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Abstract
Artemisinins were discovered to be highly effective antimalarial drugs shortly after the isolation of the parent artemisinin in 1971 in China. These compounds combine potent, rapid antimalarial activity with a wide therapeutic index and an absence of clinically important resistance. Artemisinin containing regimens meet the urgent need to find effective treatments for multidrug resistant malaria and have recently been advocated for widespread deployment. Comparative trials of artesunate and quinine for severe malaria are in progress to see if the persistently high mortality of this condition can be reduced.
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Abstract
Changes in the concentration of free calcium regulate many intracellular metabolic pathways and other important aspects of cellular function. The erythrocyte maintains intracellular calcium concentrations within a narrow range, but infection by malarial parasites disrupts these homeostatic mechanisms. The observation that infected erythrocytes have supranormal concentrations of calcium raises questions about the storage and functions of calcium ions within parasites. These are addressed in the following review by Sanjeev Krishna and Laura Squire-Pollard.
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Papadopoulos MC, Saadoun S, Binder DK, Manley GT, Krishna S, Verkman AS. Molecular mechanisms of brain tumor edema. Neuroscience 2005; 129:1011-20. [PMID: 15561416 DOI: 10.1016/j.neuroscience.2004.05.044] [Citation(s) in RCA: 201] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2004] [Revised: 05/24/2004] [Accepted: 05/25/2004] [Indexed: 10/26/2022]
Abstract
Despite their diverse histological types, most brain tumours cause brain oedema, which is a significant cause of patient morbidity and mortality. Brain tumour oedema occurs when plasma-like fluid enters the brain extracellular space through impaired capillary endothelial tight junctions in tumours. Under-expression of the tight junction proteins occludin, claudin-1 and claudin-5 are key molecular abnormalities responsible for the increased permeability of tumour endothelial tight junctions. Recent evidence suggests that the membrane water channel protein aquaporin-4 (AQP4) also plays a role in brain tumour oedema. AQP4-deficient mice show remarkably altered brain water balance after various insults, including brain tumour implantation. AQP4 expression is strongly upregulated around malignant human brain tumours in association with reduced extracellular volume, which may restrict the flow of extracellular fluid from the tumour bed into the brain parenchyma. Elimination of excess fluid leaking into brain parenchyma requires passage across three AQP4-rich barriers: a) the glia limitans externa, b) the glia limitans interna/ependyma, and c) the blood-brain barrier. Modulation of the expression and/or function of endothelial tight junction proteins and aquaporins may provide novel therapeutic options for reducing brain tumour oedema.
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Joët T, Morin C, Fischbarg J, Louw AI, Eckstein-Ludwig U, Woodrow C, Krishna S. Why is the Plasmodium falciparum hexose transporter a promising new drug target? Expert Opin Ther Targets 2005; 7:593-602. [PMID: 14498822 DOI: 10.1517/14728222.7.5.593] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Chemotherapy of malaria parasites is limited by established drug resistance and lack of novel treatment options. Intraerythrocytic stages of Plasmodium falciparum, the causative agent of severe malaria, are wholly dependent upon host glucose for energy. A facilitative hexose transporter (PfHT), encoded by a single-copy gene, mediates glucose uptake and is therefore an attractive potential target. The authors first established heterologous expression in Xenopus laevis to allow functional characterisation of PfHT. They then used this expression system to compare the interaction of substrates with PfHT and mammalian Gluts (hexose transporters) and identified important differences between host and parasite transporters. Certain Omethyl derivatives of glucose proved to be particularly useful discriminators between mammalian transporters and PfHT. The authors exploited this selectivity and synthesised an O-3 hexose derivative that potently inhibits PfHT expressed in oocytes. This O-3 derivative (compound 3361) also kills cultured P. falciparum with comparable potency. Compound 3361 acts with reasonable specificity against PfHT orthologues encoded by other parasites such as Plasmodium vivax, Plasmodium yoelii and Plasmodium knowlesi. Multiplication of Plasmodium berghei in a mouse model is also significantly impeded by this compound. These findings validate PfHT as a novel target.
