Retention of duplicated genes in evolution.

Gene duplication is a prevalent phenomenon across the tree of life. The processes that lead to the retention of duplicated genes are not well understood. Functional genomics approaches in model organisms, such as yeast, provide useful tools to test the mechanisms underlying retention with functional redundancy and divergence of duplicated genes, including fates associated with neofunctionalization, subfunctionalization, back-up compensation, and dosage amplification. Duplicated genes may also be retained as a consequence of structural and functional entanglement. Advances in human gene editing have enabled the interrogation of duplicated genes in the human genome, providing new tools to evaluate the relative contributions of each of these factors to duplicate gene retention and the evolution of genome structure.

Identification and cellular localization in Xenopus laevis photoreceptors of three Peripherin-2 family members, Prph2, Rom1 and Gp2l, which arose from gene duplication events in the common ancestors of jawed vertebrates.

Rod and cone photoreceptors are named for the distinct morphologies of their outer segment organelles, which are either cylindrical or conical, respectively. The morphologies of the stacked disks that comprise the rod and cone outer segments also differ: rod disks are completely sealed and are discontinuous from the plasma membrane, while cone disks remain partially open to the extracellular space. These morphological differences between photoreceptor types are more prominent in non-mammalian vertebrates, whose cones typically possess a greater proportion of open disks and are more tapered in shape. In mammals, the tetraspanin prph2 generates and maintains the highly curved disk rim regions by forming extended oligomeric structures with itself and a structurally similar paralog, rom1. Here we determined that in addition to these two proteins, there is a third Prph2 family paralog in most non-mammalian vertebrate species, including X. laevis: Glycoprotein 2-like protein or "Gp2l". A survey of multiple genome databases revealed a single invertebrate Prph2 'pro-ortholog' in Amphioxus, several echinoderms and in a diversity of protostomes indicating an ancient divergence from other tetraspanins. Based on phylogenetic analysis, duplication of the vertebrate predecessor likely gave rise to the Gp2l and Prph2/Rom1 clades, with a further duplication distinguishing the Prph2 and Rom1 clades. Mammals have lost Gp2l and their Rom1 has undergone a period of accelerated evolution such that it has lost several features that are retained in non-mammalian vertebrate Rom1. Specifically, Prph2, Gp2l and non-mammalian Rom1 encode proteins with consensus N-linked glycosylation and outer segment localization signals; mammalian rom1 lacks these motifs. We determined that X. laevis gp2l is expressed exclusively in cones and green rods, while X. laevis rom1 is expressed exclusively in rods, and prph2 is present in both rods and cones. The presence of three Prph2-related genes with distinct expression patterns as well as the rapid evolution of mammalian Rom1, may contribute to the more pronounced differences in morphology between rod and cone outer segments and rod and cone disks observed in non-mammalian versus mammalian vertebrates.

Convergent evolution of SWS2 opsin facilitates adaptive radiation of threespine stickleback into different light environments.

Repeated adaptation to a new environment often leads to convergent phenotypic changes whose underlying genetic mechanisms are rarely known. Here, we study adaptation of color vision in threespine stickleback during the repeated postglacial colonization of clearwater and blackwater lakes in the Haida Gwaii archipelago. We use whole genomes from 16 clearwater and 12 blackwater populations, and a selection experiment, in which stickleback were transplanted from a blackwater lake into an uninhabited clearwater pond and resampled after 19 y to test for selection on cone opsin genes. Patterns of haplotype homozygosity, genetic diversity, site frequency spectra, and allele-frequency change support a selective sweep centered on the adjacent blue- and red-light sensitive opsins SWS2 and LWS. The haplotype under selection carries seven amino acid changes in SWS2, including two changes known to cause a red-shift in light absorption, and is favored in blackwater lakes but disfavored in the clearwater habitat of the transplant population. Remarkably, the same red-shifting amino acid changes occurred after the duplication of SWS2 198 million years ago, in the ancestor of most spiny-rayed fish. Two distantly related fish species, bluefin killifish and black bream, express these old paralogs divergently in black- and clearwater habitats, while sticklebacks lost one paralog. Our study thus shows that convergent adaptation to the same environment can involve the same genetic changes on very different evolutionary time scales by reevolving lost mutations and reusing them repeatedly from standing genetic variation.

