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Biomedical subjects

M Richardson

Publications and source records attributed to M Richardson.

At least 73 records · Page 4Linked to original sources
PubMed2000

Stimulation of fructose transport across the intestinal brush-border membrane by PMA is mediated by GLUT2 and dynamically regulated by protein kinase C.

Perfusion of rat jejunum in vitro with PMA increased fructose transport by 70% compared with control values and was blocked by the protein kinase C (PKC) inhibitor chelerythrine. The brush-border membrane contained both the fructose transporters GLUT5 and GLUT2; the presence of the latter was confirmed by luminal biotinylation. PMA increased the GLUT2 level 4-fold within minutes, so that the level was comparable with that of the basolateral membrane, but had no effect on GLUT5 level. GLUT2 was functional, accessible to luminal fructose and could be inhibited selectively by phloretin to permit determination of GLUT2- and GLUT5-mediated transport components. The 4-fold increase in GLUT2 level induced by PMA was matched by a 4-fold increase in GLUT2-mediated transport: there was a compensatory fall in the GLUT5-mediated rate. The pattern of dynamic trafficking was seen only for GLUT2, not GLUT5 or SGLT1, implying that GLUT2 trafficks to the brush-border membrane by a different pathway. Trafficking of GLUT2 to the brush-border membrane correlated with activation of PKC betaII, implying that this isoenzyme is likely to control trafficking. Since PKC is activated by endogenous hormones, GLUT2 levels in vivo are 3-4-fold those in vitro; moreover, because PKC is inactivated as soon as intestine is excised, GLUT2 is lost from the brush-border within minutes in vitro. It is therefore difficult to detect GLUT2 in most in vitro preparations and its role in intestinal sugar absorption across the brush-border membrane has accordingly been overlooked.

Animals↗
PubMed2000

Regulation of GLUT5, GLUT2 and intestinal brush-border fructose absorption by the extracellular signal-regulated kinase, p38 mitogen-activated kinase and phosphatidylinositol 3-kinase intracellular signalling pathways: implications for adaptation to diabetes.

We have investigated the role of the extracellular signal-regulated kinase (ERK), p38 and phosphatidylinositol 3-kinase (PI 3-kinase) pathways in the regulation of intestinal fructose transport. Different combinations of anisomycin, PD98059 and wortmannin had very different effects on fructose transport in perfused isolated loops of rat jejunum. Transport was stimulated maximally by anisomycin (2 microM) and blocked by SB203580 (20 microM), confirming involvement of the p38 pathway. PD98059 (50 microM) alone had little effect on fructose transport. However, it had a dramatic effect on stimulation by anisomycin, diminishing the K(a) 50-fold from 1 microM to 20 nM to show that the ERK pathway restrains the p38 pathway. The K(a) for diabetic jejunum was 30 nM and PD98059 had no effect. Transport in the presence of anisomycin was 3.4-fold that for anisomycin plus PD98059 plus wortmannin. Transport was mediated by both GLUT5 and GLUT2. In general, GLUT2 levels increased up to 4-fold within minutes and with only minimal changes in GLUT5 or SGLT1 levels, demonstrating that GLUT2 trafficks by a rapid trafficking pathway distinct from that of GLUT5 and SGLT1. GLUT2 intrinsic activity was regulated over a 9-fold range. It is concluded that there is extensive cross-talk between the ERK, p38 and PI 3-kinase pathways in their control of brush-border fructose transport by modulation of both the levels and intrinsic activities of GLUT5 and GLUT2. The potential of the intracellular signalling pathways to regulate short-term nutrient transport during the assimilation of a meal and longer-term adaptation to diabetes and hyperglycaemia is discussed.

Animals↗
PubMed2000

Classification of drug-resistant tuberculosis in an epidemic area.

