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Biomedical subjects

K Nielsen

Publications and source records attributed to K Nielsen.

At least 109 records · Page 6Linked to original sources
PubMed1997

Chaos in Glycolysis

Glycolysis occurs in almost every living cell as part of the energy metabolism. It forms a complex dynamical system, and might thus be capable of exhibiting complex phenomena. Simple oscillations have been observed frequently in suspensions of intact cells and in cell extracts, but only as transients. We have obtained sustained simple and complex oscillations in glycolysis of cell-free yeast extract in a flow-reactor. Sustained oscillations enable a powerful, proven method of dynamical system theory to unravel the kinetics and make it possible to observe chaos. Chaos was predicted from models long ago but has not previously been observed experimentally. We report the first experimental observation of unforced chaotic oscillations in glycolysis. Copyright 1997 Academic Press Limited

Journal Article↗
PubMed1997

Binding of the Brucella abortus lipopolysaccharide O-chain fragment to a monoclonal antibody. Quantitative analysis by fluorescence quenching and polarization.

An antigenic O-chain polysaccharide fragment derived from Brucella abortus lipopolysaccharide was labeled with 14.8 +/- 1.8 (n = 5) and 52.3 +/- 2.4 (n = 3) micromol of fluorescein/g of polysaccharide (designated FL1 and FL2, respectively) for use in investigating the binding of O-chain to a specific murine antibody YsT9 under equilibrium conditions. Upon binding to YsT9, the fluorescence of FL1 and FL2 was quenched 45-57% with no shift in the excitation and emission spectra, and polarization of fluorescence increased by 300-335%. With fluorescence quenching and polarization as sensitive signals for antibody-bound labeled O-chains, the equilibrium constants for binding of FL1, FL2, and unlabeled O-chain to YsT9 were determined to be within a similar order (1.5 x 10(7) to 2.0 x 10(7) M-1) using a nonlinear curve fitting approach rather than Scatchard analysis. These results indicated that covalent attachment of fluorescein groups to the O-chain did not influence the recognition of the YsT9-defined epitope by the antibody. The reversibility of the O-chain-antibody reaction was also demonstrated by showing a rapid depolarization of the labeled O-chain-antibody complex in the presence of unlabeled O-chain, suggesting that this displacement experiment could be exploited to quantify the Brucella polysaccharide antigen. The study described here provides a useful model for characterization of the complex formation between a carbohydrate-binding protein and a carbohydrate ligand and also for the design of a homogeneous assay system to quantitate antigens or antibodies of clinical interest.

Animals↗
PubMed1997

Endometrial carcinomas--flow cytometric DNA content and S-phase values.

The purpose of the investigation was to determine the DNA content and S-phase value in a large material of fresh tumour tissue from endometrial carcinomas and to correlate these parameters to tumour type, grade of differentiation, depth of myometrial invasion and stage. The prospective study consisted of 290 unselected cases of endometrial carcinomas, FIGO stage I-IV where flow cytometry was performed on fresh tumour tissue blocks from hysterectomy specimens. 223 cases had more than 10% tumour tissue in tissue blocks taken adjacent to the blocks for flow cytometry. Non-diploidy was defined as 0.9 > or = DNA index > 1.10 and high S-phase value was defined as > 15%. Non-diploidy was found in 46% of the endometrioid adenocarcinoma and in 85% of the non-endometrioid carcinomas (clear cell adenocarcinoma, serous adenocarcinoma and malignant mixed mesodermal tumour) (p < 0.001). S-phase value was > 15% in 39% of the endometrioid adenocarcinoma and in 100% of the non-endometrioid carcinomas (p < 0.0001). In endometrioid adenocarcinoma there was a statistical significant relation between non-diploidy and grade of histological differentiation (p < 0.006), as well as with depth of myometrial invasion (p < 0.05). There was no relation between non-diploidy and the presence of squamous differentiation, whether benign or malignant or to FIGO stage. High S-phase values (> 15%) was related to the grade of differentiation (p < 0.002). No relation was demonstrated between S-phase > 15% and squamous differentiation, depth of myometrial invasion or FIGO stage. In conclusion, 50% of all the endometrial carcinomas were non-diploid and 43% had S-phase value > 15%. Ploidy correlated with histologic tumour types, grade of differentiation and depth on myometrial invasion while S-phase values only correlated with histologic tumour types and grade of differentiation.

