Biomedical subjects
Publications and source records attributed to K Day.
Here we review the zebrafish hemostatic system, its relevance to mammalian hemostasis, and its efficacy as a vertebrate genetic model to further the understanding of hemostasis and thrombosis.
Angiogenesis is critical for the growth and metastasis of endometrial cancer and is therefore an important therapeutic target. Vascular endothelial growth factor-A (VEGF-A) is a key molecule in angiogenesis, but the identification of related molecules and the angiopoietins suggests a more complex picture. We investigated the presence of transcripts for VEGF-A, VEGF-B, VEGF-C, VEGF-D, Angiopoietin-1 and Angiopoietin-2 in benign endometrium, atypical complex hyperplasia (ACH) and endometrioid endometrial carcinoma using in situ hybridisation. We confirmed the presence of VEGF-A mRNA in the epithelial cells of cancers examined (13 out of 13), but not in benign endometrium or ACH. We also demonstrate, using quantitative polymerase chain reaction, that levels of VEGF-B mRNA are significantly lower in endometrial cancer than benign endometrium. We conclude that loss of VEGF-B may contribute to the development of endometrial carcinoma by modulating availability of receptors for VEGF-A.
BACKGROUND: Airway clearance techniques are an important part of the routine care of patients with bronchiectasis. The use of the Flutter, a hand held pipe-like device causing oscillating positive expiratory pressure within the airways, has been proposed as an alternative to more conventional airway clearance techniques. METHODS: A randomised crossover study was performed in 17 stable patients with non-cystic fibrosis bronchiectasis at home, in which 4 weeks of daily active cycle of breathing technique (ACBT) were compared with 4 weeks of daily physiotherapy with the Flutter device. RESULTS: No significant differences between the two techniques were found. Median weekly sputum weights were similar with a median treatment difference of 7.64 g (p=0.77) and there was no evidence of treatment order or order interaction effects (p=0.70). Health status (Chronic Respiratory Disease Questionnaire) and ventilatory function did not change significantly during either treatment period. There was no significant change in peak expiratory flow rate or in breathlessness (Borg score) after individual physiotherapy sessions with either technique. A questionnaire indicated subjectively that patients preferred the Flutter (11/17) to ACBT for routine use. CONCLUSIONS: Daily use of the Flutter device in the home is as effective as ACBT in patients with non-cystic fibrosis bronchiectasis, and has a high level of patient acceptability.
Intravital microscopy allows detailed analysis of leukocyte trafficking in vivo, but fails to identify the nature of leukocytes investigated. Here, we describe the development of a CD2-enhanced green fluorescence protein (EGFP)-transgenic mouse to characterize lymphocyte trafficking during inflammation in vivo. A CD2-EGFP plasmid construct including the CD2 promoter, the EGFP transgene, and the CD2 locus control region was injected into B6CBA/F1 pronuclei. EGFP+ offspring were backcrossed into C57BL/6 mice for six generations. Flow cytometry demonstrated that all peripheral blood EGFP+ cells were positive for CD2 and negative for the granulocyte Ag Ly 6-G (GR-1). EGFP(high) cells stained positive for CD2, CD3, CD8, TCR beta-chain, and NK1.1 but did not express the B cell and monocyte markers CD45RA, CD19, and CD11b. In vitro stimulation assays revealed no difference in lymphocyte proliferation and IL-2 secretion between EGFP+ and EGFP- mice. Intravital microscopy of untreated or TNF-alpha-treated cremaster muscle venules showed EGFP+ cells in vivo, but these cells did not roll or adhere to the vessel wall. In cremaster muscle venules treated with both TNF-alpha and IFN-gamma, EGFP(high) cells rolled, adhered, and transmigrated at a rolling velocity slightly higher (11 microm/s) than that of neutrophils (10 microm/s). Blocking alpha4 integrin with a mAb increased rolling velocity to 24 microm/s. These findings show that CD8+ T cells roll in TNF-alpha/IFN-gamma-pretreated vessels in vivo via an alpha4 integrin-dependent pathway.
