Biomedical subjects

R A Abrams

Publications and source records attributed to R A Abrams.

At least 73 records · Page 4Linked to original sources

PubMed1995

Mental chronometry: beyond onset latencies in the lexical decision task.

Four experiments addressed the influence of variables on lexical decision performance after response initiation has occurred. In Experiment 1, participants made an arm movement in one direction for word trials and pressed a button with the other hand for nonword trials. The results indicated that word frequency not only modulated the speed to initiate the arm movement, but also modulated the acceleration and force of the movement after initiation. The results of Experiment 2 indicated that word frequency and stimulus degradation produced large and additive effects on response latency, accuracy, and the force of the response after initiation. In Experiments 3 and 4, participants made the same arbitrary speech response in a modified lexical decision task for both high- and low-frequency words. The results indicated that both the onset and duration of the speech response were modulated by word frequency. The results are viewed as most consistent with an enabled response model, wherein early operations can enable appropriate action systems before central decisions are made.

Adult↗

PubMed1995

Perihilar cholangiocarcinoma. Postoperative radiotherapy does not improve survival.

OBJECTIVE: The aims of this analysis were to determine prospectively the effects of surgical resection and radiation therapy on the length and quality of survival as well as late toxicity in patients with perihilar cholangiocarcinoma. BACKGROUND: Retrospective analyses have suggested that adjuvant radiation therapy improves survival in patients with perihilar cholangiocarcinoma. However, in these reports, patients receiving radiotherapy tended to have smaller, often resectable tumors, and were relatively fit. In comparison, patients who have not received radiotherapy often had unresectable tumors, metastatic disease, or poor performance status. METHODS: From 1988 through 1993, surgically staged patients with perihilar cholangiocarcinoma and 1) no evidence of metastatic disease, 2) Karnofsky score > 60, 3) no prior malignancy or radiotherapy, and 4) a patent main portal vein were analyzed. Fifty patients were stratified by resection (n = 31) versus operative palliation (n = 19) and by radiation (n = 23) versus no radiotherapy (n = 27). RESULTS: Patients undergoing resection had smaller tumors (1.9 +/- 2.8 vs. 2.4 +/- 2.1 cm, p < 0.01) that were less likely to invade the hepatic artery (3% vs. 42%, p < 0.05) or portal vein (6% vs. 53%, p < 0.05). Multiple parameters that might have affected outcome were similar between patients who did and did not receive radiation therapy. Resection improved the length (24.2 +/- 2.5 vs. 11.3 +/- 1.0 months, p < 0.05) and quality of survival. Radiation had no effect on the length (18.4 +/- 2.9 vs. 20.1 +/- 2.4 months) or quality of survival or on late toxicity. CONCLUSIONS: This analysis suggests that in patients with localized perihilar cholangiocarcinoma, resection prolongs survival whereas radiation has no effect on either survival or late toxicity. Thus, new agents or strategies to deliver adjuvant therapy are needed to improve survival in these patients.

Bile Duct Neoplasms↗

PubMed1995

Color-based inhibition of return.

The inhibition of return of visual attention based on stimulus color was examined in three experiments. In the first experiment, a discrete trial paradigm showed that subjects were slower to detect a color patch if the color matched that of a patch presented earlier in the same location. Experiment 2 showed that the inhibition only occurs if a neutral, nontarget distractor color is presented between presentation of the initial color cue and the subsequent target patch--explaining the previous failures to detect the phenomenon. Experiment 3 extended the results to a different combination of colors. Taken together, the results have important implications for the processing of stimulus attributes such as spatial location and color, and for the conditions necessary for producing inhibition of return.

Attention↗

PubMed1995

Treatment of acquired muscle spasticity using phenol peripheral nerve blocks.