BACKGROUND: Traditionally, patients with drug-resistant tuberculosis are classified as having acquired drug-resistant or primary drug-resistant disease on the basis of a history of previous tuberculosis treatment. Only cases of primary drug resistance are assumed to be due to transmission of drug-resistant strains. METHODS: This descriptive study of 63 patients with drug-resistant tuberculosis assessed the relative contribution of transmission of drug-resistant strains in a high-incidence community of Cape Town, South Africa, by restriction-fragment length polymorphism (RFLP). The RFLP results were compared with the results obtained by traditional classification methods. FINDINGS: According to RFLP definitions, 52% (33 cases) of drug-resistant tuberculosis was caused by transmission of a drug-resistant strain. The proportion of cases due to transmission was higher for multidrug-resistant (64%; 29 cases) than for single-drug-resistant (no cases) tuberculosis. By the clinical classification, only 18 (29%) patients were classified as having primary drug-resistant tuberculosis (implying transmission). The clinical classification was thus misleading in 25 patients. INTERPRETATION: The term acquired drug resistance includes patients infected with strains that truly acquired drug resistance during treatment and patients who were initially infected with or reinfected with a drug-resistant strain. This definition could lead to misinterpretation of surveillance studies, incorrect evaluation of tuberculosis programmes, and delayed diagnosis and treatment of patients with multidrug-resistant disease. The clinical term acquired drug resistance should be replaced with the term "drug resistance in previously treated cases", which includes cases with drug resistance due to true acquisition as well as that due to transmitted drug-resistant strains.

Adolescent↗
PubMed2000

Isolation of a proteinase with plasminogen-activating activity from Lachesis muta muta (bushmaster) snake venom.

A plasminogen activator enzyme (LV-PA) from Lachesis muta muta venom was purified to homogeneity using gel filtration and anion exchange chromatography. SDS-PAGE under reducing conditions showed a single protein band with an Mr of 33,000 Da. It is an acidic glycoprotein which activates plasminogen to plasmin indirectly, functioning via prior formation of a molecular complex, known as plasminogen activator. The purified preparation catalyzes the hydrolysis of several p-nitroanilide peptide substrates containing Lys at the scissile bond. In contrast, no hydrolysis was detected on the synthetic substrates TAME and BAPNA, which contain arginine. By the use of the plasmin-specific chromogenic substrate Tos-Gly-Pro-Lys-pNA, the preparation had a plasmin-like activity of 0.68 U/mg, which was 35.8-fold higher than that of the crude venom from which it was prepared. In vitro, fibrin hydrolysis using LV-PA as plasminogen activator displayed more similarity with the effect produced by streptokinase (SK). SDS-PAGE (10%) analysis showed a 115-kDa complex formation after incubation of plasminogen with either LV-PA or SK. At a molar ratio of 50:1 (fibrinogen:enzyme), the preparation exhibited weakly fibrinogenolytic activity. However, LV-PA is distinguished from thrombin in that it does not clot fibrinogen. After incubation of LV-PA with platelet-rich plasma, the enzyme (2 microM) showed no effect on platelet aggregation induced by ADP, epinephrine, or collagen. Comparison of the N-terminal sequence of LV-PA with other snake venom plasminogen activators revealed that LV-PA exhibits a high degree of sequence identity with the TsVPA from Trimeresurus stejnegeri (90%) and with the Haly-PA from Agkistrodon halys (85%). LV-PA also has homology with other snake venom serine proteinases such as the thrombin-like/gyroxin analogue (38%) from bushmaster venom and with other coagulation serine proteases. The proteinase was readily inhibited by treatment with p-nitrophenyl p-guanidinebenzoate, p-aminobenzamidine, and phenylmethanesulfonyl fluoride but was not affected by metal chelators.

Amino Acid Sequence↗
PubMed2000

Aortic endothelial cell von Willebrand factor content, and circulating plasminogen activator inhibitor-1 are increased, but expression of endothelial leukocyte adhesion molecules is unchanged in insulin-dependent diabetic BB rats.

Endothelial cell injury has been implicated in the increased incidence of vascular disease associated with diabetes mellitus. In diabetic humans, elevated plasma von Willebrand Factor (vWF) has been interpreted as an indication of endothelial damage. In contrast, in an animal model of inherited insulin-dependent diabetes, the bio-breeding (BB) rat, plasma vWF levels did not differ from those in age-matched control rats during the first 7 months of diabetes although morphological evidence of mild aortic endothelial alteration or injury was observed. In the present study efforts have been made to define the endothelial alterations in BB diabetic rats compared to controls more precisely over this time period. Thus, adhesion molecules: intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1(VCAM-1) were evaluated by in situ immunohistochemistry, vWF content was determined by biochemical analysis of aortic extracts and by quantitative immunohistochemistry, plasma vWF levels were measured by ELISA and vWF mRNA by RNAse protection assay. Neither age nor diabetic state significantly affected either the expression of adhesion molecules, or the levels of circulating vWF. Endothelial vWF content was significantly increased in the diabetic vessels, as observed by both approaches but the vWF mRNA content was not different from that in control vessels. Plasma plasminogen activator inhibitor (PAI-1) activity was significantly increased in diabetic animals. In conclusion, endothelial alterations in BB rats associated with diabetes, together with the raised plasma PAI-1 levels, promote the thrombogenic potential of the vessel wall, and are consistent with an increased risk for vascular disease.

