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M Richardson

Publications and source records attributed to M Richardson.

At least 37 records · Page 2Linked to original sources
PubMed2004

Clonal expansion of a globally disseminated lineage of Mycobacterium tuberculosis with low IS6110 copy numbers.

Knowledge of the clonal expansion of Mycobacterium tuberculosis and accurate identification of predominant evolutionary lineages in this species remain limited, especially with regard to low-IS6110-copy-number strains. In this study, 170 M. tuberculosis isolates with </=6 IS6110 insertions identified in Cape Town, South Africa, were characterized by principal genetic grouping, restriction fragment length polymorphism analysis, spoligotyping, IS6110 insertion site mapping, and variable-number tandem repeat (VNTR) typing. These analyses indicated that all but one of the isolates analyzed were members of principal genetic group 2 and of the same low-IS6110-copy-number lineage. The remaining isolate was a member of principal genetic group 1 and a different low-IS6110-copy-number lineage. Phylogenetic reconstruction suggests clonal expansion through sequential acquisition of additional IS6110 copies, expansion and contraction of VNTR sequences, and the deletion of specific direct-variable-repeat sequences. Furthermore, comparison of the genotypic data of 91 representative low-IS6110-copy-number isolates from Cape Town, other southern African regions, Europe, and the United States suggests that certain low-IS6110-copy-number strain spoligotypes and IS6110 fingerprints were acquired in the distant past. These clones have subsequently become widely disseminated and now play an important role in the global tuberculosis epidemic.

DNA Transposable Elements↗
PubMed2004

IS6110-mediated deletion polymorphism in isogenic strains of Mycobacterium tuberculosis.

Previous studies have described IS6110-mediated polymorphism as an important driving force in Mycobacterium tuberculosis genome evolution and have provided indirect evidence for IS6110-driven deletion events. This study provides the first description of an IS6110-mediated deletion event in truly isogenic strains. We also provide further support for the hypothesis that the region from Rv1754 to Rv1765 is a hot spot for IS6110 insertion and deletion events.

Chromosomes, Bacterial↗
PubMed2003

Examination on Candida spp. in refractory periapical granulomas.

AIM: To examine the occurrence of Candida spp. in refractory periapical granulomas. METHODOLOGY: One hundred and three surgically removed periapical granulomas were subjected to molecular analysis for the occurrence of Candida albicans. DNA was extracted from the samples using a modified phenol/chloroform/isoamyl alcohol method and was subjected to polymerase chain reaction (PCR) with OPA-03 and repetitive sequence (GACA)4 primers. The PCR products were separated in agarose gel electrophoresis, stained with ethidium bromide, visualized using UV light and the sequences were analysed. Samples indicating possible occurrence of Candida were further investigated by histological and immunohistological methods. Periodic acid-Shiff staining (PAS) was used to detect yeast cells and hyphae, and specific monoclonal antibodies to recognize high molecular mass mannoproteins present in the C. albicans cell wall. DNA extraction was controlled by running PCR using beta-actin primers (a housekeeping gene). C. albicans CCUG19915, C. tropicalis ATCC750, C. krusei ATCC6258, C. guilliermondii ATCC6260 and C. glabrata CCUG32725 served as positive controls in PCR. A tissue preparation of chronic atrophic candidosis in oral buccal mucosa served as a positive control for histological and immunohistological examinations. RESULTS: Polymerase chain reaction with beta-actin primers indicated successful DNA extraction in 68 out of 103 samples. The majority of the samples (50) were negative whereas 18 of the samples showed PCR products indicating possible occurrence of Candida spp. PAS-staining and immunohistological examination of these samples were, however, negative. Further analysis of the PCR products revealed sequences not typical for Candida spp. CONCLUSIONS: Candida spp. do not seem to occur in periapical granuloma.

Candida↗
PubMed2003

IS6110-mediated deletion polymorphism in the direct repeat region of clinical isolates of Mycobacterium tuberculosis.

