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Biomedical subjects

R Johnson

Publications and source records attributed to R Johnson.

At least 433 records · Page 24Linked to original sources
PubMed1988

An implantable bone conduction hearing device.

A new implantable hearing device that transmits an acoustical signal from an external electromagnetic coil to a small magnet implanted in the temporal bone has been developed and implanted in more than 350 patients. Animal research indicates that the device serves as a high-fidelity sound source throughout the audio range. Especially notable is its high-frequency performance. Human experiments using a body processor indicate that the device compares favorably with conventional bone conduction hearing aids, and patients report excellent sound quality as well as improved ability to understand conversational speech. Further development has resulted in an at-the-ear (ATE) processor. Extensive testing of the ATE unit has revealed that current models provide approximately 10 dB less output than the body processors. Further research and development are continuing to address the need for increased power output from the ATE processor and to eliminate other minor problems.

Adult↗
PubMed1988

Upper gastrointestinal endoscopy after cardiac transplantation.

Three hundred four patients have undergone cardiac transplantation at the University of Pittsburgh since 1980. Twenty patients have required 27 upper gastrointestinal (GI) endoscopic procedures. After heart transplantation the primary indications for endoscopy were epigastric pain (six patients with gastritis, one with multiple shallow gastric ulcers, and one with normal test results), mild upper GI bleeding (four patients with esophagitis, two with gastritis, and two with multiple shallow gastric ulcers), dysphagia and odynophagia (two patients with esophagitis), persistent nausea and vomiting (one with normal test results), lower GI bleeding (one with normal test results), and routine follow-up (one with normal test results). After heart-lung transplantation the primary indications for the endoscopy were massive upper GI bleeding (three patients with actively bleeding duodenal ulcers), dysphagia and odynophagia (one patient with esophagitis), mild upper GI bleeding (one patient with gastritis), and routine follow-up (one patient with normal test results). No complications resulted from endoscopy. The procedures were performed in the GI suite without cardiac monitoring. Prophylactic antibiotics were not routinely administered. No patient had a fungal infection of the upper GI tract--a finding attributed to the prophylactic use of nystatin in all patients. Opportunistic viral infections were identified histologically in six patients, including two patients with actively bleeding duodenal ulcers. The possibility of opportunistic viral infections in this immunosuppressed group required aggressive diagnostic techniques, including endoscopy and biopsy, which can be safely performed after cardiac transplantation.

Adult↗
PubMed1987

Counting the people disabled by head injury.

Figures for the incidence of head injury are frequently cited but there has been no accurate estimate and the number of individuals left with persistent disability is not exactly known. This study identified all those admitted to hospital with a diagnosis of head injury, in a known population. In 1 year there were 160 survivors of head injury per 100,000 of population. Rates of disability of 0.38 per 100,000 in need of care and 0.75 per 100,000 unemployable and primarily in need of occupation, were found, excluding those over 65 years old.

Adolescent↗
PubMed1987

A novel spinal cord slice preparation from the rat.

A spinal cord slice preparation is described. The lumbar enlargement of weanling rats is exposed by laminectomy, the dorsal and ventral roots cut and a portion of cord consisting of about 4 segments removed and chilled to 3 degrees C. A modified tissue chopper is used to produce 400 micron dorsoventral longitudinal slices. The slices are maintained in a low-volume, continuously perfused tissue chamber at the interface between warm moist 95% O2/5% CO2 and oxygenated artificial cerebrospinal fluid, and remain viable for over 8 h. An extracellular recording of excitatory amino acid-induced activity of a dorsal horn lamina IV cell is shown. Excitatory amino acid antagonists applied iontophoretically and in the perfusate have actions similar to those in the adult spinal cord in vivo. This in vitro preparation of the cord has permitted stable extracellular recordings from single cells of 2 h or more, and has the potential for intracellular investigation of spinal cord neurones.

Amino Acids↗
PubMed1987

Wound-inducible expression of a potato inhibitor II-chloramphenicol acetyltransferase gene fusion in transgenic tobacco plants.

