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Biomedical subjects

D Woodard

Publications and source records attributed to D Woodard.

At least 19 recordsLinked to original sources
PubMed1994

Monitoring furosemide in racehorses participating in an EIPH program.

Analytical procedures were developed to monitor furosemide concentrations in post-race serum and urine samples obtained from horses participating in an exercise-induced pulmonary haemorrhage (EIPH) program. High performance liquid chromatography with ultraviolet light detection proved a reliable, sensitive method for measuring urinary furosemide concentrations up to 12 h after administration of either 150 or 250 mg of the drug to race horses. However, this method was unreliable for determination of serum furosemide concentration. High performance liquid chromatography with fluorescence detection proved a reliable, sensitive method for measuring serum furosemide concentration in horses administered 250 mg of the diuretic, permitting detection of approximately 5-10 ng/ml 6 h after treatment. This method was applied to field conditions where furosemide was administered to horses (between 150 and 250 mg intravenously) 4 h prior to the race. Analytical results assisted in establishing a threshold concentration of 85 ng/ml for serum furosemide. It was found that serum furosemide concentrations are a valid measure of compliance with furosemide administration in the EIPH program.

Animals↗
PubMed1994

Phenytoin for motion sickness: clinical evaluation.

Phenytoin has previously been shown to protect against motion sickness induced by Coriolis stimulation. The purpose of our series of investigations was to investigate further the efficacy of phenytoin for motion sickness prophylaxis and to gain insight into its mechanism of action. We tested participants with electronystagmography, off-vertical rotation, sea travel, and parabolic flight after they received phenytoin or placebo. Blood levels of at least 9 micrograms/mL were found to protect against motion sickness. Electronystagmography showed significant decreases in the gain of the vestibuloocular reflex in participants receiving phenytoin. Few side effects were seen with drug levels in the 9 to 15 micrograms/mL range. Phenytoin is an effective motion sickness countermeasure that may exert its effect through a combination of central nervous system and peripheral vestibular effects.

Adult↗
PubMed1993

Mapping of electrical muscle stimulation using MRI.

The purpose of this study was to map the pattern of muscle contractile activity elicited by electromyostimulation (EMS). A secondary interest was to determine whether EMS evoked a different pattern of contractile activity than voluntary (VOL) efforts. These objectives were addressed by examining the pattern and extent of contrast shift in magnetic resonance (MR) images after isometric actions of the left m. quadriceps of seven subjects had been elicited by EMS (1-s train of 500-microseconds sine wave pulses at 50 Hz) or by VOL means. For both conditions, five sets of 10 muscle actions were executed at each of the three force levels equal to 25, 50, and 75% of maximal VOL isometric torque. There were 1-s, 1.5-min, and 30-min rests between muscle actions, sets, and torque levels, respectively. Transaxial proton MR images (TR/TE = 2,000/30, 60) of m. quadriceps femoris were obtained with a 1.5-T imager at rest and after completion of the five sets of isometric actions at each force level. MR image contrast shift, as indicated by T2 values > 1 SD above the mean resting muscle T2, was calculated per pixel. Torque declined approximately 18% (P < 0.05) during each EMS set independent of the preset relative force level but recovered between sets. EMS increased T2 values above rest (29 +/- 0.2 to 36 +/- 0.5, P < 0.05) in regions of muscle dispersed throughout a given cross section. The pattern of muscle stimulation, as reflected by increased T2 values, varied markedly among subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Short latency vestibular evoked potentials.

Auditory responses, including the well-characterized auditory brainstem response, have been used extensively in clinical investigations. Evoked responses have not been adequately developed to investigate the vestibular system. The purpose of this study is to describe a new method for the evaluation of short-latency vestibular evoked potentials in human subjects. Standard ABR equipment is used, with a customized solid-state modification of the triggering mechanism. Signal averaging is used to record responses to multiple linear decelerations. Results indicate the presence of a short-latency wave, which is absent in vestibular-deficient subjects. The literature is reviewed and illustrative cases are presented. We believe vestibular evoked potentials are a promising new modality in investigation of vestibular physiology.

Evoked Potentials, Auditory↗
PubMed1993

Phenytoin as a countermeasure for motion sickness in NASA maritime operations.

Seasickness is the most prevalent form of motion sickness and is an operational problem during Space Shuttle Solid-fueled Rocket Booster (SRB) retrieval. Phenytoin has been shown to protect against motion sickness induced by Coriolis stress. We exposed SRB recovery personnel to off-vertical rotation and sea motion after phenytoin or placebo. Phenytoin blood levels of at least 9 micrograms/ml were protective against motion sickness at sea. No change in susceptibility to nitrogen narcosis was seen in divers in chamber tests at 460 KPa. Phenytoin was used during performance of critical and hazardous tasks during training and actual SRB recovery operations. Phenytoin is an effective operational countermeasure for motion sickness for selected SRB crewmembers.

Adult↗
PubMed1992

Solid-phase extraction techniques for the determination of glycopyrrolate from equine urine by liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry.