This study investigates the phenomenon of IS6110-mediated deletion polymorphism in the direct repeat (DR) region of the genome of Mycobacterium tuberculosis. Clinical isolates and their putative predecessors were compared using a combination of DR region restriction fragment length polymorphism, IS6110 DNA fingerprinting, spoligotyping, and DNA sequencing, which allowed the mapping of chromosome structure and deletion junctions. The data suggest that adjacently situated IS6110 elements mediate genome deletion. However, in contrast to previous reports, deletions appear to be mediated by inversely oriented IS6110 elements. This suggests that these events may occur via mechanisms other than RecA-mediated homologous recombination. The results underscore the important role of IS6110-associated deletion hypervariability in driving M. tuberculosis genome evolution.

Betaine↗
PubMed2003

Use of genetic distance as a measure of ongoing transmission of Mycobacterium tuberculosis.

The stability of the genotypic marker IS6110, used to define the epidemiology of Mycobacterium tuberculosis, is one of the most important factors influencing the interpretation of DNA fingerprint data. We propose that evolved strains should be considered together with clustered strains to represent chains of ongoing transmission. For the present study we used a large set of fingerprint data for strains collected between 1992 and 1998 from residents of a community with a high incidence of tuberculosis in Cape Town, South Africa. Interstrain genetic distances were calculated by counting the banding pattern mismatches in the IS6110 DNA fingerprints of different isolates. These data demonstrate that the propensity to change by one or two bands is independent of the IS6110 copy number. Hence, the genetic distance between pairs of isolates can be simply expressed as the number of differences in the banding patterns. From this foundation, a data set which identifies newly evolved strains has been generated. Inclusion of these evolved strains into various molecular epidemiological calculations significantly increased the estimate of ongoing transmission in this study setting. The indication is that nearly all cases of tuberculosis in this community are due to ongoing transmission. This has important implications for tuberculosis control, as it indicates that the control measures used at present are unable to reduce the level of transmission. This technique may also be applicable to the study of low-incidence tuberculosis outbreaks as well as the analysis of epidemiological data from other disease epidemics.

DNA Fingerprinting↗
PubMed2003

Clinical experience of galantamine in dementia: a series of case reports.

OBJECTIVE: To use case studies to add the benefit of personal experience with galantamine to published literature and to demonstrate the type of patients that may benefit from this treatment. METHODS: We describe eleven patients, aged 57-90 years, fulfilling the consensus diagnostic criteria for probable Alzheimer's disease, mixed dementia, vascular dementia, Lewy body dementia or Parkinson's dementia. All patients were treated with galantamine that may enhance cholinergic function in the brain by inhibiting acetylcholinesterase and potentiating the effects of acetylcholine at nicotinic acetylcholine receptors. Clinical features were rated according to eight assessment scales in old age psychiatry and additional information was obtained from family and other carers. In some cases caregiver distress was measured. RESULTS: All patients described showed a general improvement in cognition and neuropsychiatric symptoms, although observed improvements and effects were not always reflected by the results of formal assessments. Several patients became more independent, particularly in their activities of daily living, and treatment was felt to have helped maintain independence in their home environment, either alone or with their family or carers. One man continued in employment. Adverse events included nausea and vomiting. CONCLUSIONS: Outcomes in this case series indicate that galantamine is well tolerated and highlight aspects of the different side-effect profiles of the anticholinesterase inhibitors. Subjective benefits were not always apparent from objective measures. These case studies demonstrate the type of patients that may benefit from galantamine.

Aged↗
PubMed2003

A hypoxic response induced in MatLyLu cells by cobalt chloride results in an enhanced angiogenic response by the chick chorioallantoic membrane.

Hypoxia is an important regulator of hypoxia inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) expression. Using Dunning rat prostate tumour cells (MatLyLu) we examined the induction of HIF-1alpha and VEGF by hypoxia and if the induction of these proteins would lead to angiogenesis in the chick chorioallantoic membrane (CAM). MatLyLu cells were exposed to 1% O2, in 5.25% CO2 and 94.75% N2, or treated with 100 mM CoCl2 to simulate hypoxia. Conditioned medium was analyzed using Western blots for HIF-1alpha or VEGF. VEGF levels were quantified using ELISA. Hypoxia significantly increased both HIF-1alpha and VEGF protein production. MatLyLu cells (1x10(6) viable cells in 50 microl of medium) grown under normoxic conditions induced in angiogenesis in the CAM, evaluated by the formation of a spoke wheel, and in cross sections by the number of blood vessels, following 5-day culture. This response was significantly increased using CoCl2-treated cells. Culture medium alone with or without CoCl2 was not angiogenic. These results provide direct evidence for the role of hypoxia in the induction of HIF-1alpha and VEGF which act as key angiogenic signals.

