age, and older adults' experiences of physical activity., Methods: A qualitative meta-ethnography was chosen as the study design as this inductive approach can provide novel insights and generate new theory about physical activity and ageing. Papers were identified by searching electronic databases and key citations. Peer-reviewed primary qualitative studies and systematic reviews were included if they met the following inclusion criteria: community-dwelling participants aged 60 years or older or in the retirement transition period; reporting on leisure-time physical activity; utilising a rigorous qualitative methodology. A line of argument approach was employed to generate a theory about how older adults think and feel about physical activity., Results: Thirty-nine papers met the inclusion criteria and were synthesised. The emergent theory suggested transition to older age can challenge people's sense of self and their role in life. Physical activity can help in regaining feelings of purpose, of being needed in collective group activity, and by creating habitual routine and structure to the day. In overcoming real and perceived barriers, and by taking up or sustaining physical activities, older adults can further build self-esteem all of which contributes to a fulfilling older age., Conclusion: Current failures to increase population levels of physical activity in older adults may be explained by an approach overly focused on the health benefits of activity. Insights from this study suggest we need to reframe our approach to consider the wider set of goals and aspirations which are of greater personal importance to older adults, and future interventions should focus on how physical activity can contribute to life satisfaction, sense of purpose, and sense of role fulfilment in older age., Trial Registration: Registered prospectively on PROSPERO on 29th March 2013: CRD42013003796 .

Background: Falls are common in Parkinson's disease so any intervention that reduced falls risk would be of value. One potential intervention is the use of cholinesterase inhibitor (ChEi) drugs., Objective: To establish the minimum clinically important difference (MCID) for fall rates to inform the effect estimate for sample size calculations of future clinical trials., Methods: We performed a Delphi study assembling a panel of experts in Parkinson's disease from academic and clinical medicine in order to reach a consensus of opinion. Responses from a panel were summarised and resent to the group, until consensus was reached., Results: 780 clinicians, who had been caring for people with Parkinson's for an average of 14 years, were contacted via three routes. The median (Interquartile range (IQR)) MCID after round 1 was 25% (IQR 20-30%) which equates to the prevention of 5 (IQR 4-6) falls per year. Increasing consensus after round two confirmed the MCID of 25%, narrowing the (IQ) range to 20%-25%. This was unchanged when the panel were shown the number of participants that would need to be recruited to a clinical trial in order to achieve this difference., Conclusions: We have established that an expert panel of PD specialists consider that an intervention that demonstrated a 25% (IQR 20-25%) relative reduction in falls rate would be clinically meaningful. This estimate can be used to help determine the sample size for any future clinical trial., (Copyright © 2018. Published by Elsevier Ltd.)

Background: More people are living longer lives leading to a growth in the population of older adults, many of whom have comorbidities and low levels of physical function. Physical activity in later life can prevent or delay age-related disability. Identifying a cost-effective means of increasing physical activity in older adults therefore remains an important public health priority.Physical Activity Facilitation (PAF) is an intervention shown to increase physical activity in adults with depression. The PAF model was modified for a population of older adults at risk of disability. This study aimed to assess the feasibility of undertaking a definitive RCT of the PAF intervention in the target population., Methods: A pilot randomised controlled trial (RCT) was delivered through primary care. Patients at risk of disability and who were not meeting recommended levels of physical activity were recruited through postal invitation and direct approach in the practice waiting room. Those meeting eligibility criteria were enrolled and randomised at a 2:1 ratio to the PAF intervention and control. Behaviour change techniques were used by facilitators with participants over the telephone and face-to-face for 6 months. Outcome measures including physical function, physical activity, depression, social support, and quality of life were collected at baseline and at 6 months., Results: A high proportion of patients responded to the initial invitation (68%), yet many were ineligible due to high levels of self-reported physical activity and baseline physical function. Fifty-one participants were recruited to the trial, with an average age of 74 years (range 65-89), and there were high rates of adherence and retention to the study (94% follow-up at 6 months). The majority of outcome data collected from participants was complete; however, the validated scale used to measure self-reported physical activity was associated with high levels of missing data., Conclusions: The findings of this pilot RCT suggest that it is feasible to deliver a definitive RCT of the PAF intervention in this population. Further work is required to improve the efficiency of recruitment and to minimise missing data from self-reported physical activity measures., Trial Registration: Current controlled trials ISRCTN80470273. Registered 25 October 2013., Competing Interests: Ethical approval was granted by the Yorkshire & the Humber - Humber Bridge National Research Ethics Service (NRES) Committee (ref 13/YH/0319). Consent was obtained from all study participants at the point of enrolment.Not applicable; no individual-level data are presented in the article.Rona Campbell is a Director of DECIPHer Impact Limited, a not-for-profit company, wholly owned by the Universities of Bristol and Cardiff, which exists to licence and support the implementation of evidence-based public health interventions. The remaining authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

