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Biomedical subjects

R W Powell

Publications and source records attributed to R W Powell.

At least 73 records · Page 4Linked to original sources
PubMed1978

Modified technique for radical transmediastinal forequarter amputation and chest wall resection.

Forequarter or interscapulothoracic amputation is a major surgical procedure indicated primarily in the treatment of malignant lesions involving the bony and soft tissue parieties of the upper part of the arm, shoulder, and scapula. It is also indicated in extensive trauma with irreparable damage to the shoulder area and as a palliative measure in intractable pain caused by incurable tumors of the shoulder girdle. Several operative techniques have been described: the classical Berger approach, an anterior pectoral approach, and posterior retroscapular approaches. A radical transthoracic approach has been described in cases in which the tumor had spread through the chest wall. The two main goals of these approaches have been early ligation of the subclavian vessels and immediate exploration for operability. This report details our experience with a modified technique for radical forequarter amputation and chest wall resection in which a transmediastinal approach is employed. This approach was used in two patients: One had a radiation-induced fibrosarcoma of the left axilla and adjacent chest wall following a radical mastectomy 19 years earlier, and the other patient had a recurrent rhabdomyosarcoma of the right axilla with invasion of the chest wall. This technique avoids time-consuming and individual excision of ribs and minimizes the amount of blood loss by early ligation of the internal mammary vessels. Safe and excellent exposure and division of the subclavian vessels and early exploration for mediastinal and intrathoracic involvement are made possible. Details of the procedure with illustrations are described.

Amputation, Surgical↗
PubMed1977

Paget disease of the male breast.

Twenty-two fully documented cases of Paget disease of the male breast are reviewed, and an additional patient is reported. The most common initial symptom was ulceration and excoriation, while a breast mass was palpable in the majority of patients. Nipple changes were surprisingly rare, in contrast to the female. The prognosis of the disease in the male appears to be worse than in the female, with the Paget carcinoma carrying a worse prognosis than the "ordinary" male breast cancer. The subareolar location and the meager volume of tissue interposed between the tumor and chest wall may be an important factor in this regard. Nipple changes or symptoms (ulceration, discharge, enlargement) are mroe apt to be due to cancer in the male than in the female. Therefore, prompt diagnosis is mandatory.

Adult↗
PubMed1976

Peritoneal lavage in children with blunt abdominal trauma.

Quantitative peritoneal lavage was performed in 52 children with blunt abdominal trauma to determine the presence of intraabdominal injuries. A strongly positive lavage was 100% accurate in diagnosing an intraabdominal injury requiring operation. A negative lavage demonstrated absence of a significant intraperitoneal injury with 100% accuracy. A weakly positive lavage was not diagnostic and required additional evaluation including intravenous pyelography echography, and arteriography. Diagnosis and treatment was prompt, and in 20 of 21 cases, operation was performed within 4 hr. Peritoneal lavage was found to be safe and much more accurate than physical examination in diagnosing significant intraabdominal injury.

Abdominal Injuries↗
PubMed1976

Inflammatory carcinoma of the breast: A correlation of clinical, radiologic and pathogic findings.

In a study of 75 patients with inflammatory carcinoma of the breast seen at Emory University Clinic over a 38 year period, the average longevity from the time of diagnosis was 22 months and the 5-year survival 5.6%. The results of treatment were poor with all methods used, although supervoltage therapy improved local control, and when followed by mastectomy, gave the longest average local control and survival. The designation of inflammatory carcinoma as primary and secondary is often not applicable and should be dropped. Instead, the terms inflammatory carcinoma and recurrent inflammatory carcinoma seem more appropriate. It is suggested that in a number of patients fulfilling certain criteria, surgery should be contemplated and all others treated by non-surgical means. The diagnosis of inflammatory cancer is still primarily clinical. However, radiologic and pathology examination are invaluable to confirming the clinical impression and occasionally suggest the diagnosis before inflammatory signs appear.

Adult↗
PubMed1976

Responding under positive and negative response contingencies in pigeons and crows.