The use of phenol motor nerve blocks is advantageous in the early period of acquired spasticity (ie, that occurring following traumatic brain injury or incomplete spinal cord injury), when increased muscle tone is often the most severe. Because acquired spasticity is dynamic and usually improves slowly, a temporary treatment method used to ameliorate increased muscle tone is desirable. Phenol nerve infiltration provides a temporary motor nerve block that lasts for weeks or months. It allows passive limb mobilization in a comprehensive rehabilitation program that attempts to prevent fixed soft tissue contractures. Permanent or irreversible methods such as operative tendon lengthening, muscle release or recession, or neurectomy are usually best delayed until the spasticity has become static, when the need for surgical correction becomes more firmly indicated, and outcomes of operative intervention are more predictable. Although phenol nerve blocks were initially administered at the spinal cord level to control spasticity, the potential side effects have caused a loss of popularity of this method of administration. The safer and more common use of phenol infiltration at the peripheral nerve level is now more accepted for brain injury and spinal cord injury patients. This report reviews the indications, current concepts, and development of the different methods used to administer phenol nerve blocks. Comparisons to other methods to control spasticity are discussed.

Animals↗

PubMed1995

The halo skeletal fixator: current concepts of application and maintenance.

The halo device provides the most rigid cervical immobilization of all cervical orthoses. Despite its established efficacy, reported complications include pin loosening (36% to 60%), pin-site infection (20% to 22%), severe pin discomfort (18%), ring migration (13%), pressure sores (4% to 11%), unacceptable scars (9% to 30%), nerve injury (2%), dysphagia (2%), prolonged bleeding at pin sites (1%), and dural puncture (1%). Appreciation of skull anatomy and established application guidelines can help minimize these complications. A relative "safe zone" for anterior pin placement is located 1 cm above the orbital rim, superior to the lateral two thirds of the orbit. This position avoids injury to the nearby frontal sinus (medially), temporalis fossa (laterally), and sensory nerves (supraorbital and supratrochlear nerves medially, and zygomaticotemporal nerve laterally). Posterior pin positions are less critical, located roughly diagonal to the contralateral anterior pins. Pins should enter the skull perpendicular to the cortex, with the ring or crown sitting below the equator of the skull, passing about 1 cm above the helix of the ear. Pins are inserted at 8 in-lbs and re-tightened once at 48 hours. A loose pin can be re-tightened to 8 in-lbs if resistance is met; otherwise, a loose pin requires replacement in a nearby site. Superficially infected pins are managed with oral antibiotics and local pin care. Refractory infections require pin removal, parenteral antibiotics, and incision and drainage as indicated. Dysphagia (difficulty in swallowing), produced by exaggerated cervical extension, may necessitate repositioning of the C-spine. Dural pin puncture is managed with hospitalization, antibiotics, and elevation of the head of the bed to decrease cerebrospinal fluid pressure and allow dural healing.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMed1995

Soft tissue attachments of the ulnar coronoid process. An anatomic study with radiographic correlation.

Regan and Morrey proposed a 3-type coronoid fracture classification observing that the incidence of concommitant elbow dislocation was proportional to fragment size. Elbow instability associated with coronoid fractures presumably is related to disrupted bony architecture and ineffective stabilizers attached to the free fragment. Twenty cadaveric elbows were dissected, measuring medial collateral ligament, anterior capsule, and brachialis muscle insertion loci on the coronoid. Radiographs were taken after radiopaque labeling of the stabilizer insertions. The anterior bundle of the medial collateral ligament insertion averaged 18.4 mm dorsal to the coronoid tip. Only in Type III fractures would it be attached to the free fragment. The capsule inserted an average of 6.4 mm distal to the coronoid tip. Rarely should Type I fractures result from a capsular avulsion, because only 3 of 20 specimens had the capsule inserting on the tip. The brachialis had a musculoaponeurotic insertion onto the elbow capsule, coronoid, and proximal ulna. The bony insertion averaged 26.3 mm in length, with its proximal margin averaging 11 mm distal to the coronoid tip. In only Type III fractures is the fragment large enough to include the brachialis bony insertion.

Adult↗

PubMed1994

Clinical use of on-line portal imaging for daily patient treatment verification.

