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PubMed2003

Parasite infracommunity diversity in eels: a reflection of local component community diversity.

The intestinal macroparasite communities of freshwater eels (Anguilla anguilla) captured in the south of England from Windsor (River Thames) during August 2001, and Leckford (River Test) during late June/July 2000, are reported for the first time. Parasite component communities were among the most species rich and diverse recorded from European eels. A total of 13 intestinal macroparasite species were encountered during the study, 8 from each eel host population with 3 being common to both. Acanthocephalans, nematodes and cestodes were recovered from each host population. Eels from Windsor additionally harboured Nicolla gallica (Digenea), which was also the most prevalent and abundant macroparasite species in these hosts. Each component community followed a log normal rank abundance distribution and demonstrated reduced species dominance and increased species equitability compared with previous studies. As such, the study component communities were suitable for testing the hypothesis of low infracommunity diversity in European eel hosts. Specifically, this hypothesis predicts that the intestinal macroparasite infracommunities of European eels are species-poor, displaying low density and diversity with high dominance, irrespective of component community diversity, and that this may be more pronounced in UK host populations. This hypothesis was not upheld; study findings demonstrate that higher infracommunity diversity in eel hosts is possible, and suggest that infracommunity diversity in individual eel hosts may be a simple, stochastic reflection of component community diversity.

Anguilla↗

PubMed2006

Influence of plant diversity and elevated atmospheric carbon dioxide levels on belowground bacterial diversity.

BACKGROUND: Changes in aboveground plant species diversity as well as variations of environmental conditions such as exposure of ecosystems to elevated concentrations of atmospheric carbon dioxide may lead to changes in metabolic activity, composition and diversity of belowground microbial communities, both bacterial and fungal. RESULTS: We examined soil samples taken from a biodiversity x CO2 grassland experiment where replicate plots harboring 5, 12, or 31 different plant species had been exposed to ambient or elevated (600 ppm) levels of carbon dioxide for 5 years. Analysis of soil bacterial communities in these plots by temporal temperature gradient gel electrophoresis (TTGE) showed that dominant soil bacterial populations varied only very little between different experimental treatments. These populations seem to be ubiquitous. Likewise, screening of samples on a high-resolution level by terminal restriction fragment length polymorphism (T-RFLP) showed that increased levels of carbon dioxide had no significant influence on both soil bacterial community composition (appearance and frequency of operational taxonomic units, OTUs) and on bacterial richness (total number of different OTUs). In contrast, differences in plant diversity levels had a significant effect on bacterial composition but no influence on bacterial richness. Regarding species level, several bacterial species were found only in specific plots and were related to elevated carbon dioxide or varying plant diversity levels. For example, analysis of T-RFLP showed that the occurrence of Salmonella typhimurium was significantly increased in plots exposed to elevated CO2 (P < 0.05). CONCLUSION: Plant diversity levels are affecting bacterial composition (bacterial types and their frequency of occurrence). Elevated carbon dioxide does not lead to quantitative alteration (bacterial richness), whereas plant diversity is responsible for qualitative changes (bacterial diversity).

Atmosphere↗

PubMed2005

Cramer-Rao bound and phase-diversity blind deconvolution performance versus diversity polynomials.

Information theoretic bounds on the estimated Zernike coefficients for various diversity phase functions are presented. We show that, in certain cases, defocus diversity may yield a higher Cramer-Rao lower bound (CRLB) than some other diversity phase functions. Using simulated images to evaluate the performance of the phase-diversity algorithm, we find that, for an extended scene and defocus diversity, the phase-diversity algorithm achieves the CRLB for known objects. Furthermore, the phase-diversity algorithm achieves the CRLB by a factor of approximately 2 for unknown objects.

Journal Article↗

PubMedDate not supplied

Organizational strategy and diversity management: diversity-sensitive orientation as a moderating influence.

Empirical studies on diversity suggest that health care organizations have been slow to embrace diversity management. We propose that sensitivity to diversity, at the corporate level, moderates strategic decision making, which influences human resource management practices such as diversity initiatives. This study of 203 hospitals explored the relationships among organizational strategy, organizational sensitivity to diversity, and diversity management practices.

Cultural Diversity↗

PubMed1991

[Urinary de-diversion after diversion with chronic bladder contamination. An experimental study in male rats].

