Order Online or Call it in? Conceptualization and Measurement of Preferences for Computer versus Human Interaction

Technology is increasingly integrated into everyday life and consequently, traditional social exchanges between human agents have evolved to include human-computer interaction, providing scientists new directions for understanding and predicting consumer behavior. Despite progress, there are conceptual and empirical limitations in current measures applied to consumer/user preferences. This paper documents the development and validation of the 10-item preference for computer versus human interaction (PCHI) scale across three distinct samples and incorporating items that (a) include direct comparisons between computers and humans, (b) are independent of specific contexts or technologies, and (c) capture major theoretical domains of social, consumer, and human factors psychology. Results support the hypothesized three-factor structure (efficiency, ease of use, and trust) and demonstrate the utility of this measure to predict everyday consumer decisions beyond extant measures. Additionally, the PCHI offers marketing, user experience, and other practitioners a brief instrument for developing interventions, training protocols, and modeling attitudes.

Toward a Typology of Counterproductive Employees: A Person-Oriented Investigation of Counterproductive Work Behavior

The study of counterproductive work behavior (CWB), intentional actions by employees that are deleterious to the organization and/or its stakeholders, has produced research on the dimensionality of CWB, as well as its situational and dispositional antecedents. Absent from these advancements have been investigations into the potential utility of a taxonomy of counterproductive employee types-a "person-oriented" approach. Our latent profile analysis (N = 522) suggested a four-profile solution which included one profile with uniformly low rates across CWBs (here termed "Angels;" 14% of the sample), and three profiles with higher CWB rates but which were distinguishable by different CWBs being most frequent in each group. Specifically, one profile was distinguished from the Angels group by higher rates of less severe CWBs (misuse of time/resources and poor attendance; 33% of the sample). The other two of the three counterproductive profiles were similar to each other except that one was characterized by higher drug use than the other (14% of the sample). The profiles also differed significantly on narcissism, psychopathy, and Machiavellianism, and on self-reports of prior arrest and censure by employers. Provided these distinctions among profiles, the treatment and assumptions of employee counterproductivity in research and practice should be revisited, particularly when using models assuming a homogenous, monotonic relationship between counterproductive behaviors across employees. Implications for our conceptual understanding of counterproductivity and applied interventions aimed at reducing CWBs are discussed, alongside recommendations for future person-oriented research on CWB.

Impact of Phylogenetic Tree Completeness and Misspecification of Sampling Fractions on Trait Dependent Diversification Models

Understanding the origins of diversity and the factors that drive some clades to be more diverse than others are important issues in evolutionary biology. Sophisticated SSE (state-dependent speciation and extinction) models provide insights into the association between diversification rates and the evolution of a trait. The empirical data used in SSE models and other methods is normally imperfect, yet little is known about how this can affect these models. Here, we evaluate the impact of common phylogenetic issues on inferences drawn from SSE models. Using simulated phylogenetic trees and trait information, we fitted SSE models to determine the effects of sampling fraction (phylogenetic tree completeness) and sampling fraction misspecification on model selection and parameter estimation (speciation, extinction, and transition rates) under two sampling regimes (random and taxonomically biased). As expected, we found that both model selection and parameter estimate accuracies are reduced at lower sampling fractions (i.e., low tree completeness). Furthermore, when sampling of the tree is imbalanced across subclades and tree completeness is ≤ 60%, rates of false positives increase and parameter estimates are less accurate, compared to when sampling is random. Thus, when applying SSE methods to empirical datasets, there are increased risks of false inferences of trait dependent diversification when some sub-clades are heavily under-sampled. Mis-specifying the sampling fraction severely affected the accuracy of parameter estimates: parameter values were over-estimated when the sampling fraction was specified as lower than its true value, and under-estimated when the sampling fraction was specified as higher than its true value. Our results suggest that it is better to cautiously under-estimate sampling efforts, as false positives increased when the sampling fraction was over-estimated. We encourage SSE studies where the sampling fraction can be reasonably estimated and provide recommended best practices for SSE modelling.

Identification of the main contributors to blood culture contamination at a tertiary care academic medical center

Background

Blood culture contamination poses an issue to all hospital systems worldwide because of the associated costs of extended length of stays, unnecessary antibiotic therapy, and additional laboratory testing that are preventable with proper handling and collection techniques.

Methods

In our study, multiple units, staff, and collection methods were compared to determine the primary culprits of contamination from a tertiary care academic medical center, which includes a pediatric hospital and both adult and pediatric emergency departments.

