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Biomedical subjects

E W Johnson

Publications and source records attributed to E W Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1989

Regulation of subtypes of beta-adrenergic receptors in rat brain following treatment with 6-hydroxydopamine.

The technique of quantitative autoradiography has been used to localize changes in the densities of subtypes of beta-adrenergic receptors in rat brain following treatment with 6-hydroxydopamine. Previously reported increases in the density of beta 1-adrenergic receptors in the cerebral cortex were confirmed. The anatomical resolution of autoradiography made it possible to detect changes in the density of beta 2-adrenergic receptors in the cortex and in a number of other brain regions. The density of beta 1-adrenergic receptors increased from 30 to 50% depending on the region of the cortex being examined. The increase in the somatomotor cortex was greater than that in the frontal or occipital cortex. The increase in the density of beta 2-adrenergic receptors in the cortex was not as widespread as that of beta 1-adrenergic receptors and occurred primarily in frontal cortex, where the density of receptors increased by 40%. The densities of both beta 1- and beta 2-adrenergic receptors increased in a number of forebrain, thalamic, and midbrain structures. Selective changes in the density of beta 1-adrenergic receptors were observed in the superficial gray layer of the superior colliculus and in the amygdala. The density of beta 2-adrenergic receptors increased in the caudate-putamen, the substantia nigra, and the lateral and central nuclei of the thalamus, whereas the density of beta 1-adrenergic receptors did not change in these regions. The densities of both subtypes of beta-adrenergic receptors increased in the hippocampus, the cerebellum, the lateral posterior nucleus of the thalamus, and the dorsal lateral geniculate.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic beta-Antagonists↗
PubMed1989

Monopolar needle stimulation: safety considerations.

Stimulation of nerves for conduction studies can be performed with a monopolar needle used routinely for electromyographic studies. Although invasive, this technique allows precise localization of stimulation and access to deeply situated nerve trunks, thus providing otherwise unobtainable information regarding peripheral nerve function. The electric current at the needle tip was measured during supramaximal stimulation of the median and peroneal nerves at distal and proximal sites. After measuring the area of uninsulated needle tip, the local current density was calculated. The maximum current during the stimulation of 0.05msec duration was 0.80mA and the resulting current density was 4.1mA/mm2. It is calculated that this current could cause a local maximum temperature rise of 2.5C in the tissue within 0.5mm of the needle tip. This current flow would not be expected to cause either direct electric or heat damage to the tissue.

Electrodiagnosis↗
PubMed1988

ACTH receptor-mediated induction of leukocyte cyclic AMP.

Studies were conducted to determine whether lymphocyte ACTH receptors behave as their structurally similar adrenal cell counterparts, in terms of adenylate cyclase activation and cyclic AMP (cAMP) production in the presence of ACTH. Treatment of mouse mononuclear splenocytes with ACTH (10(-5) to 10(-10) M) induced a consistent rise in cAMP. ACTH treatment of more homogenous cell populations, represented by Molt 4 T lymphoblast and S49A T cell lymphoma lines, yielded a dramatic, dose-related increase in cAMP levels for S49A cells but not for Molt 4 cells. Immunofluorescence assays, employing an antiserum to the adrenal cell ACTH receptor, indicated that 45% of splenocytes, 69% of S49A cells, and less than 1% of Molt 4 cells possess ACTH receptors. Radioligand binding studies confirmed that Molt 4 cells possess many fewer receptors than S49A cells, and probably fail to respond to ACTH because they lack the appropriate receptor. This is the first report of ACTH induction of leukocyte cAMP, evidence important to understanding the mechanisms by which this neuroendocrine hormone influences immune responses.

Adenylyl Cyclases↗
PubMed1988

Determining neurapraxia in carpal tunnel syndrome.

In the evaluation of carpal tunnel syndrome by nerve conduction testing it is desirable to produce prognostic as well as diagnostic information. The finding of conduction block, or neurapraxia, is regarded as evidence that treatment can result in prompt recovery of nerve function. A technique is presented for stimulating the motor branch of the median nerve in the palm in order to detect the degree of neurapraxia due to entrapment in the carpus. In 23 normal subjects the response after palmar stimulation compared to a wrist stimulation site had a mean increase in amplitude of 0.56 mV. Persons affected with carpal tunnel syndrome had a mean amplitude increase of 2.2 mV demonstrating partial conduction block. The difference between these two values is statistically significant (P = 0.001). The routine use of this method is recommended both for more accurate diagnosis and for evaluation of the degree of neurapraxia.