The Atlantic gray whale ( Eschrichtius robustus ) presents an interesting case study of climate related dispersal and extinction. While (limited) fossil records confirm its presence in the Atlantic up until the 18th Century, its abundance and distribution within the Eastern and Western basins are still not well understood. The discovery of presumed gray whale fossil remains from the Georgia Bight and the Atlantic coast of Florida, from the mid-1980s to late-2000s, provides a new opportunity to recover additional data regarding their chronology within the Western basin. Here, we apply accelerator mass spectrometry radiocarbon techniques to six fossil whale finds, identifying dates within marine isotope stage 3 (59-24 ka) and the late Holocene, ∼2,000 yr BP. We additionally confirm the taxonomic identification of two fossil bone samples as E. robustus using collagen peptide mass fingerprinting (ZooMS). The obtained dates, when combined with a larger corpus of previously published Atlantic gray whale fossil dates, support the hypothesis for the decline of the Atlantic gray whale in the late Pleistocene and the late Holocene. These new data augment the findings of the Eastern Atlantic Basin and better incorporate the Western Atlantic Basin into a pan-ocean understanding for the species., Competing Interests: The authors declare that they have no competing interests.

Background: Dating and relationship violence (DRV)-intimate partner violence during adolescence-encompasses physical, sexual and emotional abuse. DRV is associated with a range of adverse health outcomes including injuries, sexually transmitted infections, adolescent pregnancy and mental health issues. Experiencing DRV also predicts both victimisation and perpetration of partner violence in adulthood.Prevention targeting early adolescence is important because this is when dating behaviours begin, behavioural norms become established and DRV starts to manifest. Despite high rates of DRV victimisation in England, from 22 to 48% among girls and 12 to 27% among boys ages 14-17 who report intimate relationships, no RCTs of DRV prevention programmes have taken place in the UK. Informed by two school-based interventions that have shown promising results in RCTs in the USA-Safe Dates and Shifting Boundaries-Project Respect aims to optimise and pilot a DRV prevention programme for secondary schools in England., Methods: Design: optimisation and pilot cluster RCT. Trial will include a process evaluation and assess the feasibility of conducting a phase III RCT with embedded economic evaluation. Cognitive interviewing will inform survey development.Participants: optimisation involves four schools and pilot RCT involves six (four intervention, two control). All are secondary schools in England. Baseline surveys conducted with students in years 8 and 9 (ages 12-14). Follow-up surveys conducted with the same cohort, 16 months post-baseline. Optimisation sessions to inform intervention and research methods will involve consultations with stakeholders, including young people.Intervention: school staff training, including guidance on reviewing school policies and addressing 'hotspots' for DRV and gender-based harassment; information for parents; informing students of a help-seeking app; and a classroom curriculum for students in years 9 and 10, including a student-led campaign.Primary outcome: the primary outcome of the pilot RCT will be whether progression to a phase III RCT is justified. Testing within the pilot will also determine which of two existing scales is optimal for assessing DRV victimisation and perpetration in a phase III RCT., Discussion: This will be the first RCT of an intervention to prevent DRV in the UK. If findings indicate feasibility and acceptability, we will undertake planning for a phase III RCT of effectiveness., Trial Registration: ISRCTN, ISRCTN 65324176. Registered 8 June 2017., Competing Interests: This study was approved by the London School of Hygiene and Tropical Medicine Ethics Committee (reference: 11986) and by the National Society for the Prevention of Cruelty to Children Research Ethics Committee (reference: R/17/106). All study participants provide informed consent (for adults) or assent (for those under age 18) to participate in data collection.Not applicable; no study data are included in this publication.The authors declare that they have no competing interests.Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