Results

Over 33 months, 2,083 out of 88,322 total blood cultures collected were contaminated, with an overall contamination rate of 2.4%. A moderate positive correlation was found between the monthly total number of cultures and monthly contamination rate (r = 0.411 P < .01). The most notable factors associated with contamination were found to be phlebotomy teams (2.7%) (P < .01), peripheral draws (2.3%) (P <.01), adult emergency departments (2.6%) (P < .01), and pediatric intensive care units (2.7%) (P < .01). A positive correlation was present between the number of hospital beds per unit and unit contamination rates (r = 0.429 P < .01).

Conclusion

Our results were used to make recommendations for decreasing the rate of blood culture contamination in this institution, which includes acknowledgement of an overwhelmed staff and mandatory periodic training on acceptable aseptic technique and contamination awareness. Understanding the factors contributing to blood culture contamination can aid efforts to reduce contamination rates.

Effects of COVID-19 on Blood Culture Contamination at a Tertiary Care Academic Medical Center

The COVID-19 pandemic has changed health care, from increased needs of personal protective equipment (PPE) to overloaded staff and influxes of patients. Blood cultures are frequently used to detect bloodstream infections in critically ill patients, but it is unknown whether the COVID-19 pandemic has had an impact on blood culture contamination rates. A total of 88,332 blood cultures taken over a 33-month period were analyzed to compare blood culture contamination rates before the COVID-19 pandemic to rates during the pandemic. A significant increase in the average number of monthly nurse-drawn and peripherally collected cultures occurred after the start of the pandemic, but there was a decrease in the average number of phlebotomy cultures. A significant increase in contamination rates (P < 0.001) was found in all nonemergency hospital departments during the COVID-19 pandemic, increasing from 2.1% to 2.5%. Increased rates during the COVID-19 pandemic were also found for nursing staff (2.0% to 2.4%) and both peripheral (2.1% to 2.5%) and indwelling line draws (1.1% to 1.7). The number of cultures drawn monthly increased in acute adult departments and both adult and pediatric emergency departments. Blood culture contamination rates in adult acute, adult emergency, and pediatric intensive care units increased after the start of the pandemic by 23%, 75%, and 59%, respectively. A positive correlation was found between blood culture contamination rates and COVID-19 incidence rates. Additional periodic staff training on proper blood collection technique and awareness of the workload of health care workers are recommended to decrease contamination rates during the COVID-19 pandemic. IMPORTANCE Understanding factors that contribute to blood culture contamination is important in order to take steps to limit contamination events. Here, we examine the effect the COVID-19 pandemic has had on blood culture contamination rates and specifically detail the effects based on the staff, draw types, and unit types. The conclusions provided here can be used as hospitals and laboratories navigate the COVID-19 pandemic or other times of high patient volume.

The roles of experiences and risk perception in the practice of preventative behaviors of COVID-19

Understanding the variables contributing to the practice of COVID-19 preventative behaviors is important in order to provide the best education to the community. Here, we aim to determine what factors affect an individual's compliance to suggested COVID-19 preventable behaviors. We also aim to determine what contributes to an individual's willingness to get the COVID-19 vaccine. This study surveyed residents of South Carolina, USA to analyze factors relating to preventative behavior. Survey respondents were asked a series of questions using Qualtrics survey platform. The questions included demographics, experiences with COVID-19, knowledge about the disease, and the practice of preventive behaviors. Results of this study demonstrate that demographic differences (e.g. being older, female, and more educated) and psychological differences (e.g. more COVID-19 personal experiences, perceived susceptibility and severity) are all shown to be significantly correlated with COVID-19 preventative behaviors and vaccine willingness. The factors that influence an individual's preventative behaviors and vaccine willingness are important to understand so that public health officials can best tailor and target their educational efforts.

Identifying the determinants of COVID-19 preventative behaviors and vaccine intentions among South Carolina residents

Coronavirus disease 2019 (COVID-19) has presented a global pandemic in 2020 and 2021, and has therefore spurred a flurry of research, whether related directly to the disease and its treatment or regarding its spread, containment, and effect on everyday lives. In particular, two pressing streams of research have investigated antecedents to COVID-19 preventative behaviors and vaccination intentions. This nascent research has led to many interesting and practically important findings, however, there remains many segmented, compartmentalized studies that address topics that, while certainly generative and meaningful, may not provide a full lens to possible antecedents. The current study takes an interdisciplinary approach that investigates commonly studied variables from biology and public health, political science, and psychology as they relate to COVID-19 preventative behaviors and vaccine intentions in a stratified sample of South Carolina residents (N = 1695). Results from correlations and multiple regression substantiated the findings of many previous studies, however, it was found that, when controlling for shared variance among predictors via relative weights analysis, COVID-19 knowledge, trust in science, age, and Trump approval were the strongest predictors of preventative behaviors. Alternatively, trust in science, gender, age, and conservatism were the strongest predictors of vaccine intentions. Understanding the variables that contribute to the practice of preventative behaviors and vaccine intentions can be used by public health officials to better target and tailor their educational campaign in the community.