PURPOSE: To determine the ease of use by clinical staff and reliability of an electronic portal imaging system and evaluate the potential to utilize on-line imaging to assess accuracy of daily patient treatment positioning in radiation therapy. METHODS AND MATERIALS: A computer controlled fluorescent screen-mirror imaging system was used to acquire on-line portal images. A physician panel assessed on-line image quality relative to standard portal film. Clinical use of the imager was implemented through a protocol where images were obtained during the first six monitor units of external beam. The images were visually compared to a reference portal and patient setup was adjusted for errors exceeding 5 mm. Subsequent off-line analysis was utilized to give insight into the magnitude of clinical setup error in the visually accepted images. RESULTS: Physician evaluation of on-line image quality with an initial 211 images found that 70% were comparable or superior to standard film portal images. Eighty percent of treatment fields fit completely within the on-line imaging area. Eight percent of on-line images were rejected due to poor image quality. Twelve percent of the daily treatment setups imaged required adjustment overall, but specific field types predictably required more frequent adjustment (pelvic and mantle fields). Off-line analysis of accepted images demonstrates that 18% of the final images had setup errors exceeding 5 mm. CONCLUSION: On-line imaging facilitated daily portal alignment and verification. Ease of use, almost instantaneous viewing and consistent ability to identify and locate anatomical landmarks imply the potential for on-line imaging to replace film based approaches. Retrospective analysis of daily images reveals that visual assessment of setup is not sufficient for eliminating localization errors. Further improvement is required with respect to detecting localization error and fully encompassing larger field sizes.

Humans↗

PubMed1994

The gap effect and inhibition of return: interactive effects on eye movement latencies.

Three experiments are reported with two types of manipulations that are known to affect the latency with which subjects can initiate saccadic eye movements. The first manipulation involves the temporal relation between the offset of a visual fixation point and the onset of a peripheral target (the "gap effect"). The second manipulation involves the prior allocation and removal of visual attention ("inhibition of return"). In two experiments, the gap effect was smaller for saccades to previously attended locations than to previously unattended locations. The results suggest an important link between the two phenomena and provide new insights into the brain mechanisms underlying visual attention and eye movements.

Attention↗

PubMed1994

Arthroscopic portals of the wrist: an anatomic study.

Wrist arthroscopy has become an accepted diagnostic technique, and it is starting to be a useful therapeutic tool. Extensor tendons, the radial artery, and dorsal sensory nerve branches are at risk of injury during this procedure; however, understanding periportal anatomy should make wrist arthroscopy safer. Wrist arthroscopic portals were established in 19 fresh cadaver wrists, after which the limbs were dissected and periportal anatomy was described and quantified. The 1-2, 6R, and 6U portals were the most perilous, while the midcarpal, 3-4, 4-5, and distal radioulnar joint portals were relatively safe. Even "safe" portals had occasional adjacent sensory nerve branches and tendons. A safe technique of establishing wrist arthroscopy portals is emphasized.

Arthroscopy↗

PubMed1994

Breath ethane generation during clinical total body irradiation as a marker of oxygen-free-radical-mediated lipid peroxidation: a case study.

Total body irradiation (TBI) is used therapeutically for treatment of leukemias and other malignancies of the hemopoietic system. Ionizing radiation produces oxygen free radicals that contribute to cytotoxicity. Breath collected from one patient undergoing therapeutic TBI showed measurable changes in levels of ethane during treatment. Breath ethane is a marker of lipid peroxidation of n-3 fatty acids. The TBI treatment involved 4 days of irradiation. The largest changes in breath ethane occurred on Day 2. The increased levels of breath ethane on Day 2 were correlated to clinical manifestations of toxicity. The correlation of the onset of gastrointestinal side effects with higher levels of breath ethane suggests that breath ethane may be a clinically useful measure of the toxicity of various TBI fractionation treatment protocols currently in use at different medical centers. The levels of breath ethane on the other days of treatment were lower, suggesting that the oxidative-antioxidative balance of the patient may be important in protection against free radical mediated injury. These results for a single patient suggest that breath ethane may be a promising approach to elucidate the role of antioxidants in clinical TBI and should be extended for verification to a larger volunteer patient population.

