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Biomedical subjects

R J Weber

Publications and source records attributed to R J Weber.

70 records · Page 4Linked to original sources
PubMed1981

The molecular mechanism of cryoprecipitation and cold agglutination of an IgM lambda Waldenström macroglobulin with anti-Gd specificity: sedimentation analysis and localization of interacting sites.

The physicochemical properties and immunologic specificity of an IgM lambda cryoglobulin with cold agglutinin activity (designated MAT) were investigated. Discrete binding sites involved in cryoprecipitation were shown to exist on the reductive 7S subunits and tryptic Fab mu and Fc mu 5 fragments derived from MAT. Analytical ultracentrifugation indicated the nonprecipitating MAT subunits self-associated into rapidly sedimenting paucidisperse boundaries of 32S, 25S, and 8.7S at 13 degrees C, which were converted to a monodisperse 5.7S boundary at 35 degrees C. Furthermore, MAT Fab mu and Fc mu 5 fragments exhibited association with each other at 13 degrees C but not at 35 degrees C when studied by analytical ultracentrifugation. The cold agglutinin activity of MAT can be inhibited by sialyllactose or treatment of erythrocytes with neuraminidase but not papain. Therefore, the membrane determinants of human erythrocytes are Gd (glycolipid-dependent or protease-resistant glycoproteins) with terminal sialic acid. Treatment of MAT with neuraminidase abolished its precipitating properties, but had no effect on its ability to agglutinate untreated erythrocytes. The cryoprecipitation and cold agglutination phenomena exhibited by MAT therefore seem to involve identical or cross-reacting carbohydrate antigens with terminal sialic acid residues.

Agglutinins↗
PubMed1979

Electromyographic abnormalities following myelography.

Electromyographic (EMG) abnormalities were found in 13 of 32 patients with previously normal studies following myelography. These abnormalities usually developed by the first day after myelography and resolved by the fourth day. The changes were evenly divided between those restricted to a single paraspinal muscle level, thus mimicking the frequent findings in radioculopathy, and those present bilaterally and at multiple levels. We were unable to correlate these EMG changes with the clinical status of the patient or with events occurring at myelography. Thus, the performance of EMG within four days following myelography can lead to false-positive results if paraspinal muscle EMG abnormalities are used as the diagnostic criteria.

Back↗
PubMed1979

Measuring the size of mental images.

Mental images seem to have a size; the experimental problem was to map that image size onto a scale of physical measurement. To this end, two experiments were conducted to measure the size of mental images in degrees of visual angle. In Experiment 1, college students employed light pointers to indicate the horizontal extent of projected mental images of words (the letter string, not the referent). Imagined words covered about 1.0 degress of visual angle per letter. In Experiment 2, a more objective eye-movement response was used to measure the visual angle size of imagined letter strings. Visual angle of eye movement was found to increase regularly as the letter distance between the fixation point and a probed letter position increased. Each letter occupied about 2.5 degrees of visual angle for the four-letter strings in the control/default size condition. Possible relations between eye movements and images are discussed.

Attention↗
PubMed1978

Cognitive maps of environmental knowledge and preference in nursing home patients.

Two studies examined cognitive maps of environmental knowledge and preference shown by nursing home patients. In study I, knowledge of the nursing home environment was investigated. Age was found to be negatively related to accuracy in identifying the locations of slide-depicted scenes. Also, patients who had lived several years in the nursing home were less able to identify the locations than were students who received a five-minute exposure to each area. Variable identification performance across areas was determined to be the result of relative visual distinctiveness rather than differential familiarity. Study II examined preference structures for different areas of the nursing home. Patients indicated a marked preference for their own room relative to common areas. Two different models of nursing design were suggested: 1) a social facilitation model emphasizing the allocation of a large proportion of space to common areas, and 2) an ethological model emphasizing preferences of patients for more private space.

Aged↗
PubMed1978

F wave evaluation of thoracic outlet syndrome: a multiple regression derived F wave latency predicting technique.

To assess the occurrence of a neurologic verus a vascular component of thoracic outlet syndrome (TOS), ulnar nerve function via the F wave was studied in 16 patients with clinically diagnosed TOS and 38 control subjects. To simplify the procedure the following formula was developed, through multiple regression analysis, which can predict the ulnar F wave latency in an individual: [arm length (cm) x 0.31] minus [ulnar nerve forearm velocity (meters/sec) x 0.123] plus [11.05]. The mean plus 2 standard deviations, the maximum acceptable prolongation above the predicted value, is 2.5 msec. This formula can be used for assessment of any ulnar nerve conduction defect. Using this technique, some patients with clinically diagnosed TOS were shown to have slowed conduction of the ulnar nerve through the thoracic outlet.

Adolescent↗
PubMedDate not supplied

The effect of prophylactic nifedipine on renal function in patients administered contrast media.

STUDY OBJECTIVE: To determine if prophylaxis with nifedipine could decrease the frequency of contrast medium-induced renal impairment. DESIGN: Prospective, randomized clinical trial. SETTING: A university-affiliated hospital. PATIENTS: Patients undergoing scheduled radiologic examinations involving infusion of contrast media. INTERVENTIONS: Forty-two patients were randomized to receive nifedipine 10 mg orally 1 hour before the imaging procedure, and 43 to receive no treatment. MEASUREMENTS AND MAIN RESULTS: Baseline serum creatinine levels were compared with maximum levels 24 and 48 hours after administration of contrast medium. No statistically significant difference was seen in either the mean change or mean percentage change in serum creatinine between the control and nifedipine groups. The mean changes in serum creatinine were +7.4 mumol/L in the control group and +2.7 mumol/L in the nifedipine group (p = 0.33); the mean percentage changes were +10.2% and +4.8%, respectively (p = 0.54). CONCLUSION: Regardless of statistical analysis, it is unlikely that elevations in serum creatinine of this magnitude (< 0.1 mg/dl) are of clinical significance. We therefore conclude that prophylactic nifedipine is not clinically beneficial in preserving renal function in patients receiving contrast medium and that the agent should not be routinely administered for this purpose.

Aged↗
PubMedDate not supplied

Pharmacoeconomic issues in the use of granulocyte-macrophage colony-stimulating factor for bone marrow transplantation or chemotherapy-induced neutropenia.

As new treatment options become available for patients with cancer or primary bone marrow failure, the additional economic burden that these treatments may place on the already stressed health care system raises concerns. Neutropenia is a major complication of these conditions and can add substantially to patient care costs. Granulocyte-macrophage colony-stimulating factor (GM-CSF), a cytokine that enhances neutrophil production and function, has recently been recommended as an effective treatment for neutropenia. Selected clinical studies suggest that GM-CSF can reduce the costs associated with the management of neutropenic patients by reducing the need for antibiotics and the duration of hospitalization. Treatment with GM-CSF also may be associated with an improved quality of life. Pharmacoeconomic and quality-of-life studies are required, however, to document these benefits. Based on currently available data, GM-CSF represents an economically and clinically appropriate treatment approach for neutropenia in patients who have undergone bone marrow transplantation or experience chemotherapy-induced neutropenia.

Bone Marrow Transplantation↗