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Biomedical subjects

D Christensen

Publications and source records attributed to D Christensen.

At least 37 records · Page 2Linked to original sources
PubMed1996

Training case managers in cognitive-behaviour therapy.

Four case managers with a nursing background took part in a 26 week in-service programme aimed at developing basic skills in cognitive-behaviour therapy. The programme occupied about 5 hours each week and included directly supervised therapy with at least 4 patients having serious mental illness. Patients' symptoms improved significantly after an average of less than 12 one hour therapy sessions. After the programme, case managers began treating patients autonomously, although all recognised the need for some continuing supervision and the necessity of referring unusually complex or challenging cases to clinical psychologists or others highly skilled in the area.

Adult↗
PubMed1995

Ranking of static non-neutral postures around the joints of the upper extremity and the spine.

Constrained body postures are usually cited as the major cause of musculoskeletal static loading. Thus, the main goal of the present study was to develop a ranking system for the stressfulness of the non-neutral static postures around the wrist, elbow, shoulder, neck and lower back. This was based on the ratings of perceived discomfort. Sixteen men participated in the study. The results indicated that static postural stresses yielded varying effects on the discomforting rating levels. On the basis of these preliminary findings, a ranking system was developed for the stressfulness of non-neutral postures around the joints of the upper extremity and the spine.

Adult↗
PubMed1995

A cross-validation of the NIOSH limits for manual lifting.

The psychophysical, biomechanical, and physiological criteria used in establishing the NIOSH limits for manual lifting were cross-validated against the data published by different researchers in the subject literature. Assessment of the 1991 NIOSH lifting equation indicated that: (1) NIOSH-based limits are significantly different from the psychophysical limits in the (i) low and high frequencies of lift, and (ii) small and large horizontal distances; (2) NIOSH limits are highly correlated with the data of Snook and Ciriello (1991) in the low frequency range, with the Recommended Weight Limit (RWL) protecting about 85% of the female population and 95% of the male population; (3) the 3.4kN limit for compression on the lumbosacral joint cannot protect the majority of the worker population on the basis of damage load concept; and (4) energy expenditure limits used in development of the RWL index can be sustained by 57 to 99% of worker population when compared to the physiological limits based on previous fatigue studies. Results of the cross-validation for psychophysical criterion confirmed the validity of assumptions made in the 1991 NIOSH revised lifting equation. However, the results of cross-validation for the biomechanical and physiological criteria were not in total agreement with the 1991 NIOSH model.

Adult↗
PubMed1993

Bepridil improves left ventricular performance in patients with angina pectoris.

Patients with coronary artery disease and angina pectoris have abnormalities of left ventricular (LV) diastolic performance. These abnormalities, which exist when the patients are at rest and not experiencing angina, are presumably secondary to abnormalities of intracellular calcium metabolism. Twenty-three patients with chronic exertional angina pectoris participated in a placebo-controlled, randomized, cross-over trial of bepridil hydrochloride. Angina frequency, nitroglycerin (NTG) consumption, and treadmill exercise capacity were assessed, and each patient underwent first-pass radionuclide cineangiography while receiving placebo or bepridil to assess LV performance. Bepridil decreased angina frequency from 8.5 +/- 0.6 to 4.4 +/- 1.5 episodes per week (p < 0.01) and NTG consumption from 7.2 +/- 2.4 to 3.6 +/- 1.5 tablets per week (p < 0.01). Total treadmill exercise time, time to onset of angina, and time to 1-mm ST segment depression increased significantly during bepridil therapy. Cardiac output (CO), stroke volume (SV), and ejection fraction (EF) increased at rest and during peak upright bicycle exercise. Peak ejection rate and peak filling rate increased, and time to peak ejection rate and time to peak filling rate decreased at rest and at peak exercise during bepridil therapy. In addition, early diastolic filling fraction increased and atrial filling volume decreased during bepridil treatment. Bepridil is effective as monotherapy for treatment of patients with exertional angina; its use is associated with increased exercise capacity and decreased angina frequency and NTG consumption as well as improved LV systolic and diastolic performance at rest and during peak exercise.

Adult↗
PubMed1990

Biochemical purification and crystallographic characterization of the fiber-forming protein pilin from Neisseria gonorrhoeae.