Action Potentials↗
PubMed1988

Struggle for identity: the turbulent 1960s.

I. STRUGGLE FOR IDENTITY. The controversy about the name of the Academy surfaced again soon after the 3rd International Congress in Washington in 1960. Watkins reemphasized the need to pronounce it "phys-i-a'trist" and suggested that we be called the American Academy of Physiatrics. Krusen responded by suggesting that the name, American Academy of Physical Medicine & Rehabilitation should be retained since the rest of the world wouldn't recognize us. He pointed out that he had just surveyed 40 countries in the developing phase of physical medicine and rehabilitation, and would not want to confuse the issue. Clearly the field of PM&R will be defined by those who practice the specialty. II. LEGISLATION. The legislation initiating Medicare was extraordinarily influential in redefining the specialty. The legislation creating the Office of Vocational Rehabilitation and the subsequent funding of rehabilitation research and training centers engendered an increased awareness in the academic community of the need for rehabilitation medicine. III. CHANGES IN EDUCATION. The Academy gradually increased in number of members, and began to influence the training of residents with the development of a Resident Guide. Many of the senior members of the Academy re-emphasized the need for research to expand new knowledge and all generated a plea for more academic physiatrists. The R&T centers did provide a mechanism to increase the residency training. The role of the physiatrist in the medical school was defined and promoted in colleague with other specialties.(ABSTRACT TRUNCATED AT 250 WORDS)

History, 20th Century↗
PubMed1988

Wrist ratio correlation with carpal tunnel syndrome in industry.

Employees from a large midwestern automobile manufacturing plant completed a preemployment evaluation which included a personal and family history, physical examination, and wrist ratio determinations obtained by dividing the anteroposterior diameter by the mediolateral diameter of the wrist. Over a 3-year period, 80 of these employees who developed symptoms compatible with carpal tunnel syndrome within 4-12 months of employment were entered into the study and were evaluated with standard electrodiagnostic techniques. The symptoms included nocturnal hand pain, paresthesia and weak grasp. Thirty-nine of the 80 employees had wrist ratios equal to or greater than 0.70. Twenty-four percent of the employees with wrist ratios less than 0.70 had abnormal electrodiagnostic studies compared with 74% of employees with wrist ratios greater than or equal to 0.70. Regression analysis performed on the data revealed a significant positive correlation between distal median motor latency and wrist ratio (P = 0.001). The study suggests the practical value of wrist ratio determination in job placement.

Adult↗
PubMed1988

History of the AAP.

Explore the source record for details and available documents.

History, 20th Century↗
PubMed1988

Bilateral obturator nerve injuries during urologic surgery.

Obturator nerve injury can result from prolonged acute hip flexion. Bilateral obturator nerve compromise developed in a patient as a result of prolonged urologic surgery. The clinical and electromyographic findings were consistent with this diagnosis. The nerve injury was believed to result from stretching at the bony obturator foramen. Management included a trial of steroids, gait training, and instruction on avoiding acute hp flexion. The clinical and EMG abnormalities disappeared. Awareness of this occurrence and an understanding of the anatomy may avoid confusion with other conditions and permit accurate diagnosis.

Adult↗
PubMed1987

Electrodiagnostic characteristics of acute carpal tunnel syndrome.

Carpal tunnel syndrome (CTS) exemplifies a cumulative trauma disorder which may occur in industrial settings. Occasionally, industrial workers develop CTS acutely over the course of a few days to a few weeks. We recently performed electrodiagnostic studies on 22 workers at a midwestern automobile manufacturing plant who developed symptoms compatible with CTS. All tests were within eight weeks of symptom onset; 70% were within four weeks. The acute syndrome was manifested by a conduction block of sensory, motor, or both fiber types beneath the carpal ligament. All patients received sensory studies; nine had motor studies as well. Sensory nerve latencies were not prolonged in proportion to the symptoms, which were short in comparison to the low amplitude sensory nerve action potential evoked proximal to the carpal ligament. Sensory nerve action potential amplitude at midpalm averaged 200% of the value obtained proximally. Because of short distance and residual latency, comparison of motor latencies proximal and distal to the carpal ligament was less helpful than the difference in amplitude of the evoked potentials. Amplitude of the distal response increased an average of 32%. Prompt identification of acute CTS was followed by a recommendation for job change which, along with conservative therapy, led to resolution of symptoms in 77% of patients. The diagnosis of acute CTS leading to avoidance of inciting activities is beneficial in the industrial setting.

