Search PubMed⌕ Search

Biomedical subjects

R Wall

Publications and source records attributed to R Wall.

At least 73 records · Page 4Linked to original sources
PubMed1999

Widespread B29 (CD79b) gene defects and loss of expression in chronic lymphocytic leukemia.

Chronic Lymphocytic Leukemia (CLL) is the most prevalent form of leukemia in Western countries, and is characterized by a monoclonal proliferation of primarily immature CD5+ B lymphocytes. The molecular biology of chronic leukemias and lymphomas remains largely unresolved. Surface immunoglobulin (Ig) expression, which is often decreased in CLL, requires the protein product of the B29 gene for translocation of the B cell antigen receptor complex (BCR) to the cell surface and for signal transduction. Because B29 is essential for intracellular assembly and transport of the B cell antigen receptor complex to the cell surface, we postulate that a perturbation in B29 could result in the diminished expression and function of surface Ig in leukemic CLL cells. We have found recurrent aberrations affecting the B29 gene in CLL cells. Analyses of 27 unselected cases of CLL demonstrate that over 75% had low to absent B29 expression which correlated directly to their level of surface Ig expression. Half of these surface B29(low/-) cases had either no or barely detectable levels of B29 mRNA by RNAse protection assay. To date, all of the CLL samples with normal B29 mRNA levels have been found to have point mutations or truncations which would significantly effect the structure and/or function of B29 protein. Strategies directed at correcting these B29 mutations are expected to induce increased Ig surface expression in CLL and may improve the sensitivity of CLL cells to conventional cytotoxic chemotherapy.

Aged↗
PubMed1998

The effect of farm management strategies on the incidence of sheep strike in Britain: a simulation analysis.

A deterministic model is used to simulate the seasonal incidence of sheep myiasis (strike) on farms in Britain and to explore the effects of different farm management strategies on strike incidence. The model is based on two sub-components: the seasonal pattern of abundance of the primary agent of sheep myiasis in northwest Europe, the blowfly Lucilia sericata and the range of factors known to influence ewe and lamb susceptibility to strike. The results of these simulations show that familiar farm management strategies, such as shearing, reduction in scouring caused by endoparasitic worms and insecticide use can have an important role in the reduction of strike incidence in ewes and lambs. However, the effectiveness of these techniques can be highly dependent of their timing in relation to seasonal changes in blowfly abundance and the effects of temperature and rainfall.

Animal Husbandry↗
PubMed1998

The incidence of sheep strike by Lucilia sericata on sheep farms in Britain: a simulation model.

Using a combination of a temperature-dependent simulation of the population dynamics of Lucilia sericata and a logistic model of sheep susceptibility, based on patterns of faecal soiling, fleece length and fleece humidity, a deterministic simulation model has been constructed to predict the incidence of sheep strike by L. sericata on lambs and ewes in Britain. Strikes are assigned to individual sheep in the flock according to a negative binomial distribution. The model shows that the majority of the first strikes of the season occur equally on ewes and lambs, when ewe fleeces are long and before lamb susceptibility increases though faecal soiling. With each subsequent generation of gravid blowflies, however, a greater proportion of strikes occur on lambs, while the number of strikes observed on ewes remains relatively consistent throughout the season. The increase in strike of lambs is due to the seasonal increase in lamb faecal soiling, associated with rising helminth infections and lamb fleece growth. The model shows that at the beginning of the season the incidence of strike is limited by the low number of flies present: towards the end of seasons, however, the blowfly population had grown large enough for the number of strikes to be limited by the number of susceptible ewes and lambs. The model shows that the seasonal incidence of strike is highly sensitive to the interactions between temperature, rainfall and would length. Strike was most prevalent under warm, wet conditions. However, there is a critical period during spring, where the short fleeces of lambs and ewes, in the latter case due to shearing, results in the desiccation of egg batches. If this coincides with dry conditions, the high levels of mortality result in suppression of the fly population and a reduction in the subsequent incidence of strike.