Opsin gene repertoires in northern archaic hominids.

The Neanderthals' northern distribution, hunting techniques, and orbit breadths suggest that they were more active in dim light than modern humans. We surveyed visual opsin genes from four Neanderthals and two other archaic hominids to see if they provided additional support for this hypothesis. This analysis was motivated by the observation that alleles responsible for anomalous trichromacy in humans are more common in northern latitudes, by data suggesting that these variants might enhance vision in mesopic conditions, and by the observation that dim light active species often have fewer opsin genes than diurnal relatives. We also looked for evidence of convergent amino acid substitutions in Neanderthal opsins and orthologs from crepuscular or nocturnal species. The Altai Neanderthal, the Denisovan, and the Ust'-Ishim early modern human had opsin genes that encoded proteins identical to orthologs in the human reference genome. Opsins from the Vindija Cave Neanderthals (three females) had many nonsynonymous substitutions, including several predicted to influence colour vision (e.g., stop codons). However, the functional implications of these observations were difficult to assess, given that "control" loci, where no substitutions were expected, differed from humans to the same extent. This left unresolved the test for colour vision deficiencies in Vindija Cave Neanderthals.

Conservation of the Host-Interacting Proteins Tp0750 and Pallilysin among Treponemes and Restriction of Proteolytic Capacity to Treponema pallidum.

The spirochete Treponema pallidum subsp. pallidum is the causative agent of syphilis, a chronic, sexually transmitted infection characterized by multiple symptomatic and asymptomatic stages. Although several other species in the genus are able to cause or contribute to disease, T. pallidum differs in that it is able to rapidly disseminate via the bloodstream to tissue sites distant from the site of initial infection. It is also the only Treponema species able to cross both the blood-brain and placental barriers. Previously, the T. pallidum proteins, Tp0750 and Tp0751 (also called pallilysin), were shown to degrade host proteins central to blood coagulation and basement membrane integrity, suggesting a role for these proteins in T. pallidum dissemination and tissue invasion. In the present study, we characterized Tp0750 and Tp0751 sequence variation in a diversity of pathogenic and nonpathogenic treponemes. We also determined the proteolytic potential of the orthologs from the less invasive species Treponema denticola and Treponema phagedenis. These analyses showed high levels of sequence similarity among Tp0750 orthologs from pathogenic species. For pallilysin, lower levels of sequence conservation were observed between this protein and orthologs from other treponemes, except for the ortholog from the highly invasive rabbit venereal syphilis-causing Treponema paraluiscuniculi. In vitro host component binding and degradation assays demonstrated that pallilysin and Tp0750 orthologs from the less invasive treponemes tested were not capable of binding or degrading host proteins. The results show that pallilysin and Tp0750 host protein binding and degradative capability is positively correlated with treponemal invasiveness.

Sablefish (Anoplopoma fimbria) chromosome-level genome assembly.

Sablefish (Anoplopoma fimbria) are in the suborder Cottioidei, which also includes stickleback and lumpfish. This species inhabits coastal regions of the northeastern and northwestern Pacific Ocean from California to Japan. A commercial fishery for sablefish began to flourish in the 1960s, though a downward trend in stock biomass and landings has been observed since 2010. Aquaculture protocols have been developed for sablefish; eggs and sperm from wild-caught and hatchery-reared captive broodstock are used to generate offspring that reach market size in about two years. Parentage analyses show that survival in aquaculture varies among families. Growth rate and disease resistance also vary among individuals and cohorts, but the extent to which genetics and the environment contribute to this variation is unclear. The sablefish genome assembly reported here will form the foundation for SNP-based surveys designed to detect genetic markers associated with survival, growth rate, and pathogen resistance. Beyond its contribution to sablefish domestication, the sablefish genome can be a resource for the management of the wild sablefish fishery. The assembly generated in this study had a length of 653 Mbp, a scaffold N50 of 26.74 Mbp, a contig N50 of 2.57 Mbp, and contained more than 98% of the 3640 Actinopterygii core genes. We placed 620.9 Mbp (95% of the total) onto 24 chromosomes using a genetic map derived from six full-sib families and Hi-C contact data.

