Mechanistic Studies of ABCR, the ABC Transporter in Photoreceptor Outer Segments Responsible for Autosomal Recessive Stargardt Disease

ABCR is an ABC transporter that is found exclusively in vertebrate photoreceptor outer segments. Mutations in the human ABCR gene are responsible for autosomal recessive Stargardt disease, the most common cause of early onset macular degeneration. In this paper we review our recent work with purified and reconstituted ABCR derived from bovine retina and from cultured cells expressing wild type or site-directed mutants of human ABCR. These experiments implicate all-trans-retinal (or Schiff base adducts between all-trans-retinal and phosphatidylethanolamine) as the transport substrate, and they reveal asymmetric roles for the two nucleotide binding domains in the transport reaction. A model for the retinal transport reaction is presented which accounts for these experimental observations.     

Astronomical Sources of Circularly Polarized Light and the Origin of Homochirality

Possible astronomical sources of ultraviolet circularly polarized light(UVCPL) which might be responsible for enantiomeric selection in interstellarorganic molecules are considered, Synchrotron radiation from magnetic neutronstars has been suggested as a possible source of UVCPL. However, synchrotronradiation in these situations is not predicted to be strongly circularlypolarized. Very few such sources show optical synchrotron radiation and in thefew that do circular polarization has not been observed. Magnetic white dwarfsand white dwarf binaries (Polars) can be highly circularly polarized but anyeffect on molecular clouds and star formation regions must rely on rare chance encounters. Recent observations show that substantial levels of circularpolarization are present in reflection nebulae in star formation regions. Thismechanism produces polarized light exactly when and where it is needed inregions where star formation is occurring and organic molecules are known to be present.     

Cell-mediated immune responses (CMIR) in human rhinosporidiosis

Cell mediated immune responses (CMIR) to Rhinosporidium seeberi in human patients with rhinosporidiosis have been studied. With immuno-histochemistry, the cell infiltration patterns in rhinosporidial tissues from 7 patients were similar. The mixed cell infiltrate consisted of many plasma cells, fewer CD68+ macrophages,a population of CD3+ T lymphocytes, and CD56/57+ NK lymphocytes which were positive for CD3 as well. CD4+ T helper cells were scarce. CD8+suppressor/cytotoxic-cytolytic cells were numerous. Most of the CD8+ cells were TIA-l+ and therefore of the cytotoxic subtype. CD8+ T cells were not sub-typed according to their cytokine profile; 1L2, IFN-γ (Tcl); IL4, ILS (Tc2).In lympho-proliferative response (LPR) assays in vitro, lymphocytes from rhinosporidial patients showed stimulatory responses to Con A but lymphocytes from some patients showed significantly diminished responses to rhinosporidial extracts as compared with unstimulated cells or cells stimulated by Con A, indicating suppressor immune responses in rhinosporidiosis. The overall stimulatory responses with Con A suggested that the rhinosporidial lymphocytes were not non-specifically anergic although comparisons of depressed LPR of rhinosporidial lymphocytes from individual patients, to rhinosporidial antigen with those to Con A, did not reveal a clear indication as to whether the depression was antigen specific or non-specific. The intensity of depression of the LPR in rhinosporidial patients bore no relation to the site, duration, or the number of lesions or whether the disease was localized or disseminated. Rhinosporidial extracts showed stimulatory activity on normal control lymphocytes, perhaps indicating mitogenic activity. These results indicate that CMIR develops in human rhinosporidiosis, while suppressed responses are also induced. This revised version was published online in June 2006 with corrections to the Cover Date.     

A note on the effect of gestation housing environment on approach test measures in gilts

Systems’ welfare evaluation, including behavioural testing, is becoming increasingly popular in farm animal assurance schemes. The aims of this study were to investigate whether fairly short-term exposure to gestation housing systems, which varied in physical, environmental and human-input factors, influenced behavioural and physiological measures during a human approach test—often used to identify problems in human–animal interactions. Twenty-four Large White×Landrace gilts were initially subjected to identical human contact and daily husbandry. Forty-two days after service, the gilts were randomly assigned to either an indoor housing system (n=16) or an outdoor housing system (n=8), which differed physically and in the amount of human contact and daily husbandry. The indoor system used an electronic sow feeder (ESF), was more space-limited and thermally-controlled and had human contact centered on cleaning out. The outdoor system was more extensive, had much greater space accessible, was not thermally-controlled and had human contact that centered around feeding. The human approach test was carried out on all gilts 30–44 days after entry to the gestation system. At testing, each individual was fitted with heart rate monitor and then moved into a test arena. After 2 min an unfamiliar human entered the pen and stood motionless for 3 min against one wall and then approached the gilt and touched her snout. Throughout the experimental period, behaviour and sound within the test arena were recorded continuously. During the 2 min familiarisation period, outdoor gilts had lower heart rates (108.2 bpm versus 123.7 bpm, P<0.05) and tended to perform fewer short vocalisations (0.5 calls per min versus 3.4 calls per min, P<0.1). Outdoor-housed gilts also carried out less locomotor behaviour (2.2 sections crossed versus 4.0 sections crossed, P<0.05) and tended to perform fewer short (1.4 calls per min versus 5.0 calls per min, P<0.1) and long vocalisations (0.2 calls per min versus 1.8 calls per min, P<0.1) over the 3 min test period. Outdoor gilts tended to be slower to approach within 0.5 m of the human (69.9 s versus 19.3 s, P<0.1) but they then took less extra time to make physical contact (3.3 s versus 52.7 s, P<0.1). Mean heart rate was significantly lower in outdoor sows over the whole 3 min period (99.5 bpm versus 115.5 bpm, P<0.05). The results demonstrate that short-term exposure to different housing systems did influence behavioural and physiological measures during a standard human approach test and thus, systems differences should be taken into account before making judgements about the human–animal relationship on any commercial farm, based on results of behavioural tests of this type.     

