Electric and magnetic fields: what do we know?
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Electromagnetic Fields↗
Biomedical subjects
R M Patterson
Publications and source records attributed to R M Patterson.
Fetal growth: a comparison of growth curves with mathematical modeling.
This study compared the use of fetal growth curves with the Rossavik mathematical model in predicting third trimester fetal growth in 27 Hispanic patients. The parameters tested were BPD, HC, AC, and FL. The growth curve method of predicting third trimester fetal growth was significantly more accurate than the mathematical model for three of the four fetal parameters tested: BPD, HC, and FL. We conclude that the mathematical model method offered no advantage over the more commonly used growth curve method for predicting third trimester fetal growth. In addition, growth curves do not require complex calculations and are conceptually simpler and easier to use.
Adult↗
Improved protein detection with a polyvinylidene fluoride transfer membrane for two-dimensional gel electrophoresis.
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Animals↗
Simulated scaphoid proximal pole fracture.
Five fresh cadaver upper extremities were studied with use of a static positioning frame, pressure-sensitive film, a microcomputer-based videodigitizing system, and a Sun station image analysis system to assess the load bearing characteristics of the scaphoid in the proximal carpal joint. Specimens were studied in their normal condition, after a proximal pole osteotomy of the scaphoid, and after resection of the proximal pole of the scaphoid. The amount of contact area born through the scaphoid fossa was essentially the same whether the scaphoid was intact, or after a simulated scaphoid fracture of its proximal pole, or after resection of the proximal pole. The scaphoid contact area and pressure, although overall relatively constant, was redistributed after osteotomy, resulting in increased contact area under the distal fragment and no change or a slight decrease in the contact area under the proximal fragment of the scaphoid. After resection of the proximal fragment, all scaphoid contact area and pressure was born by the distal scaphoid fragment. The contact area and pressure characteristics of the lunate remained unchanged in all conditions compared with the normal condition. There were no significant changes in the locations of the centroids of the scaphoid segments and the lunate in any of the conditions tested.
Adult↗
The silicone scaphoid: a biomechanical study.
Five fresh cadaver upper extremities were studied by use of a static positioning frame, pressure-sensitive film, and a microcomputer-based videodigitizing system, to assess the load-bearing characteristics of a scaphoid silicone implant within the radioulnarcarpal joint. Specimens were studied in their "normal" condition, after resection of the scaphoid, after placement of a scaphoid implant, and with a scaphoid implant and a simulated capitate-lunate-triquetrum-hamate fusion. The scaphoid silicone implant bore significant, although less, load than the normal scaphoid. Decreasing the size of the scaphoid implant decreased the load born by the implant. Decreased load through the scaphoid implant was compensated by the lunate. The addition of a limited carpal fusion did not significantly decrease the load born by a scaphoid implant. Therefore, the silicone scaphoid implant is a load-bearing implant even when undersized or placed in association with a limited carpal fusion.
Adult↗
Comparison of cortical and cancellous screw pull-out strengths about the posterior column and sacroiliac joint.
This study addresses the comparative pull-out strengths of cortical (4.5 mm) and fully threaded cancellous (6.5 mm) bone screws from sites about the pelvis commonly used in the fixation of posterior column acetabular fractures and sacroiliac (SI) disruptions. These sites include one from lateral to medial through the posterior column, two from posterolateral to anteromedial across the SI joint, one vertically through the sacral ala, and one vertically through the iliopubic column. Statistical analysis showed no significant difference in the force required for pull-out failure of the cortical versus the cancellous screws at any of the sites tested.
Acetabulum↗
ras gene activation in rat tumors induced by benzidine congeners and derived dyes.
Dimethoxybenzidine (DMO) and dimethylbenzidine (DM) are used to synthesize dyes such as C.I. Direct Blue 15 and C.I. Acid Red 114, respectively. These commercially used dyes are metabolically degraded to DMO or DM in the intestinal tract of rodents and subsequently DMO and DM are absorbed into the blood stream. Animals were exposed to DMO, DM, or the dyes in the drinking water. Tumors obtained from control and chemical-treated animals were examined for the presence of activated oncogenes by the NIH 3T3 DNA transfection assay. Activated oncogenes were detected in less than 3% (1/38) of the tumors from control animals whereas 68% (34/50) of the tumors from chemical-treated animals contained detectable oncogenes. Activated oncogenes were detected in both malignant (25/36) and benign (9/14) tumors from the chemically treated animals but only in one of 13 malignant tumors from the control animals. The presence of oncogenes in the chemically induced benign tumors suggests that oncogene activation was an early event in those tumors. Southern blot analysis of transfectant DNA showed that the transforming properties of the chemically induced rat tumor DNAs were due to the transfer of an activated H-ras (31/34) or N-ras (3/34) gene. One spontaneous rat tumor DNA was found to contain an activated H-ras gene. Oligonucleotide hybridization analysis indicated that the H-ras oncogenes from chemical-associated tumors contained mutations at codons 12, 13, or 61 whereas the spontaneously activated H-ras gene contained a point mutation at codon 61. These data suggest that activation of cellular ras genes by point mutation is an important step in the induction of tumors, at least in rats, by this class of benzidine-derived dyes. Moreover, in light of common histogenesis of the normal counterparts of many of the chemically induced neoplasms and histological evidence of varied tissue differentiation in some basal cell neoplasms, it is possible that most or all of the chemically induced neoplasms were derived from a common epidermal progenitor stem cell population.