The polyphenol oxidase gene family in land plants: Lineage-specific duplication and expansion.

BACKGROUND: Plant polyphenol oxidases (PPOs) are enzymes that typically use molecular oxygen to oxidize ortho-diphenols to ortho-quinones. These commonly cause browning reactions following tissue damage, and may be important in plant defense. Some PPOs function as hydroxylases or in cross-linking reactions, but in most plants their physiological roles are not known. To better understand the importance of PPOs in the plant kingdom, we surveyed PPO gene families in 25 sequenced genomes from chlorophytes, bryophytes, lycophytes, and flowering plants. The PPO genes were then analyzed in silico for gene structure, phylogenetic relationships, and targeting signals. RESULTS: Many previously uncharacterized PPO genes were uncovered. The moss, Physcomitrella patens, contained 13 PPO genes and Selaginella moellendorffii (spike moss) and Glycine max (soybean) each had 11 genes. Populus trichocarpa (poplar) contained a highly diversified gene family with 11 PPO genes, but several flowering plants had only a single PPO gene. By contrast, no PPO-like sequences were identified in several chlorophyte (green algae) genomes or Arabidopsis (A. lyrata and A. thaliana). We found that many PPOs contained one or two introns often near the 3' terminus. Furthermore, N-terminal amino acid sequence analysis using ChloroP and TargetP 1.1 predicted that several putative PPOs are synthesized via the secretory pathway, a unique finding as most PPOs are predicted to be chloroplast proteins. Phylogenetic reconstruction of these sequences revealed that large PPO gene repertoires in some species are mostly a consequence of independent bursts of gene duplication, while the lineage leading to Arabidopsis must have lost all PPO genes. CONCLUSION: Our survey identified PPOs in gene families of varying sizes in all land plants except in the genus Arabidopsis. While we found variation in intron numbers and positions, overall PPO gene structure is congruent with the phylogenetic relationships based on primary sequence data. The dynamic nature of this gene family differentiates PPO from other oxidative enzymes, and is consistent with a protein important for a diversity of functions relating to environmental adaptation.

Opsin gene duplication and divergence in ray-finned fish.

Opsin gene sequences were first reported in the 1980s. The goal of that research was to test the hypothesis that human opsins were members of a single gene family and that variation in human color vision was mediated by mutations in these genes. While the new data supported both hypotheses, the greatest contribution of this work was, arguably, that it provided the data necessary for PCR-based surveys in a diversity of other species. Such studies, and recent whole genome sequencing projects, have uncovered exceptionally large opsin gene repertoires in ray-finned fishes (taxon, Actinopterygii). Guppies and zebrafish, for example, have 10 visual opsin genes each. Here we review the duplication and divergence events that have generated these gene collections. Phylogenetic analyses revealed that large opsin gene repertories in fish have been generated by gene duplication and divergence events that span the age of the ray-finned fishes. Data from whole genome sequencing projects and from large-insert clones show that tandem duplication is the primary mode of opsin gene family expansion in fishes. In some instances gene conversion between tandem duplicates has obscured evolutionary relationships among genes and generated unique key-site haplotypes. We mapped amino acid substitutions at so-called key-sites onto phylogenies and this exposed many examples of convergence. We found that dN/dS values were higher on the branches of our trees that followed gene duplication than on branches that followed speciation events, suggesting that duplication relaxes constraints on opsin sequence evolution. Though the focus of the review is opsin sequence evolution, we also note that there are few clear connections between opsin gene repertoires and variation in spectral environment, morphological traits, or life history traits.