A potato inhibitor II gene (IIK) was isolated from a library of potato genes in lambda bacteriophage. An 8-kilobase-pair (kbp) insert was identified using a tomato inhibitor II cDNA as a hybridization probe, and a 2.6-kbp fragment containing the gene was subcloned into the plasmid pUC13 and characterized. The nucleotide sequence of the isolated gene exhibited 87% identity with the wound-inducible tomato inhibitor II cDNA sequence. The amino acid sequence of inhibitor IIK, deduced from the potato gene, exhibited 84% identity with the tomato inhibitor II protein. A 1000-bp restriction fragment from the 5' flanking region of the gene was fused to the open reading frame of the chloramphenicol acetyltransferase (CAT) gene. This fusion was terminated in two ways: (i) with a terminator sequence from the potato inhibitor II gene and (ii) with a terminator from the 6b gene of Ti plasmid pTiA6. These chimeric genes were transferred into tobacco cells via a binary Ti vector system, and transgenic plants were regenerated. The CAT gene was expressed in leaves of transformed plants in response to wounding when fused with the inhibitor IIK promoter and terminator regions. The chimeric gene containing the 6b terminator did not express CAT in response to wounding. The wound-inducible expression of CAT activity was systemic and was induced in tissues distal to the wounded tissues. The time course of wound induction of CAT activity in transgenic tobacco leaves is similar to that found for wound-inducible inhibitor I and II mRNAs in tomato leaves. These results demonstrate that sequences necessary and sufficient for wound inducibility are present within approximately 1000 bp of the control regions of the inhibitor IIK genes and that wound-inducible components of tobacco leaf cells can regulate these sequences.

Journal Article↗
PubMed1987

A metabolic comparison of a pure long-chain triglyceride lipid emulsion (LCT) and various medium-chain triglyceride (MCT)-LCT combination emulsions in dogs.

Two 20% lipid emulsions containing mixtures of long-(LCT) and medium-chain triglycerides (MCT) were compared with a 20% LCT lipid emulsion. Beagles were infused with emulsions containing either 100% LCT, 75% LCT-25% MCT, or 50% LCT-50% MCT. The emulsions were part of a total parenteral nutrition (TPN) regimen that included 10% dextrose and 5.5% amino acids. Basic nutritional parameters as well as elimination kinetics were monitored. Plasma linoleic acid, ketone, lactate, pyruvate, insulin, glucose, and carnitine were analyzed. The 75% LCT-25% MCT emulsion offers little advantage over 100% LCT as a metabolic substrate. The 50% LCT-50% MCT combination proved to be a potentially better caloric source due to rapid elimination kinetics, increased ketone production, lack of deposition, and no interference with linoleic acid metabolism.

Animals↗
PubMed1987

Serum fructosamine as a screening method for diabetes mellitus in patients with suspected acute myocardial infarction.

It is important to identify diabetic patients in a coronary care population because they have a higher risk of suffering congestive heart failure, dysrhythmias and death following myocardial infarction. In order to determine the most efficient screening method for diabetes, we compared fructosamine and glucose measurements on admission blood specimens from 256 consecutive patients. Of 15 (5.9%) known diabetic patients, 12 had glucose results greater than or equal to 7.8 mmol/l and nine had fructosamine levels greater than 2.87 mmol/l. However, elevated glucose results were also found in a high proportion (49.2%) of patients with no previous history of diabetes. We performed glucose tolerance tests in 107 patients after discharge to determine the frequency of false-positive observations. Fructosamine yielded five (4.6%) false-positive results, whereas plasma glucose yielded 47 (43.9%) false-positive observations. We conclude that serum fructosamine provides a more specific screening method for diabetes in this population because the results are unaffected by stress hyperglycemia.

Adult↗
PubMed1987

Return to work after severe head injury.

This paper reports attempts of a series of head-injured people to regain employment. Return to work after a severe head injury is generally considered to be a function of age, severity of injury, and nature of disability. The results showed that it was the opportunity to go back to the previous job, the provision of a work trial or easier work, and a lengthy period of support that were the more important factors. This demonstrates the importance of working to provide an environment that will help the individual learn to make adaptations and accommodate his or her disabilities.

Adult↗