Animals↗
Effect of tocolytic agents on fetal umbilical velocimetry.
In this prospective study, we sought to examine the changes in umbilical vascular resistance induced by tocolytic therapy. Umbilical artery velocimetry was performed in 46 patients with preterm labor before tocolysis and at 1 hour and 24 hours after tocolysis was initiated. Raw systolic/diastolic ratios were corrected for concomitant changes in fetal heart rate. Thirty patients received subcutaneous terbutaline and 16 were treated with intravenous magnesium. Systolic/diastolic ratios decreased in patients treated with terbutaline. This decline persisted after correction for increases in fetal heart rate. No significant changes in systolic/diastolic ratios were seen in patients treated with magnesium. We conclude that terbutaline may affect umbilical vascular resistance. Possible clinical implications of these findings are discussed.
Blood Pressure↗
A prospective randomized comparison of oral terbutaline and magnesium oxide for the maintenance of tocolysis.
We compared oral magnesium oxide with oral terbutaline sulfate in a prospective, randomized manner to determine efficacy and side effects. Preterm labor patients whose labor was arrested with parenteral tocolysis were randomized to oral tocolysis with either magnesium oxide, 200 mg every 3 to 4 hours (n = 23), or terbutaline, 2.5 to 5 mg every 3 to 4 hours (n = 27). The number of patients who were delivered of infants before 36 weeks' gestation was similar between groups (18.5% receiving terbutaline versus 17.4% receiving magnesium). At least one side effect occurred in 81.5% of patients in the terbutaline group and 47.8% in the magnesium group (p less than 0.01). Finally, the cost for 1 day of magnesium (20 cents) is approximately one third the cost of terbutaline (56 cents). These data suggest that oral magnesium oxide is as effective as terbutaline for the maintenance of tocolysis, with fewer side effects and at a lower cost.
Administration, Oral↗
Adjusting the loading dose of magnesium sulfate for tocolysis.
The purpose of this prospective study was to establish a method to calculate a loading dose of magnesium sulfate so as to achieve therapeutic levels of tocolysis more quickly. Fifty patients in preterm labor were enrolled. In the first phase 25 patients were studied so that the apparent volume of distribution for the loading dose of magnesium sulfate could be estimated and an adjusted loading dose could be calculated. The efficacy of this adjusted loading dose was then tested on a further 25 patients in the second phase. We found that the apparent volume of distribution could be accurately estimated and an adjusted loading dose calculated, with the use of ideal body weight, degree of underweight, and current use of beta-sympathomimetics. In the adjusted loading dose group therapeutic levels were achieved more often, with higher postloading magnesium levels and a greater decrease in contraction index immediately after the loading dose. We conclude that an adjusted loading dose can be calculated for magnesium sulfate to optimize tocolytic therapy.
Adrenergic beta-Agonists↗
Ulnar-sided perilunate instability: an anatomic and biomechanic study.
A staging system for ulnar-sided perilunate instability is presented based on a series of cadaver dissections and load studies. Stage I: partial or complete disruption of the lunotriquetral interosseous ligament, without clinical and/or radiographic evidence of dynamic or static volar intercalated segment instability deformity; stage II: complete disruption of the lunotriquetral interosseous ligament and disruption of the palmar lunotriquetral ligament, with clinical and/or radiographic evidence of dynamic volar intercalated segment instability deformity; and stage III: complete disruption of the lunotriquetral interosseous and the palmar lunotriquetral ligaments, attenuation or disruption of the dorsal radiocarpal ligament, with clinical and/or radiographic evidence of static volar intercalated segment instability deformity.
Adult↗
Effects of distal radius fracture malunion on wrist joint mechanics.
An experimental model using a static positioning frame, pressure-sensitive film (Fuji), and a microcomputer-based videodigitizing system was used to measure contact areas and pressures in the wrist. Contact areas and pressures were compared in a group of wrists between the normal state and with simulated distal radius fracture malunions of varying degrees. In simulated malunions, radial shortening to any degree slightly increased the total contact area in the lunate fossa, and was significant at 2 mm of shortening. By angulating the distal radius more than 20 degrees either palmar or dorsal, there was a dorsal shift in the scaphoid and lunate high pressure areas, and the loads were more concentrated, but there was no change in the load distribution between the scaphoid and lunate. Decreasing the radial inclination shifted the load distribution so that there was more load in the lunate fossa and less load in the scaphoid fossa.
Adult↗
Effects of radioulnar instability on the radiocarpal joint: a biomechanical study.
