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Biomedical subjects

M Rathbun

Publications and source records attributed to M Rathbun.

9 recordsLinked to original sources
PubMed2001

An automated flinch detecting system for use in the formalin nociceptive bioassay.

The biphasic display of paw-flinch behavior in the rat after injection of formalin into the dorsum of the hind paw is used for the screening of anti-hyperalgesic agents. Described and characterized here is a less labor-intensive system for counting flinch activity by detecting movement of a small metal band placed on the formalin-injected paw. A signal is generated as the band breaks the electromagnetic field of a loop antenna located under the rat and processed through an algorithm that determines flinch activity using 1) amplitude, 2) zero-voltage crossing, and 3) signal duration. Flinches are summed and stored over a selected collection interval throughout the assay for later analysis. Studies have validated the measures with respect to 1) system stability over time; 2) system-to-"practiced observer" correlation on flinch detection, r2 = 0.94; 3) system variables including time of day, sex, age, and body weight; and 4) 50% effective dose values similar to those previously reported for intrathecal morphine and the NMDA antagonist MK-801.

Analgesics↗
PubMed1994

Pharmacology and toxicology of chronically infused epidural clonidine.HCl in dogs.

To evaluate the physiological effects and toxicity of epidural clonidine.HCl, male Beagle dogs were prepared with chronic lumbar epidural catheters and administered constant infusions of either saline (N = 10), or 80 micrograms/hr (N = 6), 200 micrograms/hr (N = 6), or 320 micrograms/hr (N = 12) clonidine.HCl at a rate of 4 ml/24 hr for 28 days. Saline infusion had no effect upon any behavioral measure. Epidural clonidine produced a dose-dependent increase in thermal skin-twitch response latency (antinociception), lowering of respiration rate, heart rate, and blood pressure, and increased sedation. The effects were maximum from approximately Day 1 to Day 3 when, with the exception of respiration which remained depressed, a progressive adaptation was observed over the course of the study. There were no negative effects on body weight, body temperature, motor function, bowel or bladder function, or clinical pathology values. After 28 days of continuous infusion, the dogs were deeply anesthetized and terminated. Cisternal cerebrospinal fluid taken at termination displayed no clinically significant differences in protein or glucose concentration. All groups, including control, had dogs which had a chronic inflammatory response in the epidural space, as represented by fibrosis, foreign body giant cells, and lymphocytes, but no spinal cord pathology. Both the steady-state plasma and CSF concentrations of clonidine were proportional to the dose; the ratio of CSF to plasma concentration was approximately 0.5. The failure to see any change in CSF composition, significant spinal cord pathology, or signs of tissue or organ toxicity emphasizes the safety of epidurally administered clonidine at infusion rates up to 320 micrograms/hr and at infusate concentrations up to 2 mg/ml.

Analgesia↗
PubMed1991

Risk factors for carriage of meningococcus in the Los Angeles County men's jail system.

Ten cases of meningococcal meningitis in the Los Angeles County men's jail system in 1986 were the first known reported cases in this population. New cases have continued into 1990. Nineteen of 21 symptomatic cases identified by serogroup from the men's jail occurring through 1988 had serogroup C. The prevalence of meningococcal carriage and potential risk factors were studied in 1988 among 150 men booked to enter the jail, 350 inmates being released, and 100 jail staff. The prevalence of meningococcal carriage among releases, bookings, and staff were 25.4%, 18.7%, and 5.0%, respectively. Among releases, imprisonment longer than a threshold of 28 days increased carriage of serogroup C 10.0 times (95% confidence interval (CI) 4.6-21.6). Among bookings, household crowding increased serogroup C carriage 8.2 times (95% CI 1.5-45.3). Direct and passive smoking at home increased carriage of any serogroup 5.2 (95% CI 1.2-47.5) and 2.5 (95% CI 1.1-5.8) times, respectively. Feasible potential interventions include banning smoking in the jail and immunization with quadrivalent meningococcal vaccine of booked men sentenced for one month or more.

Carrier State↗
PubMed1985

Intermittent tracheostomy in sheep.

A modified tracheostomy was designed for respiratory function studies in sheep. Our primary objective was to prevent development of severe tracheal stenosis, which was observed with procedures designed for canine tracheostomy. Surgery consisted of an intercartilaginous tracheal slit, with apposition of tracheal mucosa to skin. This procedure produced no significant stenosis at postmortem evaluation in 19 sheep. In contrast, 5 of 20 sheep with excision of the ventral 1/3 of the third and fourth tracheal rings, had severe tracheal stenosis.

Animals↗
PubMed1984

Lung volume and VA/Q distribution response to intravenous versus inhalation anesthesia in sheep.

The effects of intravenous pentobarbital versus nitrous oxide/halothane inhalation anesthesia on blood gases, distribution of ventilation-perfusion ratios (VA/Q), and lung volume (FRC) were compared in 8 tracheostomized sheep in the lateral decubitus position. Pentobarbital anesthesia produced no significant changes (from awake control) in arterial blood PO2 or PCO2, ventilation-perfusion inequality, intrapulmonary shunt, or FRC during either spontaneous breathing or mechanical ventilation with muscle paralysis. With inhalation anesthesia, PaO2 decreased from 132 +/- 13 mmHg awake to 106 +/- 11 mmHg and 104 +/- 6 mmHg (FIO2 all 0.3) during spontaneous and mechanical ventilation. Shunt increased from 1.4 +/- 1.0% awake to 10.6 +/- 4.5 and 13.9 +/- 5.3%, respectively. Mean VA/Q decreased from 0.39 +/- 0.07 awake, to 0.21 +/- 0.06 and 0.29 +/- 0.07. Log standard deviation of VA/Q increased from 0.66 +/- 0.12 awake to 0.83 +/- 0.28 and 0.89 +/- 0.15. FRC decreased from 1.66 +/- 0.65 1 to 1.46 +/- 0.62 and 1.22 +/- 0.63 1, respectively. Differences in response to intravenous versus inhalation anesthesia for the above variables all were statistically significant at P less than 0.05. FRC and shunt changes with anesthesia showed significant correlation for both spontaneous (r = -0.80) and mechanical ventilation (r = 0.77), P less than 0.005 for both. We therefore propose that the differences between lung volume and gas exchange effects of intravenous versus inhalation anesthesia in sheep may have been related causally.

Anesthesia, Inhalation↗
PubMed1982

Carotid artery exteriorization for percutaneous catheterization in sheep and dogs.

Summary and reliable physiologic or pharmacologic investigation in animal models often requires arterial catheterization in awake animal subjects. This can be facilitated by surgical exteriorization of the carotid artery for subsequent percutaneous catheterization. A simplified surgical procedure is described that has been demonstrated to have limited morbidity and excellent applicability for multiple use, as well as to ensure high blood flow rates when needed. The surgical technique involves transfer of the carotid artery from a deep paratracheal position to a ventrolateral neck subcutaneous position, protected from the underlying mattress sutures by the sternomastoid muscle.

Animals↗
PubMed1978

Chromatographic analysis of multiple tracer inert gases in the presence of anesthetic gases.

A gas chromatographic method for simultaneous analysis of multiple tracer inert gases in blood and expired gas samples is described. The method enables determination of the distribution of ventilation-perfusion ratios in the lungs during anesthesia with nitrous oxide and halothane. In addition, simultaneous analysis of anesthetic gas concentration in blood permits calculation of the amount of uptake or elimination of anesthetic gases from the Fick principle.

Anesthesia, Inhalation↗