In the four-eyed fish (Anableps anableps), the regions of the retina exposed to aquatic and aerial light do not express the same set of opsin genes.

The four-eyed fish, Anableps anableps, has eyes with unusual morphological adaptations for simultaneous vision above and below water. The retina, for example, is divided such that one region receives light from the aerial field and the other from the aquatic field. To understand better the adaptive value of this partitioned retina, we characterized photoreceptor distribution using in situ hybridization. Cones expressing sws1, sws2b and rh2-2 (i.e. UV, and short wavelength-sensitive) opsins were found throughout the retina, whereas cones expressing rh2-1 (middle wavelength-sensitive) were largely limited to the ventral retina and those expressing lws (long wavelength-sensitive) opsins were only expressed in the dorsal retina. We next asked when this pattern evolved relative to the 'four-eyed' morphology. We characterized opsin expression in Jenynsia onca, a member of the sister genus to Anableps with typical teleost eye morphology. In J. onca, sws1, sws2b, rh2-2 and rh2-1 opsins were expressed throughout the retina; while lws opsins were not expressed in the ventral retina. Thus, the change that coincides with the evolution of unusual anablepid eye morphology is the loss of rh2-1 expression in the dorsal retina, probably to accommodate increased lws opsin expression. The retinal area that samples aerial light appears not to have changed with respect to photoreceptor transcription.

RT-qPCR reveals opsin gene upregulation associated with age and sex in guppies (Poecilia reticulata) - a species with color-based sexual selection and 11 visual-opsin genes.

BACKGROUND: PCR-based surveys have shown that guppies (Poecilia reticulata) have an unusually large visual-opsin gene repertoire. This has led to speculation that opsin duplication and divergence has enhanced the evolution of elaborate male coloration because it improves spectral sensitivity and/or discrimination in females. However, this conjecture on evolutionary connections between opsin repertoire, vision, mate choice, and male coloration was generated with little data on gene expression. Here, we used RT-qPCR to survey visual-opsin gene expression in the eyes of males, females, and juveniles in order to further understand color-based sexual selection from the perspective of the visual system. RESULTS: Juvenile and adult (male and female) guppies express 10 visual opsins at varying levels in the eye. Two opsin genes in juveniles, SWS2B and RH2-2, accounted for > 85% of all visual-opsin transcripts in the eye, excluding RH1. This relative abundance (RA) value dropped to about 65% in adults, as LWS-A180 expression increased from approximately 3% to 20% RA. The juvenile-to-female transition also showed LWS-S180 upregulation from about 1.5% to 7% RA. Finally, we found that expression in guppies' SWS2-LWS gene cluster is negatively correlated with distance from a candidate locus control region (LCR). CONCLUSIONS: Selective pressures influencing visual-opsin gene expression appear to differ among age and sex. LWS upregulation in females is implicated in augmenting spectral discrimination of male coloration and courtship displays. In males, enhanced discrimination of carotenoid-rich food and possibly rival males are strong candidate selective pressures driving LWS upregulation. These developmental changes in expression suggest that adults possess better wavelength discrimination than juveniles. Opsin expression within the SWS2-LWS gene cluster appears to be regulated, in part, by a common LCR. Finally, by comparing our RT-qPCR data to MSP data, we were able to propose the first opsin-to-λmax assignments for all photoreceptor types in the cone mosaic.

The incidence of Parkinsonism in patients with type 1 Gaucher disease: data from the ICGG Gaucher Registry.