Improved Understanding of the Bacterial Vaginal Microbiota of Women before and after Probiotic Instillation

The vaginal bacterial microbiota of 19 premenopausal women was examined by PCR-denaturing gradient gel electrophoresis (DGGE) and sequencing of the V2-V3 region of the 16S rRNA gene. Ten of the women were studied further to investigate the effect and persistence of vaginally inserted capsules containing viable lactobacilli. PCR-DGGE indicated that most subjects had a microbiota represented by one to three dominant DNA fragments. Analysis of these fragments revealed that 79% of the women possessed sequences with high levels of similarity to Lactobacillus species sequences. Sequences homologous to Lactobacillus iners sequences were the most common and were detected in 42% of the women tested. Alteration of the vaginal microbiota could be detected by PCR-DGGE in several women after the instillation of lactobacilli. Additionally, randomly amplified polymorphic DNA analysis of lactobacilli isolated from selective media demonstrated that the exogenous strains could be detected for up to 21 days in some subjects. This study demonstrates that non-culture-based techniques, such as PCR-DGGE, are useful adjuncts for studies of the vaginal microbiota.     

Mobility of Stichodactyla Gigantea Sea Anemones and Implications for Resident False Clown Anemonefish, Amphiprion Ocellaris

For reef fishes that do not move between habitat patches following settlement, habitat selection is expected during settlement. Although false clown anemonefish, Amphiprion ocellaris, are sedentary following settlement, they are not especially discriminating during settlement, and are commonly found occupying anemones at which no apparent nest site exists. In this study I report on mobility of Stichodactyla gigantea sea anemones, including anemones with resident false clowns. I argue that anemone mobility can help explain why settling false clowns are not more discriminating: although the per annum probability of an anemone moving is low, the probability of that anemone moving over the course of a resident's life is considerably higher. Therefore, an anemone's current microhabitat may not be a good predictor of its microhabitat and suitability as a host in the future.     

Relationships between spatial environmental heterogeneity and plant species diversity on a limestone pavement

No empirical studies have examined the relationship between diversity and spatial heterogeneity across unimodal species richness gradients. We determined the relationships between diversity and environmental factors for 144 0.18 m² plots in a limestone pavement alvar in southern Ontario, Canada, including within-plot spatial heterogeneity in soil depth, microtopography and microsite composition. Species richness was unimodally related to mean soil depth and relative elevation. Microsite heterogeneity and soil depth heterogeneity were positively correlated with species richness, and the richness peaks of the unimodal gradients correspond to the maximally spatially heterogeneous plots. The best predictive models of species richness and evenness, however, showed that other factors, such as ramet density and flooding, are the major determinants of diversity in this system. The findings that soil depth heterogeneity had effects on diversity when the effects of mean soil depth were factored out, and that unimodal richness peaks were associated with high spatial heterogeneity in environmental factors represent significant contributions to our understanding of how spatial heterogeneity might contribute to diversity maintenance in plant communities.     

An Analysis of Single Clutch Paternity in the Burrower Bug Sehirus cinctus Using Microsatellites

Recent studies of the burrower bug, Sehirus cinctus, have examined the genetic basis of parental care. An understanding of the burrower bug mating system, and the subsequent pattern of offspring relatedness that this system generates, is critical to further interpret genetic data. To this end, we developed three consistently amplifiable highly polymorphic microsatellite loci and used them to determine genotypic patterns at the level of both the population and the single clutch. We found that all clutches were sired by single males. Further, we find no evidence for inbreeding. We hypothesize that single paternity within a clutch may play an important role in reducing the potential for sibling rivalry, by increasing the relatedness among clutchmates.     

Identification, Detection, and Enumeration of Human Bifidobacterium Species by PCR Targeting the Transaldolase Gene

Methods that enabled the identification, detection, and enumeration of Bifidobacterium species by PCR targeting the transaldolase gene were tested. Bifidobacterial species isolated from the feces of human adults and babies were identified by PCR amplification of a 301-bp transaldolase gene sequence and comparison of the relative migrations of the DNA fragments in denaturing gradient gel electrophoresis (DGGE). Two subtypes of Bifidobacterium longum, five subtypes of Bifidobacterium adolescentis, and two subtypes of Bifidobacterium pseudocatenulatum could be differentiated using PCR-DGGE. Bifidobacterium angulatum and B. catenulatum type cultures could not be differentiated from each other. Bifidobacterial species were also detected directly in fecal samples by this combination of PCR and DGGE. The number of species detected was less than that detected by PCR using species-specific primers targeting 16S ribosomal DNA (rDNA). Real-time quantitative PCR targeting a 110-bp transaldolase gene sequence was used to enumerate bifidobacteria in fecal samples. Real-time quantitative PCR measurements of bifidobacteria in fecal samples from adults correlated well with results obtained by culture when either a 16S rDNA sequence or the transaldolase gene sequence was targeted. In the case of samples from infants, 16S rDNA-targeted PCR was superior to PCR targeting the transaldolase gene for the quantification of bifidobacterial populations.