Pilus fibers are long protein filaments on many pathogenic bacteria that participate in attachment to host cells. Although the self-assembling protein pilin is the major structural component of the Neisseria gonorrhoeae pilus fiber, several other proteins co-purified with pilin through the repeated solubilization-reassociation steps of the biochemical purification. Pilin solubilized in the nondenaturing detergent n-octyl-beta-D-glucopyranoside remained an aggregate of about 100 kDa at pH 9.5, but was reduced to a 40-kDa dimer at pH 10.5, suggesting that assembly involves electrostatic interactions of lysine, tyrosine, or other side chains with high pKa values. Pilin dimers and aggregates of higher molecular mass were partially stable even in the presence of sodium dodecyl sulfate and beta-mercaptoethanol. Removal of pilus-associated proteins and stabilization of pilin multimers permitted the reproducible crystallization of pilin. Three-dimensional needle- and plate-shaped crystals of purified N. gonorrhoeae pilin (strain MS11 variant C30) grew from 36 to 40% polyethylene glycol 400, pH 8.0-9.0, in space group C222, with cell dimensions a = 126.4, b = 121.2, c = 26.7 A and Vm = 2.84 A3/dalton for one molecule per asymmetric unit. The best crystals diffracted to 2.4 A resolution using synchrotron radiation, were stable to x-ray damage, and appear suitable for determination of the atomic structure. This approach of stabilizing and crystallizing an intermediate assembly state may be useful for other fiber-forming proteins, which have previously not been successfully crystallized in forms that diffract to atomic resolution.

Bacterial Outer Membrane Proteins↗
PubMed1989

Effect of 67Cu and 99Mo labeled tetrathiomolybdate on the distribution of 67Cu, Cu, and 99Mo in bile fractions in sheep.

The effect of intravenous administration of 67Cu and 99Mo labeled tetrathiomolybdate (TTM) on the appearance of 67Cu, stable Cu, and 99Mo in gel chromatographic fractions of bile was examined in sheep fed either 5 or 35 mg Cu kg-1 DM. Peak excretory periods of biliary 67Cu, stable Cu, and 99Mo were observed at 30 min-1.25 hr, 2-3 hr, and 11-13 hr after 67Cu and after 99Mo labeled TTM. Sephadex G-75 gel filtration of bile samples collected at 1, 3, and 12 hr after 67Cu administration revealed two major protein peaks of molecular weights of greater than 80,000 (peak I) and 7,000 (peak II) containing both 67Cu and Cu. But the ratio of 67Cu in the two peaks varied with time of bile collection. The ratio of areas of peak I:II 1 hr after 67Cu administration was approximately 0.48; at 3 hr, 0.62, and at 12 hr 1.35. Tetrathiomolybdate administration increased both 67Cu and stable Cu in bile by severalfold and induced a major shift of Cu into the higher molecular weight protein fraction. The experiments confirm the effectiveness of TTM as a "decoppering" agent. Furthermore, TTM not only promoted bile Cu excretion, but it also increased the incorporation of Cu into the macromolecular fraction. This may limit enterohepatic circulation of biliary Cu and thereby cause an overall Cu depletion and a negative Cu balance.

Animals↗
PubMed1989

Detection of bovine herpesvirus-1-specific IgM using a capture enzyme immune assay with isotype-specific monoclonal antibodies.

The detection of virus-specific immunoglobulin M (IgM) antibodies in acute-phase serum samples offers the possibility of making an accurate and rapid serologic diagnosis. We have developed a solid-phase capture assay that uses murine monoclonal antibodies specific for bovine IgM to separate the whole IgM fraction of a bovine serum sample. The IgM specific for bovine herpesvirus-1 (BHV-1) is then detected by the addition of viral antigen, which in turn is detected by BHV-1-specific monoclonal antibodies conjugated to horseradish peroxidase. A BHV-1 IgM antibody response was detected during the early postinfection period (7-40 days PI). Bovine herpesvirus-1 IgM antibody was not detected in sera taken from 3 animals following dexamethasone-induced viral reactivation. This method compares favorably with viral isolation, antigen detection in the clinical samples, and paired serology in the diagnosis of BHV-1 infection at a herd level.

Acute Disease↗
PubMed1987

Comparison of nifedipine and propranolol used in combination with diuretics for the treatment of hypertension.

One hundred patients participated in a double-blind, randomized study to compare the antihypertensive efficacy of sustained-release nifedipine and propranolol in hypertensive patients whose diastolic blood pressure exceeded 95 mm Hg while receiving diuretic therapy. Nifedipine (mean dose, 79.6 mg per day) decreased blood pressure by 11.4/10.5 mm Hg; propranolol (mean dose, 198.4 mg per day) decreased blood pressure by 13.5/10.3 mm Hg. Reduction of diastolic blood pressure to below 90 mm Hg was achieved in 63 percent of nifedipine-treated patients and in 57 percent of propranolol-treated patients. Nifedipine therapy was associated with an increase in high-density lipoprotein cholesterol levels and a decrease in serum triglyceride levels. In contrast, propranolol therapy was associated with a decrease in high-density lipoprotein cholesterol levels and an increase in serum triglyceride levels. Nifedipine is as effective as propranolol in the treatment of patients with mild to moderate hypertension whose blood pressure is inadequately controlled by diuretic therapy.