The late Miocene was an important time to understand the geological, climatic, and biotic evolution of the ancient New World tropics and the context for the Great American Biotic Interchange (GABI). Despite this importance, upper Miocene deposits containing diverse faunas and floras and their associated geological context are rare in Central America. We present an integrated study of the geological and paleontological context and age of a new locality from Lago Alajuela in northern Panama (Caribbean side) containing late Miocene marine and terrestrial fossils (plants, invertebrates, and vertebrates) from the Alajuela Formation. These taxa indicate predominantly estuarine and shallow marine paleoenvironments, along with terrestrial influences based on the occurrence of land mammals. Sr-isotope ratio analyses of in situ scallop shells indicate an age for the Alajuela Formation of 9.77 ± 0.22 Ma, which also equates to a latest Clarendonian (Cl3) North American Land Mammal Age. Along with the roughly contemporaneous late Miocene Gatun and Lago Bayano faunas in Panama, we now have the opportunity to reconstruct the dynamics of the Central America seaway that existed before final closure coincident with formation of the Isthmus of Panama., Competing Interests: The authors have declared that no competing interests exist.

New World monkeys (platyrrhines) are a diverse part of modern tropical ecosystems in North and South America, yet their early evolutionary history in the tropics is largely unknown. Molecular divergence estimates suggest that primates arrived in tropical Central America, the southern-most extent of the North American landmass, with several dispersals from South America starting with the emergence of the Isthmus of Panama 3-4 million years ago (Ma). The complete absence of primate fossils from Central America has, however, limited our understanding of their history in the New World. Here we present the first description of a fossil monkey recovered from the North American landmass, the oldest known crown platyrrhine, from a precisely dated 20.9-Ma layer in the Las Cascadas Formation in the Panama Canal Basin, Panama. This discovery suggests that family-level diversification of extant New World monkeys occurred in the tropics, with new divergence estimates for Cebidae between 22 and 25 Ma, and provides the oldest fossil evidence for mammalian interchange between South and North America. The timing is consistent with recent tectonic reconstructions of a relatively narrow Central American Seaway in the early Miocene epoch, coincident with over-water dispersals inferred for many other groups of animals and plants. Discovery of an early Miocene primate in Panama provides evidence for a circum-Caribbean tropical distribution of New World monkeys by this time, with ocean barriers not wholly restricting their northward movements, requiring a complex set of ecological factors to explain their absence in well-sampled similarly aged localities at higher latitudes of North America.

A new species of Apatemyidae, Sinclairella simplicidens, is based on four isolated teeth that were screenwashed from fissure fillings at the late Oligocene Buda locality, Alachua County, Florida. Compared to its only congener Sinclairella dakotensis, the new species is characterized by upper molars with more simplified crowns, with the near absence of labial shelves and stylar cusps except for a strong parastyle on M1, loss of paracrista and paraconule on M2 (paraconule retained but weak on M1), lack of anterior cingulum on M1-M3, straighter centrocristae, smaller hypocone on M1 and M2, larger hypocone on M3, distal edge of M2 continuous from hypocone to postmetacrista supporting a large posterior basin, and with different tooth proportions in which M2 is the smallest rather than the largest molar in the toothrow. The relatively rare and poorly-known family Apatemyidae has a long temporal range in North America from the late Paleocene (early Tiffanian) to early Oligocene (early Arikareean). The new species from Florida significantly extends this temporal range by roughly 5 Ma to the end of the Paleogene near the Oligocene-Miocene boundary (from early Arikareean, Ar1, to late Arikareean, Ar3), and greatly extends the geographic range of the family into eastern North America some 10° of latitude farther south and 20° of longitude farther east (about 2,200 km farther southeast) than previously known. This late occurrence probably represents a retreat of this subtropically adapted family into the Gulf Coastal Plain subtropical province at the end of the Paleogene and perhaps the end of the apatemyid lineage in North America.