The microbiome of diabetic foot ulcers: a comparison of swab and tissue biopsy wound sampling techniques using 16S rRNA gene sequencing

Background

Health-care professionals need to collect wound samples to identify potential pathogens that contribute to wound infection. Obtaining appropriate samples from diabetic foot ulcers (DFUs) where there is a suspicion of infection is of high importance. Paired swabs and tissue biopsies were collected from DFUs and both sampling techniques were compared using 16S rRNA gene sequencing.

Results

Mean bacterial abundance determined using quantitative polymerase chain reaction (qPCR) was significantly lower in tissue biopsies (p = 0.03). The mean number of reads across all samples was significantly higher in wound swabs \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Big(\overline{X} $$\end{document}(X¯ = 32,014) compared to tissue (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{X} $$\end{document}X¯ = 15,256, p = 0.001). Tissue biopsies exhibited greater overall diversity of bacteria relative to swabs (Shannon’s H diversity p = 0.009). However, based on a presence/absence analysis of all paired samples, the frequency of occurrence of bacteria from genera of known and potential pathogens was generally higher in wound swabs than tissue biopsies. Multivariate analysis identified significantly different bacterial communities in swabs compared to tissue (p = 0.001). There was minimal correlation between paired wound swabs and tissue biopsies in the number and types of microorganisms. RELATE analysis revealed low concordance between paired DFU swab and tissue biopsy samples (Rho = 0.043, p = 0.34).

Conclusions

Using 16S rRNA gene sequencing this study identifies the potential for using less invasive swabs to recover high relative abundances of known and potential pathogen genera from DFUs when compared to the gold standard collection method of tissue biopsy.

Population Genomics of the Euryhaline Teleost Poecilia latipinna

Global climate change and increases in sea levels will affect coastal marine communities. The conservation of these ecologically important areas will be a challenge because of their wide geographic distribution, ecological diversity and species richness. To address this problem, we need to better understand how the genetic variation of the species in these communities is distributed within local populations, among populations and between distant regions. In this study we apply genotyping by sequencing (GBS) and examine 955 SNPs to determine Sailfin molly (Poecilia latipinna) genetic diversity among three geographically close mangrove salt marsh flats in the Florida Keys compared to populations in southern and northern Florida. The questions we are asking are whether there is sufficient genetic variation among isolated estuarine fish within populations and whether there are significant divergences among populations. Additionally, we want to know if GBS approaches agree with previous studies using more traditional molecular approaches. We are able to identify large genetic diversity within each saltmarsh community (π ≈ 36%). Additionally, among the Florida Key populations and the mainland or between southern and northern Florida regions, there are significant differences in allele frequencies seen in population structure and evolutionary relationships among individuals. Surprisingly, even though the cumulative F_ST value using all 955 SNPs within the three Florida Key populations is small, there are 29 loci with significant F_ST values, and 11 of these were outliers suggestive of adaptive divergence. These data suggest that among the salt marsh flats surveyed here, there is significant genetic diversity within each population and small but significant differences among populations. Much of the genetic variation within and among populations found here with GBS is very similar to previous studies using allozymes and microsatellites. However, the meaningful difference between GBS and these previous measures of genetic diversity is the number of loci examined, which allows more precise delineations of population structure as well as facilitates identifying loci with excessive F_ST values that could indicate adaptive divergence.

Differential fertility as a major mode of selection

Population genetic models have focused Primarily on the differential survival of genotypes as the vehicle through which selection can lead to evolutionary change. A growing body of diverse evidence suggests that differential fertility is an equally important mode of selective action. Laboratory studies with Drosophila and field studies in natural populations of plants and animals have provided direct demonstrations. Experimental ecology and reproductive biology have offered indirect but compelling evidence for the importance of differential fertility. Selection through differential fertility is not always interchangeable with selection through differential survival: the genetic dynamics can be far more complicated and can lead to unpredictable results when driven by fertility differences. The study of fertility selection in natural populations poses several problems: selection differentials can be difficult to estimate; they are likely to be very sensitive to changes in environmental conditions, and when generations overlap the fertility differential cannot be estimated correctly without demographic data. Describing the role of differential fertility in natural populations represents an emerging challenge for theoreticians and empiricists alike.