Analysis of Variance↗
PubMed2000

Post-cardiac transplantation gout: incidence of therapeutic complications.

OBJECTIVE: To study the clinical impact of gout treatment following cardiac transplantation. METHODS: We performed an audit of all cardiac transplant recipients of the Alfred Hospital before August 1998 who lived in Victoria. RESULTS: We studied 225 patients (81% men), with a mean post-transplant follow-up of 50.8 months (SD 36). Forty-three (19%) had pre-transplant gout, 19 recurring post-transplantation. Twenty-three patients developed gout de novo. Of the 24 patients who received allopurinol, 6 developed pancytopenia and required hospitalization. Fourteen received a change in immunosuppression: in 5 patients following pancytopenia, and in 9 to enable safe use of allopurinol. Thirty-two patients received colchicine; 5 developed neuromyopathy. Impaired renal function, diuretic use, and hypertension were more common in this sub-group. Non-steroidal anti-inflammatory agents, used in 16 patients, caused serious complications in 1 patient (life-threatening peptic ulceration and hemorrhage, precipitating dialysis-dependent chronic renal failure). CONCLUSIONS: Cardiac transplant recipients, when treated for gout, are at high risk of therapeutic complications. Thus, gout treatment significantly affects care, health, and immunosuppression of these patients.

Adolescent↗
PubMed2000

How we live: participatory research with six people with learning difficulties.

Drawing from the Social Model of disability, six people with learning difficulties participated over 18 months in researching their own lived experiences. The method involved weekly group discussions supplemented by participant observation. The study's value stems from in-depth inquiry, which included the participants in the data collection, analysis, dissemination and consequences that they found meaningful. The participants lived in nurse managed community homes. They described how they had faced social and economic exclusion, for example, concerning marriage, child rearing and decently paid employment. With the assistance of nursing staff, the participants had overcome many other social barriers and were enjoying a wide range of activities and choices. Consequently, the participants lived varied lives which they described as interesting and worthwhile. Contemporary models of nursing had successfully directed nursing staff to support 'ordinary living'. However, some disabling assumptions were evident within contemporary nursing. Hence, models of nursing and service delivery were helping both to create lifestyles that the participants valued, whilst simultaneously contributing to their disempowerment.

Adult↗
PubMed2000

Patient satisfaction with emergency nurse practitioners in A & E.

In recent years the complex process of managing services for patients requiring emergency care has been increasingly under scrutiny and considerable diversity has arisen in the organization of emergency care in both hospital and community settings. One innovation which has been particularly widespread is the development of Emergency Nurse Practitioners (ENPs): experienced Accident and Emergency nurses who assume entire responsibility for patients with minor injuries, in emergency settings. The present paper reports on a study which compared patients' satisfaction with care given by Emergency Nurse Practitioners with that provided by doctors and nurses working together in a traditional A & E. Patients were significantly more likely to have received health education and first aid advice from an ENP than from a doctor. They were also significantly more likely to have been given written instructions to take home and told whom to contact if they needed more help and advice following discharge. Those seen by an ENP also reported that they were subsequently significantly less worried about their health, than did patients seen in a traditional A & E.

Adolescent↗
PubMed2000

Mapping of IS6110 flanking regions in clinical isolates of Mycobacterium tuberculosis demonstrates genome plasticity.