Animals↗
PubMed2003

Adult-to-child transmission of tuberculosis: household or community contact?

SETTING: If a child develops tuberculosis, it is assumed that the source was an adult infectious case, usually living in the same house. Restriction fragment length polymorphism (RFLP) was used in this study to establish transmission from source cases to children. DESIGN: Adult and child tuberculosis cases were prospectively identified from 1993 to 1998 and cultures of Mycobacterium tuberculosis collected. Interviews and RFLP analysis of M. tuberculosis strains were performed to establish epidemiological links and to confirm household transmission. RESULTS: Tuberculosis was confirmed by culture in 1139 (91%) of 1291 adults and 65 (16%) of 417 children. Due to problems in recovering specimens or extracting DNA, RFLP analysis was done in 832 adults and 35 children: 19 (54%) children had household members identified with tuberculosis, 12 with the same strain as the child. Twenty-nine (83%) strains from children formed part of community clusters, but definite contact with source cases was established in only 15. CONCLUSION: The presence of an adult with infectious tuberculosis in the same house as a child with tuberculosis does not necessarily imply adult-to-child transmission. Young children may be infected in the community or in the household. These findings have implications for contact tracing and treatment strategies in high incidence areas.

Adult↗
PubMed2003

An outbreak of Methicillin-resistant Staphylococcus aureus cutaneous infection in a saturation diving facility.

We present a molecular epidemiological investigation of an outbreak of cutaneous tissue infection, which involved six divers during a 45 day saturation exposure dive. The cutaneous infection manifested as boils, foliculitis and small abscesses involving different body sites, including nose, external ear canal, necks, back, extremities, and buttocks. Staphylococcus aureus was consistently isolated from the skin lesions of affected divers. A study of the antibiogram revealed that all Staphylococcus aureus isolates were uniformly resistant to penicillin, oxacillin and erythromycin, but sensitive to clindamycin, tetracycline, trimethoprim-sulfamethoxazole, rifampin and vancomycin. Molecular typing by pulse field gel electrophoresis (PFGE) demonstrated that all the Methicillin-resistant Staphylococcus aureus (MRSA) isolates had an indistinguishable pulsed field gel electrophoresis pattern. The source of outbreak was identified as a colonized diver (diver D). Personal contact was most likely the mode of transmission among the six divers. Infection with MRSA should be suspected in outbreaks of boils that are not responding to standard antibiotic therapy among healthy divers and their close contacts. To our knowledge, this is the first report of Methicillin-resistant Staphylococcus aureus (MRSA) outbreak in a saturation diving facility.

Adult↗
PubMed2002

Malignant ascites fluid (MAF), including ovarian-cancer-associated MAF, contains angiostatin and other factor(s) which inhibit angiogenesis.

OBJECTIVE: The aim was to determine whether human malignant ascites fluid (MAF) associated with abdominal cancer, including ovarian cancer, contained factors which inhibit angiogenesis as well as others which stimulate this process. METHODS: MAF was collected from six patients, four with ovarian cancer, one with gastric cancer, and one with liver metastases. Using the chick chorioallantoic membrane (CAM) the effect of MAF on 7-day-old CAM capillaries was examined for 48 h. Vascular endothelial growth factor (VEGF) was evaluated by ELISA. Five samples of MAF were fractionated by lysine-Sepharose chromatography and the lysine-bound and -unbound fractions were eluted by epsilon-amino-n-hexanoic acid. Whole MAF, the lysine-bound and -unbound fractions, and human angiostatin were subjected to SDS-PAGE/Western blot analysis and immunostained after exposure to anti-human plasminogen. Human plasminogen was exposed to conditioned medium from ovarian epithelial cancer (HEY) cells and subjected to similar Western blot analysis. RESULTS: Despite containing VEGF, each MAF sample examined caused a loss of capillaries from the CAM; a similar response was seen using purified human angiostatin. Whole MAF and the lysine-bound fraction contained plasminogen (90 kDa) and a 55-kDa protein which migrated in a similar manner to human angiostatin on Western blot. Both the lysine-bound and -unbound fractions caused a loss of capillaries in the CAM. Human plasminogen exposed to conditioned medium from HEY cells yielded a fragment which was similar in size to angiostatin. CONCLUSIONS: MAF from patients with various clinical presentations contains angiostatin and VEGF as well as other factors which are capable of inhibiting angiogenesis.