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Edwards G, Krishna S. Pharmacokinetic and pharmacodynamic issues in the treatment of parasitic infections. Eur J Clin Microbiol Infect Dis 2004; 23:233-42. [PMID: 15029513 DOI: 10.1007/s10096-004-1113-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Despite increases in the incidence of many parasitic infections in recent years, the number of studies designed to improve the treatment of these infections has failed to keep pace with their huge impact on public health. Unfortunately, research and development in this field is not an economically attractive proposition for the pharmaceutical industry, and this neglect is exacerbated by the fact that many parasitic diseases have negligible profiles in countries that have the funds to research them. An absence of effective vaccines means that, for the foreseeable future, chemotherapy is likely to be the mainstay of disease management. This review describes the advances gained in our understanding of the relationship between pharmacokinetics and pharmacodynamics, with the aim of improving the way in which we use antiparasitic agents while at the same time highlighting those areas where there is an urgent need for further investigation. Unsurprisingly, much of our success has been in the chemotherapy of malaria, where the link between drug concentration and response is reasonably well characterised. For many other diseases, however, this link is poorly understood, in some cases because the mechanism of action of the drug has not been fully elucidated, or in other cases because a true pharmacodynamic endpoint may be unavailable. Overcoming these problems is critical if the clinician is to have the information necessary to enable optimal treatment of patients who may be severely ill and in need of immediate, life-saving attention.
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Saadoun S, Papadopoulos MC, Krishna S. Water transport becomes uncoupled from K+ siphoning in brain contusion, bacterial meningitis, and brain tumours: immunohistochemical case review. J Clin Pathol 2004; 56:972-5. [PMID: 14645363 PMCID: PMC1770130 DOI: 10.1136/jcp.56.12.972] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
Specimens of normal human brain, contused brain, brain with bacterial meningitis, and brain tumours were immunolabelled for aquaporin 4 (AQP4) and Kir4.1. In normal brain tissue, AQP4 and Kir4.1 were detected around the microvessels. In pathological brain tissue, AQP4 was upregulated in astrocytes in oedematous regions and Kir4.1 was upregulated in astrocytes in damaged brain. Changes in alpha syntrophin expression paralleled those of AQP4 and Kir4.1. The following hypothesis is proposed: in astrocytes, under normal conditions, AQP4 couples water transport with Kir4.1 mediated K+ siphoning, but in pathological states, AQP4 facilitates the flow of brain oedema fluid, and Kir4.1 buffers increased extracellular K+.
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Eckstein-Ludwig U, Webb RJ, Van Goethem IDA, East JM, Lee AG, Kimura M, O'Neill PM, Bray PG, Ward SA, Krishna S. Artemisinins target the SERCA of Plasmodium falciparum. Nature 2003; 424:957-61. [PMID: 12931192 DOI: 10.1038/nature01813] [Citation(s) in RCA: 684] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2003] [Accepted: 05/12/2003] [Indexed: 11/08/2022]
Abstract
Artemisinins are extracted from sweet wormwood (Artemisia annua) and are the most potent antimalarials available, rapidly killing all asexual stages of Plasmodium falciparum. Artemisinins are sesquiterpene lactones widely used to treat multidrug-resistant malaria, a disease that annually claims 1 million lives. Despite extensive clinical and laboratory experience their molecular target is not yet identified. Activated artemisinins form adducts with a variety of biological macromolecules, including haem, translationally controlled tumour protein (TCTP) and other higher-molecular-weight proteins. Here we show that artemisinins, but not quinine or chloroquine, inhibit the SERCA orthologue (PfATP6) of Plasmodium falciparum in Xenopus oocytes with similar potency to thapsigargin (another sesquiterpene lactone and highly specific SERCA inhibitor). As predicted, thapsigargin also antagonizes the parasiticidal activity of artemisinin. Desoxyartemisinin lacks an endoperoxide bridge and is ineffective both as an inhibitor of PfATP6 and as an antimalarial. Chelation of iron by desferrioxamine abrogates the antiparasitic activity of artemisinins and correspondingly attenuates inhibition of PfATP6. Imaging of parasites with BODIPY-thapsigargin labels the cytosolic compartment and is competed by artemisinin. Fluorescent artemisinin labels parasites similarly and irreversibly in an Fe2+-dependent manner. These data provide compelling evidence that artemisinins act by inhibiting PfATP6 outside the food vacuole after activation by iron.