PURPOSE: Investigate the incidence of Parkinsonism among patients with Gaucher disease type 1 (GD1) and describe demographics, genotypes, and Gaucher disease (GD)-related characteristics for affected and non-affected patients. STUDY TYPE: Cohort study with age- and gender-matched nested case-control analysis. Calculation of event incidence, standardized morbidity ratio, and event-free survival (Kaplan-Meier). DATA SOURCE: The International Collaborative Gaucher Group (ICGG) Gaucher Registry data as of June 2010. Study cohort: GD1 patients with any report of Parkinsonism. Pre-matching control group: All GD1 patients with no report of Parkinsonism. RESULTS: The matched study cohort comprised of 68 patients with reports of Parkinsonism and 649 patients without Parkinsonism. Demographic and clinical characteristics suggest a milder GD phenotype in patients with Parkinsonism compared to the control group. The most prevalent GD1 genotype was N370S/N370S (39% for controls; 46% for patients with Parkinsonism). Patients with Parkinsonism were diagnosed with GD1 at a mean age of 37 years compared to 31 years in control patients. The standardized morbidity ratio for the development of Parkinsonism among all GD1 patients indicated an approximately 6 to 17 fold increase over that of 2 reference populations. The mean age of reported Parkinsonism onset was 57 years compared to 60 years in the general population (Lees, Hardy, and Revesz, 2009 [1]). The probability that a patient with GD1 will develop Parkinsonism before age 70 years is 5 to 7% and 9 to 12% before age 80 years. CONCLUSIONS: The incidence of Parkinsonism among GD1 patients is significantly increased compared to two reference populations. GD1 patients with Parkinsonism have a later median age at GD diagnosis, later age at the start of treatment, and later age at death than patients with GD1 alone. The Gaucher-related clinical profile of GD1 patients with Parkinsonism is similar to or milder than the GD1 alone group. Therefore, severity of the common GD1 clinical manifestations does not appear to be predictive for the onset of Parkinsonism.

Intra-retinal variation of opsin gene expression in the guppy (Poecilia reticulata).

Although behavioural experiments demonstrate that colouration influences mate choice in many species, a complete understanding of this form of signalling requires information about colour vision in the species under investigation. The guppy (Poecilia reticulata) has become a model species for the study of colour-based sexual selection. To investigate the role of opsin gene duplication and divergence in the evolution of colour-based mate choice, we used in situ hybridization to determine where the guppy's nine cone opsins are expressed in the retina. Long wavelength-sensitive (LWS) opsins were more abundant in the dorsal retina than in the ventral retina. One of the middle wavelength-sensitive opsins (RH2-1) exhibited the opposite pattern, while the other middle wavelength-sensitive opsin (RH2-2) and the short wavelength-sensitive opsins (SWS1, SWS2A and SWS2B) were expressed throughout the retina. We also found variation in LWS opsin expression among individuals. These observations suggest that regions of the guppy retina are specialized with respect to wavelength discrimination and/or sensitivity. Intra-retinal variability in opsin expression, which has been observed in several fish species, might be an adaptation to variation in the strength and spectral composition of light entering the eye from above and below. The discovery that opsin expression varies in the guppy retina may motivate new behavioural experiments designed to study its role in mate choice.

Development of video animations to encourage patient-driven deprescribing: A Team Alice Study.

OBJECTIVE: Patient-driven deprescribing initiatives aim to increase patient knowledge and strengthen self-advocacy skills. This article describes the development of three animated videos designed to educate older adults about unsafe prescribing and medication harm, based on the actionable lessons from the death, by polypharmacy, of an older adult in our community. METHODS: Using a community based participatory research approach (CBPR), members of three senior centers (n = 53) and the Deprescribing Partnership of Western New York (n = 30) were recruited and participated in two rounds of focus groups to guide the video development. RESULTS: Stakeholder input led to changes in content, wording, and visual presentation. The final versions of the videos emphasize the following messages (1) "New medications and what you should know about the risks", (2) "What you should do when a doctor tells you never to take a certain medication", (3) "What you should know about medications when you are in the hospital." CONCLUSION: The study highlights the successful process of using CBPR to develop a series of videos designed to provide information on the risks of polypharmacy, and empower older adults to advocate for themselves. PRACTICE IMPLICATIONS: Animated educational videos are a novel strategy to address medication harm in older adults. This research is a critical first step to increasing patient-led discussions that reduce the incidence of medication harm and inappropriate medication use among older adults.