Factors for choosing prostate cancer treatment and resulting impact on health related quality of life

9601

Background: The equivalence of surgery (RP), external beam radiation (EBRT), and expectant management (EM) on overall survival of prostate cancer (PCa) patients and their respective impact on health-related quality of life (HRQoL) is controversial. Thus, the benefit of screening has been raised. There is a scarcity of information on demographic factors that influence patient treatment choice and the resulting impact treatment has on HRQoL. Methods: Patients presenting to an equal access military multi-disciplinary PCa clinic are enrolled in a HRQoL database after informed consent. Surveys are administered prior to treatment and at 3, 6, 9, and 12 months. The instruments are the EPIC, EPIC Demographic, and the MOS Short-Form 36. Chi-square analysis compared frequency of race, income, and education level by treatment choice. Multivariate analysis was used to predict changes in HRQoL outcomes over time. Results: The study consisted of 538 patients. Caucasians chose EM twice as frequently as African Americans (AA) (p=0.0033). Caucasians were 3 times more likely to choose RP over EBRT, whereas AA were more evenly divided. Patients who earned over $100,000 annually disproportionately chose RP while the other treatment groups were disproportionately represented by those earning less than $100,000 (p<0.0001). Those having a graduate school degree disproportionately chose RP while the other treatment options were disproportionately represented in those with college education or less (p<0.0001). Mean age for RP, EBRT, and EM was 58, 67, and 69 respectively. Patients undergoing RP had significantly worse HRQoL outcomes in the following domains: urinary function, sexual function, and sexual bother at 12 months despite having the highest baseline scores (p<0.0001). The only domain that differed between patients undergoing EBRT and EM was bowel bother (p<0.0001). Conclusions: Patients choosing RP tend to be younger Caucasians with higher income and educational levels. This cohort chose the option with the greatest impact on HRQoL, which gives evidence that patients with certain demographics may emphasize other factors in their treatment decisions. HRQoL between EBRT and EM differed in only one domain. EBRT may be offered to older patients with minimal HRQoL impact.

No significant financial relationships to disclose.

Retrospective review of Pneumocystis jirovecii pneumonia over two decades

The aim of the study was to compare a retrospective case note review of all cases of Pneumocystis carinii (now Pneumocystis jirovecii) pneumonia (PJP) over the period 1997-2004 at North Manchester General Hospital with a previous audit covering the years 1986-1995. During 1986-1995, 777 patients were diagnosed with HIV. One hundred and eighty-one were also diagnosed with PJP. Of these, 11 patients required ventilation with a mortality rate of 100%. For the current review during 1997-2004, 210 patients were diagnosed with PJP, and 64 with severe PJP. Median age was 39 years (interquartile range [IQR] 22-61). Twenty-four patients had a prior diagnosis of HIV (median 43 months, IQR 6-72 months), and for 38 patients this was the presenting diagnosis of HIV. Median CD4 was 34 cells/L (IQR of 12-80 cells/L). Median viral load was 3.5 x 10(5) copies/mL (IQR 1-5.8 x 10(5) copies/mL). Eighteen patients required intubation during this period. Nine (50%) were alive at 30 days postextubation. We believe that the 50% reduction in mortality seen between 1997-2004 in intubated patients with severe PJP is due to the improvement in intensive care management of severe respiratory failure rather than changes in the specific management of PJP. The necessity of ventilation in HIV patients is no longer a mandatory death sentence.

Gingipain enzymes from Porphyromonas gingivalis preferentially bind immobilized extracellular proteins: a mechanism favouring colonization?

BACKGROUND AND OBJECTIVE

Porphyromonas gingivalis, an anaerobic bacterium associated with adult periodontal disease, employs a number of pathogenic mechanisms, including protease/adhesin complexes (gingipains), fimbriae and hemagglutinins, to maintain attachment within colonized hosts. Here we examined the binding of gingipains and whole, live P. gingivalis cells to immobilized extracellular matrix proteins in the presence of soluble forms of the same proteins, to investigate whether this may constitute a colonization mechanism in the oral environment.

MATERIAL AND METHODS

Binding of purified gingipain molecules and whole bacterial cells to immobilized matrix proteins was examined in the presence and absence of soluble competitors using enzyme-linked immunosorbent assays.

RESULTS

Purified gingipains or whole, live bacteria preferentially bound immobilized forms of matrix proteins, even in the presence of soluble forms of the same proteins. Fimbriae appeared to be redundant for adhesion to immobilized proteins in the presence of the gingipains, indicating that the protease/adhesins and hemagglutinins may be more important for adhesion under these conditions.

CONCLUSION

The data presented here provide evidence for a model of adhesion for P. gingivalis within the fluid environment of the oral cavity, where preferential binding of matrix-located proteins over soluble forms facilitates colonization of the host.