Four crows were trained to key peck for food. Then, they were exposed to a positive response contingency that required them to peck the key when it was illuminated briefly (the trial) in order to receive food. This procedure resulted in consistent within-trial pecking. When the contingency changed so that food was presented at the end of a trial when no response occurred, but the trial terminated immediately and food was omitted when a response occurred (negative response contingency), responding decreased markedly. Eight pigeons were studied under the same change in contingencies. These birds varied in their response histories from naive to having several years' experience. The previously naive pigeons also showed rapid declines in responding under the negative contingency; the responding of the birds with extended training histories declined much more slowly. Eventually, however, six of the eight pigeons showed little or no responding under the negative contingency, while they responded consistently when re-exposed to the positive contingency. These findings question the power and the generality of the negative automaintenance phenomenon.

Journal Article↗
PubMed1976

DELRO update.

Explore the source record for details and available documents.

Delaware↗
PubMed1975

A method for the objective study of tool-using behavior.

Key pecking for food was shaped in four crows within a conventional operant-conditioning test chamber. When pecking stabilized, a metal screen with openings 2.5 cm high by 1.0 cm wide, was placed over the response key, so that the crow could still see but could no longer peck the key. At the same time, several dozen wooden matchsticks, which could be used to operate the key, were placed in the test chamber. The crows made no use of these during 50 to 75 hr of exposure to this condition. Subsequently, the behavior of two crows was shaped so that they approached the matchsticks, picked one up in their beaks, approached the response key with the matchstick in their beak, and finally operated the response key by poking the matchstick through the screen. This shaping procedure was ineffective with the two other crows. However, these birds were successfully trained through positional fading of the tool. This involved suspending a metal rod from the ceiling so that it hung directly in front of the response key, and the crow had only to peck it to operate the key. Then, the rod was gradually lowered by lengthening its tether until it eventually rested on the floor of the test chamber. The principal advantage of this methodology is the automatic recording of the terminal (tool-using) behavior under study.

Journal Article↗
PubMed1973

Effects of stimulus control and deprivation upon discriminative responding.

Discriminative responding in pigeons was studied under multiple variable-interval extinction schedules in which extinction was correlated with either a tone or a white keylight. The two procedures resulted in weak and strong stimulus control, respectively. In the first experiment, there was no interaction between schedule components when stimulus control was strong and reinforcement was omitted under the previously reinforced component. However, there was marked induction between components when stimulus control was weak and responding was extinguished under the previously reinforced component. In the second experiment, hours of food deprivation was varied under two levels of stimulus control. Deprivation mainly influenced response rates under the extinction stimulus, with greater absolute rate increases occurring the lower the existing level of stimulus control. Increases in responding during the extinction stimulus were four times as great from 24 to 72 hours of deprivation as from 24 to 48 hours under conditions of both high and low stimulus control.

Acoustic Stimulation↗
PubMed1971

Some effects of punishment shock intensity upon discriminative responding.

Three pigeons received visual discrimination training under both multiple variable-ratio extinction and variable-interval extinction schedules. All birds developed nearly perfect discrimination. When punishment for every tenth response during food reinforcement was presented, responding decreased as shock intensity increased. At the same time, responding during extinction, which was not punished, increased at intermediate punishment intensities, but returned to low levels under severe punishment. A second procedure, in which punishment and no-punishment sessions alternated unsystematically, was employed with two of the birds. The results under this procedure essentially replicated the data obtained as punishment shock intensity increased gradually.

Animals↗
PubMed1971

Evidence of interaction between deprivation effects and stimulus control.

Discriminative responding in pigeons was studied under multiple variable-interval extinction and variable-ratio extinction schedules, as deprivation was varied. Generally, the greater the accuracy of discrimination that developed during training, the smaller the effect of deprivation upon subsequent performance. This was true both in terms of changes in response rates, and in the relationship between response rates during food reinforcement and extinction. When discrimination was inaccurate, increases in deprivation resulted in disproportionate increases in responding during extinction, as compared to increases during food reinforcement components of the schedule. The results suggest that as stimulus control (accuracy) of responding increases, discriminative performance becomes less and less susceptible to influence by deprivation.

Acoustic Stimulation↗