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Krishna S, Balas EA, Boren SA, Maglaveras N. Patient acceptance of educational voice messages: a review of controlled clinical studies. Methods Inf Med 2003; 41:360-9. [PMID: 12501806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/28/2023]
Abstract
OBJECTIVES The objective of this study was to evaluate controlled evidence on the impact of automated computer-based telephone messaging technology upon health outcomes, cost savings and acceptance by patients, caregivers and care providers. METHODS Systematic searches of electronic databases were conducted to find controlled clinical studies of automated phone messaging used in patient care. Studies were selected based on the three criteria: 1) randomized controlled trials or controlled trials; 2) patients receiving health care related education, information, advice or reminder for a specific action to be taken in their home setting; and 3) use of automated computer-based phone technology to deliver the messages. Information abstracted from studies included information about the institution, persons targeted, intervention and its effect on health outcomes, costs and acceptance by patients and caregivers. RESULTS A total of nineteen studies were identified for review. Sixteen studies were randomized controlled trials and three were controlled studies with no randomization. Studies were placed in two categories, preventive care education and chronic care studies. Preventive care education studies covered childhood immunizations, medication compliance, influenza vaccinations, tuberculosis and health prevention activities and chronic care studies were related to cholesterol, diabetes, hypertension and congestive heart failure. More than 80% of studies showed significant impact upon measurable health outcomes. CONCLUSIONS Controlled evidence substantiates the efficacy of automated telephone communication in improving the quality of care. Educational voice messages are acceptable in patients and represent an important opportunity to enhance telemedicine and telehealth applications.
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Pukrittayakamee S, Krishna S, Ter Kuile F, Wilaiwan O, Williamson DH, White NJ. Alanine metabolism in acute falciparum malaria. Trop Med Int Health 2002; 7:911-8. [PMID: 12390595 DOI: 10.1046/j.1365-3156.2002.00955.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We investigated the integrity of the gluconeogenic pathway in severe malaria using alanine metabolism as a measure. Alanine disposition and liver blood flow, assessed by indocyanine green (ICG) clearance, were measured simultaneously in 10 patients with falciparum malaria (six severe and four moderately severe malaria). After intravenous infusion of alanine (0.3 g/kg), glucose increments (AUC0-55 min) were lower in patients with severe malaria than in those with moderately severe malaria (median = 508 vs. 808 mmol/min/l; P = 0.055). There were no significant differences in the other metabolite increments (alanine, lactate and pyruvate; P >/= 0.27). The two fatal cases had markedly delayed alanine removal (larger AUC0-55 min), prolonged T(1/2) and slower clearance (P </= 0.007). Overall the increments in blood alanine correlated directly with lactate increments (rs = 0.84; P = 0.002) and inversely with glucose (rs = -0.70; P = 0.025). Between acute and convalescent studies, the increments (AUC0-55 min) of alanine and glucose were not significantly different (P >/= 0.07) but the increments of lactate and pyruvate were lower in convalescence. Thus, the ratio of the increments of alanine to those of lactate and pyruvate were significantly higher in the convalescent study (P </= 0.017). The mean (SD) ICG clearance during acute malaria was not significantly different to that in convalescence (21.6 +/- 9.3 vs. 34.1 +/- 15.5 ml/min/kg; P = 0.25). During the acute study, there was a significant inverse correlation between ICG clearance and the post-infusion increments of lactate (rs = -0.63, P = 0.049) and pyruvate (rs = -0.74, P = 0.014). These data indicate that alanine clearance is impaired in acute falciparum malaria in proportion to the severity of illness and suggest an important role for anaerobic glycolysis in the pathogenesis of hypoglycaemia in severe malaria.