Human leucocyte elastase and cathepsin G: structural and functional characteristics

Two of the major enzymes present in an released from neutrophil granulocytes are the endoproteinases elastase and cathepsin G. While the former is believed to be one of the major causative agents responsible for tissue destruction in emphysema and rheumatoid arthritis, little is known about the function of cathepsin G. We have recently developed simple procedures for isolating the isoenzymes of each type of proteinase as well as for their specific controlling plasma inhibitors. We have also prepared synthetic substrates and inhibitor analogues. Some sequence studies have been initiated and the results indicate homology of these enzymes not only with each other and with the pancreatic proteinases but also between cathepsin G and proteolytic enzymes present in muscle and mast cell tissue. Significantly, both types of enzyme can degrade the structural protein myosin, as well as elastin and proteoglycan. However, their relative importance in muscle protein turnover or muscle disease has not yet been clarified.

Gingipains from Porphyromonas gingivalis synergistically induce the production of proinflammatory cytokines through protease-activated receptors with Toll-like receptor and NOD1/2 ligands in human monocytic cells

Gingipains (HRgpA, RgpB and Kgp) are cysteine proteinases and virulence factors of Porphyromonas gingivalis, the major causative bacterium of periodontal disease. To study synergistic effects of gingipains and signalling via Toll-like receptors (TLRs) and NOD1/2, we investigated effects of a gingipain on the secretion of proinflammatory cytokines from monocytic THP-1 cells in the presence of pathogen-associated molecular patterns (PAMPs). Gingipains stimulated interleukin (IL)-8's secretion from THP-1 cells, which was completely inhibited by proteinase inhibitors of gingipain and increased in the presence of PAMPs. Synergistic effects of gingipains and PAMPs were also seen in the secretion of IL-6 and MCP-1 and reduced to about 50% the secretion of IL-8 from THP-1 cells treated with siRNA targeting either protease-activated receptor (PAR)-1, -2 or -3. PAR agonist peptides mimicked the synergistic effects of gingipains with PAMPs. These results indicate that gingipains stimulate the secretion of cytokines from monocytic cells through the activation of PARs with synergistic effects by PAMPs. This is the first report of synergism of signalling via PARs, and TLRs or NOD1/2. The host defence system against P. gingivalis may be triggered through the activation of PARs by gingipains and augmented by PAMPs from this pathogen via TLRs or NOD1/2.

Poison-antidote systems in bacteria: the co-evolution of functional counterparts

Bacterial pathogens secrete a multitude of factors, many of which exhibit enzymatic activity that is directed against host-specific targets or are activated by host-specific functions. To counter these toxic molecules, producing organisms have developed several mechanisms in order to protect themselves against enzymes that have the ability to adversely affect both the microbe and the host cell. Potentially toxic molecules are strictly controlled by several strategies often involving a functional counterpart. Through the work of ourselves and others it has recently become apparent that certain bacterial extracellular proteases require inhibition by dedicated intracellular inhibitors in order that they may function only in their specific niche and cause no harm to the producing cell. Thus, it is our contention that these protease-inhibitor couplings represent a fascinating example of functional co-evolution, and are analogous to the protective mechanisms observed with the toxin-antitoxin pairings, and other such protective systems discussed within this review.

Inhibition of Porphyromonas gingivalis proteinases (gingipains) by chlorhexidine: synergistic effect of Zn(II)

BACKGROUND/AIMS

Gingipains, proteolytic enzymes produced by the periodontal pathogen Porphyromonas gingivalis, are regarded as virulence factors in the pathogenesis of periodontitis. Inhibition of gingipain activity therefore may have therapeutic potential, and it has been suggested that chlorhexidine may inhibit the activities of these enzymes. The purposes of the present study were to examine systematically the inhibitory effects of chlorhexidine on three purified gingipains and to determine the effect of Zn(II) on chlorhexidine inhibition.

METHODS

The activities of lys-gingipain (Kgp) and two forms of arg-gingipain (RgpB and HRgpA) were measured in the presence of varying concentrations of chlorhexidine and with chlorhexidine supplemented with Zn(II). Inhibition constants (K(i)'s) were determined for chlorhexidine alone and in the presence of Zn(II). Fractional inhibitory constant indices were calculated to assess the synergy of the chlorhexidine-Zn(II) inhibition.

RESULTS

RgpB, HRgpA, and Kgp were all inhibited by chlorhexidine with K(i)'s in the micromolar range. For RgpB and HRgpA, the inhibitory effects of chlorhexidine were enhanced 3-30-fold by Zn(II). The chlorhexidine-Zn(II) interaction was synergistic for inhibition of HRgpA and RgpB. For Kgp, the effect of Zn(II) on chlorhexidine inhibition was antagonistic.

CONCLUSIONS

Chlorhexidine is an effective inhibitor of gingipains, and the inhibition of R-gingipains is enhanced by Zn(II). A mixture of chlorhexidine and Zn(II) may be useful as an adjunct in the treatment of periodontitis and in the post-treatment maintenance of periodontitis patients.