Southern hybridization was used in combination with IS6110 insertion-locus-specific probes in a comparative study to determine the structure of chromosomal domains flanking IS6110 elements in clinical isolates of Mycobacterium tuberculosis. The resulting restriction fragment length polymorphism (RFLP) data demonstrated three mutational mechanisms responsible for the polymorphisms observed: IS6110 insertion, chromosomal mutation and deletion. The frequency of IS6110 insertion within many of the chromosomal regions demonstrates that preferential integration regions are common in M. tuberculosis. Mapping the IS6110 insertion positions and chromosomal deletions in relation to the M. tuberculosis H37Rv and M. bovis BCG genome sequences reveals numerous disruptions of predicted open reading frames (ORFs). A phylogenetic tree, based on the mutational data, showed a number of independently evolving lineages of M. tuberculosis, while analysis of the mutational events occurring at each branch point suggests both divergent and convergent evolution. A significant positive correlation was demonstrated between the mutation rate and the frequency of occurrence of different isolates in families of strains, suggesting that evolution may impact on strain 'fitness' or that strain proliferation may increase the chance of mutation. We conclude that the genome of clinical isolates of M. tuberculosis continues to evolve.

Biological Evolution↗
PubMed2000

Prevalence and duration of postmenopausal hormone replacement therapy use in a managed care organization, 1990-1995.

OBJECTIVE: To determine the prevalence and duration of postmenopausal hormone replacement therapy (HRT) use and identify correlates of adherence to therapy. DESIGN: Population-based cohort study. SETTING: Staff-model health maintenance organization. PARTICIPANTS: Female members, 40 years and older. MEASUREMENTS AND MAIN RESULTS: Prevalence and duration of use were measured between 1990 and 1995. Duration was assessed by Kaplan-Meier and proportional hazards methods. Hormone replacement therapy use increased from 10.3% in 1990 to 20.7% in 1995. Greatest use (24%) occurred among menopausal women age 50 to 54 years. Less than 5% of women 75 and older used HRT. Among 1,680 first-time recipients of HRT, two thirds of initial prescriptions were written by internists. Thirty-eight percent discontinued HRT within 1 year. For the subset whose indication for therapy was ascertained, prevention of chronic disease was associated with a 33% 1-year discontinuation rate. Factors associated with longer duration of therapy included white race (relative risk [RR], 1.63; 95% confidence interval [95% CI], 1.32 to 2.02), younger age (RR, 1.02 per year; 95% CI 1.01 to 1.03), and changing the preparation or dose of estrogen (RR, 5.62; 95% CI, 4.33 to 7.25). The formulation (esterified estrogens 0.625 mg versus conjugated estrogens 0.625 mg) was also associated with greater duration of use; all other estrogens were, as a group, associated with shorter duration of use. Those who received their initial HRT prescription from an internist were more likely to continue therapy than those who received it from a gynecologist. CONCLUSIONS: Despite increased use of HRT, only a minority of women in this population used HRT, and many of those discontinued therapy within 1 year.

Age Distribution↗
PubMed2000

An evaluation of the care of patients with minor injuries in emergency settings.

This paper describes a study which evaluated three models of emergency care for patients with minor injuries; a traditional Accident and Emergency (A&E) department where patients with minor injuries were seen by senior house officers and nurses working together; a Minor Accident Treatment Service (MATS) unit, located in a main A&E, where patients with minor injuries were seen by Emergency Nurse Practitioners (ENPs) and a nurse-led Minor Injuries Unit (MIU), where patients with minor injuries were also seen by ENPs. Information about waiting times and length of stay was recorded by the researchers and patients were asked to complete a satisfaction questionnaire at the end of their stay. A sample of 181 patients were included in the study (57 in the traditional A&E, 57 in the MATS unit and 67 in the nurse-led MIU). Patients in the traditional A&E waited significantly longer to be seen than patients seen by an ENP, by an average of 40 minutes, and spent an average of 33 minutes longer in the department. ENPs spent an average of 12 minutes longer than doctors undertaking the first consultation where patients' needs were assessed and documented. Patients were very satisfied with care given by all health professionals. Those seen by ENPs were significantly more likely to have been given health advice and information, written instructions on discharge and told who to contact if they needed further advice. They were found to be subsequently significantly less worried about their health than patients seen in the traditional A&E. It is suggested that although ENPs spent longer with patients, this resulted in an improvement in the quality and depth of information and advice provided.

Efficiency, Organizational↗
PubMed2000

Panfungal PCR and multiplex liquid hybridization for detection of fungi in tissue specimens.

