Effect of postinjury intravenous or intrathecal methylprednisolone on spinal cord excitatory amino-acid release, nitric oxide generation, PGE2 synthesis, and myeloperoxidase content in a pig model of acute spinal cord injury.

STUDY DESIGN: Prospective, randomized, in vivo acute spinal cord injury in pigs. SETTING: Department of Anesthesiology, University of Washington, Seattle, WA, USA. OBJECTIVES: To determine whether postinjury methylprednisolone could reduce the generation of known mediators of secondary neurological injury. METHODS: Intrathecal microdialysis probes were used to sample cerebrospinal fluid (CSF) for measurement of PGE(2), glutamate, and citrulline (a byproduct of nitric oxide generation), before and after spinal cord injury in anesthetized pigs. The spinal cord was removed at the end of the study for measurement of myeloperoxidase and methylprednisolone concentrations. Animals were randomly allocated to receive intravenous methylprednisolone (30 mg/kg bolus then 3.4 mg/kg/h), intrathecal methylprednisolone (5 mg bolus then 5 mg/h), or saline, beginning 30 min after the spinal cord was injured by using a modification of the Allen weight drop technique. RESULTS: Spinal cord injury significantly increased the amount of glutamate, PGE(2), myeloperoxidase, and citrulline, recovered from the CSF dialysates. However, neither intravenous nor intrathecal methylprednisolone administered after injury had any effect on the magnitude of the increase in any of the measured biochemicals. Intrathecal methylprednisolone administration produced a spinal cord methylprednisolone concentration that was eight times greater, and a plasma concentration that was 32 times less, than that achieved with intravenous administration. CONCLUSIONS: Contrary to earlier animal studies in which methylprednisolone was administered either before or immediately after spinal cord injury, we found no effect of intravenous or intrathecal methylprednisolone on any of the parameters measured when administered 30 min postinjury.

Potential health risks from exposure to indoor formaldehyde.

An indoor air quality survey was conducted in Southern Louisiana to determine levels of airborne formaldehyde. Gas chromatography analyses of 419 air samples collected from 53 houses revealed levels of formaldehyde ranging from non-detectable to 6.60 mg/m3. Seventy four percent (312/419) of the samples had detectable amounts of airborne formaldehyde. Of the 312 positive samples, approximately 60% exceeded the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) guideline of 0.123 mg/m3. The highest number of samples exceeding the formaldehyde benchmark were collected in winter. It would appear that in some Southern Louisiana houses, a high level of formaldehyde could serve as a potential upper respiratory irritant.

Potential health risks from indoor exposure to chlorpyrifos (O,O-diethyl O-[3,5,6-trichloro-2-pyridyl] phosphorothioate).

A four-season, indoor air quality survey was conducted in Southern Louisiana to determine the indoor air levels of the pesticide chlorpyrifos. Gas chromatographic analysis of 213 air samples collected from 53 houses revealed levels of chlorpyrifos ranging from non-detected to 2.13 micrograms/m3. Using the Florida-Pinella exposure guideline (24-hr exposure to chlorpyrifos at 0.48 microgram/m3), it was noted that 14% of the samples exceeded this guideline. The exposure of occupants to the indoor air concentrations of the pesticide, however, were below either the irritation or the odor thresholds, and effects on acute and chronic health responses remains uncertain.

Health risks from exposure to metals in household dusts.

The levels of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), mercury (Hg), and nickel (Ni) were determined in a total of 315 indoor and outdoor dust samples collected from 53 households in Louisiana. Inductively coupled plasma analysis revealed that in many samples, the metal content exceeded the United States Environmental Protection Agency (EPA) Risk-Based Concentration (RBC) guidelines. For example, the number of dust samples above the EPA-RBC included 64 for Cd, 52 for Hg, 43 for As, 4 for Fe, 4 for Cu, 3 for Cr, and 2 for Ni. One-hundred fifty-two samples exceeded the street-dust level for Pb published by the U.S. Agency for Toxic Substances and Disease Registry. The results of this study indicate that exposure to indoor and/or outdoor dust presents a potential health risk for Louisiana residents.

Hyperbaric hyperoxia exaggerates respiratory membrane defects in the copper-deficient rat lung.