Animals↗
PubMed1998

Measurement of age and population age structure in the blowfly, Lucilia sericata (Meigen) (Diptera: Calliphoridae).

For field samples of the blowfly Lucilia sericata (Meigen), the degree of wing abrasion, corrected for individual size, was shown to give a useful estimate of age, by calibration against a known measure of chronological age, the fluorescence of pteridines in the head capsule. In more extensive field studies, therefore, wing fray was used to indicate the likely ovarian cycle of each female, after which the length of the most advanced egg follicle was used to give a more precise estimate of age within this cycle. Using these two complementary techniques, the ages of 806 female L. sericata, from two farms in the south-west of England, were estimated over a complete field season in 1996. Analysis of median age of these females revealed distinct peaks and troughs over time. The observed periods of low median age corresponded with predicted periods of high adult emergence; the periods of increasing and high median age corresponded with the predicted senescence of the L. sericata population. Hence, by analysis of population age structure, this study supports the view that fluctuations in abundance of L. sericata, observed in the field, represent the emergence and senescence of relatively discrete generations of adults.

Journal Article↗
PubMed1998

The cost-effectiveness of routine pathology consultation in knee arthroscopy.

Regulations in Ontario, Canada, as in most provinces and states in North America, require human tissues (with few exceptions) removed at surgery to be sent to a pathology laboratory for examination and report. We hypothesized that this practice is inconsistently followed and that routine pathological consultation is costly and rarely results in a change in treatment for patients undergoing knee arthroscopy. Chiefs of pathology, orthopaedic surgeons, and orthopaedic operating room nurse managers in Ontario hospitals that perform arthroscopic knee surgery were surveyed for compliance. We determined cost using pathology department procedure codes and evaluated effectiveness as the correlation between the postoperative diagnoses of orthopaedic surgeons and pathologists for 1,036 consecutive knee arthroscopy cases. In only one case (0.1%) was it felt that pathology consultation had the potential to significantly alter patient care. The total cost of pathology consultation for the 1,036 cases reviewed was $234,147.00 (mean cost per case, $226.00). Ninety percent of hospitals do not comply with the regulations regarding the processing of these tissues. Poor compliance is justified by the lack of diagnostic value and the need to contain health care costs.

Arthroscopy↗
PubMed1998

Suppression of the blowfly Lucilia sericata using odour-baited triflumuron-impregnated targets.

Field trials were carried out in 1995 and 1996 on farms in the south-west of England to assess the extent to which odour-baited targets could be used to suppress populations of the ectoparasitic blowfly, Lucilia sericata, in sheep pastures. Targets were constructed from 41 x 41 cm squares of aluminium sheet, covered by white cloth which had been dipped in a mixture of sucrose solution (50% w/v) and the chitin synthesis inhibitor triflumuron (10% suspension concentrate). Each target was baited with approximately 300 g of liver and sodium sulphide solution (10%). Three matched sheep farms were used in the trials. In 1995, triflumuron-impregnated targets were placed around the periphery of sheep pastures at one of the farms in late June, at approximately one target per hectare. In 1996, triflumuron-impregnated targets were placed around the periphery of sheep pastures of a second of the farms in early May, at approximately five targets per hectare. Each year, five sticky targets, used to monitor the L. sericata populations, were also placed in fields at the experimental and the other two farms, which acted as controls. In 1995, the results provided some, although inconclusive, evidence that the triflumuron-impregnated targets had reduced the numbers of L. sericata relative to the populations on the two control farms. In 1996, however, the density of L. sericata on the experimental farm was reduced to almost zero and remained significantly lower than on two control farms throughout the period during which the triflumuron-impregnated targets remained in the field. The results are discussed in relation to the use of triflumuron-treated targets as a practical means of controlling L. sericata and sheep blowfly strike.

Animals↗
PubMed1998

Fluorescent amplified-fragment length polymorphism analysis of an outbreak of group A streptococcal invasive disease.