Adult↗
PubMed2002

Assessing the burden of respiratory disease in the UK.

This review explores the health and social burden of some of the main respiratory diseases (asthma, chronic obstructive pulmonary disease, cryptogenic fibrosing alveolitis, cystic fibrosis, lung cancer, mesothelioma, obstructive sleep apnoea and tuberculosis) in order to increase awareness of these diseases and highlight areas where improvements in care are required. The overall impact of respiratory diseases in the U.K. in terms of prevalence, mortality, morbidity and economic costs, with particular reference to secondary care has been considered and comparisons made with the rest of Europe where data are available. Respiratory diseases are responsible for a significant proportion of serious morbidity and premature death among the population of the U.K. and they will continue to present a growing challenge; special support is needed to tackle this burden.

Adolescent↗
PubMed2002

Microevolution of the direct repeat region of Mycobacterium tuberculosis: implications for interpretation of spoligotyping data.

The direct repeat (DR) region has been determined to be an important chromosomal domain for studying the evolution of Mycobacterium tuberculosis. Despite this, very little is known about microevolutionary events associated with clonal expansion and how such events influence the interpretation of both restriction fragment length polymorphism (RFLP) and spoligotype data. This study examined the structure of the DR region in three independently evolving lineages of M. tuberculosis with a combination of DR-RFLP, spoligotyping, and partial DNA sequencing. The results show that the duplication of direct variable repeat (DVR) sequences and single-nucleotide polymorphisms is rare; conversely, the deletion of DVR sequences and IS6110-mediated mutation is observed frequently. Deletion of either single or contiguous DVR sequences was observed. The deletion of adjacent DVR sequences occurred in a dependent manner rather than as an accumulation of independent events. Insertion of IS6110 into either the direct repeat or spacer sequences influenced the spoligotype pattern, resulting in apparent deletion of DVR sequences. Homologous recombination between adjacent IS6110 elements led to extensive deletion in the DR region, again demonstrating a dependent evolutionary mechanism. Different isolates from the same strain family and isolates from different strain families were observed to converge to the same spoligotype pattern. In conclusion, the binary data of the spoligotype are unable to provide sufficient information to accurately establish genotypic relationships between certain clinical isolates of M. tuberculosis. This has important implications for molecular epidemiologic strain tracking and for the application of spoligotype data to phylogenetic analysis of M. tuberculosis isolates.

Bacterial Typing Techniques↗
PubMed2002

Evolution of the IS6110-based restriction fragment length polymorphism pattern during the transmission of Mycobacterium tuberculosis.

Interpretation of the molecular epidemiological data of Mycobacterium tuberculosis is dependent on the validity of the assumptions that have been made. It is assumed that the IS6110 banding pattern is sufficiently stable to define epidemiological events representing ongoing transmission. However, molecular epidemiological data also support the observation that the IS6110 banding pattern may change over time. Factors affecting this rate may include the nature and duration of disease in a host and the opportunity to experience different host environments during the transmission cycle. To estimate the rate of IS6110 change occurring during the process of transmission, M. tuberculosis isolates from epidemiologically linked patients were genotypically characterized by restriction fragment length polymorphism (RFLP) analysis. The identification of IS6110 banding pattern changes during ongoing transmission suggested that a rate could be estimated. IS6110 change was significantly associated with strains with >5 IS6110 elements (P = 0.013) and was not observed in low-copy-number isolates. The minimum rate of appearance of variant strains was calculated to be 0.14 variant cases per source-case per year. This data suggest that clustering of isolates based on identical RFLP patterns is expected to underestimate transmission in patients infected with high-copy-number isolates. A model based on the rate of appearance of both variant and invariant strains demonstrates that the genotypically defined population structure may change by 18.6% during the study period of approximately 6.5 years. The implications for the use of RFLP data for epidemiologic study are discussed.

