101
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Larsen C, Tsapis A, Lanotte M, Soussi T, Berger R. Dorian Gray mice exposed. Nature 1993. [DOI: 10.1038/363666c0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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102
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Couturier E, Brossard Y, Larsen C, Larsen M, Du Mazaubrun C, Paris-Llado J, Gillot R, Henrion R, Breart G, Brunet JB. HIV infection at outcome of pregnancy in the Paris area, France. Int J Gynaecol Obstet 1993. [DOI: 10.1016/0020-7292(93)90728-f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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103
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Gaisser TK, Stanev T, Tilav S, Corbato SC, Dai HY, Dawson BR, Elbert JW, Emerson B, Kieda DB, Luo M, Ko S, Larsen C, Loh EC, Salamon MH, Smith JD, Sokolsky P, Sommers P, Tang J, Thomas SB, Bird DJ. Cosmic-ray composition around 10(1)8 eV. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1993; 47:1919-1932. [PMID: 10015774 DOI: 10.1103/physrevd.47.1919] [Citation(s) in RCA: 87] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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104
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Kamper J, Wulff K, Larsen C, Lindequist S. Early treatment with nasal continuous positive airway pressure in very low-birth-weight infants. Acta Paediatr 1993; 82:193-7. [PMID: 8477167 DOI: 10.1111/j.1651-2227.1993.tb12637.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
During 1988 and 1989, a regional cohort of 81 infants with birth weights less than 1501 g were treated with oxygen only (n = 11), early continuous positive airway pressure (CPAP) (n = 68) or mechanical ventilation from birth (n = 2). We used an easily applicable lightweight CPAP system with nasal prongs and a gas jet supplemented with ventilator treatment if necessary, but with conservative criteria for ventilator treatment with tolerance of high PCO2. A total of 65 infants (80%) survived to discharge, 61 of whom were supported solely with CPAP or oxygen. Nineteen infants (26%) developed periventricular-intraventricular haemorrhage, but only 4 survivors (6%) developed prognostically significant bleedings grade 2-4. No survivors had bronchopulmonary dysplasia. Follow-up at 12-39 months of age revealed definite disabilities in 6 (10%) and suspected disabilities in 2 of 62 long-term survivors. The results suggest that treatment by early CPAP with nasal prongs with tolerance of high PCO2 may be effective and lenient in most infants more than 25 weeks' gestation.
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105
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Larsen C. [Oncogenes in human hematopoietic neoplasia]. PATHOLOGIE-BIOLOGIE 1992; 39:867-8. [PMID: 1538913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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106
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Gheorvassaki E, Papadakis D, Alikaridis F, Kephalas T, Larsen C, Palaiologos G. Incorporation of 15N from L-leucine into isoleucine by rat brain cerebral cortex slices. J Neurosci Res 1992; 33:306-9. [PMID: 1453492 DOI: 10.1002/jnr.490330214] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The fate of leucine nitrogen in the central nervous system was investigated by incubating rat cerebral cortex slices in the presence of 0.5 mM each of L-[15N]-leucine, L-isoleucine, and L-valine. Analysis of the slices and incubation media for free amino acids by gas chromatography-mass spectrometry revealed that the 15N from leucine is incorporated into isoleucine only. No 15N was detected in valine or any other amino acid. These results suggest that leucine, valine, and their corresponding aminotransferases may be compartmentalized in brain cerebral cortex.
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107
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Couturier E, Brossard Y, Larsen C, Larsen M, Du Mazaubrun C, Paris-Llado J, Gillot R, Henrion R, Bréart G, Brunet JB. HIV infection at outcome of pregnancy in the Paris area, France. Lancet 1992; 340:707-9. [PMID: 1355808 DOI: 10.1016/0140-6736(92)92241-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The prevalence of HIV infection in women at end of pregnancy, irrespective of outcome, was determined in a comprehensive survey of both women and medical centres during successive 4-week periods in four areas of the Paris region, France. Blood samples were tested anonymously for antibodies to human immunodeficiency virus (HIV)-1 and HIV-2. Of the 11,593 blood samples 0.40% (95% confidence interval [CI] 0.28-0.51) were positive for HIV-1 and 0.02% (95% binomial interval [BI] 0.002-0.065) for HIV-2. Seroprevalence was higher among women with ectopic pregnancy (2%) (95% BI 0.24-7.04); the rate in women having an elective or therapeutic abortion was more than twice that in those delivering babies (0.70% vs 0.28%, p less than 0.05, relative risk 2.54, 95% CI 1.36-4.75). Studies with neonatal HIV seroprevalence as a surrogate for HIV prevalence in pregnant women would underestimate prevalence in these women.