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Saadoun S, Papadopoulos MC, Davies DC, Bell BA, Krishna S. Increased aquaporin 1 water channel expression in human brain tumours. Br J Cancer 2002; 87:621-3. [PMID: 12237771 PMCID: PMC2364235 DOI: 10.1038/sj.bjc.6600512] [Citation(s) in RCA: 224] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2002] [Revised: 06/13/2002] [Accepted: 06/25/2002] [Indexed: 11/09/2022] Open
Abstract
Aquaporin 1 is a water channel protein. There was little aquaporin 1 immunoreactivity in normal brain parenchyma. In astrocytomas, aquaporin 1 was expressed in microvessel endothelia and neoplastic astrocytes. In metastatic carcinomas, aquaporin 1 was present in microvessel endothelia and reactive astrocytes. Aquaporin 1 may participate in the formation of brain tumour oedema.
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Papadopoulos MC, Saadoun S, Krishna S, Bell BA, Davies DC. The aquaporin-1 water channel protein is abnormally expressed in oedematous human brain tumours. J Anat 2002. [DOI: 10.1046/j.1469-7580.2002.00047_24.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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88
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Saadoun S, Papadopoulos MC, Bell BA, Krishna S, Davies DC. The aquaporin-4 water channel and brain tumour oedema. J Anat 2002. [DOI: 10.1046/j.1469-7580.2002.00047_16.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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89
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Adjuik M, Agnamey P, Babiker A, Borrmann S, Brasseur P, Cisse M, Cobelens F, Diallo S, Faucher JF, Garner P, Gikunda S, Kremsner PG, Krishna S, Lell B, Loolpapit M, Matsiegui PB, Missinou MA, Mwanza J, Ntoumi F, Olliaro P, Osimbo P, Rezbach P, Some E, Taylor WRJ. Amodiaquine-artesunate versus amodiaquine for uncomplicated Plasmodium falciparum malaria in African children: a randomised, multicentre trial. Lancet 2002; 359:1365-72. [PMID: 11978332 DOI: 10.1016/s0140-6736(02)08348-4] [Citation(s) in RCA: 206] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
BACKGROUND Increasing drug resistance limits the choice of efficacious chemotherapy against Plasmodium falciparum malaria in Africa. Amodiaquine still retains efficacy against P falciparum in many African countries. We assessed the safety, treatment efficacy, and effect on gametocyte carriage of adding artesunate to amodiaquine in three randomised trials in Kenya, Sénégal, and Gabon. METHODS We enrolled 941 children (400 in Kenya, 321 in Sénégal, and 220 in Gabon) who were 10 years or older and who had uncomplicated P falciparum malaria. Patients were randomly assigned amodiaquine (10 mg/kg per day for 3 days) plus artesunate (4 mg/kg per day for 3 days) or amodiaquine (as above) and placebo (for 3 days). The primary endpoints were parasitological cure rates at days 14 and 28. Analysis was by intention to treat and by an evaluability method. FINDINGS Both regimens were well tolerated. Six patients in the amodiaquine-artesunate group and five in the amodiaquine group developed early, drug-induced vomiting, necessitating alternative treatment. By intention-to-treat analysis, the day-14 cure rates for amodiaquine-artesunate versus amodiaquine were: 175/192 (91%) versus 140/188 (74%) in Kenya (D=16.7% [95% CI 9.3-24.1], p<0.0001), 148/160 (93%) versus 147/157 (94%) in Sénégal (-1.1% [-6.7 to 4.5], p=0.7), and 92/94 (98%) versus 86/96 (90%) in Gabon (8.3% [1.5-15.1], p=0.02). The corresponding rates for day 28 were: 123/180 (68%) versus 75/183 (41%) in Kenya (27.3% [17.5-37.2], p<0.0001), 130/159 (82%) versus 123/156 (79%) in Sénégal (2.9% [-5.9 to 11.7], p=0.5), and 80/94 (85%) versus 70/98 (71%) in Gabon (13.7% [2.2-25.2], p=0.02). Similar rates were obtained by evaluability analysis. INTERPRETATION The combination of artesunate and amodiaquine improved treatment efficacy in Gabon and Kenya, and was equivalent in Sénégal. Amodiaquine-artesunate is a potential combination for use in Africa. Further investigations to assess the potential effect on the evolution of drug resistance, disease transmission, and safety of amodiaquine-artesunate are warranted.