Adult↗

PubMed1994

Inhibition of return: effects of attentional cuing on eye movement latencies.

Inhibition of return refers to a bias against attending to and/or detecting visual stimuli at recently attended locations. In the present experiments, Ss were slower to initiate eye movements to previously attended locations. Furthermore, there was more inhibition when a peripheral (exogenous) flash signaled the target, compared with when a central (endogenous) arrow cue was used as an imperative stimulus. That pattern suggests that some of the inhibition is due to processes involved in detecting visual stimuli, and some of the inhibition is related to the movement of the eye. Subsequent experiments showed that the eye-movement component of the inhibition is not object-centered and does not move if the previously attended object moves, although the stimulus-detection component is object-centered. The results have implications for visual attention in general and for the link between overt and covert orienting.

Attention↗

PubMed1994

Rapid aimed limb movements: age differences and practice effects in component submovements.

Two experiments are reported in which younger and older adults practiced rapid aimed limb movements toward a visible target region. Ss were instructed to make the movements as rapidly and as accurately as possible. Kinematic details of the movements were examined to assess the differences in component submovements between the 2 groups and to identify changes in the movements due to practice. The results revealed that older Ss produced initial ballistic submovements that had the same duration but traveled less far than those of younger Ss. Additionally, older Ss produced corrective secondary submovements that were longer in both duration and distance than those of the younger subjects. With practice, younger Ss modified their submovements, but older Ss did not modify theirs even after extensive practice on the task. The results show that the mechanisms underlying movements of older adults are qualitatively different from those in younger adults.

Acceleration↗

PubMed1994

Eye-hand coordination: spatial localization after saccadic and pursuit eye movements.

Subjects produced speeded and unspeeded hand movements to a target location after either saccadic or pursuit eye movements to the target. Hand movements began either aligned with the initial position of gaze or from some other location. Subjects generally underestimated the extent of the pursuit eye movements relative to estimates made after saccades. With speeded hand movements, however, the underestimation was reduced considerably if the hand movements began aligned with a location other than the initial position of gaze. The results reveal details of the mechanisms underlying eye-hand coordination and show that important differences exist in the information used for localization for slow and rapid limb movements.

Journal Article↗

PubMed1993

Treatment of posttraumatic radioulnar synostosis with excision and low-dose radiation.

Two cases of posttraumatic radioulnar synostosis treated with excision and low-dose radiation are presented. Routine postoperative hand therapy was employed. Nearly full range of motion was restored in both cases. No wound healing problems were encountered. We suggest that low-dose radiation may be a useful method of prophylaxis against recurrence after excision of radioulnar synostosis.

Adult↗

PubMed1993

Rapid aimed limb movements: differential effects of practice on component submovements.

Three experiments are reported in which subjects practiced rapid aimed limb movements (arm pointing and wrist rotation) toward a visible target region. Subjects were required to minimize their movement durations while still landing in the target. The movement trajectories were examined to assess the effects of practice on separate component submovements of the limb movements. The results revealed that practice improved primarily temporal, not spatial, aspects of performance. Practice reduced the overall movement durations, but had different effects on the individual submovements. Practice allowed subjects to reduce the amount of time spent performing final corrective submovements, but actually increased slightly the time needed to produce the initial ballistic submovement. The results suggest that practice in the present task primarily enhanced the ability to use feedback information, but there was also some evidence of changes in the ballistic, preprogrammed portion of the movements. The results demonstrate that analysis of submovements can reveal important details of the underlying motor control processes.

Journal Article↗

PubMed1993

Gamekeeper thumb: differentiation of nondisplaced and displaced tears of the ulnar collateral ligament with MR imaging. Work in progress.