We have carried out an experimental model of urinary diversion and dis-diversion on male Wistar rats in order to study the complications that are produced after diversion, as well as to see whether the alterations continue unchanged, or increase, or diminish after dis-diversion. The following experimental design was used: a control group made up of 48 animals an a problem group of 200 animals all submitted to vesicosigmoidostomy of which 100 were designed to be subsequently dis-diverted. The sacrificed animals (n = 112) were studied for somatic, biochemical and histological parameters. Statistical comparison of the problem group with the controls showed significant differences for the somatic and biochemical parameters, especially in the form of weight-size retardation, increase of urea, creatinine, calcium, phosphorus, uric acid, cholesterol, transaminase, alkaline phosphatase, sodium and chlorine and decrease in albumin and total proteins. After dis-diversion there is an improvement of some of these parameters without reaching total normalization. This leads us to think that either the lesions are irreversible, or more time after dis-diversion is needed for there to be reversibility. We also describe the histological lesions found at the level of the vesicointestinal anastomosis, and the mortality of our series which is higher than that presented by females, a fact inducing us to think that factors exist in the male which increase the mortality.

Animals↗

PubMed1995

[Current practice and controversies in urinary diversion--the selection of the operation method of urinary diversion and postoperative care].

Since Kock et al. reported a low pressure continent reservoir using detubularized ileal segment as urinary diversion following cystectomy, continent urinary diversion including neobladder has been focused upon. On the other hand, ureterocutaneostomy, or ileal conduit as an incontinent urinary diversion is still commonly used, and especially the latter form is usually performed in many hospitals. These facts suggest that it is difficult to conclude that continent urinary diversion regarded as an excellent operation with good quality of life (QOL) is a generally acceptable method and that there are still some problems to decide the indication for urinary diversion. We discuss the problems about the postoperative complications and care of urinary diversion after cystectomy and our opinion about the selection of these operations.

Humans↗

PubMed1997

Analysis of the sequence diversity of the P1, HC, P3, NIb and CP genomic regions of several yam mosaic potyvirus isolates: implications for the intraspecies molecular diversity of potyviruses.

Partial sequences from serologically characterized yam mosaic potyvirus (YMV) isolates were determined in conserved (helper-component proteinase, HC; nuclear inclusion b, NIb) and variable (first protein, P1; third protein, P3; and coat protein, CP) regions of the potyviral genome in order to investigate the intraspecies molecular diversity of YMV. Multiple sequence alignments and pairwise comparisons were used to quantify the sequence polymorphism in these regions. Two levels of diversity were observed among YMV isolates: above 90% nucleotide (nt) sequence identities were found between YMV isolates of the same group (intragroup) regardless of the region considered, whereas identities between isolates from different groups (intergroup) were lower and depended upon the protein chosen. For instance, the average intergroup nt sequence identity between YMV isolates was about 65% in the P1 protein and the N terminus of the CP while there was more than 80% nt identity in the HC, P3 and NIb proteins. Thus P3 appeared to be conserved between YMV isolates even though this region was variable between potyvirus species. Similar analysis of the intraspecies molecular diversity of other potyviruses (potato virus Y, zucchini yellow mosaic virus, plum pox virus, pea seed-borne mosaic virus) led to the same results: (i) two levels of intraspecies molecular diversity were found (intragroup and intergroup); (ii) intraspecies molecular diversity differed from interspecies molecular diversity in the P3, P1 and N-terminal regions.

Amino Acid Sequence↗

PubMed2003

Diversity selection for phase-diverse phase retrieval.

Wavefront-sensing performance is assessed for focus-diverse phase retrieval as the aberration spatial frequency and the diversity defocus are varied. The analysis includes analytical predictions for optimal diversity values corresponding to the recovery of a dominant spatial-frequency component in the pupil. The calculation is shown to be consistent with the Cramér-Rao lower bound by considering a sensitivity analysis of the point-spread function to the spatial frequency being estimated. A maximum value of diversity defocus is also calculated, beyond which wavefront-sensing performance decreases as diversity defocus is increased. The results are shown to be consistent with the Talbot imaging phenomena, explaining multiple periodic regions of maximum and minimum contrast as a function of aberration spatial frequency and defocus. Wavefront-sensing performance for an iterative-transform phase-retrieval algorithm is also considered as diversity defocus and aberration spatial frequency are varied.

