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Biomedical subjects

J T Watson

Publications and source records attributed to J T Watson.

At least 163 records · Page 9Linked to original sources
PubMed1973

Effects of a false neurotransmitter, p-hydroxynorephedrine, on the function of adrenergic neurons in hypertensive patients.

Previous studies have shown that amphetamine and p-hydroxyamphetamine impair adrenergic transmission, and it has been suggested that this effect is mediated by an active metabolite, p-hydroxynorephedrine (PHN). Studies in experimental animals have shown that PHN can deplete and substitute for norepinephrine (NE) in the transmitter pool, thus meeting the criteria of a false neurotransmitter. The pharmacologic effects of PHN on adrenergic function and NE synthesis were studied in eight hypertensive patients and compared with placebo. Mean erect and supine blood pressure (BP) decreased 22/14 and 9/6 mm Hg, respectively, during PHN 600 mg daily. The post-Valsalva diastolic overshoot was abolished. The pressor sensitivity to tyramine decreased whereas the pressor response to NE was enhanced. A mild natriuresis occurred. The 24 h urinary excretion of catecholamines and catecholamine metabolites during the administration of PHN compared with placebo changed as follows: vanillylmandelic acid (VMA), 42% decrease; NE. 42% decrease; normetanephrine (NM), 400% increase: metanephrine, unchanged; dopamine, 40% decrease; while homovanillic acid was unchanged. The sum of VMA, NE, and NM decreased 23%. The posttreatment urinary excretion of PHN was biexponential with first and second phase half-lives of 13 and 55 h. respectively. The time of the second phase closely approximated the recovery of the changes in BP and excretion of VMA. No effects of PHN on the central nervous system were observed. These studies show that PHN acts peripherally to interfere with adrenergic function and NE synthesis in hypertensive patients with a resultant decrease in BP.

Adult↗
PubMedDate not supplied

Charge derivatization of peptides for analysis by mass spectrometry.

The analysis of peptide derivatives by fast atom bombardment, liquid secondary-ionization mass spectrometry, plasma desorption, electrospray ionization, and matrix-assisted laser desorption/ionization is reviewed. The fragmentation patterns of peptides and of charge-derivatized peptides are compared, and the proposed fragment ion structures are summarized. A variety of derivatization approaches and the distinguishing features of mass spectra produced from these derivatives are described. The most promising derivatization approaches are evaluated, and the strengths and limitations of these approaches are discussed.

Amino Acid Sequence↗
PubMedDate not supplied

Combined intracellular stimulation and high speed video motion analysis of motor control neurons in the cockroach.

A complete understanding of motor control circuitry requires detailed analysis of the behavior produced by the circuitry as well as the connections between individual neurons. A technique is described for combining high speed video motion analysis of leg movements in the cockroach with electrophysiological techniques such as intracellular stimulation/recording from central neurons and EMG recording from leg muscles. Using a restrained preparation, we have quantified leg movements evoked by intracellular stimulation of individual motor neurons and local interneurons. By incorporating motion analysis into the recording paradigm, the transfer functions from electrical activity to movements can be derived. Because distinct and characteristic responses to single and multiple action potentials are seen in slow, intermediate, and fast motor neurons, it is often possible to identify the motor neuron targets of local interneurons. The ability to analyze movement in any plane is especially useful in situations such as blind neuropilar penetrations, where a more restricted motion transducer arrangement may not be in register with the impaled cell. In addition, it is possible to record and analyze such complex phenomena as coordinated movements in multiple joints produced by local interneurons and reflexes produced by proprioceptive feedback due to activity of one motor neuron.

Animals↗
PubMedDate not supplied

Orthopedic implants: a guide to radiographic analysis.

Orthopedic technology is growing at a rapid rate. New implants reflect this technology whether it pertains to fracture fixation, joint replacement, spine stabilization, or soft-tissue reconstruction. This monograph is designed to assist both the radiologist and the orthopedist in accurately assessing plain radiographs of commonly used orthopedic implants. We discuss the biologic response of the surrounding bone to these devices; herein lies the key to understanding the radiographic presentation of these devices.

Arthritis↗
PubMedDate not supplied

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation.

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Clinical Trials as Topic↗
PubMedDate not supplied

Ultrasound for the early diagnosis of tibial fracture healing after static interlocked nailing without reaming: clinical results.

OBJECTIVE: Based on the results of a pilot study indicating the potential value of ultrasound (US) as a diagnostic tool for the early assessment of fracture healing and the related need for secondary operative procedures in patients treated by statically locked intramedullary (IM) nailing without reaming, a protocol was established for a larger scale prospective trial. The purpose of this study was to evaluate the outcome of this follow-up trial. DESIGN/METHODS: All skeletally mature patients admitted to the Henry Ford Hospital (Detroit, Michigan) from January 1993 to August 1994 who had sustained an acute fracture of the tibial shaft and who were treated by statically locked IM nailing, without reaming, were candidates for study. Forty-seven patients with fifty fractures that could be evaluated by US were included. The adopted determinants for fracture healing were complete disappearance of the IM nail on US examination performed at six weeks postoperatively, or progressive disappearance of the nail noted between the initial six-week study and a second nine-week US examination, both in conjunction with periosteal callus formation. Radiographs were obtained to monitor maintenance of reduction and to further evaluate fracture healing. RESULTS: Of thirty-eight fractures with a positive US (thirty-two at six weeks, six at nine weeks), thirty-seven healed uneventfully, a positive predictive value of 97 percent. Radiographic fracture healing was not evident until, on average, nineteen weeks after injury. The single false-positive fracture progressed to nonunion. Of the twelve fractures with negative US studies, ten underwent secondary procedures (nine dynamization, one bone graft), with four progressing to nonunion. Two patients refused secondary surgery; screw failure occurred in both. Otherwise, there were no hardware failures in this series. CONCLUSIONS: The results of this study indicate that US may provide important prognostic information concerning fracture healing after unreamed tibial nailing, upon which subsequent treatment can be based.

Adolescent↗