Background: As people live longer, their risk of disability increases. Disability affects quality of life and increases health and social care costs. Preventing or delaying disability is therefore an important objective, and identifying an effective intervention could improve the lives of many older people. Observational and interventional evidence suggests that physical activity may reduce the risk of age-related disability, as assessed by physical performance measures. However it is unclear what approach is the most cost-effective intervention in changing long-term physical activity behaviour in older adults. A new theory-driven behavioural intervention has been developed, with the aim of increasing physical activity in the everyday lives of older adults at risk of disability. This pilot study tests the feasibility and acceptability of delivering this intervention to older adults., Methods/design: A randomised controlled trial (RCT) design will be used in the pilot study. Sixty patients aged 65 years and older will be recruited from primary care practices. Patients will be eligible to participate if they are inactive, not disabled at baseline, are at risk of developing disability in the future (Short Physical Performance Battery score <10/12), and have no contraindications to physical activity. Following baseline measures, participants will be randomised in a 2:1 ratio to the intervention or to a control arm and all participants will be followed-up after 6 months. Those randomised to the intervention arm will receive sessions with a trained Physical Activity Facilitator, delivering an intervention based on self-determination theory. Control participants receive a booklet on healthy ageing. The main outcomes of interest are recruitment, adherence, retention and acceptability. Data will also be collected on: self-report and accelerometer-recorded physical activity; physical performance; depression; wellbeing; cognitive function; social support; quality of life, healthcare use, and attitudes to physical activity. A mixed-methods process evaluation will run alongside the RCT., Discussion: The intervention, if effective, has the potential to reduce disability and improve quality of life in older adults. Before proceeding to a full-scale trial a pilot trial is necessary to ensure intervention feasibility and acceptability, and that the intervention shows evidence of promise., Trial Registration: Current Controlled Trials ISRCTN80470273 . Registered 25 October 2013.

Social psychology is not a very politically diverse area of inquiry, something that could negatively affect the objectivity of social psychological theory and research, as Duarte et al. argue in the target article. This commentary offers a number of checks to help researchers uncover possible biases and identify when they are engaging in hypothesis confirmation and advocacy instead of hypothesis testing.

Hibbing et al. argue that the liberal-conservative continuum is (a) universal and (b) grounded in psychological differences in sensitivity to negative stimuli. Our commentary argues that both claims overlook the importance of context. We review evidence that the liberal-conservative continuum is far from universal and that ideological differences are contextually flexible rather than fixed.

People expressed many different reactions to the events of September 11th, 2001. Some of these reactions were clearly negative, such as political intolerance, discrimination, and hate crimes directed toward targets that some, if not many, people associated with the attackers. Other reactions were more positive. For example, people responded by donating blood, increasing contributions of time and money to charity, and flying the American flag. The goal of this article is to review some of Americans' negative and positive reactions to 9/11. We also describe two frameworks, value protection and terror management theory, that provide insights into Americans' various reactions to the tragedy of 9/11., (© 2011 American Psychological Association)

Conservatives tend to make dispositional whereas liberals make situational attributions for social problems and alleged misconduct (the "ideo-attribution effect"). Three studies demonstrated a reversal of the ideo-attribution effect. Conservatives made stronger situational attributions than liberals for the behavior of Marines accused of killing Iraqi civilians (Studies 1 and 2) and police officers accused of wrongly killing a cougar running loose in a Chicago neighborhood (Study 3). Reversals of the ideo-attribution effect occurred because conservative values were more consistent with excusing the Marines' and police officers' behavior, whereas liberal values were more consistent with blaming the Marines and police officers. These results suggest that the ideo-attribution effect-and attributions more generally-are shaped by whether people's attributional conclusions are consistent or inconsistent with their salient values.

Nurses are key leaders and team members for the implementation of clinical documentation systems. This paper reviews key success factors during implementation of clinical documentation systems to overcome traditional barriers, ensure commitment to universal goals and facilitate the use of technology for patient safety and continuous quality improvement efforts. Top level management support, particularly from nursing executives, is vital.