A new insight into phagocytosis of apoptotic cells: proteolytic enzymes divert the recognition and clearance of polymorphonuclear leukocytes by macrophages

The recognition of phosphatidylserine (PS) on the surface of any apoptotic cell is considered to be a key event for its clearance. We challenge this concept by showing that pretreatment of neutrophils with either host or bacterial protease affects their uptake by human monocyte-derived macrophages without having an effect on cell-surface PS presentation. Specifically, whereas preincubation of apoptotic neutrophils with cathepsin G or thrombin significantly inhibited their uptake, gingipains R or clostripain enhanced phagocytosis by macrophages. Moreover, bacterial proteinases sensitized healthy neutrophils for uptake by macrophages, whereas endogenous proteinases were unable to elicit this effect. This stimulation was apparently owing to the combined effect of proteolytic cleavage of an antiphagocytic signal (CD31) and the generation of a novel 'eat-me' signal on the neutrophil surface. These results argue that neutrophil recognition and phagocytosis by macrophages is mediated by a protein ligand whose proteolytic modification could affect the local inflammatory process.

Effects of multiple predator species on green treefrog (Hyla cinerea) tadpoles

Prey species that occur across a range of habitats may be exposed to variable communities of multiple predator species across habitats. Predicting the combined effects of multiple predators can be complex. Many experiments evaluating the effects of multiple predators on prey confound either variation in predator density with predator identity or variation in relative predator frequency with overall predation rates. We develop a new experimental design of factorial predator combinations that maintains a constant expected predation rate, under the null hypothesis of additive predator effects. We implement this design to evaluate the combined effects of three predator species (bass, aeshnid and libellulid odonate naiads) on mortality rate of a prey species, Hyla cinerea (Schneider, 1799) tadpoles, that occurs across a range of aquatic habitats. Two predator treatments (libellulid and aeshnid + libellulid) resulted in lower tadpole mortality than any of the other predator treatments. Variation in tadpole mortality across treatments was not related to coarse variation in microhabitat use, but was likely due to intraguild predation, which occurred in all predator treatments. Hyla cinerea tadpoles have constant, low survival values when exposed to many different combinations of predator species, and predation rate probably increases linearly with predator density.

Genetic and environmental variation in the visual properties of bluefin killifish, Lucania goodei

Animals use their sensory systems to detect information about the external environment in order to find mates, locate food and habitat and avoid predators. Yet, there is little understanding of the relative amounts of genetic and/or environmental variation in sensory system properties. In this paper, we demonstrate genetic and environmental variation in opsin expression in a population of bluefin killifish. We measured expression of five opsins (which correlates with relative frequency of corresponding cones) using quantitative, real-time polymerase chain reaction for offspring from a breeding study where offspring were raised under different lighting conditions. Sire (i.e. genetic) effects were present for opsin found in yellow photopigment. Dam effects were present for opsins that create violet, blue and red photopigment. Lighting conditions affected expression of all opsins except SWS2A and mimicked the pattern found among populations. These results highlight the fact that sensory systems are both plastic and yet readily evolvable traits.

Characterization of an extracellular dipeptidase from Streptococcus gordonii FSS2

PepV, a dipeptidase found in culture fluids of Streptococcus gordonii FSS2, was purified and characterized, and its gene was cloned. PepV is a monomeric metalloenzyme of approximately 55 kDa that preferentially degrades hydrophobic dipeptides. The gene encodes a polypeptide of 467 amino acids, with a theoretical molecular mass of 51,114 Da and a calculated pI of 4.8. The S. gordonii PepV gene is homologous to the PepV gene family from Lactobacillus and Lactococcus spp.

Population variation in opsin expression in the bluefin killifish, Lucania goodei : a real-time PCR study

Quantitative genetics have not been used in vision studies because of the difficulty of objectively measuring large numbers of individuals. Here, we examine the effectiveness of a molecular technique, real-time PCR, as an inference of visual components in the bluefin killifish, Lucania goodei, to determine whether there is population variation in opsin expression. Previous work has shown that spring animals possess a higher frequency of UV and violet cones and a lower frequency of yellow and red cones than swamp animals. Here, we found a good qualitative match between the population differences in opsin expression and those found previously in cone frequency. Spring animals expressed higher amounts of SWS1 and SWS2B opsins (which correspond to UV and violet photopigments) and lower amounts of RH2 and LWS opsins (which correspond to yellow and red photopigments) than swamp animals. The counterintuitive pattern between color pattern, lighting environment, and vision remains. Males with blue anal fins are more abundant in swamps where animals express fewer SWS1 and SWS2B opsins and where transmission of UV/blue wavelengths is low. Understanding this system requires quantitative genetic studies. Real-time PCR is an effective tool for studies requiring inferences of visual physiology in large numbers of individuals.