The subterranean catfish Phreatobius cisternarum provides insights into visual adaptations to the phreatic environment.

Vertebrate eyes share the same general organization, though species have evolved morphological and functional adaptations to diverse environments. Cave-adapted animals are characterized by a variety of features including eye reduction, loss of body pigmentation, and enhanced non-visual sensory systems. Species that live in perpetual darkness have also evolved sensory mechanisms that are independent of light stimuli. The subterranean catfish Phreatobius cisternarum lives in the Amazonian phreatic zone and displays a diversity of morphological features that are similar to those observed in cavefish and appear to be adaptations to life in the dark. Here we combine histological and transcriptome analyses to characterize sensory adaptations of P. cisternarum to the subterranean environment. Histological analysis showed that the vestigial eyes of P. cisternarum contain a rudimentary lens. Transcriptome analysis revealed a repertoire of eleven visual and non-visual opsins and the expression of 36 genes involved in lens development and maintenance. In contrast to other cavefish species, such as Astyanax mexicanus, Phreatichthys andruzzii, Sinocyclocheilus anophthalmus and Sinocyclocheilus microphthalmus, DASPEI neuromast staining patterns did not show an increase in the number of sensory hair cells. Our work reveals unique adaptations in the visual system of P. cisternarum to underground habitats and helps to shed light into troglomorphic attributes of subterranean animals.

Amphioxus (Branchiostoma floridae) has orthologs of vertebrate odorant receptors.

BACKGROUND: A common feature of chemosensory systems is the involvement of G protein-coupled receptors (GPCRs) in the detection of environmental stimuli. Several lineages of GPCRs are involved in vertebrate olfaction, including trace amine-associated receptors, type 1 and 2 vomeronasal receptors and odorant receptors (ORs). Gene duplication and gene loss in different vertebrate lineages have lead to an enormous amount of variation in OR gene repertoire among species; some fish have fewer than 100 OR genes, while some mammals possess more than 1000. Fascinating features of the vertebrate olfactory system include allelic exclusion, where each olfactory neuron expresses only a single OR gene, and axonal guidance where neurons expressing the same receptor project axons to common glomerulae. By identifying homologous ORs in vertebrate and in non-vertebrate chordates, we hope to expose ancestral features of the chordate olfactory system that will help us to better understand the evolution of the receptors themselves and of the cellular components of the olfactory system. RESULTS: We have identified 50 full-length and 11 partial ORs in Branchiostoma floridae. No ORs were identified in Ciona intestinalis. Phylogenetic analysis places the B. floridae OR genes in a monophyletic clade with the vertebrate ORs. The majority of OR genes in amphioxus are intronless and many are also tandemly arrayed in the genome. By exposing conserved amino acid motifs and testing the ability of those motifs to discriminate between ORs and non-OR GPCRs, we identified three OR-specific amino acid motifs common in cephalochordate, fish and mammalian and ORs. CONCLUSION: Here, we show that amphioxus has orthologs of vertebrate ORs. This conclusion demonstrates that the receptors, and perhaps other components of vertebrate olfaction, evolved at least 550 million years ago. We have also identified highly conserved amino acid motifs that may be important for maintaining receptor conformation or regulating receptor activity. We anticipate that the identification of vertebrate OR orthologs in amphioxus will lead to an improved understanding of OR gene family evolution, OR gene function, and the mechanisms that control cell-specific expression, axonal guidance, signal transduction and signal integration.