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108
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Larsen F, Jensen BH, Olesen HP, Larsen C. Multiple oral administration of a ketoprofen-dextran ester prodrug in pigs: assessment of gastrointestinal bioavailability by deconvolution. Pharm Res 1992; 9:915-9. [PMID: 1279651 DOI: 10.1023/a:1015805000595] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Deconvolution has been applied to estimate the in vivo dissolution/release process of ketoprofen from a ketoprofen-dextran ester prodrug in pigs. The prodrug was given to three pigs at intervals of 12 hr and in seven doses corresponding to 4 mg ketoprofen/kg body weight. Frequent blood sampling was carried out at the first, third, and seventh intervals. Plasma steady-state concentrations of ketoprofen following the prodrug administration were between 2 and 4 micrograms/ml. The reference consisted of a single p.o. dose of parent ketoprofen (4 mg/kg body weight). For each pig the response following the multiple dosing was deconvolved with the reference response using an algebraic deconvolution procedure adopted from the literature. The obtained cumulated in vivo dissolution/release profiles revealed similar release rates for the three pigs and similar extents of release (59, 70, and 65%). The mean in vivo dissolution/release times (MDT) were calculated to be 5.4, 6.1, and 5.7 hr, respectively. In conclusion, following administration of the dextran prodrug the plasma concentration curves and the dissolution/release profiles are uniform, with small interindividual variations.
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109
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Fiedler W, Weh HJ, Zeller W, Fonatsch C, Hillion J, Larsen C, Wörmann B, Hossfeld DK. Translocation (14; 18) and (8; 22) in three patients with acute leukemia/lymphoma following centrocytic/centroblastic non-Hodgkin's lymphoma. Ann Hematol 1991; 63:282-7. [PMID: 1958753 DOI: 10.1007/bf01698379] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Three patients with centrocytic/centroblastic lymphoma developed a rapidly fatal leukemic transformation of the disease after a transient remission. At the time of transformation, cytogenetic analysis revealed in all patients abnormal karyotypes with coexistence of t (14; 18) and t (8; 22). Molecular analysis in one patient showed rearrangement of the BCL 2 oncogene and c-myc m-RNA expression. These findings imply that translocation t (14; 18) was present during the first phase of the disease and that acquisition of translocation t (8; 22) was accompanied by leukemic transformation.
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MESH Headings
- Acute Disease
- Aged
- Blotting, Southern
- Chromosomes, Human, Pair 14
- Chromosomes, Human, Pair 18
- Chromosomes, Human, Pair 22
- Chromosomes, Human, Pair 8
- Gene Rearrangement
- Humans
- Karyotyping
- Leukemia/genetics
- Lymphoma/genetics
- Lymphoma, Non-Hodgkin/complications
- Male
- Translocation, Genetic
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110
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Rasmussen F, Lindequist S, Larsen C, Justesen P. Therapeutic effect of hysterosalpingography: oil- versus water-soluble contrast media--a randomized prospective study. Radiology 1991; 179:75-8. [PMID: 1848716 DOI: 10.1148/radiology.179.1.1848716] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In a prospective randomized study, the number of pregnancies after hysterosalpingography (HSG) was estimated in 398 patients who had been infertile for longer than 1 year. Iohexol was used in 101 patients, ioxaglate in 102 patients, diatrizoate meglumine in 97 patients, and ethiodized poppy-seed oil in 98 patients. Ten months after HSG, the patient, referring physician, and/or hospital department was consulted for information about pregnancies. Questionnaires were obtained from the patients who became pregnant during the waiting period of 3 months. No differences in demographic parameters, infertility status, or diagnosis made with HSG were detected among the four contrast media groups. Significantly more patients became pregnant after HSG in the ethiodized poppy-seed oil group than in the three water-soluble contrast media groups (P less than .01). When only intrauterine pregnancies resulting in full-term births were considered, significant differences in pregnancy rates between the oil-soluble and the water-soluble contrast media groups became more obvious. In the group that received ethiodized poppy-seed oil, almost one-third of the infertile women had normal pregnancies and childbirths after HSG.