Ulnar collateral ligament (UCL) injury of the first metacarpophalangeal joint (gamekeeper thumb) is common. If the UCL becomes displaced superficially to the adductor pollicis aponeurosis, surgical treatment has been advocated. Radiography cannot help differentiate between displaced and nondisplaced tears. The authors investigated the use of magnetic resonance (MR) imaging in the evaluation of UCL injury. Ten displaced and six nondisplaced UCL tears were surgically created in 16 nonembalmed cadaveric specimens. Twelve unaltered specimens served as controls. Coronal MR images were obtained and interpreted by two observers. The MR images were compared with corresponding anatomic slices. MR imaging depicted UCL displacement in all 10 specimens with displaced tears. A displaced tear was interpreted in one control specimen. Non-displaced tears were diagnosed in four control specimens. Although MR imaging was only 67% specific for all tears, it was 100% sensitive and 94% specific for depicting UCL displacement and, therefore, may be useful for evaluating gamekeeper thumb.

Adult↗

PubMed1993

Yttrium 90-labeled antiferritin followed by high-dose chemotherapy and autologous bone marrow transplantation for poor-prognosis Hodgkin's disease.

PURPOSE: This study was undertaken to examine the feasibility of combining radiolabeled antibody therapy with high-dose chemotherapy followed by autologous bone marrow transplantation in patients with poor-prognosis Hodgkin's disease. PATIENTS AND METHODS: Patients were entered onto this protocol if they had chemotherapy-resistant disease, bulky disease, or extensive prior therapy. Patients received yttrium-labeled antiferritin on day -13, -12, or -11, followed by high-dose cyclophosphamide, carmustine, and etoposide (CBV) on days -6 to -3, and then bone marrow infusion on day 0. RESULTS: Twelve patients received both radiolabeled antibody and high-dose chemotherapy followed by autologous transplantation. Two additional patients started the study, but were unable to complete all therapy. Four of 12 patients experienced early transplant-related mortality. Four patients are alive more than 2 years following transplantation and three are free from disease progression at 24+, 25+, and 28+ months following transplantation. The progression-free survival rate at 1 year is estimated to be 21%. Considering the poor prognostic characteristics of these patients, toxicity on this protocol was not necessarily greater than that observed with high-dose chemotherapy alone. CONCLUSION: This report demonstrates the feasibility of combining radiolabeled antibody therapy with high-dose chemotherapy and autologous bone marrow transplantation.

Adolescent↗

PubMed1992

Architecture of selected muscles of the arm and forearm: anatomy and implications for tendon transfer.

The architectural features of twenty-one different forearm muscles (n = 154 total muscles) were studied. Muscles included the extensor digitorum communis to the index, middle, ring, and small fingers, the extensor digit quinti, the extensor indicis proprius, the extensor pollicis longus, the flexor digitorum superficialis, the flexor digitorum profundus, the flexor pollicis longus, the pronator quadratus, the palmaris longus, the pronator teres, and the brachioradialis. Muscle length, mass, fiber pennation angle, fiber length, and sarcomere length were determined with the use of laser diffraction techniques. From these values, physiologic cross-sectional area and fiber length/muscle length ratio were calculated. The individual digital extensor muscles were found to be relatively similar in architectural structure. Similarly, the deep and superficial digital flexors were very similar architecturally, with the exception of the small finger flexor digitorum superficialis, which was much smaller and shorter than the rest of the digital flexors. The brachioradialis and the pronator teres had dramatically different architectural properties. While the masses of the two muscles were nearly identical, the muscles had significantly different predicted contractile properties based on their different fiber arrangement. The brachioradialis, with its long fibers arranged at a small pennation angle, had a physiologic cross-sectional area that was only one third that of the pronator teres, with its short fibers that were more highly pennated. Using these architectural data and the statistical method of discriminant analysis, we provide additional information that might be useful in the selection of potential donor muscles to restore thumb flexion, thumb extension, finger extension, and finger flexion.

Arm↗