Angiogenesis is essential for endometrial growth and repair, and disruption of this process may lead to common disorders of women, including menorrhagia and endometriosis. In pregnancy, failure of the endometrial spiral arterioles to undergo remodeling leads to preeclampsia. Here we report that in addition to vascular endothelial growth factor A (VEGF-A), human endometrium expresses messenger ribonucleic acids (mRNAs) encoding VEGF-C, placenta growth factor (PlGF), the angiopoietins, angiopoietin 1 (Ang1) and Ang2, and the receptors VEGFR-3 (Flt-4), Tie 1, and Tie 2. Levels of VEGF-C, PlGF, and Tie 2 changed during the menstrual cycle. Intense hybridization for VEGF-C and PlGF mRNAs was found in uterine nature killer cells in secretory phase endometrium and for Ang2 mRNA in the same cells in the late secretory phase. Interleukin-2 (IL-2) and IL-15 up-regulated VEGF-C, but not PlGF or Ang2, mRNA levels in isolated NK cells. Conditioned medium from decidual NK cells did not induce human umbilical vein endothelial cell apoptosis. These results indicate that human endometrium expresses a wide range of angiogenic growth factors and that uterine nature killer cells may play an important role in the abnormal endometrial angiogenesis that underlies a range of disorders affecting women.
Pigs show epitheliochorial placentation, in which the maternal uterine epithelium and the fetal trophectoderm become closely apposed. There is no invasion of trophoblast into the maternal tissue, and nutrient and waste exchange take place across two epithelial layers beneath which a complex network of capillaries forms. Later in gestation, the epithelial cells become indented by blood vessels, which greatly reduces the distance for diffusion between the two circulatory systems. Vascular endothelial growth factor is a secreted homodimeric angiogenic growth factor that is involved in physiological and pathological angiogenesis. Its receptors are generally restricted to endothelial cells. Ligand binding, in situ hybridization and immunohistochemistry were carried out in pig placenta throughout gestation to investigate the possible role of vascular endothelial growth factor and its receptors in non-invasive placentation. In situ hybridization and immunohistochemistry revealed that mRNA and immunoreactivity for vascular endothelial growth factor were localized in both maternal and fetal epithelial cells at the maternal-fetal interface and over the maternal glands, although the signal was generally weaker in the maternal glands. Ligand binding was used to localize for vascular endothelial growth factor receptors; no binding was observed over the maternal glands, but very strong binding was localized to the endometrial blood vessels. At the interface between maternal and fetal tissue, a similar pattern was observed whereby the numerous small capillaries at the bases of the two apposed epithelia bound vascular endothelial growth factor specifically. It is concluded that vascular endothelial growth factor produced by the maternal and fetal epithelial layers promotes the growth of capillaries locally, which would facilitate the development of two vascular networks for the efficient transfer of nutrients and waste products.
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Both cholera and pertussis toxins were used to label and study the expression of heterotrimeric G protein alpha subunits in Plasmodium falciparum extracts. Expression of these proteins is developmentally regulated throughout the erythrocytic cycle with peak expression during early asexual development and in mature sexual stages. Treatment of P. falciparum cultures with cholera toxin causes an increase in conversion to sexual development, and at the same concentration has a marginal inhibitory effect on asexual growth and division. Through precise synchronisation of the parasites' asexual cell cycle, we have defined the period of sensitivity to this induction at around the time of invasion, one cycle before the development of the sexual form. Fluorescent microscopy confirmed that access of the toxin to the parasite is limited to the invasive form - the free merozoite, while further labelling studies revealed expression of a single G protein alpha subunit in these stages. These observations are consistent with the view that a G protein-dependent signal transduction pathway is involved in coupling the parasite's environment to commitment to sexual development (gametocytogenesis). This means of artificially stimulating the pathways leading to sexual development can now be used to biochemically follow the activation of the signalling pathways involved.