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111
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Lindequist S, Justesen P, Larsen C, Rasmussen F. Diagnostic quality and complications of hysterosalpingography: oil- versus water-soluble contrast media--a randomized prospective study. Radiology 1991; 179:69-74. [PMID: 1848715 DOI: 10.1148/radiology.179.1.1848715] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
In a prospective randomized study of 417 patients, side effects and complications of contrast media and the diagnostic quality of images obtained after hysterosalpingography (HSG) were evaluated after use of diatrizoate meglumine (104 patients), ioxaglate (105 patients), iohexol (105 patients), or ethiodized poppy-seed oil (103 patients). The authors detected no differences among these groups in the prevalence of pain during HSG. The prevalence of lower abdominal pain and vaginal bleeding after HSG was significantly lower in the group that received ethiodized poppy-seed oil than in the three other groups. The prevalence of pelvic infection or inflammation was significantly lower with ethiodized poppy-seed oil than with water-soluble media. All contrast media provided acceptable diagnostic image quality with regard to fallopian tubes, peritoneal spill, and intraperitoneal distribution. Visualization of the uterine cavity and ampullary rugae was significantly better with water-soluble media than with ethiodized poppy-seed oil, which was associated with a high conception rate and which the authors consider preferable for HSG.
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112
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Henriksen U, Larsen C, Karup G, Jeppesen C, Nielsen PE, Buchardt O. Photochemistry of quinolylmethylisothioronium salts. Guanine selective DNA photocleavage reagents. Photochem Photobiol 1991; 53:299-305. [PMID: 2062877 DOI: 10.1111/j.1751-1097.1991.tb03632.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Quinolylmethylisothioronium salts (1a and 4a) cleave DNA upon irradiation. The cleavage is more than 10-fold enhanced by piperidine treatment and subsequently shows a high preference for guanines. Photolysis of 1a, 2a and 4a in water at lambda greater than 300 nm resulted in photoheterolysis. Irradiation of 1a in 2-propanol gave only products from photohomolysis, irradiation of 1a in methanol and 2a and 4a in 2-propanol resulted in products from both photoheterolysis and photohomolysis. Quantum yields for the disappearance of 1a in water and 2-propanol were determined. The presence or absence of oxygen had no effect in water, whereas oxidation products were observed upon irradiation in methanol and 2-propanol in the presence of oxygen. The guanine specific DNA photoreaction is proposed to take place by alkylation at N7 via the quinolylmethyl carbocation and thus to represent a photoalkylation.
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113
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Hougaard L, Anthoni U, Christophersen C, Larsen C, Nielsen P. Characterization and quantitative estimation of quaternary ammonium compounds in marine demosponges. ACTA ACUST UNITED AC 1991. [DOI: 10.1016/0305-0491(91)90072-l] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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114
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Larsen C, Ourø B, Wentzel S. [Professional nursing guidance. Help for isolated nurses]. SYGEPLEJERSKEN 1990; 90:20-2. [PMID: 2237796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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115
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Lindequist S, Larsen C, Schrøder HD. Ultrasound guided needle biopsy of skeletal muscle in neuromuscular disease. Acta Radiol 1990. [DOI: 10.3109/02841859009172017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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116
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Lindequist S, Larsen C, Schrøder HD. Ultrasound guided needle biopsy of skeletal muscle in neuromuscular disease. Acta Radiol 1990; 31:411-3. [PMID: 2206699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Guided by ultrasonography percutaneous needle biopsy of skeletal muscle was performed in 24 patients, using the one hand held Biopty system and a 2 mm Tru-Cut needle. The specimens were graded with regard to diagnostic quality and utility and almost all specimens (96%) were of highest quality. The use of ultrasonography was helpful in selecting a suitable area for the biopsy and vascular structures could be avoided. The procedure was well tolerated and easy to perform, and no complications were recorded.
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117
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Krowka J, Stites D, Debs R, Larsen C, Fedor J, Brunette E, Düzgünes N. Lymphocyte proliferative responses to soluble and liposome-conjugated envelope peptides of HIV-1. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1990; 144:2535-40. [PMID: 1969450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The proliferation of lymphocytes from HIV-seronegative (HIV Ab-) and seropositive (HIV Ab+) individuals in response to two synthetic peptide epitopes of HIV envelope glycoproteins (ENVgp) was evaluated as an index of cell-mediated immunity in infected individuals. All HIV Ab- and most HIV Ab+ individuals' lymphocytes failed to proliferate in primary cultures in response to the two soluble HIV ENVgp peptides, ENVP346 and ENVP466 even in the presence of rIL-2. After stimulation with liposome-conjugates of ENVP346 or ENVP466 and soluble rIL-2, however, CD4 lymphocytes from some HIV Ab+ individuals were able to proliferate. Significantly higher frequencies of rIL-2-augmented proliferative responses to liposome-conjugated ENVP346 or ENVP466 were observed in HIV Ab+ asymptomatic individuals as compared to patients with AIDS-related conditions or AIDS. These studies indicate that the conjugation of HIV peptides or proteins to liposomes and stimulation with rIL-2 may enhance cell-mediated responses to these peptides.