Multiple paternity and population genetic structure in natural populations of the poeciliid fish, Heterandria formosa

Heterandria formosa Agassiz, exhibits internal fertilization, internal brooding of embryos, sperm storage and an extreme level of superfetation. In this study we used microsatellite markers to examine variation among seven populations that exhibited significant variance in their histories of population density. We found that the populations were genetically distinct and that the heterozygosity increased as population density increased. We also examined paternity in three of those populations and found that the number of sires per female and the number of sires per brood increased with population density. Overall, the rates of multiple paternity are quite low relative to other species. The correlations with population density suggest that contact rates play a critical role in the breeding system in this species but the low rates of multiple paternity suggest that females may exert control over fertilization of their ova.

Proteolysis of ICAM-1 on human oral epithelial cells by gingipains

Cysteine proteinases (gingipains) from Porphyromonas gingivalis are considered key virulence factors of severe periodontitis and host immune evasion. Since expression of intercellular adhesion molecule-1 (ICAM-1) on gingival epithelium is indispensable in polymorphonuclear leukocyte (PMN) migration at the site of periodontitis, we examined the effects of gingipains on the expression of ICAM-1 on human oral epithelial cell lines (KB and HSC-2) by flow cytometry and Western blotting. We found that three purified forms of gingipains efficiently reduced ICAM-1 expression on the cells in a time- and dose-dependent manner. Gingipains reduced the expression on fixed cells and degraded the ICAM-1 in the cell membranes, indicating that the reduction resulted from direct proteolysis. They then disturbed the ICAM-1-dependent adhesion of PMNs to the cells. These results indicate that gingipains cleave ICAM-1 on oral epithelial cells, consequently disrupting PMN-oral epithelial cell interaction, and are involved in immune evasion by the bacterium in periodontal tissues.

Intraspecific variation in retinal cone distribution in the bluefin killifish, Lucania goodei

Studies of visual ecology have typically focused on differences among species while paying less attention to variation among populations and/or individuals. Here, we show that the relative abundance of UV, violet, yellow, and red cones varies between two populations of bluefin killifish, Lucania goodei. Animals from a spring population (high-transmission UV/blue light) have a higher frequency of UV and violet cones and a lower frequency of yellow and red cones than animals from a swamp population (low-transmission UV/blue light). Visual sensitivity does not vary significantly between the populations, but spring animals tend to be more sensitive in the UV/blue wavelengths (360-440 nm) and less sensitive in longer wavelengths (560-600 nm) than swamp animals. The results have two important implications. First, the tight conservation of functional regions of opsin genes across taxa does not imply that visual systems are constrained in their evolution; differential sensitivity can arise through differential expression of cone classes within the retina. Second, intraspecific visual signals in this species may evolve to maximize contrast between the signaler and the background (as opposed to brightness); males with blue anal fins are most abundant in swamp habitats where animals express fewer UV and violet cones.

Extracellular arginine aminopeptidase from Streptococcus gordonii FSS2

Streptococcus gordonii is a primary etiological agent in the development of subacute bacterial endocarditis (SBE), producing thrombus formation and tissue damage on the surfaces of heart valves. This is ironic, considering its normal role as a benign inhabitant of the oral microflora. However, strain FSS2 of S. gordonii has been found to produce several extracellular aminopeptidase- and fibrinogen-degrading activities during growth in a pH-controlled batch culture. In this report, we describe the purification, characterization, and partial cloning of a predicted serine class arginine aminopeptidase (RAP) with some cysteine class characteristics. Isolation of this enzyme by anion-exchange, gel filtration, and isoelectric focusing chromatography yielded a protein monomer of approximately 70 kDa, as shown by matrix-assisted laser desorption ionization, gel filtration, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis under denaturing conditions. Nested-PCR cloning enabled the isolation of a 324-bp-long DNA fragment encoding the 108-amino-acid N terminus of RAP. Culture activity profiles and N-terminal sequence analysis indicated the export of this protein from the cell surface. Homology was found with a putative dipeptidase from Streptococcus pyogenes and nonspecific dipeptidases from Lactobacillus helveticus and Lactococcus lactis. We believe that RAP may serve as a critical factor for arginine acquisition during nutrient stress in vivo and also in the proteolysis of host proteins and peptides during SBE pathology.