Fluorescent amplified-fragment length polymorphism (FAFLP) analysis was carried out for an outbreak of group A streptococcal (GAS) invasive disease. Streptococcal genomic DNAs were digested with endonucleases EcoRI and MseI, site-specific adaptors were ligated, and PCR amplification was carried out with an EcoRI adaptor-specific primer labelled with fluorescent dye. Amplified fragments of up to 600 bp in size were separated on a polyacrylamide sequencing gel which contained internal size markers in each lane. These data were automatically scanned and analyzed, fragments were precisely sized (+/-1 bp), and electropherograms were generated for each genome with GeneScan 2.1 software. All isolates were compared in this way. Among 27 GAS isolates examined, we found 18 FAFLP profiles, compared with 12 macrorestriction profiles by pulsed-field gel electrophoresis. FAFLP readily distinguished genotypes for two clones of GAS serotype M77 which were responsible for outbreaks of invasive disease in a care-of-the-elderly system. It provided an automated analysis of the whole genome of bacterial isolates. It was reproducible, more discriminatory, and capable of higher throughput than other molecular typing methods. Given agreed conditions, FAFLP would be reproducible between laboratories for rapid characterization of outbreak strains.

Aged↗
PubMed1998

Characteristics of European family and household systems.

"This article establishes that there was considerable diversity in the size and composition of the kin group within the household that is not captured by the conventional classification of family systems according to the relative proportions of simple and complex household forms. Three case studies are presented from England, Corsica and Hungary. English households fulfilled an important welfare role in that they incorporated relatives and non-relatives who were not members of core families-- couples or parent(s) and unmarried child(ren). The societies of Corsica and Hungary provided a greater proportion of their populations with membership of a core family."

Developed Countries↗
PubMed1998

A large outbreak of cryptosporidiosis associated with a public water supply from a deep chalk borehole. Outbreak Investigation Team.

Three hundred and forty-five confirmed cases were reported in a large waterborne outbreak of cryptosporidiosis in North Thames in the spring of 1997. The descriptive epidemiology, attack rates, a case control study, and the detection of oocysts in the water suggested strongly that the outbreak was associated with drinking unboiled tap water that originated from one deep chalk borehole. The 746,000 people living in the water distribution area were advised to boil their drinking water. Investigations did not reveal how oocysts entered the borehole. This is the first published report of a cryptosporidium outbreak caused by filtered borehole water and we believe it to be the largest outbreak due to groundwater to have been reported. Borehole supplies are regarded as relatively pure sources of water and this outbreak has implications for the future monitoring and treatment of drinking water extracted from boreholes.

Adolescent↗
PubMed1997

Silencer elements controlling the B29 (Igbeta) promoter are neither promoter- nor cell-type-specific.

The murine B29 (Igbeta) promoter is B cell specific and contains essential SP1, ETS, OCT, and Ikaros motifs. Flanking 5' DNA sequences inhibit B29 promoter activity, suggesting this region contains silencer elements. Two adjacent 5' DNA segments repress transcription by the murine B29 promoter in a position- and orientation-independent manner, analogous to known silencers. Both these 5' segments also inhibit transcription by several heterologous promoters in B cells, including mb-1, c-fos, and human B29. These 5' segments also inhibit transcription by the c-fos promoter in T cells suggesting they are not B cell-specific elements. DNase I footprint analyses show an approximately 70-bp protected region overlapping the boundary between the two negative regulatory DNA segments and corresponding to binding sites for at least two different DNA-binding proteins. Within this footprint, two unrelated 30-bp cis-acting DNA motifs (designated TOAD and FROG) function as position- and orientation-independent silencers when located directly 5' of the murine B29 promoter. These two silencer motifs act cooperatively to restrict the transcriptional activity of the B29 promoter. Neither of these motifs resembles any known silencers. Mutagenesis of the TOAD and FROG motifs in their respective 5' DNA segments eliminates the silencing activity of these upstream regions, indicating these two motifs as the principal B29 silencer elements within these regions.