Adult↗
PubMed1987

Left ventricular ejection fraction response during exercise in asymptomatic systemic hypertension.

To study the effect of mild-to-moderate elevations in diastolic blood pressure (BP) on systolic left ventricular (LV) function, 28 hypertensive patients and 20 normal subjects underwent upright exercise first-pass radionuclide angiography. All were asymptomatic, had normal rest and exercise electrocardiographic findings and no evidence of LV hypertrophy or coronary artery disease. LV function at rest was similar in the 2 groups, but with exercise hypertensive patients had a greater end-systolic volume (69 +/- 19 vs 51 +/- 19 ml, p less than 0.002) and lower ejection fraction (EF) (0.59 +/- 0.09 vs 0.72 +/- 0.07, p less than 0.0001), stroke volume (101 +/- 28 vs 130 +/- 36 ml, p less than 0.005) and peak oxygen uptake (23 +/- 7 vs 33 +/- 9 ml/kl/min, p less than 0.05). Hypertensive patients were separated into 3 groups: group 1-12 patients with an increase in EF with exercise greater than or equal to 0.05; group 2-7 patients with a change in EF with exercise less than 0.05; and group 3-9 patients with a decrease in EF with exercise greater than or equal to 0.05. Group 3 hypertensive patients were older, had a higher heart rate at rest and lower peak oxygen uptake. Rest LV function was similar in the 3 hypertensive subgroups, but exercise end-systolic volumes were higher in groups 2 and 3. Exercise thallium-201 images was normal in all but 1 of 14 hypertensive group 2 or 3 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Effects of ouabain on monovalent cation transport in mammalian tissue.

We measured the effects of ouabain on sodium-potassium ATPase (Na-K ATPase) specific activity (SA) and rubidium (Rb) transport in newborn (NB) and adult (Ad) sheep myocardium (myo), guinea pig myo and red blood cells (RBC), and human RBC. 50% inhibition of Na-K ATPase SA and Rb transport occurred at ouabain concentrations between 10(-4.8) and 10(-7.6) M in different species; within a species, 50% inhibition of Rb transport occurred at lower ouabain concentrations than 50% inhibition of Na-K ATPase SA. No differences between mature and immature tissues were found. Ouabain binding stability to Na-K ATPase extracted from myo and RBC did not vary with age. Binding studies revealed a KD X 10(-8) M of 0.87 +/- 0.09 for NB human RBC and 0.88 +/- 0.14 for Ad human RBC. Calculated RBC receptor density however, was higher in the Ad (1.25 +/- 0.08 sites/micron2) than in the NB (1.03 +/- 0.04 sites/micron2, p less than 0.01). Binding studies in extracted myocardial specimens showed a KD X 10(-8) M of 1.23 +/- 0.27 for NB and 1.09 +/- 0.46 for Ad; mM ouabain bound X 10(-12)/Na-K ATPase unit were 355 +/- 120 (SEM) for NB and 316 +/- 51 for Ad. These studies of cardiac glycosides reveal few age-related differences in drug binding or inhibition of monovalent cation transport.

Aging↗
PubMed1985

Effect of bepridil in patients with chronic stable angina: results of a multicenter trial.

The effects of bepridil, a calcium antagonist with a half-life of approximately 42 hr, were assessed in a double-blind, randomized, placebo-controlled crossover trial. Forty-four patients (39 men, five women) with exercise-induced angina pectoris and ST segment depression with exercise testing (modified Bruce protocol) were studied. Compared with placebo bepridil (400 mg daily) increased total exercise time, time to onset of angina, time to 1 mm of ST segment depression, time to 2 mm of ST segment depression, and total work achieved (all p less than or equal to .001). Both frequency of angina and nitroglycerin consumption decreased during the bepridil compared with the placebo period (p = .02 and .03, respectively). Minor side effects were noted during both the bepridil and placebo phases. Four patients experienced side effects that limited therapy (dizziness in three and abnormal results of liver function tests in one) and one patient died during the bepridil phase. This study suggests that bepridil, 400 mg daily, is effective for the treatment of exercise-induced myocardial ischemia and angina pectoris.

Angina Pectoris↗