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Planche T, Dzeing A, Emmerson AC, Onanga M, Kremsner PG, Engel K, Kombila M, Ngou-Milama E, Krishna S. Plasma glutamine and glutamate concentrations in Gabonese children with Plasmodium falciparum infection. QJM 2002; 95:89-97. [PMID: 11861956 DOI: 10.1093/qjmed/95.2.89] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Low plasma glutamine levels in critical illness, neonates and burns patients are associated with poor outcome and increased risk of intercurrent infection. AIM To investigate the relationship between plasma glutamine/glutamate levels and severity/outcome of malaria. DESIGN Two-hospital prospective study, with both febrile and healthy controls. METHODS We measured plasma glutamine and glutamate concentrations in 239 Gabonese patients: 145 children with malaria (86 with severe, 36 with moderate and 23 with uncomplicated disease), 42 healthy children, 44 febrile controls and eight healthy adults, and related findings to conventional markers of disease severity such as plasma lactate. RESULTS Median (IQR) plasma glutamine was lower in uncomplicated falciparum malaria and in moderate malaria than in healthy controls: 353 (287-474) and 379 (293-448) vs. 485 (428-531) micromol/l, respectively; p<0.01 for both malaria groups vs. controls. In contrast, plasma glutamine was within the normal range in those with severe malaria and in febrile control children: 431 (342-525) and 472 (338-547) micromol/l, respectively. Furthermore, plasma glutamine was significantly higher in the children who died with malaria than in survivors: 514 (374-813) (n=12) vs. 399 (316-475) micromol/l (n=133), respectively; p=0.001. There were no significant differences in plasma glutamate concentrations between any of the study groups. DISCUSSION In severe malaria, there was a positive correlation between plasma glutamine and lactate levels (p=0.009, r=0.281). This correlation may reflect impaired gluconeogenesis. Glutamine supplementation is probably not justified in severe P. falciparum infection.
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Saadoun S, Papadopoulos MC, Davies DC, Krishna S, Bell BA. Aquaporin-4 expression is increased in oedematous human brain tumours. J Neurol Neurosurg Psychiatry 2002; 72:262-5. [PMID: 11796780 PMCID: PMC1737753 DOI: 10.1136/jnnp.72.2.262] [Citation(s) in RCA: 278] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Aquaporin-4 (AQP4) is a highly conserved water channel protein. In rats, AQP4 is expressed in astrocyte foot processes and is important in brain water homeostasis. AQP4 expression has not been investigated in non-neoplastic human brain or oedematous brain tumours, where water homeostasis is disrupted. Therefore, immunohistochemistry was used to study AQP4 expression in non-neoplastic and neoplastic human brain and blood-brain barrier permeability was assessed using contrast enhanced computed tomograms. AQP4 was present around microvessels in five specimens of non-neoplastic brain and five low grade (Daumas-Duport I or II) astrocytomas. AQP4 was massively upregulated in four and absent in one high grade (Daumas-Duport III or IV) astrocytoma. Massive upregulation of AQP4 was also found in reactive astrocytes in five metastatic adenocarcinomas. There was significant (p<0.0001) correlation between blood-brain barrier opening and upregulated AQP4 expression. Increased AQP4 expression in high grade astrocytomas and adenocarcinomas may facilitate the flow of oedema fluid.