Journal Article↗

PubMed2005

Maize diversity and ethnolinguistic diversity in Chiapas, Mexico.

The objective of this study is to investigate whether ethnolinguistic diversity influences crop diversity. Factors suggest a correlation between biological diversity of crops and cultural diversity. Although this correlation has been noted, little systematic research has focused on the role of culture in shaping crop diversity. This paper reports on research in the Maya highlands (altitude >1,800 m) of central Chiapas in southern Mexico that examined the distribution of maize (Zea mays) types among communities of two groups, the Tzeltal and Tzotzil. The findings suggest that maize populations are distinct according to ethnolinguistic group. However, a study of isozymes indicates no clear separation of the region's maize into two distinct populations based on ethnolinguistic origin. A reciprocal garden experiment shows that there is adaptation of maize to its environment but that Tzeltal maize sometimes out-yields Tzotzil maize in Tzotzil environments. Because of the proximity of the two groups and selection for yield, we would expect that the superior maize would dominate both groups' maize populations, but we find that such domination is not the case. The role of ethnolinguistic identity in shaping social networks and information exchange is discussed in relation to landrace differentiation.

Biodiversity↗

PubMed2003

Simple sequence repeat marker diversity in cassava landraces: genetic diversity and differentiation in an asexually propagated crop.

Cassava (Manihot esculenta) is an allogamous, vegetatively propagated, Neotropical crop that is also widely grown in tropical Africa and Southeast Asia. To elucidate genetic diversity and differentiation in the crop's primary and secondary centers of diversity, and the forces shaping them, SSR marker variation was assessed at 67 loci in 283 accessions of cassava landraces from Africa (Tanzania and Nigeria) and the Neotropics (Brazil, Colombia, Peru, Venezuela, Guatemala, Mexico and Argentina). Average gene diversity (i.e., genetic diversity) was high in all countries, with an average heterozygosity of 0.5358 +/- 0.1184. Although the highest was found in Brazilian and Colombian accessions, genetic diversity in Neotropical and African materials is comparable. Despite the low level of differentiation [F(st)(theta) = 0.091 +/- 0.005] found among country samples, sufficient genetic distance (1-proportion of shared alleles) existed between individual genotypes to separate African from Neotropical accessions and to reveal a more pronounced substructure in the African landraces. Forces shaping differences in allele frequency at SSR loci and possibly counterbalancing successive founder effects involve probably spontaneous recombination, as assessed by parent-offspring relationships, and farmer-selection for adaptation.

Alleles↗

PubMed1999

Generation of the primary antibody repertoire in rabbits: expression of a diverse set of Igk-V genes may compensate for limited combinatorial diversity at the heavy chain locus.

In mouse and human, generation of combinatorial diversity through use of different heavy and light chain variable region genes in immunoglobulin rearrangements can be a major contributor to the primary antibody repertoire. In rabbits, the contribution of the combinatorial mechanism to heavy chain diversity is minimal, as only a few Igh-V genes are rearranged and expressed. To investigate the contribution of combinatorial diversity toward generation of the rabbit V(kappa) repertoire, we constructed five genomic libraries from rabbit kidney DNA and 1 cDNA library from the bone marrow of a 1-day-old rabbit using a series of polymerase chain reaction-based strategies. Our analyses indicate that most of the sequences that we recovered from our libraries belong to a single family and some are extremely similar. The actual number of germline Igk-V genes is potentially greater than our conservative estimate of at least 39, 28 of which we found expressed as mRNA. The germline Igk-V genes display different lengths of the coding region 3' of Cys 88 ranging from 7 to 12 amino acids, resulting in CDR3 length heterogeneity among functional V(kappa)J(kappa) sequences ranging from 8 to 15 amino acids. Some of the V(kappa)J(kappa) junctions had N and P nucleotide additions. Thus, in contrast to limited combinatorial diversity of its heavy chain, the rabbit can draw upon a diverse set of germline Igk-V genes. The kappa light chain has the potential to be a major contributor toward generation of the antibody specificities of the rabbit pre-immune repertoire.

Amino Acid Sequence↗

PubMed2002

Does herbivore diversity depend on plant diversity? The case of California butterflies.