Adult↗
PubMed2002

Calculation of the stability of the IS6110 banding pattern in patients with persistent Mycobacterium tuberculosis disease.

The interpretation of molecular epidemiologic data of Mycobacterium tuberculosis infection is dependent on the understanding of the stability and evolutionary characteristics of the DNA fingerprinting marker used to classify clinical isolates. This study investigated the stability of the IS6110 banding pattern in serial tuberculosis isolates collected from patients resident in an area with a high incidence of tuberculosis. Evolutionary changes were observed in 4% of the strains, and a half-life (t(1/2)) of 8.74 years was calculated, assuming a constant rate of change over time. This rate may be composed of a high rate of change seen during the early disease phase (t(1/2) = 0.57 years) and a low rate of change seen in the late disease phase (t(1/2) = 10.69 years). The early rate probably reflects change occurring during active growth prior to therapy, while the low late rate may reflect change occurring during or after treatment. We demonstrate that the calculation of these rates is strongly influenced by the time interval between onset of disease and sputum sampling. These calculations are further complicated by partial replacement of the original strain population, resulting in the sporadic appearance of clonal variants in sputum specimens. Therefore, the true extent of genetic diversity may be underestimated within each host, thereby influencing molecular epidemiological data used to establish transmission chains.

Adult↗
PubMed2002

Historic and recent events contribute to the disease dynamics of Beijing-like Mycobacterium tuberculosis isolates in a high incidence region.

SETTING: A retrospective study in an urban setting with a high tuberculosis incidence. OBJECTIVE: To study the molecular epidemiology and disease dynamics of a prevalent Mycobacterium tuberculosis strain family, F29, a subset of the Beijing strains. DESIGN: Multi-locus DNA fingerprinting and genomic analysis was used to characterise F29 isolates. Demographic and molecular epidemiologic data were correlated with those of other isolates from the setting. The geographic locations of five F29 strain clusters were plotted using a geographic information system (GIS) and an index for geographic distribution was calculated. Their cumulative temporal occurrence was also plotted. RESULTS: The genomic similarity of F29 to the Beijing-strains was confirmed. A high degree of clustering predicted high disease transmission. Spatial distribution was mostly widespread except for one cluster. Smaller foci of transmission were observed. The temporal spread showed ongoing transmission. CONCLUSION: F29 belongs to the Beijing strain group. The prevalence and high degree of strain clustering, with limited geographic clustering, indicates that F29 strains are endemic in the study community. However, recent epidemiologic events also contributed to the disease spread. The combination of molecular epidemiologic, spatial and temporal data has enhanced our understanding of the disease dynamics of Beijing strains in our study community.

Adolescent↗
PubMed2001

Founding editorial: embryology--an integrated approach.

We introduce the Embryology domain of TheScientificWorld and outline the scope and aims. We argue for an interdisciplinary approach to problems in develop-mental biology. Three areas are identified as being of particular relevance to this domain: evolutionary developmental biology, teratology, and descriptive or experimental embryology.

Animals↗
PubMed2001

Parametrically dissociating speech and nonspeech perception in the brain using fMRI.

Candidate brain regions constituting a neural network for preattentive phonetic perception were identified with fMRI and multivariate multiple regression of imaging data. Stimuli contrasted along speech/nonspeech, acoustic, or phonetic complexity (three levels each) and natural/synthetic dimensions. Seven distributed brain regions' activity correlated with speech and speech complexity dimensions, including five left-sided foci [posterior superior temporal gyrus (STG), angular gyrus, ventral occipitotemporal cortex, inferior/posterior supramarginal gyrus, and middle frontal gyrus (MFG)] and two right-sided foci (posterior STG and anterior insula). Only the left MFG discriminated natural and synthetic speech. The data also supported a parallel rather than serial model of auditory speech and nonspeech perception.

Adult↗