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Warwick-Davies J, Watson AJ, Griffin GE, Krishna S, Shattock RJ. Enhancement of Mycobacterium tuberculosis-induced tumor necrosis factor alpha production from primary human monocytes by an activated T-cell membrane-mediated mechanism. Infect Immun 2001; 69:6580-7. [PMID: 11598025 PMCID: PMC100030 DOI: 10.1128/iai.69.11.6580-6587.2001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis alone induces small, donor-variable amounts of tumor necrosis factor alpha (TNF-alpha) from primary human monocytes in vitro. However, TNF-alpha release is increased 5- to 500-fold when fixed activated T cells (FAT) or their isolated, unfixed membranes are added to this system. This FAT-induced synergy was at least as potent as that induced by gamma interferon (IFN-gamma) at 100 U/ml. FAT-enhanced TNF-alpha production is at least in part transcriptionally mediated, as reflected by quantitative changes in TNF-alpha mRNA between 2 and 6 h poststimulation. Unlike IFN-gamma-cocultured cells, FAT-treated monocytes appeared not to have enhanced TNF-alpha message stability, suggesting that de novo transcription may be involved in this effect. Furthermore, M. tuberculosis alone induced only minimal DNA binding of monocyte NF-kappaB, but cells treated with M. tuberculosis and FAT potentiated NF-kappaB activity more effectively. It is therefore possible that one mechanism by which FAT synergize with M. tuberculosis to stimulate TNF-alpha production is via NF-kappaB-enhanced transcription. These data strongly suggest that in the interaction of cells involved in the immune response to M. tuberculosis, T-cell stimulation of monocyte TNF-alpha production involves a surface membrane interaction(s) as well as soluble mediators.
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Planche T, Krishna S, Kombila M, Engel K, Faucher JF, Ngou-Milama E, Kremsner PG. Comparison of methods for the rapid laboratory assessment of children with malaria. Am J Trop Med Hyg 2001; 65:599-602. [PMID: 11716121 DOI: 10.4269/ajtmh.2001.65.599] [Citation(s) in RCA: 169] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Rapid diagnosis and accurate quantification of Plasmodium falciparum parasitemia are important for the management of malaria. The assessment of disease severity also depends on evaluation of metabolic indexes such as blood glucose and lactate concentrations. Here we describe an accurate and rapid alternative to conventional thick film examination (Lambaréné method). We also assess near-patient methods for measuring blood glucose (OneTouch) and lactate (Accusport). The accuracy of the Lambaréné method is similar to that of thin films. Results from the OneTouch glucose meter also are in good agreement with a YSI 2300 reference meter. Overall, the Accusport lactate meter agrees poorly with the YSI 2300 reference meter. However, the sensitivity and specificity to detect hyperlactatemia (blood lactate > or = 5 mmol/L) are 0.94 and 0.98, respectively.
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Denhardt DT, Burger EH, Kazanecki C, Krishna S, Semeins CM, Klein-Nulend J. Osteopontin-deficient bone cells are defective in their ability to produce NO in response to pulsatile fluid flow. Biochem Biophys Res Commun 2001; 288:448-53. [PMID: 11606063 DOI: 10.1006/bbrc.2001.5780] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Osteopontin (OPN) is a noncollagenous component of bone matrix. It mediates cell attachment and activates signal transduction pathways. In this work, bone cells, cultured from fragments of long bones derived from wild-type and OPN-/- ("knock-out") mice, were exposed to pulsatile fluid flow (PFF) over a 60-min period. The medium was assayed periodically for nitric oxide (NO) and prostaglandin E(2) (PGE(2)) release. OPN+/+ cells exhibited a peak of NO production 5-10 min after the onset of PFF, decreasing to a stable plateau at 15 min; much less NO was produced by the OPN-/- cells. PFF resulted in reduced PGE(2) release by both cell types, although the reduction was less for the OPN-/- cells in the 15-30 min window. Both cell types exhibited a similar enhancement of cyclooxygenase2 mRNA levels 60 min after initiation of PFF. These results suggest that bone cells require OPN to respond fully to PFF as assessed by increased NO and reduced PGE(2) synthesis.