It is widely believed that the diversity of plants influences the diversity of animals, and this should be particularly true of herbivores. We examine this supposition at a moderate spatial extent by comparing the richness patterns of the 217 butterfly species resident in California to those of plants, including all 5,902 vascular plant species and the 552 species known to be fed on by caterpillars. We also examine the relationships between plant/butterfly richness and 20 environmental variables. We found that although plant and butterfly diversities are positively correlated, multiple regression, path models, and spatial analysis indicate that once primary productivity (estimated by a water-energy variable, actual evapotranspiration) and topographical variability are incorporated into models, neither measure of plant richness has any relationship with butterfly richness. To examine whether butterflies with the most specialized diets follow the pattern found across all butterflies, we repeated the analyses for 37 species of strict monophages and their food plants and found that plant and butterfly richness were similarly weakly associated after incorporating the environmental variables. We condude that plant diversity does not directly influence butterfly diversity but that both are probably responding to similar environmental factors.

Animals↗

PubMed2006

Evolutionary and ecological causes of the latitudinal diversity gradient in hylid frogs: treefrog trees unearth the roots of high tropical diversity.

Why are there more species in the tropics than in temperate regions? In recent years, this long-standing question has been addressed primarily by seeking environmental correlates of diversity. But to understand the ultimate causes of diversity patterns, we must also examine the evolutionary and biogeographic processes that directly change species numbers (i.e., speciation, extinction, and dispersal). With this perspective, we dissect the latitudinal diversity gradient in hylid frogs. We reconstruct a phylogeny for 124 hylid species, estimate divergence times and diversification rates for major clades, reconstruct biogeographic changes, and use ecological niche modeling to identify climatic variables that potentially limit dispersal. We find that hylids originated in tropical South America and spread to temperate regions only recently (leaving limited time for speciation). There is a strong relationship between the species richness of each region and when that region was colonized but not between the latitudinal positions of clades and their rates of diversification. Temperature seasonality seemingly limits dispersal of many tropical clades into temperate regions and shows significant phylogenetic conservatism. Overall, our study illustrates how two general principles (niche conservatism and the time-for-speciation effect) may help explain the latitudinal diversity gradient as well as many other diversity patterns across taxa and regions.

Animals↗

PubMed2006

Complete genome analysis of 33 ecologically and biologically diverse Rift Valley fever virus strains reveals widespread virus movement and low genetic diversity due to recent common ancestry.

Rift Valley fever (RVF) virus is a mosquito-borne RNA virus responsible for large explosive outbreaks of acute febrile disease in humans and livestock in Africa with significant mortality and economic impact. The successful high-throughput generation of the complete genome sequence was achieved for 33 diverse RVF virus strains collected from throughout Africa and Saudi Arabia from 1944 to 2000, including strains differing in pathogenicity in disease models. While several distinct virus genetic lineages were determined, which approximately correlate with geographic origin, multiple exceptions indicative of long-distance virus movement have been found. Virus strains isolated within an epidemic (e.g., Mauritania, 1987, or Egypt, 1977 to 1978) exhibit little diversity, while those in enzootic settings (e.g., 1970s Zimbabwe) can be highly diverse. In addition, the large Saudi Arabian RVF outbreak in 2000 appears to have involved virus introduction from East Africa, based on the close ancestral relationship of a 1998 East African virus. Virus genetic diversity was low (approximately 5%) and primarily involved accumulation of mutations at an average of 2.9 x 10(-4) substitutions/site/year, although some evidence of RNA segment reassortment was found. Bayesian analysis of current RVF virus genetic diversity places the most recent common ancestor of these viruses in the late 1800s, the colonial period in Africa, a time of dramatic changes in agricultural practices and introduction of nonindigenous livestock breeds. In addition to insights into the evolution and ecology of RVF virus, these genomic data also provide a foundation for the design of molecular detection assays and prototype vaccines useful in combating this important disease.

Animals↗

PubMed2000

Increasing the power of psychiatric court diversion: a new model of supra-district diversion centre.