Animals↗
PubMed1997

Differential interaction of nuclear factors with the leukocyte-specific pp52 promoter in B and T cells.

The leukocyte-specific, cytoskeleton-binding pp52 (LSP-1, WP-34) protein is widely expressed in multiple leukocyte lineages, including B and T lymphocytes, granulocytes, and macrophages. We previously detected a tissue-specific promoter preceding the exon encoding the N terminus of the pp52 leukocyte protein. Here we describe the functional characterization of this promoter and identification of the factors in B and T cells that regulate its activity. The pp52 promoter contains an initiator specifying the unique 5' terminus of pp52 mRNA, tandem pairs of Ets and SP1 motifs, and a lone C/EBP motif. All these motifs are essential and collectively control transcriptional activity. DNA binding studies and Ab supershift assays revealed that different combinations of factors interact with these motifs in B cells vs T cells. The Ets motifs are preferentially bound by PU-1 in B cell extracts from all stages of development, whereas a different Ets family member reacts with these motifs in T cell extracts. The C/EBP motif is bound by Ig/EBP-1 in pre-B cell and T cell extracts, but is replaced by nuclear factor-IL-6beta or a nuclear factor-IL-6beta-Ig/EBP-1 heterodimer in plasmacytoma cell extracts. Despite its reported role as a negative regulator of transcription, Ig/EBP-1 appears to exert a stimulatory effect on this promoter. These findings reveal the features controlling the pp52 promoter in B and T cells and provide the foundation for determining the regulation of this promoter in other leukocyte lineages.

Base Sequence↗
PubMed1997

Aberrations of the B-cell receptor B29 (CD79b) gene in chronic lymphocytic leukemia.

Leukemic B cells in chronic lymphocytic leukemia (B-CLL) typically exhibit low or undetectable surface Ig. Because the B29 (CD79b and Ig beta) and mb-1 (CD79a and Ig alpha) gene products are required for surface Ig display in the B-cell receptor complex (BCR), we analyzed the expression of these genes in B-CLL cells. The majority (83%) of the randomly selected B-CLL patient samples analyzed exhibited low or undetectable surface BCR measured by mu heavy chain and B29 expression. Levels of mb-1 mRNA in these B-CLL samples with low surface BCR were similar to those in normal B cells. Among those with decreased surface expression, B29 mRNA was not detected in half of these B-CLL samples. The remaining B-CLL samples with diminished surface BCR contained normal levels of B29 mRNA. Further analysis of cDNA clones from the majority of these latter samples contained point mutations, insertions, or deletions that were largely located in the B29 transmembrane and cytoplasmic domains. These results indicate the occurrence of somatic mutations predicted to affect B29 expression and/or function in the majority of B-CLL and suggest that these aberrations underlie the diminished surface BCR display and loss of BCR signaling characteristic of this leukemia.

Antigens, CD↗
PubMed1997

The evolution of ectoparasitism in the genus Lucilia (Diptera:Calliphoridae).

To consider the evolutionary origin of the ectoparasitic habit in the blowfly genus Lucilia (Diptera:Calliphoridae), phylogenetic analyses of mitochondrial DNA sequence data were performed for 10 species, including all the common Lucilia agents of myiasis, collected from Africa, Australasia, North America and Europe. Complementary genetic distance and parsimony analyses are used to consider inter and intraspecific relationships within the genus with reference to previous morphological work. The results support the hypothesis of independent multiple evolution of the ectoparasitic habit in Lucilia sericata, Lucilia cuprina and the Lucilia caesar/Lucilia illustris group and suggest that it has coevolved in relatively recent history along with the domestication and husbandry of sheep. The geographic differences in pathogenic importance of various species of Lucilia also suggest that there is a strong climatic influence determining which species has dominated. Lucilia cuprina has become the predominant pathogenic species in sub-tropical and warm temperate habitats (e.g., Australia and South Africa), L. sericata in cool temperate habitats (e.g., Europe and New Zealand) and L. caesar and L. illustris become more common in sheep myiasis in more northerly Palaearctic regions.