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Papadopoulos MC, Saadoun S, Woodrow CJ, Davies DC, Costa-Martins P, Moss RF, Krishna S, Bell BA. Occludin expression in microvessels of neoplastic and non-neoplastic human brain. Neuropathol Appl Neurobiol 2001; 27:384-95. [PMID: 11679090 DOI: 10.1046/j.0305-1846.2001.00341.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The tight junction protein occludin 'glues' normal, adjacent brain microvessel endothelial cells together. Malignant brain tumours cause cerebral oedema because they have leaky endothelial tight junctions, which allow plasma fluid to enter the brain from the microvessel lumen. In order to identify molecular abnormalities in tumour endothelial tight junctions, we investigated occludin expression in microvessels from adult human non-neoplastic brain tissue using immunohistochemistry and immunoblotting. The proportions of microvessels immunolabelling for occludin were >2/3 in 5/5 non-neoplastic brain tissue samples, >1/3 in 5/5 low grade (Daumas-Duport I or II) astrocytomas and <1/3 in 5/5 high grade (III or IV) astrocytomas and 6/6 metastatic adenocarcinomas. Six non-neoplastic brain tissue immunoblots gave a 55-kDa occludin band, three low-grade astrocytomas gave 55-kDa and 60-kDa bands, 13 high-grade astrocytomas gave 60-kDa or no band and four adenocarcinomas did not give an occludin band. Expression of 55-kDa occludin inversely correlated with the presence of contrast enhancement on computed tomograms (P < 0.001). Electron microscopy showed open endothelial tight junctions in 0/2 non-neoplastic human brain specimens and 2/2 high-grade astrocytomas. We suggest that loss of 55-kDa occludin expression in human brain tumours may contribute to endothelial tight junction opening. Characterizing the molecular pathology of brain endothelial tight junctions may facilitate the design of novel drugs against cerebral oedema.
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Krishna S, Webb R, Woodrow C. Transport proteins of Plasmodium falciparum: defining the limits of metabolism. Int J Parasitol 2001; 31:1331-42. [PMID: 11566301 DOI: 10.1016/s0020-7519(01)00254-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In this review we give an account of transport processes occurring at the membrane interface that separates the asexual stage of Plasmodium falciparum from its host, the infected erythrocyte, and also describe proteins whose activities may be important at this location. We explain the potential clinical value of such studies in the light of the current spread of parasite resistance to conventional antimalarial strategies. We discuss the uptake of substrates critical to the survival of the intracellular malaria parasite, and also the parasite's homeostatic and disposal mechanisms. The use of the Xenopus laevis expression system in the characterisation of a hexose transporter ("PfHT1") and a Ca(2+) ATPase ("PfATP4") of the parasite plasma membrane are described in detail.
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Rozmajzl PJ, Kimura M, Woodrow CJ, Krishna S, Meade JC. Characterization of P-type ATPase 3 in Plasmodium falciparum. Mol Biochem Parasitol 2001; 116:117-26. [PMID: 11522345 DOI: 10.1016/s0166-6851(01)00319-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We report the nucleotide sequence, derived amino acid sequence and expression profile of P-type ATPase 3 (PfATPase3) from Plasmodium falciparum. An open reading frame of 7362 nucleotides, interrupted by a single intron of 168 nt, encoded a protein product of 2394 amino acids with a predicted MW of 282791 Da. Hydropathy analysis of PfATPase3 revealed six amino-terminal and six carboxyl-terminal membrane spanning regions (M1-12) flanking a large hydrophilic domain with a smaller hydrophilic loop between M4 and M5. Based on a phylogenetic comparison of conserved domains present in P-type ATPases from other organisms, PfATPase3 resembled a Type-V ATPase for which the transport affinity is unknown. The PfATPase3 topology was interrupted by four regions, termed 'inserts', unique to malarial P-type ATPases, which were high in asparagine residues and charged amino acids (inserts I1-I4). Inserts I1 and I3 also contained repeated amino acid motifs. The number and composition of repeated amino acid motifs in insert I3 were variable in seven P. falciparum strains tested. PfATPase3 was 80.2% similar to the non-insert portions of P. yoelii ATPase3, although their inserts differed in length and composition. PfATPase3 mRNA was most abundant relative to beta-tubulin during the latter half of the erythrocytic cycle and was also present in gametocytes. Using affinity-purified antibody to a 14 amino acid PfATPase3 epitope, a 260 kDa protein was detected by Western analysis. Based on immunofluorescence, the PfATPase3 protein was located intracellularly in gametocytes and, to a lesser extent, in late erythrocytic stages.