Adult↗
PubMed1997

Development and validation of an indirect enzyme immunoassay for detection of ovine antibody to Brucella ovis.

An indirect enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Brucella ovis infection was developed. The assay uses a mouse monoclonal antibody to bovine IgG1 horseradish peroxidase (HRPO) conjugate that cross-reacts with immunoglobulin from sheep and a purified antigen from Brucella ovis. The ELISA data were read and analyzed according to a targeting procedure. The ELISA results were compared with a cold complement fixation test (CFT). Sera from 675 rams from three uninfected flocks were used to determine the ELISA cut-off value (O.D. 405 nm: 0.095) and the diagnostic specificity of the ELISA (100%) and the CFT (99.69% +/- 0.42). The ELISA cut-off value was corroborated by receiver operating characteristic (ROC) analysis. Six hundred and forty semen and serum samples from 419 rams from two naturally infected flocks were collected before and after mating-time during two consecutive years. All semen samples were cultured and Brucella ovis was isolated from 28 samples. Sera from the 28 rams with positive semen were used to determine the diagnostic sensitivity of the ELISA (96.43% +/- 6.8) and of the CFT (including suspected positive samples with titers of 1:5; 88.89% +/- 11.85). Considering the CFT suspicious and the anti-complementary reactions as positive resulted in a diagnostic sensitivity value of 89.28% +/- 11.46. Six hundred and ten serum samples from the 640 sera were used to determine relative sensitivity (excluding sera with 1:5) at: ELISA/CFT 97.26% +/- 3.74 and CFT/ELISA was 71.72% +/- 8.87. The percent agreement, beyond chance measured by the Kappa index was 79.7. Relative sensitivity ELISA/CFT (including 1:5 titers in the CFT as positive) was 94.9% +/- 4.83 and CFT/ELISA was 72.84% +/- 8.59. The Kappa index was 79.4.

Animals↗
PubMed1997

Detection of Clostridium perfringens type D epsilon antitoxin in serum of goats by competitive and indirect ELISA.

Indirect and competitive ELISA techniques were developed and their ability to detect antibodies to Clostridium perfringens epsilon toxin in goat serum was compared. Different dilutions of a hyperimmune goat serum, in serum from a colostrum-deprived kid, were used as positive controls, while sera from eleven colostrum-deprived kids were used as negative controls. The epsilon toxin antibodies in the hyperimmune serum were also measured by mouse neutralisation test (MNT). The correlation coefficient between both the indirect ELISA technique and MNT was 0.99, while the same coefficient for the competitive ELISA was 0.98. Both the indirect and competitive ELISAs proved to be rapid, simple, sensitive and specific for detecting antibodies to C. perfringens epsilon toxin in serum of goats.

Animals↗
PubMed1997

A time-dose study of the effect of topical ipratropium bromide on methacholine-induced rhinorrhoea in patients with perennial non-allergic rhinitis.

Intranasal application of the anticholinergic drug, ipratropium bromide, is used for the treatment of watery rhinorrhoea. We have performed a time-dose study of ipratropium bromide in patients with perennial non-allergic rhinitis, using rhinorrhoea, induced by nasal methacholine challenge, as a laboratory model. Two doses of ipratropium bromide, 40 microg and 80 microg, delivered from a pressurized aerosol, were both very effective, reducing the volume of methacholine-induced secretion by 85 to 95%. The maximum effect lasted for at least 4 h and then slowly diminished. A significant effect was demonstrable for 12 h with 40 microg and for 18 h with 80 microg ipratropium bromide. These results from a laboratory challenge study indicate that the presently used frequency of ipratropium bromide, namely four times daily, may not be necessary in many patients. Perhaps once in the morning, followed by an as-needed medication, will be a better way to use intranasal ipratropium bromide in perennial non-allergic rhinitis.