Glycopyrrolate (Robinul) is a quaternary ammonium salt which serves as a respiratory enhancing drug. It is reportedly used in horse racing to improve breathing. Extraction of glycopyrrolate from equine urine employing unique solid-phase extraction techniques gave a residue suitable for liquid chromatography-tandem mass spectrometry (LC-MS-MS) and gas chromatography-mass spectrometry (GC-MS). LC-MS-MS analysis employed an extract derived from 5 ml of urine subjected to cation-exchange chromatography. The daughter ion of m/z 318 monitored in the positive-ion mode was m/z 116. Recovery of glycopyrrolate was 99.5% and the within-run coefficient of variation of two quality control samples (1.0 and 10 ng/ml) was less than 5%. The between-run coefficient of variation for the same two quality control samples was less than 6.5%. The minimal detectable concentration for the assay was 250 pg/ml. Due to the extremely low concentration of glycopyrrolate in urine, qualitative detection via full-scan GC-MS required XAD-2 extraction of 50 ml of urine, cation-exchange chromatography clean-up and a tandem hydrolysis-derivatization procedure. The target analyte for GC-MS qualitative analysis was the methyl ester of hydrolyzed glycopyrrolate. Glycopyrrolate could be detected in post-administration (1 mg intravenously) urine samples for up to 9 h by both LC-MS-MS and GC-MS. The success of the method was due to a combination of the extreme sensitivity of the LC-MS-MS method and the very selective extraction process for quaternary ammonium salts.

Animals↗
PubMed1992

Emergency medical operations at Kennedy Space Center in support of space shuttle.

The unique environment of the Kennedy Space Center includes a wide variety of industrial processes culminating in launch and spaceflight. Many are potentially hazardous to the work force and the astronauts. Technology, planning, training, and quality control are utilized to prevent contingencies and expedite response should a contingency occur.

Aerospace Medicine↗
PubMed1989

Renal necrosis and the involvement of a single enzyme of the de novo pathway for the biosynthesis of platelet-activating factor in the rat kidney inner medulla.

2-Bromoethylamine hydrobromide (BEA), when administered to rats, induces a highly specific papillary necrosis associated with the inner medulla. PAF levels in the blood were lowered by 50% and of the three enzymes that comprise the de novo route for PAF in the cortex/medulla, only the cholinephosphotransferase activity in the inner medulla microsomes was reduced (33%) by the BEA treatment. Moreover, BEA did not affect phosphatidylcholine synthesis in either the cortex or inner medulla. Our studies indicate that the de novo pathway for PAF synthesis in the renal inner medulla is responsible for the secretion of newly formed PAF into the blood stream and that a single enzyme in the de novo route accounts for the decreased rate of PAF synthesis during the development of renal necrosis.

Animals↗
PubMed1987

Provisional assignment of the gene for uridine monophosphatase-2 (Umph-2) to mouse chromosome 11.

The segregation of the mouse gene for uridine monophosphatase-2 (Umph-2) was examined in 14 independent mouse-Syrian hamster hybrids and 10 hybrid subclones. Umph-2 cosegregated with the mouse galactokinase (Glk) gene in 23 of the 24 hybrids and showed at least four discordances with all other mouse marker isozymes examined. The observed synteny of Umph-2 and Glk, which has also been observed in humans, indicates that the mouse Umph-2 gene is on chromosome 11.

Animals↗
PubMed1987

Effects of a visual-vestibular stimulus on the vestibulo-ocular reflex.

Exposure before flight to an environment that provides altered visual-vestibular relationships similar to those seen in weightlessness might facilitate adaptation to spaceflight. Fifteen normal subjects were exposed for 0, 5, and 20 min to an abnormal visual-vestibular environment in which the vestibular sensation of lateral tilt was associated with the visual impression of lateral translation. Lateral eye movement elicited by similar tilt in darkness was measured before and at intervals after the exposure. Of the 15 subjects, 12 showed increased VOR amplitude following the exposure, but this increase appeared unrelated to the duration of exposure to the visual stimulus and may be an effect of the VOR measurement procedure. Most subjects showed little shift in the phase relationship between tilt and eye motion. Three subjects showed changes in VOR and five reported changes in perception of motion which appear clearly related to the visual-vestibular exposure.

Adaptation, Physiological↗
PubMed1986

Anabolic steroids as a countermeasure against bone demineralization during space flight.

A progressive loss of bone mass is consistently reported in humans exposed to weightlessness during space flight. The mechanism of this metabolic alteration is unknown but may be due in part to the effects of disuse osteoporosis along with the influence of elevated corticosteroid levels. With a goal toward mankind's permanent presence in space, effective countermeasures against bone demineralization will be required. Synthetic anabolic steroids have been shown to prevent bone loss in ground-based immobilization studies and in excess corticosteroid states. These agents may offer a means of slowing or preventing bone loss thus facilitating long term space habitation.

Anabolic Agents↗
PubMed1981

Clinical experience in the diagnosis and treatment of infections in the compromised host.

A number of disorders of host resistance to infections occur in cancer patients. Defects in granulocytes, complement synthesis and antibody formation, cellular immunity, and mucocutaneous boundaries are discussed. Most infections in these compromised patients are caused by a few gram-negative rods and gram-positive cocci, although other bacteria, opportunistic fungi, intracellular parasites, and DNA viruses also cause severe disease. Cefotaxime was found to be an effective antimicrobial in the treatment of 40 cancer patients with infections of the urinary or lower respiratory tracts, bacteremia, soft-tissue infections, and fever of undetermined origin. Cefotaxime in combination with ticarcillin or an aminoglycoside may improve response in infections due to opportunistic organisms such as Pseudomonas.

Animals↗