The molecular basis of color vision in colorful fish: four long wave-sensitive (LWS) opsins in guppies (Poecilia reticulata) are defined by amino acid substitutions at key functional sites.

BACKGROUND: Comparisons of functionally important changes at the molecular level in model systems have identified key adaptations driving isolation and speciation. In cichlids, for example, long wavelength-sensitive (LWS) opsins appear to play a role in mate choice and male color variation within and among species. To test the hypothesis that the evolution of elaborate coloration in male guppies (Poecilia reticulata) is also associated with opsin gene diversity, we sequenced long wavelength-sensitive (LWS) opsin genes in six species of the family Poeciliidae. RESULTS: Sequences of four LWS opsin genes were amplified from the guppy genome and from mRNA isolated from adult guppy eyes. Variation in expression was quantified using qPCR. Three of the four genes encode opsins predicted to be most sensitive to different wavelengths of light because they vary at key amino acid positions. This family of LWS opsin genes was produced by a diversity of duplication events. One, an intronless gene, was produced prior to the divergence of families Fundulidae and Poeciliidae. Between-gene PCR and DNA sequencing show that two of the guppy LWS opsins are linked in an inverted orientation. This inverted tandem duplication event occurred near the base of the poeciliid tree in the common ancestor of Poecilia and Xiphophorus. The fourth sequence has been uncovered only in the genus Poecilia. In the guppies surveyed here, this sequence is a hybrid, with the 5' end most similar to one of the tandem duplicates and the 3' end identical to the other. CONCLUSION: Enhanced wavelength discrimination, a possible consequence of opsin gene duplication and divergence, might have been an evolutionary prerequisite for color-based sexual selection and have led to the extraordinary coloration now observed in male guppies and in many other poeciliids.

Parallel opsin switches in multiple cone types of the starry flounder retina: tuning visual pigment composition for a demersal life style.

Variable expression of visual pigment proteins (opsins) in cone photoreceptors of the vertebrate retina is a primary determinant of vision plasticity. Switches in opsin expression or variable co-expression of opsins within differentiated cones have been documented for a few rodents and fishes, but the extent of photoreceptor types affected and potential functional significance are largely unknown. Here, we show that both single and double cones in the retina of a flatfish, the starry flounder (Platichthys stellatus), undergo visual pigment changes through opsin switches or variable opsin co-expression. As the post-metamorphic juvenile (i.e., the young asymmetric flatfish with both eyes on one side of the body) grows from ~5 g to ~196 g, some single cones and one member of unequal double cones switched from a visual pigment with maximum wavelength of absorbance, λmax, at shorter wavelengths (437 nm and 527 nm) to one with longer λmax (456 nm and 545 nm, respectively) whereas other cones had intermediate visual pigments (λmax at 445 nm or 536 nm) suggesting co-expression of two opsins. The shift toward longer wavelength absorbing visual pigments was in line with maximizing sensitivity to the restricted light spectrum at greater depths and achromatic detection of overhead targets.

The impacts of subsidized health insurance on employees' use of preventive health services.

This study presents an uncontrolled preliminary evaluation of a pilot health insurance subsidy program and addresses whether provision of subsidized insurance that required employee contribution had an impact upon preventive health utilization among small businesses and their employees. Self-report questionnaires were mailed to the employees; these included questions on use of preventive health services before and after enrollment in the subsidy program. The analysis was stratified by self-reported prior enrollment in an insurance program to compare employees with and without prior health insurance. The findings suggest significant increases in health service utilization among the previously uninsured. Regular checkups more than doubled (p < .0001), as did the number of individuals receiving regular blood work (p < .0001). Nearly twice the number of individuals filled regular prescriptions after enrollment in the subsidy program as compared with before (p < .0001). This study suggests that employees of small businesses are willing to contribute to the cost of a health insurance premium, and once insured are more likely to use preventive services. A model of shared cost responsibility is an effective way to provide affordable insurance to small-business employees, thus increasing preventive services in these populations.