Administration, Intranasal↗
PubMed1997

Chronic systemic treatment with epidermal growth factor induces smooth muscle cell hyperplasia and hypertrophy in the urinary tract of mature Goettingen minipigs.

OBJECTIVE: To determine the effect of systemic treatment with epidermal growth factor (EGF) on the induction of growth in the urinary tract. MATERIALS AND METHODS: Mature Goettingen minipigs were treated daily with vehicle (Tris-HCl; n = 5) or EGF (30 micrograms/kg) (n = 6) for 4 weeks. The total number of smooth muscle cells was counted using an optical disector in a 20 microns thick cross-section of the ureter and the mean smooth muscle cell volume estimated. Cell proliferation was detected by immunostaining for the marker Ki67. RESULTS: The ureters of the animals treated with EGF were longer and thicker than those of the controls and the median cross-sectional area of the ureter was 3.3-fold larger; the growth involved all wall layers. The median (range) number of smooth muscle cells in a 20 microns thick cross-section of the ureter was 11 (9-12) x 10(3) in the pigs treated with placebo and 55 (19-80) x 10(3) in those treated with EGF, and the median (range) volume of the smooth muscle cells was 2.3 (2.2-2.4) x 10(3) and 4.0 (3.0-4.5) x 10(3) mm3, respectively. CONCLUSIONS: There were two likely mechanisms contributing to smooth muscle cell hyperplasia, the division of fully differentiated smooth muscle cells and division of fibroblasts in the borderline between the submucosal layer and muscular coat, with ensuing differentiation into smooth muscle cells. Treatment with EGF induces the growth of all wall layers in the urinary tract with remarkable hyperplastic and hypertrophic changes of the smooth muscle cells in the muscular coat.

Actins↗
PubMed1997

Effect of long-term refeeding on protein metabolism in patients with cirrhosis of the liver.

Patients with cirrhosis of the liver require an increased amount of protein to achieve N balance. However, the utilization of protein with increased protein intake, i.e. the slope from regression analysis of N balance v. intake, is highly efficient (Nielsen et al. 1995). In the present study, protein requirement and protein utilization were investigated further by measuring protein synthesis and degradation. In two separate studies, five or six patients with cirrhosis of the liver were refed on a balanced diet for an average of 2 or 4 weeks. Protein and energy intakes were doubled in both studies. Initial and final whole-body protein metabolism was measured in the fed state by primed continuous [15N]glycine infusion. Refeeding caused a statistically significant increase of about 30% in protein synthesis in both studies while protein degradation was only slightly affected. The increase in protein synthesis was associated with significant increases in plasma concentrations of total amino acids (25%), leucine (58%), isoleucine (82%), valine (72%), proline (48%) and triiodothyronine (27%) while insulin, growth hormone, insulin-like growth factor (IGF)-I and IGF-binding protein-3 were not changed significantly. The results indicate that the efficient protein utilization is due to increased protein synthesis, rather than decreased protein degradation, and suggest that increases in plasma amino acids may be responsible for the increased protein synthesis. A comparison of the patients who had a normal protein requirement with the patients who had an increased protein requirement suggests that the increased protein requirement is due to a primary increase in protein degradation. It is speculated that this is due to low levels of IGF-I secondary to impaired liver function, since initial plasma concentration of IGF-I was about 25% of control values and remained low during refeeding.

Dietary Proteins↗
PubMed1997

Identification of a 35-kilodalton serovar-cross-reactive flagellar protein, FlaB, from Leptospira interrogans by N-terminal sequencing, gene cloning, and sequence analysis.