Health care organizations are increasingly using computer systems to support nursing care documentation; however, processes used to deploy such systems are widely varied. The purpose of this survey was to understand current practices related to implementation of computerized nursing and interdisciplinary documentation systems with the goal to establish best practice guidelines. In Spring 2007, members from the Healthcare Information Management and Systems Society Nursing Informatics Working Group interviewed a sample of 15 hospitals to solicit information regarding the following processes: leadership activities, clinical transformation processes, project management activities, implementation processes, evaluation metrics, terminology and other standards used, and methods used to facilitate end-user adoption. This poster will report the results of this survey. Implications for Nurses will be discussed. The results are valuable to nursing informatics professionals who plan to implement systems and to their nursing executives responsible for the systems that are implemented.

We report Quaternary vertebrate and plant fossils from Sawmill Sink, a "blue hole" (a water-filled sinkhole) on Great Abaco Island, The Bahamas. The fossils are well preserved because of deposition in anoxic salt water. Vertebrate fossils from peat on the talus cone are radiocarbon-dated from approximately 4,200 to 1,000 cal BP (Late Holocene). The peat produced skeletons of two extinct species (tortoise Chelonoidis undescribed sp. and Caracara Caracara creightoni) and two extant species no longer in The Bahamas (Cuban crocodile, Crocodylus rhombifer; and Cooper's or Gundlach's Hawk, Accipiter cooperii or Accipiter gundlachii). A different, inorganic bone deposit on a limestone ledge in Sawmill Sink is a Late Pleistocene owl roost that features lizards (one species), snakes (three species), birds (25 species), and bats (four species). The owl roost fauna includes Rallus undescribed sp. (extinct; the first Bahamian flightless rail) and four other locally extinct species of birds (Cooper's/Gundlach's Hawk, A. cooperii/gundlachii; flicker Colaptes sp.; Cave Swallow, Petrochelidon fulva; and Eastern Meadowlark, Sturnella magna) and mammals (Bahamian hutia, Geocapromys ingrahami; and a bat, Myotis sp.). The exquisitely preserved fossils from Sawmill Sink suggest a grassy pineland as the dominant plant community on Abaco in the Late Pleistocene, with a heavier component of coppice (tropical dry evergreen forest) in the Late Holocene. Important in its own right, this information also will help biologists and government planners to develop conservation programs in The Bahamas that consider long-term ecological and cultural processes.

A deposit of fossil seabirds from the late Pliocene of Florida includes more than 130 skeletons of an extinct cormorant that is related phylogenetically to Recent species currently restricted to the eastern north Pacific. Evidence suggests the birds died in a single catastrophic event, perhaps a red tide. The fossil cormorant, along with other extinct seabirds and marine mammals, supports molluscan evidence for cold-water upwelling along the Florida Gulf Coast during the Pliocene. A decline in species richness of marine vertebrates throughout the Pliocene of Florida coincides with cessation of upwelling after emergences of the Panamanian Land Bridge.

1. Porphobilinogen deaminase [porphobilinogen ammonia-lyase (polymerizing), EC 4.3.1.8] from Euglena gracilis was purified more than 200-fold. 2. The enzyme has a molecular weight of 41 000 +/- 2000, does not contain a chromophoric prosthetic group, and appears not to require metal ions for activity. 3. The stoicheiometry of the overall reaction at pH 7.4 was shown to be: 4 Porphobilinogen leads to uroporphyrinogen-I + 4 NH4+. This stoicheiometry for porphobilinogen and uroporphyrinogen was also observed over a wide range of pH values. 4. Initial-velocity studies showed a hyperbolic dependence of velocity on substrate concentration, demonstrating the existence of a displacement-type mechanism. 5. Vmax. varied with pH as a typical bell-shaped curve, indicating that two ionizable groups with pK values of 6.1 and 8.9 are important for catalysis. A plot of Vmax./Km against pH showed a single ionization (pK 8.2) to influence binding of substrate.