Degradation of host heme proteins by lysine- and arginine-specific cysteine proteinases (gingipains) of Porphyromonas gingivalis

Porphyromonas gingivalis can use hemoglobin bound to haptoglobin and heme complexed to hemopexin as heme sources; however, the mechanism by which hemin is released from these proteins has not been defined. In the present study, using a variety of analytical methods, we demonstrate that lysine-specific cysteine proteinase of P. gingivalis (gingipain K, Kgp) can efficiently cleave hemoglobin, hemopexin, haptoglobin, and transferrin. Degradation of hemopexin and transferrin in human serum by Kgp was also detected; however, we did not observe extensive degradation of hemoglobin in serum by Kgp. Likewise the beta-chain of haptoglobin was partially protected from degradation by Kgp in a haptoglobin-hemoglobin complex. Arginine-specific gingipains (gingipains R) were also found to degrade hemopexin and transferrin in serum; however, this was observed only at relatively high concentrations of these enzymes. Growth of P. gingivalis strain A7436 in a minimal media with normal human serum as a source of heme correlated not only with the ability of the organism to degrade hemoglobin, haptoglobin, hemopexin, and transferrin but also with an increase in gingipain K and gingipain R activity. The ability of gingipain K to cleave hemoglobin, haptoglobin, and hemopexin may provide P. gingivalis with a usable source of heme for growth and may contribute to the proliferation of P. gingivalis within periodontal pockets in which erythrocytes are abundant.

Inhibition of trypsin-like cysteine proteinases (gingipains) from Porphyromonas gingivalis by tetracycline and its analogues

Extracellular cysteine proteinases, referred to as gingipains, are considered important virulence factors for Porphyromonas gingivalis, a bacterium recognized as a major etiologic agent of chronic periodontitis. We investigated the effect of tetracycline and its analogues, doxycycline and minocycline, on the enzymatic activities of gingipains. Tetracyclines at 100 microM totally inhibited the amidolytic activity of arginine-specific gingipains (HRgpA and RgpB). In contrast, inhibition of Kgp was less efficient and required a somewhat higher concentration of the antibiotic to achieve the same effect. Among tetracycline derivatives, the most potent gingipain inhibitor was doxycycline, followed by tetracycline and minocycline. RgpB was inhibited by doxycycline in an uncompetitive and reversible manner with a 50% inhibitory concentration of 3 microM. Significantly, inhibition was unaffected by calcium, excluding the chelating activity of tetracyclines as the mechanism of gingipain inactivation. In contrast, the inhibitory activities of the tetracyclines were reduced by cysteine, a reducing agent, suggesting an interference of the drug at the oxidative region with the catalytic system of the enzyme. Doxycycline, at 10 microM, significantly inhibited the RgpB-mediated production of vascular permeability-enhancing activity from human plasma, thus proving an effective inhibition of gingipain in vivo. These results indicate a new activity of tetracyclines as cysteine proteinase inhibitors and may explain the therapeutic efficiency of these antibiotics in the treatment of periodontitis.

Novel extracellular x-prolyl dipeptidyl-peptidase (DPP) from Streptococcus gordonii FSS2: an emerging subfamily of viridans Streptococcal x-prolyl DPPs

Streptococcus gordonii is generally considered a benign inhabitant of the oral microflora, and yet it is a primary etiological agent in the development of subacute bacterial endocarditis (SBE), an inflammatory state that propagates thrombus formation and tissue damage on the surface of heart valves. Strain FSS2 produced several extracellular aminopeptidase and fibrinogen-degrading activities during growth in culture. In this report we describe the purification, characterization, and cloning of a serine class dipeptidyl-aminopeptidase, an x-prolyl dipeptidyl-peptidase (Sg-xPDPP, for S. gordonii x-prolyl dipeptidyl-peptidase), produced in a pH-controlled batch culture. Purification of this enzyme by anion exchange, gel filtration, and hydrophobic interaction chromatography yielded a protein monomer of approximately 85 kDa, as shown by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) under denaturing conditions. However, under native conditions, the protein appeared to be a homodimer on the basis of gel filtration and PAGE. Kinetic studies indicated that purified enzyme had a unique and stringent x-prolyl specificity that is comparable to both the dipeptidyl-peptidase IV/CD26 and lactococcal x-prolyl dipeptidyl-peptidase families. Nested PCR cloning from an S. gordonii library enabled the isolation and sequence analysis of the full-length gene. A 759-amino-acid polypeptide with a theoretical molecular mass of 87,115 Da and a calculated pI of 5.6 was encoded by this open reading frame. Significant homology was found with the PepX gene family from Lactobacillus and Lactococcus spp. and putative x-prolyl dipeptidyl-peptidases from other streptococcal species. Sg-xPDPP may serve as a critical factor for the sustained bacterial growth in vivo and furthermore may aid in the proteolysis of host tissue that is commonly observed during SBE pathology.