During the screening of antibodies to pathogenic leptospires, a murine monoclonal antibody (designated M138) was found to react with various serovars. An antigen of approximately 35 kDa from Leptospira interrogans serovar pomona, which reacted strongly with M138, was characterized by N-terminal amino acid sequencing and identified as a flagellin, a class B polypeptide subunit (FlaB) of the periplasmic flagella. The gene encoding the FlaB protein, flaB, was amplified from the genomic DNA of several pathogenic serovars by PCR with a single pair of oligonucleotide primers, suggesting that FlaB is highly conserved among these serovars. Cloning and sequence analysis of flaB from serovar pomona revealed that it contains an 849-bp open reading frame with a G + C content of 46.88% which encodes a 283-amino-acid protein with a calculated molecular mass of 31.297 kDa and a predicted pI of 9.065. A sequence comparison of flagellin proteins revealed that the amino acid sequence is most variable in the central portion of the serovar pomona FlaB, which is believed to contain specific sequence information and which may thus be useful in the design of DNA or synthetic peptide probes suitable for the detection of infection with pathogenic leptospires.

Amino Acid Sequence↗
PubMed1997

Dose-effect study of carboplatin in ovarian cancer: a Danish Ovarian Cancer Group study.

PURPOSE: To elucidate the effect of a doubled carboplatin dose-intensity in epithelial ovarian cancer in combination with a fixed dose of cyclophosphamide. PATIENTS AND METHODS: A total of 222 patients with epithelial ovarian cancer stages II to IV were included in the study. Following surgery, patients were randomly assigned to receive carboplatin at an area under the concentration-versus-time curve (AUC) of 4 (AUC4) or carboplatin at an AUC of 8 (AUC8) and cyclophosphamide 500 mg/m2 given every 4 weeks for six courses. The AUC was calculated according to Calvert's formula. In 123 patients, the carboplatin AUC was also measured based on a single-sample method and the results were compared with the calculated AUC. The end points of the trial were complete pathologic remission (CPR) and crude survival. RESULTS: Approximately 50% of patients in both arms underwent second-look surgery. The frequency of CPR was 32% and 30%, respectively. The survival curves showed no significant difference (P = .84). The dose-intensity of cyclophosphamide was almost identical in the two arms, whereas that of carboplatin was different. In the AUC8 arm, the dose-intensity was 1.86 times that of the AUC4 arm. The results also demonstrated good agreement between the calculated and the measured AUC in most patients. Bone marrow toxicity was significantly higher in the AUC8 arm. CONCLUSION: A doubling of the carboplatin dose-intensity did not result in any significant improvement of pathologic remission or survival. Calvert's formula can be used to give a fairly accurate estimate of the carboplatin AUC. Bone marrow toxicity increased with higher dose-intensity, and a further increase of dose is only feasible with growth-factor or stem-cell support.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1997

A descriptive survey of pediatric human immunodeficiency virus-infected long-term survivors.