A procedure based on panfungal PCR and multiplex liquid hybridization was developed for the detection of fungi in tissue specimens. The PCR amplified the fungal internal transcribed spacer (ITS) region (ITS1-5.8S rRNA-ITS2). After capture with specific probes, eight common fungal pathogens (Aspergillus flavus, Aspergillus fumigatus, Candida albicans, Candida krusei, Candida glabrata, Candida parapsilosis, Candida tropicalis, and Cryptococcus neoformans) were identified according to the size of the amplification product on an automated sequencer. The nonhybridized products were identified by sequencing. The performance of the procedure was examined with 12 deep-tissue specimens and 8 polypous tissue biopsies from the paranasal sinuses. A detection level of 0.1 to 1 pg of purified DNA (2 to 20 CFU) was achieved. Of the 20 specimens, PCR was positive for 19 (95%), of which 10 (53%) were hybridization positive. In comparison, 12 (60%) of the specimens were positive by direct microscopy, but only 7 (35%) of the specimens showed fungal growth. Sequencing of the nonhybridized amplification products identified an infecting agent in six specimens, and three specimens yielded only sequences of unknown fungal origin. The procedure provides a rapid (within 2 days) detection of common fungal pathogens in tissue specimens, and it is highly versatile for the identification of other fungal pathogens.

Adult↗
PubMed2000

Evaluation of the Oricult-N dipslide for laboratory diagnosis of vaginal candidiasis.

The Oricult-N semiquantitative dipslide (Orion Diagnostica, Espoo, Finland) was evaluated for the laboratory diagnosis of vaginal candidiasis. It was compared with broth culture (Vagicult; Orion Diagnostica). Oricult-N was positive for 14.5% of 124 symptomatic patients and 12% of 50 asymptomatic controls. The results for broth cultures were 17 and 22%, respectively. Thus, the test group and the control group did not differ significantly by either method. High vaginal yeast counts (>/=10(5) CFU/ml) were detected by Oricult-N in 7% of patients and in 0% of controls, but both groups harbored low numbers of yeasts. An accurate quantitative cutoff point separating a level of yeast associated with infection from vaginal yeast carriage could not be defined in the study. Nevertheless, the easy semiquantitation allowed by the Oricult-N method could be helpful because, especially in low-count carriers of Candida, other potential causes of vaginal symptoms should be considered. The Oricult-N method was technically simple and could be applied in primary health care. Further studies are required, however, before Oricult-N can be recommended as a routine diagnostic tool.

Adult↗
PubMed2000

Transdominant activity of human immunodeficiency virus type 1 Vpr with a mutation at residue R73.

The 96-amino-acid-long human immunodeficiency virus type 1 virion-encoded accessory protein Vpr is of particular interest, as this protein, which is found in association with viral particles, can exert a regulatory effect on both virus replication and host cell function. Evidently, Vpr, through interaction with several host regulatory proteins, can modulate transcription from the viral long terminal repeat promoter. Expression of Vpr in cells results in deregulation of cell proliferation during the cell cycle pathway at the G(2) stage. Vpr has unique structural features consisting of multiple functional domains. In this study, we have focused on the leucine/isoleucine-rich domain near the carboxyl terminus of Vpr at residue 73 (arginine) and have demonstrated that alterations at this residue result in ablation of transcriptional activity of Vpr and its ability to block cell cycle events at the G(2) stage. Interestingly, substitution mutations at R73 have resulted in a peptide with dominant negative activities on wild-type functions in transcription and host proliferation events. Results from in vitro and in vivo protein-protein interaction studies have revealed that functionally inactive mutant Vpr can be associated with wild-type protein, presumably through the N-terminal regions of the protein which have been shown to be important for Vpr oligomerization. Thus, it is likely that complexation of the mutant Vpr with wild-type protein functionally inactivates Vpr. The importance of these findings in light of the development of therapeutic strategies is discussed.

Arginine↗
PubMed2000

Epidemiology.

Invasive fungal infections have emerged as important causes of hospital related morbidity and mortality. They are increasingly seen in patients not previously considered at risk, e.g. patients on an intensive care unit. Candida albicans and Aspergillus spp. are the most common pathogens, posing challenges in epidemiology, control and treatment.

Aspergillosis↗
PubMed2000

Clinical and laboratory diagnosis.

Clinical diagnosis of invasive fungal infections demands a high clinical acumen, but both under- and over-diagnosis are common. Laboratory mycological tests have traditionally been limited by a range of complications. Development of methodologies to detect fungal-specific immunoglobulins, cell wall antigens and nucleic acid have improved dramatically in recent years.

Aspergillosis↗