Both cholera and pertussis toxins were used to label and study the expression of heterotrimeric G protein alpha subunits in Plasmodium falciparum extracts. Expression of these proteins is developmentally regulated throughout the erythrocytic cycle with peak expression during early asexual development and in mature sexual stages. Treatment of P. falciparum cultures with cholera toxin causes an increase in conversion to sexual development, and at the same concentration has a marginal inhibitory effect on asexual growth and division. Through precise synchronisation of the parasites' asexual cell cycle, we have defined the period of sensitivity to this induction at around the time of invasion, one cycle before the development of the sexual form. Fluorescent microscopy confirmed that access of the toxin to the parasite is limited to the invasive form--the free merozoite, while further labelling studies revealed expression of a single G protein alpha subunit in these stages. These observations are consistent with the view that a G protein-dependent signal transduction pathway is involved in coupling the parasite's environment to commitment to sexual development (gametocytogenesis). This means of artificially stimulating the pathways leading to sexual development can now be used to biochemically follow the activation of the signalling pathways involved.
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Design of the physical environment is increasingly recognized as an important aid in caring for people with dementia. This article reviews the empirical research on design and dementia, including research concerning facility planning (relocation, respite and day care, special care units, group size), research on environmental attributes (noninstitutional character, sensory stimulation, lighting, safety), studies concerning building organization (orientation, outdoor space), and research on specific rooms and activity spaces (bathrooms, toilet rooms, dining rooms, kitchens, and resident rooms). The analysis reveals major themes in research and characterizes strengths and shortcomings in methodology, theoretical conceptualization, and applicability of findings.
Endometrial growth and repair after menstruation are associated with profound angiogenesis. Abnormalities in these processes result in excessive or unpredictable bleeding patterns and are common in many women. It is therefore important to understand which factors regulate normal endometrial angiogenesis. Vascular endothelial growth factor (VEGF) is an endothelial cell-specific mitogen that plays an important role in normal and pathological angiogenesis. In this study we show that expression of VEGF is regulated by hypoxia in human endometrium. Culture in vitro for 24 h under hypoxic conditions resulted in a 2- to 6-fold increase in VEGF secretion by both stromal and epithelial cells isolated from human endometrium. Quantitative RT-PCR was used to measure VEGF messenger ribonucleic acid (mRNA) levels in these cells. After hypoxia, VEGF mRNA levels increased 1.8-fold in stromal cells and 3.4-fold in glandular epithelial cells. The mRNA for each VEGF splice variant increased to an equal extent. The increase in VEGF secretion by stromal and epithelial cells in response to hypoxia was not altered by treatment at the same time with estradiol or progesterone. In situ hybridization of human endometrium during menstruation, when steroid levels are low but the tissue is subject to ischemia, showed strong hybridization to VEGF mRNA in both stromal and glandular cells. These results show that local factors, such as hypoxia, can regulate VEGF expression in the endometrium. This may play an important part in normal endometrial repair after menstruation. The secretion of VEGF by endometrial cells under hypoxic conditions may also be important in the pathogenesis of endometriosis, because it would be predicted to assist revascularization of desquamated endometrial explants when they attach at ectopic sites.
Recent research has shown that many parasite populations are made up of a number of epidemiologically distinct strains or genotypes. The implications of strain structure or genetic diversity for parasite population dynamics are still uncertain, partly because there is no coherent framework for the interpretation of field data. Here, we present an analysis of four published data sets for vector-borne microparasite infections where strains or genotypes have been distinguished: serotypes of African horse sickness (AHS) in zebra; types of Nannomonas trypanosomes in tsetse flies; parasite-induced erythrocyte surface antigen (PIESA) based isolates of Plasmodium falciparum malaria in humans, and the merozoite surface protein 2 gene (MSP-2) alleles of P. falciparum in humans and in anopheline mosquitoes. For each data set we consider the distribution of strains or types among hosts and any pairwise associations between strains or types. Where host age data are available we also compare age-prevalence relationships and estimates of the force of infection. Multiple infections of hosts are common and for most data sets infections have an aggregated distribution among hosts with a tendency towards positive associations between certain strains or types. These patterns could result from interactions (facilitation) between strains or types, or they could reflect patterns of contact between hosts and vectors. We use a mathematical model to illustrate the impact of host-vector contact patterns, finding that even if contact is random there may still be significant aggregation in parasite distributions. This effect is enhanced if there is non-random contact or other heterogeneities between hosts, vectors or parasites. In practice, different strains or types also have different forces of infection. We anticipate that aggregated distributions and positive associations between microparasite strains or types will be extremely common.