OBJECTIVE: To identify the population of human immunodeficiency virus-infected pediatric long- term survivors (LTS) followed in major medical institutions in California, Florida and New Jersey. METHODS: A cross-sectional survey was performed with data collection forms sent to all investigators. Demographic, clinical, and laboratory data were obtained on all living patients >/=8 years infected in the perinatal period with human immunodeficiency virus. RESULTS: A total of 143 perinatally infected and 54 children infected by neonatal transfusion were identified. Fifty-four children (27%) had absolute CD4 counts >/=500 cells/mm (group 1: mean age 9.8 years), 54 children (27%) had CD4 counts between 200 and 500 cells/mm (group 2: mean age 10.1 years), and 89 children (45%) had CD4 counts <200 cells/mm (group 3: mean age 10.4 years). Ninety-five (48%) patients had developed AIDS defining conditions; 14 (26%) in group 1, 26 (48%) in group 2, and 55 (62%) in group 3. Ninety-two percent of patients had received antiretrovirals. Perinatally human immunodeficiency virus-infected children tended to be younger (mean age 9.8 years) than children infected via a blood transfusion (mean age 11 years). Generalized lymphadenopathy was the most prevalent clinical finding. Lymphoid interstitial pneumonia and recurrent bacterial infections were the most prevalent acquired immune deficiency syndrome-defining conditions. Twenty percent of LTS had CD4 counts >/=500 cells/mm and no immune deficiency syndrome-defining conditions. CONCLUSIONS: Pediatric LTS were in variable stages of disease progression. The proportion of children within each CD4 strata did not differ by mode of acquisition of infection. Increased CD4 counts were inversely proportional to age. Only 20% of pediatric LTS had minimal to no disease progression.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Importance of selected inhaler characteristics and acceptance of a new breath-actuated powder inhalation device.

The degree of patient comfort and satisfaction with an inhaler can have an important effect on compliance with asthma treatment and, hence, therapeutic success. The objective of this study was to assess, from the patient's perspective, the importance of various inhaler characteristics and then evaluate patient satisfaction with a new breath-actuated powder inhaler (Diskhaler) based on those characteristics. Self-administered patient satisfaction questionnaires were completed as part of a randomized, double-blind, placebo-controlled study of fluticasone propionate powder in the treatment of asthma. At baseline, patients rated the importance of five inhaler characteristics (convenient to carry, durability, easy to load, easy to hold and operate, and easy to clean). Following exposure to the Diskhaler over a period of 8 weeks, patients rated the inhaler on those same characteristics. They also rated their comfort using the inhaler and their overall satisfaction with the inhaler. Data were available from 274 patients, the majority of whom expressed a high or very high level of satisfaction with the Diskhaler on each of the five characteristics. These ratings were congruent with their ratings of the importance of those same characteristics; 80-90% rated "convenient to carry," "durability," "easy to load," and "easy to hold and operate" as important or very important characteristics for an inhaler, while "easy to clean" was considered somewhat less important, with 63% rating this characteristic as important or very important. Following the initial exposure to the Diskhaler, 67% of patients were comfortable or very comfortable with the inhaler; that percentage increased to 79% after 8 weeks of use. Following 2 and 8 weeks of use, 61 and 62%, respectively, were satisfied or very satisfied with the Diskhaler. In general, satisfaction ratings were not affected by treatment, indicating that patients were evaluating only the inhaler and not the efficacy of the study drug they received. This study helped to identify which selected inhaler characteristics are most important to patients with asthma. The Diskhaler inhaler performed well on those characteristics deemed important to the patients. From their first exposure to the Diskhaler, patients were comfortable using the device, and this overall acceptance of the inhaler was maintained throughout the study.

Adult↗
PubMed1996

Development and validation of an indirect enzyme immunoassay for detection of antibody to Anaplasma marginale in bovine sera.

An indirect enzyme immunoassay (IELISA) for detection of bovine antibody activity to Anaplasma marginale was developed. This assay used a crude antigen prepared from erythrocytes of infected calves, immobilized in a polystyrene matrix and a mouse monoclonal antibody to bovine IgG1, conjugated with horseradish peroxidase. Negative sera (n = 1842) were tested and the diagnostic specificity was 98.4 +/- 0.6% before retesting 29 positive samples. After retesting, eight samples remained positive and the specificity was calculated to be 99.6 +/- 0.3%. The diagnostic sensitivity, using 831 serum samples collected from naturally or experimentally infected cattle in Argentina, 370 from Mexico and 525 sera from experimentally vaccinated or infected cattle from Texas, was 87.3 +/- 1.6%.

Agglutination Tests↗
PubMed1996

A homogeneous fluorescence polarization assay for detection of antibody to Brucella abortus.