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118
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Krowka J, Stites D, Debs R, Larsen C, Fedor J, Brunette E, Düzgünes N. Lymphocyte proliferative responses to soluble and liposome-conjugated envelope peptides of HIV-1. THE JOURNAL OF IMMUNOLOGY 1990. [DOI: 10.4049/jimmunol.144.7.2535] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Abstract
The proliferation of lymphocytes from HIV-seronegative (HIV Ab-) and seropositive (HIV Ab+) individuals in response to two synthetic peptide epitopes of HIV envelope glycoproteins (ENVgp) was evaluated as an index of cell-mediated immunity in infected individuals. All HIV Ab- and most HIV Ab+ individuals' lymphocytes failed to proliferate in primary cultures in response to the two soluble HIV ENVgp peptides, ENVP346 and ENVP466 even in the presence of rIL-2. After stimulation with liposome-conjugates of ENVP346 or ENVP466 and soluble rIL-2, however, CD4 lymphocytes from some HIV Ab+ individuals were able to proliferate. Significantly higher frequencies of rIL-2-augmented proliferative responses to liposome-conjugated ENVP346 or ENVP466 were observed in HIV Ab+ asymptomatic individuals as compared to patients with AIDS-related conditions or AIDS. These studies indicate that the conjugation of HIV peptides or proteins to liposomes and stimulation with rIL-2 may enhance cell-mediated responses to these peptides.
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119
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Pettengell KE, Larsen C, Garb M, Mayet FG, Simjee AE, Pirie D. Gastrointestinal tuberculosis in patients with pulmonary tuberculosis. THE QUARTERLY JOURNAL OF MEDICINE 1990; 74:303-8. [PMID: 2385737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Proven or suspected intestinal tuberculosis was diagnosed in 23 (46 per cent) of 50 patients with smear-positive, cavitating pulmonary tuberculosis. The diagnosis was regarded as proven in 14 patients and suspected in the remaining nine. The frequency of proven gastrointestinal disease increased with the severity of the pulmonary tuberculosis. Small intestinal disease was encountered in only two patients. Small mucosal lesions in the caecum were the most commonly detected pathological features. Colonoscopy was of particular value in establishing the diagnosis, which could not be predicted from the patients' abdominal signs or gastrointestinal symptoms.
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120
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Rasmussen F, Dyreborg U, Larsen C, Waaler A, Tove Kristofferson D. Intravenous urography with a new non-ionic contrast media in a clinical phase III study: iopentol vs iohexol. Clin Radiol 1990; 41:37-41. [PMID: 2404650 DOI: 10.1016/s0009-9260(05)80930-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The safety and diagnostic efficacy of iopentol 300 mg I/ml were compared with iohexol 300 mg I/ml in 300 patients submitted for urography. The study was carried out as a double-blind, randomised parallel study where 149 patients received iopentol and 150 patients iohexol. There were no significant differences between the patients receiving the two contrast media with regard to demographic parameters, rate of injection or total dose of injected contrast media. No changes in blood pressure and no clinically important changes in heart rate were detected in the two groups. No serious adverse effects occurred. Seven patients (5%) in the iohexol and 12 patients (8%) in the iopentol group experienced adverse effects other than a sensation of warmth. Fourteen iohexol patients (9%) and 18 iopentol patients (12%) experienced warmth related to the contrast injection. Excellent films were obtained in most patients and no difference in diagnostic quality between iopentol and iohexol was observed.