Scanning (SEM) and transmission electron microscopy (TEM) were used to examine the effect of dietary copper deficiency and hyperbaric hyperoxia, alone and in combination, on lung structure. Male, weanling Sprague-Dawley rats were fed a copper-deficient (CuD, 0.2 microgram/g) or copper-adequate diet (CuA, 5.1 micrograms/g). After 35-41 d on their respective diets, rats from each group were placed inside a pressure vessel kept at 27 degrees C under one of two pressure protocols. Air controls were maintained at 1 atm for 75 min. Rats exposed to oxygen were maintained at 1 atm of air plus 3 atm of oxygen for 1 h and then decompressed for 15 min. Under SEM, none of the treated lungs (CuD, CuA-O2 exposed, or CuD-O2 exposed) showed abnormal lung morphology from the conducting bronchioles down to the alveoli. Copper-deficient red blood cells were abnormally shaped. Under TEM, CuA-O2-exposed lungs showed thicker respiratory membranes, especially basement membranes and endothelial cells, and alveolar Type II cells having more than the usual number of surfactant vacuoles. CuD lungs also showed thicker endothelial and basement membrane components of the respiratory membrane, but normal looking Type II cells. CuD-O2-exposed lungs showed greatly thickened respiratory membranes and severe disruption of both endothelium and basement membrane and, judging by the increased number of nuclei per field, an increase in the number of both Type I and Type II cells. We conclude that copper deficiency enhances the damage caused by O2 toxicity, an effect that may be caused by reduced antioxidant status.

The physiology teacher, a facilitator of learning at all levels.

Academic physiologists in universities have three jobs: teaching, research, and service. They also operate at many levels of education: undergraduate, graduate, and medical. Each level carries special problems and special rewards. It is argued in this paper that teachers should be facilitators in learning no matter what level or what aspect of the job. If physiologists behave as facilitators of learning at all levels, then they will be able to help undergraduates by the most appropriate choice of textbooks and handbooks; to develop case histories, scenarios, and summaries; and to show students how physiology got to where it is, developing in the students a healthy concept of skepticism. This can be expanded when the students are graduate students and the teacher acts as an advisor and is still facilitating the students' learning.

Commonalities between gas anesthetics (nitrous oxide, nitrogen and/or argon) and ethanol intoxication in hot and cold selection line mice.

Argon, nitrogen, nitrous oxide were administered hyperbarically in doses (atmosphere) that caused loss of righting reflex (LORR). Nitrous oxide requires pressure somewhat less than two atmospheres, eighteen atmospheres were required for argon and thirty-six atmospheres roughly for nitrogen all in 0.5 atmospheres oxygen. Loss of righting reflex was assessed by using a rolling cage method of Wilson and Miller. Since nitrogen is the least liposoluble and nitrous oxide the most liposoluble of these three gases, greater pressures were needed for nitrogen to attain sufficient concentration in the membrane for anesthesia. Due to the low lipid solubility (1.4), nitrous oxide was administered hyperbarically at a compression rate of less than 0.5 atm/min at chamber temperature of 86 degrees plus or minus 2 degrees. Body temperatures were measured by minimitter transmitters. Two types of transmitters: an AM frequency and an FM frequency were used; a comparison of the two systems were made. The ED50 (atmospheres) required to produce a given score on the LORR were determined for each strain or line of mice. This ED50 value was determined for the Hot and Cold selection lines which have been specifically bred to differ as much as possible in a hypothermic response to acute doses of ethanol. These experiments demonstrate quite clearly a degree of commonality exists among CNS depressants with regard to anesthesia, loss of righting reflex and hypothermia.

Low magnetic field effects on embryonic bone growth.

Pulsed electromagnetic fields [EMF] and electric fields have been demonstrated to promote osteogenesis and wound healing. Pulsed EMF's have been approved since 1979 by the FDA, and are highly effective in the treatment of non-union fractures. Increased linear growth, cellular proliferation, cAMP and uptake of tritiated thymidine have been documented on short term exposure. Yet the mechanisms and the changes that occur have been difficult to quantify. Fluorescence, light, and electron microscopy were utilized in this study to assess any histological changes in bone. During incubation chick embryos were exposed to magnets oriented in various positions. Controls were oriented similarly using galvanized steel plugs. Field density in the center of the field was measure by a gaussmeter with a transverse probe. Each chick embryo in its magnetic field was isolated from the magnetic fields of others by being encased in a steel box. Intramembranous [calvaria] and endochondral [tibia] ossification were studied. Fluorescent dyes were micropipetted intravascularly at various stages of chick development. The tissues were fixed in methacrylate and stained for histomorphological study.