Five fresh cadaver upper extremities were studied with use of a static positioning frame, pressure-sensitive film and a microcomputer-based videodigitizing system to assess the effect of increasing radioulnar instability on the load distribution within the proximal carpal joint. Three stages of radioulnar instability were studied: (1) an avulsion fracture at the base of the ulna styloid; (2) an avulsion fracture at the base of the ulna styloid plus disruption of the dorsal portion of the distal radioulnar joint capsule; and (3) an avulsion fracture at the base of the ulna styloid, disruption of the dorsal portion of the distal radioulnar joint capsule, and disruption of the radioulnar interosseous membrane. All stages of radioulnar instability demonstrated a decrease in the lunate contact area in positions with the forearm in supination. In stage 3 instability there was also less lunate contact area in positions with the forearm in neutral pronation/supination. In stage 3 instability the lunate high pressure area centroid was abnormally palmar in all positions and the scaphoid high pressure area centroid was abnormally palmar in positions with the forearm in pronation or supination.
Adult↗
Evaluation of the biomechanical efficacy of limited intercarpal fusions for the treatment of scapho-lunate dissociation.
An experimental model that uses a static positioning frame, pressure-sensitive film, and a microcomputer-based videodigitizing system was used to measure the contact areas and pressures in a group of wrists in their "normal" state, after ligament sectioning, which resulted in stage III perilunate instability and then following different types of simulated carpal fusions. Compared with a normal wrist, there is an overall decrease in load in the lunate fossa and a significant increase in load in the scaphoid fossa in the wrist with stage III perilunate instability. Scaphoid-trapezium-trapezoid and scaphoid-capitate fusions transmitted almost all load through the scaphoid fossa. Scaphoid-lunate, scaphoid-lunate-capitate, and capitate-lunate fusions all distributed load more proportionately through both scaphoid and lunate fossae. The positioning of the carpal bones within a limited carpal fusion was also found to affect the load distribution in the wrist. The scaphoid-lunate, scaphoid-lunate-capitate, or capitate-lunate fusions, with attention to the relative carpal alignment within the limited fusion seem to offer more promise for treatment of perilunate instability biomechanically than the scaphoid-trapezium-trapezoid or scaphoid-capitate fusions.
Adult↗
What is twin birthweight discordance?
The purpose of this study was to define the level of twin birthweight discordance across gestational age at which perinatal morbidity, neonatal death, or congenital anomalies were more likely to occur. One hundred ninety-four sets of twins (1982-1985) were retrospectively studied. Discordance was defined as (birthweight of larger-birthweight of smaller/birthweight of larger) x 100. The mean discordance was 10.3 +/- 8.5% (26 to 32 weeks = 7.6 +/- 5.9%; 33 to 36 weeks = 9.5 +/- 9.5%; 37 to 42 weeks = 11.4 +/- 8.5%) (p = 0.07). The occurrence of morbidity, neonatal death, and anomalies was increased with prematurity or the occurrence of small for gestational age in both twins. However, neither morbidity, neonatal death, nor anomalies were significantly related to level of discordance. These data demonstrate that prematurity and birthweight below the tenth percentile may present a greater threat to twins than does birthweight discordance. These findings should be given due consideration in planning antepartum management.
Birth Weight↗
Seizure disorders in pregnancy.
For maternal and fetal safety, active seizure disorders require treatment during pregnancy. Since all anticonvulsant medications have been implicated in teratogenesis, an obvious clinical dilemma exists. For maximal safety, the minimal effective dose of a single drug should be used. With careful management, over 90 per cent of patients can expect a healthy child.
Anticonvulsants↗
Acute effects of a superoxide radical-generating system on DNA double-strand stability in Chinese hamster ovary cells. Determination by a modified fluorometric procedure.
The rate of oxyradical generation by a xanthine oxidase-xanthine system to acutely cause DNA strand breakage in Chinese hamster ovary cells was studied in a phosphate-buffered saline system. DNA strand breakage, measured by a fluorometric procedure, was found to increase curvilinearly as a function of oxyradical generation. Results of studying the ability of 5 mM mannitol, 10 mM dimethylthiourea, 300 micrograms superoxide dismutase/ml, or 1 mg catalase/ml to interfere with DNA damage at a high rate of oxyradical production best supported a hydrogen peroxide-promoted mechanism for DNA breakage.
Animals↗
Oncogene activation in spontaneous and chemically induced rodent tumors: implications for risk analysis.
The validity of rodent tumor end points in assessing the potential hazards of chemical exposure to humans is a somewhat controversial but very important issue since most chemicals are classified as potentially hazardous to humans on the basis of long-term carcinogenesis studies in rodents. The ability to distinguish between genotoxic, cytotoxic, or receptor-mediated promotion effects of chemical treatment would aid in the interpretation of rodent carcinogenesis data. Activated oncogenes in spontaneously occurring and chemically induced rodent tumors were examined and compared as one approach to determine the mechanism by which chemical treatment caused an increased incidence of rodent tumors. Different patterns of activated oncogenes were found not only in spontaneous versus chemically induced mouse liver tumors but also in a variety of spontaneous rat tumors versus chemically induced rat lung tumors. In the absence of cytotoxic effects, it could be argued that the chemicals in question activated protooncogenes by a direct genotoxic mechanism. These results provided a basis for the analysis of activated oncogenes in spontaneous and chemically induced rodent tumors to provide information at a molecular level to aid in the extrapolation of rodent carcinogenesis data to human risk assessment.
Animals↗