A homogeneous fluorescence polarization (FP) assay (FPA) was developed for detection of antibody in bovine sera to Brucella abortus. The assay used O-polysaccharide prepared from B. abortus lipopolysaccharide in the molecular weight range of 20-30 kDa which was conjugated with fluorescein isothiocyanate and used as a tracer. Fluorescence polarization was measured with a FPM-1 fluorescence polarization analyzer. Sample (20 microliters) was added to 2.0 ml of diluent buffer at ambient temperature. A serum blank reading was taken and tracer (10 microliters) to yield approx. 1.5 nM fluorescein equivalents was added. The FP of the tracer was determined after a period of greater than 2 min. A positive reaction was indicated by a significant elevation of the FP reading over the negative control. In a blind study, 9480 bovine sera were tested in addition to sets of four controls which were included with each lot of 100 samples tested. The controls were a strong positive, a weak positive, a negative and a serum derived from a B. abortus strain 19 vaccinated cow. Test sera included 8669 sera from Canadian cattle which were negative by routine serological tests, 561 sera from cows from which B. abortus had been isolated either from tissues or milk and 250 sera from cattle previously vaccinated with B. abortus strain 19 at various times. One lot of O-polysaccharide tracer was used for all tests. The initial cut-off for negative samples in the fluorescence polarization assay was set at 107.2 mP. This resulted in a sensitivity estimate of 98.1 +/- 1.1% and the specificity was 99.8 +/- 0.09%. After decoding the samples and retesting false positive and negative reactions, the sensitivity estimate was 98.5 +/- 1.0% and the specificity was 100%. It became evident that the initial cut-off value was set too high and, using ROC analysis, a cut-off of 90 mP increased the sensitivity to 99.02% while the specificity decreased to 99.96%. Of the 250 sera from vaccinated cattle, 248 were negative giving a point specificity value of 99.2%.

Animals↗
PubMed1996

An indirect ELISA using a monoclonal anti IgG1 enzyme conjugate for the diagnosis of bovine brucellosis.

An indirect ELISA using a monoclonal anti-IgG1 enzyme conjugate for diagnosis of bovine brucellosis was evaluated. Three groups of sera from negative non-vaccinated, from negative vaccinated and from positive cows were used. The specificity of the ELISA for negative non-vaccinated cows was 99.2 and 99.6% for negative but vaccinated cows. The sensitivity of this technique estimated with positive sera was 99.5%. The ELISA evaluated appears to be a very useful tool in the diagnosis of bovine brucellosis, particularly for regions where little epidemiological information is available about this disease and where large numbers of sera should be tested to obtain such information.

Animals↗
PubMed1996

Development and validation of an indirect enzyme immunoassay for detection of antibody to Brucella abortus in milk.

An indirect enzyme immunoassay for detection of antibody to Brucella abortus in bovine milk was developed and validated using 6238 milk samples from Canadian herds (brucellosis free) and 202 samples from herds infected with B. abortus (from Argentina and Chile). The assay utilized lipopolysaccharide as the antigen, immobilized on the polystyrene matrix, whole milk to test and a mouse monoclonal antibody, specific for an epitope of bovine IgG1, conjugated with horseradish peroxidase. The sensitivity of the assay was 95.2% +/- 3.7% at a confidence limit of 95% for samples from B. abortus infected herds obtained from chile and 98.7% +/- 0.3% at a confidence limit of 95% for samples from similar herds in Argentina. Of the negative milk samples tested, 77 gave a result above the threshold value of 0.200 optical density units. When the 77 false positive samples were retested using 7.5 mM (final concentration) of EDTA and ethyleneglycol-bis-aminoether-N,N,N', N'-tetraacetic acid (EGTA), the number of false positive reactions was reduced to 3, giving a diagnostic specificity of 99.95%. The divalent cation chelating agents did not affect positive reactions and the sensitivity remained the same. Based on control samples included with each assay, the performance of the assay was consistent.

Animals↗