Muscle afferents and the neural dynamics of limb position and velocity sensations.

Today muscle spindles are thought to be the primary receptor responsible for limb position and velocity. A mathematical model describing the muscle spindle's complex dynamical behavior was developed recently by Hasan. Other researchers have observed neuronal firing in the cortex of primates when muscles surrounding a joint have been passively stretched by joint movement. The purpose of this paper is to apply the muscle spindle model to a "two-muscle joint" and quantitate the resultant firing rates for various joint positions and velocities. With this information insights into the required neuronal dynamics for extracting position and velocity information from muscle spindles can be gained.

BCE: a tool for software integration.

The integration of software into special-purpose systems (e.g. for gene sequence analysis) can be a difficult task. We describe a general-purpose software integration tool, the BCE program, that facilitates assembly of VAX-based software into application systems and provides an easy-to-use, intuitive user interface. We describe the use of BCE to integrate a heterogeneous collection of sequence analysis tools. Many BCE design features are generally applicable and can be implemented in other language or hardware environments.

Reiterative RNA folding and occupancy rate analysis for mRNA modelling.

We describe computer programs that predict the most energetically favorable secondary structures in growing RNA sequences, generate a sequential display of the growing structures, and monitor the predicted participation of intramolecular sites in secondary structure. These programs may provide insight into the relationships between messenger RNA secondary structure and expressibility.

Into deepest lung with drug and camera.

Alveoli of guinea pigs subjected to high partial pressures of oxygen (pO2 500 mmHg) for 6 days were studied with the scanning electron microscope. After six days the alveoli of untreated guinea pigs were engorged with an increased volume of alveolar type II cells and macrophages resulting in death of approximately half of the animals. Guinea pigs that had been pretreated with reserpine and phenoxybenzamine catecholamine inhibitors did not show the damaging ultrastructural changes seen in the untreated controls, although phenoxybenzamine was less effective in preventing the changes than reserpine. The results support previous experiments implicating the sympathetic nervous system in the production of pulmonary pathology due to oxygen toxicity.

Effect of high voltage stimulation on edema reduction in the rat hind limb.

The purpose of this study was to test the effect of high voltage stimulation (HVS) on edema reduction in the rat hindpaw. The animals were divided into a control group (n = 20) and a treated group (n = 20). The right hindpaw volume was measured, and then the animal's paw was traumatized. The animals in the treated group were treated with HVS at 24, 48, and 72 hours posttrauma. Paw volume measurements were made on all animals at 0, 24, 48, 72, and 96 hours posttrauma. In addition, the paw volume was measured in the treated group both before and after HVS. The results showed that animals in both groups had a significant decrease in paw volume over the experimental period, but no significant difference was found between the two groups in the amount of edema reduction. The HVS treatment did not produce a significant change in paw volume immediately after treatment.

Effect of high voltage stimulation on blood flow in the rat hind limb.

The purpose of this study was to test the effect of high voltage stimulation (HVS) on blood flow velocity (BFV) in the rat hind limb. A 20-MHz pulsed Doppler device was used to measure BFV changes in the femoral artery of 20 anesthetized rats after electrical stimulation. The animals were stimulated under the following conditions: four different pulse rates, changes in stimulus voltage, and changes in polarity. Blood flow velocity also was measured in the unstimulated hind limb. Although each of the four pulse rates caused significant increases in BFV, the 20-pulse-per-second rate produced BFV increases significantly greater than the other three pulse rates. The BFV changes, on the average, occurred less than 1 minute from the onset of stimulation and lasted up to 14 minutes after the cessation of the stimulation. The BFV increased with increases in voltage intensity. Both the positive and negative poles elicited significant increases in BFV, but the negative pole produced the greatest increases. Blood flow in the unstimulated hind limb was unchanged after stimulation. This study indicates that HVS of muscle does cause significant increases in blood flow to the stimulated rat hind limb.