Action Potentials↗
PubMed1987

Median and radial sensory latencies to digit I: normal values and usefulness in carpal tunnel syndrome.

Median and radial sensory latencies were recorded from digit I at a distance of 10cm in 78 neurologically healthy people aged 20 to 79 years. The mean median latency was 2.5 +/- 0.3ms, and mean radial latency was 2.4 +/- 0.2ms. Both were measured to the negative peak. Twenty individuals with carpal tunnel syndrome determined by traditional electrodiagnostic techniques had at least 1ms longer latency in median nerve than the median latency for the healthy control group. This technique is useful in diagnosis of carpal tunnel syndrome.

Adult↗
PubMed1986

Heparin inhibition of increased bacterial adherence following overdistension, ischemia and partial outlet obstruction of the rabbit urinary bladder.

While it is well established clinically that urinary tract infection in the presence of outflow obstruction may be associated with difficulty in eradicating bacteria, it is not clear whether this is secondary to the presence of residual urine volume or other local effects of the obstruction such as attenuation of the intrinsic antibacterial defense mechanisms of the mucosal surface. Experiments in our laboratory and others over the past several years have demonstrated that the primary antibacterial defense mechanism of the bladder is the antiadherence effect of the bladder surface mucin layer. Additional studies have shown that heparin can duplicate this antiadherence activity of bladder mucin. The present report demonstrates that one hour of overdistension or ischemia and one week of partial outlet obstruction cause a functional defect in the intrinsic antiadherence effect of the bladder mucosa as evidenced by increased bacterial adherence. This defect can be reversed by heparin exposure prior to bacterial challenge. These results indicate that partial outlet obstruction and its potential sequelae such as overdistension and, particularly, mucosal ischemia, have dramatic adverse effects on the intrinsic antiadherence defense mechanism of the bladder. These effects can be reversed by intravesical exposure to an exogenous anionic polyelectrolyte (heparin).

Animals↗
PubMed1986

Supracondylar fracture of the femur after total knee arthroplasty.

We reviewed the data on thirty-six supracondylar fractures of the femur (in thirty-four patients) that occurred after total knee arthroplasties that were done between April 1974 and December 1981. Patients who had osteoporosis, rheumatoid arthritis, one or more previous arthroplasties of the knee, or inadvertent breeching of the anterior aspect of the femoral cortex at operation appeared to be particularly at risk for a supracondylar femoral fracture. Malalignment of the component could not be implicated as a cause. Twenty-six fractures (in twenty-five patients) were treated by non-operative methods. Seventeen of them (65.4 per cent) healed and required no surgical treatment. Fourteen of the seventeen were followed for more than two years; they had no significant difference in the knee score and lost less than 10 degrees of motion. The nine remaining knees required revision of the arthroplasty because of non-union in four knees, malunion in two, loosening of the component in two, and extension lag in one. At an average of forty months after revision, the nine knees were rated as having one excellent, four good, three satisfactory, and one failed result. In contrast, only three of the five fractures that were treated by early open reduction and internal fixation had a satisfactory result, and one of them required a second bone-grafting procedure. One patient died perioperatively and another required an above-the-knee amputation because of sepsis. Of the three fractures that were initially treated by external fixation, one had an excellent and two had a good result at an average of forty-five months after fracture. We have found that supracondylar fractures that occur after total knee arthroplasty can be managed by either traction or application of a cast, or both, which usually results in healing of the fracture and a satisfactory outcome of the arthroplasty. Patients who have a poor arthroplasty result after non-operative treatment of the fracture usually can undergo a revision arthroplasty with the expectation of a satisfactory outcome. Operative treatment of the fracture should be reserved for patients who do not have osteopenia and in whom stable fixation can be achieved, for those who demand a highly functional arthroplasty, and for those in whom adequate closed reduction cannot be maintained.

Aged↗