Africa↗
PubMed1997

Application of molecular methods to a nosocomial outbreak of Salmonella enteritidis phage type 4.

A nosocomial outbreak of Salmonella enteritidis phage type 4 occurred in July 1995. Seven definite cases were identified over 13 days affecting four wards in a London hospital. The outbreak strain was characterized by plasmid profile typing and pulsed-field gel electrophoresis (PFGE), and was unusual in that it did not possess a 38 MDa plasmid common to most isolates of S. enteritidis PT 4 made from humans and food animals in England and Wales. Seven asymptomatic excreters were identified on screening. No additional cases occurred on wards after standard isolation procedures were implemented. No common or continuing food or dietary source was identified. Results of epidemiological, microbiological and environmental investigations suggested that the outbreak was due to person-to-person transmission within the hospital. The source of the outbreak was not established but was probably due to admission of a patient with an unrecognized infection of S. enteritidis PT 4. The study highlights the importance of close collaboration between hospital staff, epidemiologists and microbiologists, and demonstrates the value of molecular techniques for strain subdivision in outbreak investigations.

Aged↗
PubMed1997

The use of carrion as breeding sites by the blowfly Lucilia sericata and other Calliphoridae.

To examine the species composition of flies breeding in carrion in the field, the carcasses of mice and quail were exposed on sheep farms in the South West of England. Calliphora vicina was the dominant species of Diptera; 19,294 individuals emerged from 175 of the 241 infested carcasses recovered. Lucilia sericata emerged from only 39 of the infested carcasses, at a median of 10 adults per infested carcass. Other species of Lucilia present were L.ampullacea, L.caesar and L.illustris. The highest number of L.sericata emerged from carcasses placed in open pasture, the highest numbers of C.vicina emerged from carcasses in hedgerow, whereas the highest numbers of L.caesar, L.ampullacea and L.illustris emerged from carcasses in woodland. The duration of exposure of carcasses in the field was negatively related to the size of the adult L.sericata which emerged and, in woodland and hedgerow habitats, to the number of L.sericata which emerged. These data indicate that the larvae of L.sericata in carcasses experience significant levels of competition and that the intensity of this competition may be sufficient to reduce the numbers of L.sericata able to emerge successfully. The size distributions of female L.sericata which emerged from carcasses or which were caught as adults in the field showed only a small degree of overlap, suggesting that only a relatively small proportion of the wild L.sericata population emerge from carcass breeding sites. The results are discussed in relation to the development of new approaches to the control of blowfly strike of sheep.

Animals↗
PubMed1997

The potential for control of the blowfly Lucilia sericata using odour-baited targets.

A deterministic simulation model is used to explore the potential for control of the sheep blowfly, Lucilia sericata, using odour-baited targets. The simulations show that the ambient temperatures of 15 degrees C or 20 degrees C, 13% and 24% of the females present in a population would need to be killed per day, respectively, to prevent the population growing from its initial spring density during the summer blowfly season. In contrast, if both sexes could be sterilized, so that sterilized males were also able to disrupt the fertility of unsterilized females, only 6.5-13% of both sexes would need to be attracted and sterilized at 15 degrees C or 20 degrees C respectively. To examine whether these numbers of individuals could be attracted by targets baited with liver and sodium sulphide, mark-release-recapture studies in sheep pastures were used to quantify sticky target efficiencies. The percentage of the L.sericata population caught on any one day was shown to be positively related to average ambient temperature. At 15 degrees C each sticky target caught approximately 13% and at 20 degrees C, 41% of the females within a 20 m radius. The results indicate that, at ambient temperatures between 15 and 20 degrees C, if distributed at a density of approximately 5/ha, targets baited with liver and sodium sulphide could effectively suppress a population of L.sericata. Lower densities of targets would be required if they were able to sterilize both sexes rather than kill or if more attractive synthetic semiochemical baits could be developed.

Animals↗