The object was to develop and evaluate a new concentrated model of psychiatric diversion scheme at the magistrates' court, designed to maximize the potential of such interventions. A one-year prospective study was undertaken of a consecutive series of 264 referrals to the new diversion project at an Inner London magistrates' court, with concurrent examination of police station custody records, magistrates' court returns, hospital admission data and remand prison transfer records for an area with a population of 500,000. The results showed that this one scheme originated 12.8% of all the unrestricted hospital orders in England under section 37 of the Mental Health Act 1983, 4.2% of section 35 orders, and 6.4% of section 48 and 48/49 remand prisoner transfers. Of all arrests in the central London area, 0.46% were referred to the scheme, with 0.28% being admitted. The seriousness of the charge did not have a significant effect on whether or not admission was achieved (p = 0.5365). The new model is a powerful intervention in the assessment and diversion of mentally disordered offenders. Similar supra-district diversion centres may have a role to play in other areas, complementing other local diversion exercises, some of which might better be relocated to the police station.

Adolescent↗

PubMed2005

Urinary diversion in children and adolescents with neurogenic bladder: the Mainz experience. Part II: Continent cutaneous diversion using the Mainz pouch I.

After failure of conservative treatment of neurogenic bladders (deterioration of the upper urinary tract/incontinence) continent cutaneous diversion has to be considered in those patients with irreparable urethral sphincter defects or those who are unable to perform trans-urethral self-catheterization. In this second part of the study we investigated the long-term safety of using the Mainz pouch I with regard to protecting the upper urinary tracts and to provide urine continence. Between 1985 and 2002, operations to form an ileocaecal pouch with umbilical stoma (Mainz pouch I) were performed on 70 children and adolescents of median age 15.3 years (range 5.7-20 years). During the follow-up period five patients died 2.4-14 years postoperatively of causes not related to urinary diversion. A follow-up period of 8.7 years (0.9-18) was achieved in 65 patients with 118 renal units (RUs). As compared to preoperatively, the upper urinary tracts had remained stable or improved in 113/118 RUs (95.8%) at the latest follow-up. Complete continence was achieved in 97% of patients with a continent cutaneous diversion. Surgical revisions were required for: incontinence of the outlet mechanism in 9%, stoma prolapse in 2%, stoma stenosis in 23%, pouch calculi in 15%, symptomatic reflux in 1%, ureter stenosis in 16% of the RUs with submucosal tunnel and in 3% of the RUs with an extramural tunnel. We conclude that, in patients with irreparable sphincter defect and those who are unable to perform urethral self-catheterization, continent cutaneous urinary diversion with the Mainz pouch I provides a high continence rate with preservation of the upper urinary tracts in the long run. In patients with dilated ureters, the extramural tunnel technique results in a lower complication rate.

Acid-Base Equilibrium↗

PubMed2006

Making sense of diversity in the workplace: organizational justice and language abstraction in employees' accounts of diversity-related incidents.

To discern patterns of employee sense-making about workplace diversity, the authors analyzed 751 natural language accounts of diversity incidents from 712 workers in one department of a large organization. Six generic incident types emerged: discrimination, representation, treatment by management, work relationships, respect between groups, and diversity climates. Consistent with hypotheses, incidents that respondents viewed as negative, accounts from women, and those involving members of respondents' in-groups were more likely to cite justice issues. Partially consistent with research on the linguistic intergroup bias, both negative and positive accounts involving out-group members and accounts from men were more likely to be expressed using abstract verb forms. The authors discuss future opportunities to integrate research on diversity, justice, and the linguistic category model.

Conflict, Psychological↗

PubMed1995

Trends in pediatric ostomy surgery: intestinal diversion for necrotizing enterocolitis and biliary diversion for biliary hypoplasia syndromes.

Ostomies are placed in children for different indications than in the older population. Many ostomies of childhood are placed because of congenital or neonatal problems that require temporary or long-term diversion to stabilize the neonatal patient. Necrotizing enterocolitis, the most common reason for placement of neonatal colostomies and ileostomies, is increasing in frequency as more prematurely born infants survive. Recently, there has been an increase in treatment of various biliary hypoplasia syndromes with biliary cutaneous diversion. Children with biliary hypoplasia syndromes are a challenging group of patients who frequently can be helped by ostomies. This article reviews current information on biliary cutaneous diversion for the biliary hypoplasia syndromes and intestinal diversion for necrotizing enterocolitis.

Bile Ducts↗