Nurses, particularly those working in antenatal, maternity and paediatrics, can greatly assist their patients to reduce the harms associated with tobacco use. Senior nursing staff from the Division of Women's and Child's Health, and Primary Health in the Liverpool Health Service were surveyed to identify action currently taken with patients, on active and passive smoking. The survey showed that there was an emphasis on assessment and education. Barriers that hindered staff action included the lack of resources, particularly for people of non-English speaking background (NESB), and training. This research also suggests the need for policy development as a way to achieve consistency and maintenance of action.
The purpose of prophylactic vaccination is to reduce morbidity and mortality in a population. Many questions related to the design of vaccines and vaccination programs require a population standpoint for their sharp formulation and laboratory and field studies to understand their immunologic background. Practical suggestions of the workshop included increased studies of age-specific immunity, better immunoepidemiologic surveillance, better design of efficacy studies, and more systematic sampling of parasite strains to study the evolutionary pressure exerted by vaccines. Theoretical immunology has much to contribute. One of the realizations of the workshop was the value of a strong interdisciplinary approach in vaccine development, utilizing relevant contributions from immunology, population biology, mathematical modeling, epidemiology, molecular biology, and virology.
The purpose of the study was to examine the cost-effectiveness of managed care interventions with respect to prescriptions for chronic illness sufferers enrolled with a specific medical scheme. The illnesses included, were epilepsy, hypertension, diabetes and asthma. The managed care interventions applied were a primary discount; the use of preferred provider pharmacies, and drug utilization review. It was concluded that the managed care interventions resulted in some real cost savings.
BACKGROUND: Cardiac mechanical and electrical activity are closely interrelated. While excitation-contraction coupling is rather well characterized, less is known about cellular mechanisms that promote mechanically induced changes in cardiac electrical activity--mechano-electric feedback. OBJECTIVE: To integrate experimental findings on stretch activation of ion channels and length-dependent changes in intracellular calcium handling into a mathematical description of cardiac cellular activity. METHODS: Simulations are based on the cellular OXSOFT HEART v4.8 models of electrical activity of single cardiac cells of different populations and species. Sarcolemmal stretch-activated channels, mechanically induced changes in the affinity of troponin C to calcium, and length-dependent modulation of calcium handling by the sarcoplasmic reticulum were introduced into the models and linked to a description of sarcomere length or isometric tension. RESULTS: Transient or sustained stretch of cardiomyocytes was simulated during electrical systole and diastole. The electrophysiological response observed in the model depended on timing and severity of mechanical stimulation and on the main subcellular target of the intervention. Responses ranged from triggering of premature action potentials, over changes in action potential shape and duration, to length-dependent variations in contractile behaviour. Modelling findings could be related to experimental observations and may help to explain some of the contradictory data in the literature. The model is sufficiently complete to reproduce experimental findings and to help identify causally linked events.
All individuals with Down's syndrome (trisomy 21-DS) develop the pathogenic hallmarks of Alzheimer's disease in old age (+40 years). The extent of pathology is variable, but it has been shown that the amount of beta-amyloid pathology is variable and related to age and the degree of dementia. Thus, in DS, growing old is associated with a progressive pathological process which results in cognitive decline. However, neuropsychological studies of older DS subjects have identified a clinical dementia in only a proportion of cases. These contradictory observations could be reconciled if some factor existed which modulated the rate and amount of beta-amyloid pathology. Recent studies demonstrate an association between the apolipoprotein E4 (ApoE4) allele and the earlier age of onset in both sporadic and familial AD. Increased amounts of beta-amyloid pathology can also be related to the E4 allele. However, at present there are no data documenting the effects of ApoE genotype on the expression or degree of clinical symptoms of the disease. We have examined the ApoE genotype in a cohort of clinically evaluated elderly patients with DS in order to examine the effects of ApoE genotype on the clinical symptoms of dementia. We report here that, despite the presence of an active disease process, the ApoE E2 allele is associated with longevity and preservation of cognitive functioning.