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98
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Teerijoki H, Krasnov A, Gorodilov Y, Krishna S, Mölsä H. Rainbow trout glucose transporter (OnmyGLUT1): functional assessment in Xenopus laevis oocytes and expression in fish embryos. J Exp Biol 2001; 204:2667-73. [PMID: 11533116 DOI: 10.1242/jeb.204.15.2667] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
SUMMARY
Recently, we reported the cloning of a putative glucose transporter (OnmyGLUT1) from rainbow trout embryos. In this paper, we describe the functional characteristics of OnmyGLUT1 and its expression during embryonic development of rainbow trout. Transport of d-glucose was analysed in Xenopus laevis oocytes following microinjection of mRNA transcribed in vitro. These experiments confirmed that OnmyGLUT1 is a facilitative Na+-independent transporter. Assessment of substrate selectivity, sensitivity to cytochalasin B and phloretin and kinetic parameters showed that the rainbow trout glucose transporter was similar to a carp transporter and to mammalian GLUT1. Embryonic expression of OnmyGLUT1 was studied using whole-mount in situ hybridization. Ubiquitous distribution of transcripts was observed until the early phase of somitogenesis. During the course of organogenesis, somitic expression decreased along the rostro-caudal axis, finally ceasing in the mature somites. The OnmyGLUT1 transcripts were detected in the neural crest during the whole study period. Transcripts were also found in structures that are likely to originate from the neural crest cells (gill arches, pectoral fins, upper jaw, olfactory organs and primordia of mouth lips). Hexose transport activity was detected at all developmental stages after blastulation. Cytochalasin B blocked the accumulation of phosphorylated 2-deoxy-d-glucose by dissociated embryonic cells, suggesting an important role for transport in glucose metabolism.
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Rangarajan A, Syal R, Selvarajah S, Chakrabarti O, Sarin A, Krishna S. Activated Notch1 signaling cooperates with papillomavirus oncogenes in transformation and generates resistance to apoptosis on matrix withdrawal through PKB/Akt. Virology 2001; 286:23-30. [PMID: 11448155 DOI: 10.1006/viro.2001.0867] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Invasive cervical tumors, a major subset of human epithelial neoplasms, are characterized by the consistent presence of papillomavirus oncogenes 16 or 18 E6 and E7 products. Cervical tumors also consistently exhibit cytosolic and nuclear forms of Notch1, suggesting the possible persistent activation of the Notch pathway. Here we show that activated Notch1 synergizes with papillomavirus oncogenes in transformation of immortalized epithelial cells and leads to the generation of resistance to anoikis, an apoptotic response induced on matrix withdrawal. This resistance to anoikis by activated Notch1 is mediated through the activation of PKB/Akt, a key effector of activated Ras in transformation. We suggest that activated Notch signaling may serve to substitute for the lack of activated Ras mutations in the majority of human cervical neoplasms.
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100
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Krishna S, Chang VT, Shoukas JA, Donahoo J. Video-assisted thoracoscopic sympathectomy-splanchnicectomy for pancreatic cancer pain. J Pain Symptom Manage 2001; 22:610-6. [PMID: 11516603 DOI: 10.1016/s0885-3924(01)00297-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Patients with unresectable pancreatic cancer often suffer severe pain. Various techniques are available for pain control. We present a patient with pancreatic cancer who underwent unilateral video-assisted thoracoscopic sympathectomy-splanchnicectomy and had complete pain relief. This minimally invasive procedure offers promise in carefully selected patients with severe pain from pancreatic cancer and other conditions which are not amenable to conventional interventions.
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