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121
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Vilarem MJ, Kellermann O, Gras MP, Larsen C, Buc-Caron MH. Lineage-specific patterns of p21ras proteins in immortalized cell lines derived from mouse teratocarcinoma. RESEARCH IN VIROLOGY 1990; 141:45-55. [PMID: 2183321 DOI: 10.1016/0923-2516(90)90055-n] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The expression of proteins coded by the ras oncogene family was examined in mouse embryonal carcinoma (EC) cells and in immortalized cell lines derived from EC. These cell lines, which correspond to early stages of differentiation, express the simian virus 40 (SV40) T antigen and still proliferate. By 2-D gel electrophoresis of the immune complexes formed with monoclonal anti-ras antibodies, it was possible to distinguish the products of the Ha-, N- and Ki-ras genes and to correlate the observed patterns with the differentiation state of the cells. We show in this report (1) that the 2-D gel pattern of ras protein is identical for the various EC tested and is not influenced by SV40 transformation, (2) that p21Ki-ras is not detected in EC cells, although some EC cell lines are known to express a Ki-ras transcript, and (3) that the complex patterns of N- and Ha-ras observed in EC cells becomes simpler as differentiation proceeds, with a different, characteristic pattern for neuroectodermal, mesodermal and endodermal derivatives. Such patterns could prove useful as differentiation markers.
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122
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Lindequist S, Larsen C, Schrøder HD. Ultrasound guided needle biopsy of skeletal muscle in neuromuscular disease. Acta Radiol 1990. [DOI: 10.1080/02841859009172017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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123
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Krogh P, Christensen DH, Hald B, Harlou B, Larsen C, Pedersen EJ, Thrane U. Natural occurrence of the mycotoxin fusarochromanone, a metabolite of Fusarium equiseti, in cereal feed associated with tibial dyschondroplasia. Appl Environ Microbiol 1989; 55:3184-8. [PMID: 2619307 PMCID: PMC203244 DOI: 10.1128/aem.55.12.3184-3188.1989] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The mycotoxin fusarochromanone, a metabolite of Fusarium fungi, is able to induce tibial dyschondroplasia (TD) in chickens under experimental conditions. On the basis of health surveillance data on TD, two broiler farms with TD prevalence rates of up to 56% were identified. In the corresponding pelleted feed samples, fusarochromanone was detected in all 12 samples analyzed by column purification and TLC, with concentrations 4 to 59 micrograms/kg. No Fusarium fungi were available from the feed because of the pelleting process, but seven Fusarium equiseti strains previously isolated from Danish cereals were checked for fusarochromanone production, and all produced fusarochromanone at 57 to 1,435 mg/kg. Thus, the potential for fusarochromanone production by F. equiseti is considerable. The identification of fusarochromanone from feed and F. equiseti was confirmed by mass, infrared, and nuclear magnetic resonance spectral analyses. This is the first report of fusarochromanone as a naturally occurring contaminant.
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124
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Larsen C, Harboe E, Johansen M, Olesen HP. Macromolecular prodrugs. XVI. Colon-targeted delivery--comparison of the rate of release of naproxen from dextran ester prodrugs in homogenates of various segments of the pig gastrointestinal (GI) tract. Pharm Res 1989; 6:995-9. [PMID: 2622863 DOI: 10.1023/a:1015914101233] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have determined initial rates of naproxen formation from dextran-naproxen ester prodrugs incubated in homogenates of various segments of the pig GI tract. Drug liberation proceeded 15-17 times faster in cecum and colon homogenates than in aqueous pH 7.4 buffer or homogenates of the small intestine. The degree of conjugate substitution did not affect the liberation rates, whereas enhanced drug activation was observed with decreasing molecular size of the carrier dextran. During incubation in colon homogenates the average molecular weight of the dextran prodrugs decreased. The mechanism of drug activation from the prodrugs may therefore involve an initial depolymerization step of the dextran chains by dextranases secreted from bacteria in the pig colon. The generated small fragments then serve as substrates for esterases and other hydrolases.
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125
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Harboe E, Larsen C, Johansen M, Olesen HP. Macromolecular prodrugs. XV. Colon-targeted delivery--bioavailability of naproxen from orally administered dextran-naproxen ester prodrugs varying in molecular size in the pig. Pharm Res 1989; 6:919-23. [PMID: 2480587 DOI: 10.1023/a:1015981126732] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The bioavailability of naproxen after oral administration of aqueous solutions of various dextran-naproxen ester prodrugs in pigs was determined. The dextran prodrugs employed ranged in molecular weight from 10,000 to 500,000. As calculated relative to an equivalent oral dose of parent naproxen, the absorption fractions of all the derivatives were close to 100%. Only small interindividual variation of naproxen bioavailability was observed. The naproxen plasma profiles for all the administered prodrugs exhibited a characteristic lag time of naproxen appearance in the blood (2-3 hr). Compared to administration of the prodrugs alone, coadministration of excess of the parent dextran further delayed the absorption of naproxen from the GI tract. The results of the present study demonstrate the potential of dextran prodrugs for colon site-specific delivery of drugs containing a carboxylic acid functional group.
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