PubMed Health⌕ Search

Biomedical subjects

R B Leonard

Publications and source records attributed to R B Leonard.

At least 19 recordsLinked to original sources
PubMed1992

Variations in cerebellar morphology of the Atlantic stingray, Dasyatis sabina.

The cerebellar corpus of the Atlantic stingray consists of an anterior lobe which is divided into rostral and caudal lobules, and a posterior lobe. The long axis of the posterior lobe and rostral lobule of the anterior lobe both lie along the midline, whereas the orientation of the caudal lobule varies. We examined this variation in 127 animals. In 52% the long axis of the caudal lobule lay on the right of the midline, in 21% it was on the left, and in 27% across the midline. While this distribution is not random, it is not related to size or sex. It is proposed that the observed variation is the reflection of variation in the cerebellar developmental program.

Animals↗
PubMed1992

Effects of isopropyl alcohol, ethanol, and polyethylene glycol/industrial methylated spirits in the treatment of acute phenol burns.

STUDY OBJECTIVE: To compare the effects of water rinse with those of isopropyl alcohol, polyethylene glycol with industrial methylated spirits, or ethanol on cutaneous phenol burns. DESIGN: Controlled trial with all animals receiving all treatments applied to different cutaneous phenol burn sites. TYPE OF PARTICIPANTS: Swine weighing 9 to 18 kg. INTERVENTIONS: In phase 1, each burn site was treated with water rinse for zero, one, or five minutes combined with either isopropyl alcohol, polyethylene glycol with industrial methylated spirits, ethanol, or no other treatment. Biopsies of treatment sites were done at 30 minutes and at 48 hours. In phase 2, a pilot study, the effect of isopropyl alcohol, polyethylene glycol with industrial methylated spirits, or water treatment on serum phenol levels was noted in animals with 5%, 10%, and 15% body surface area burns. MEASUREMENTS AND MAIN RESULTS: In phase 1, on histological examination of biopsy specimens, significant differences in tissue damage occurred among the groups (P < .05). Isopropyl alcohol and polyethylene glycol with industrial methylated spirits were the most efficacious treatments; the duration of water rinse had no significant effect. In phase 2, the systemic absorption of phenol may be greater with water treatment than with isopropyl alcohol treatment. CONCLUSION: Isopropyl alcohol and polyethylene glycol with industrial methylated spirits are equally effective in the amelioration of phenol burns of less than 5% total surface area. The wider availability of isopropyl alcohol makes it potentially the most useful treatment for these small burns. Further studies of its risks are needed.

1-Propanol↗
PubMed1992

Characterization of antibiotic-resistant Corynebacterium striatum strains.

Antibiotic-resistant Corynebacterium strains were isolated from 14 Harborview and one Veterans Administration Hospital patients in Seattle during the period 1987-90. These clindamycin-erythromycin resistant strains were shown to hybridize with the ermCd gene, which was cloned from a Corynebacterium diphtheriae plasmid and encodes for a rRNA methylase. Thirteen of these strains also hybridized with the tetM gene probes, and were tetracycline resistant. The ermCd gene could be transferred, by conjugation, while the tetM gene was not transferable.

Blotting, Southern↗
PubMed1992

Laboratory aspects of "Mycobacterium genavense," a proposed species isolated from AIDS patients.

"Mycobacterium genavense" is a proposed new species recently reported to cause disseminated infections in 18 patients with AIDS in Europe. We have recovered "M. genavense" as slowly growing fastidious mycobacteria in blood cultures of seven patients with AIDS. In the original studies of "M. genavense," the fastidious organism grew only in BACTEC 13A vials. The Seattle, Washington, isolates of "M. genavense" also failed to grow when subcultured from 13A vials to routine solid media, but dysgonic colonies were produced on Middlebrook 7H11 agar supplemented with mycobactin J. The mycolic acid pattern of patients' isolates closely resembled that of the type strain of Mycobacterium simiae when analyzed by one- and two-dimensional thin-layer chromatography and by high-performance liquid chromatography. Whole-cell fatty acid analyses by gas-liquid chromatography distinguished the isolates from M. simiae but misidentified them as Mycobacterium fortuitum. Sequence determinations of the hypervariable regions of the 16S rRNA gene indicate that these organisms belong to the recently proposed new species "M. genavense." Growth from Middlebrook 7H11 agar supplemented with mycobactin J consistently yielded positive tests for catalase (semiquantitative and at 68 degrees C), pyrazinamidase, and urease which enable mycobacteriology laboratories to presumptively identify "M. genavense" without nucleic acid analyses. The failure of "M. genavense" to grow on conventional mycobacterial solid media suggests that mycobacterial blood cultures should include a broth medium incubated for at least 8 weeks.

AIDS-Related Opportunistic Infections↗
PubMed1992

Evaluation of the rapid CORYNE identification system for Corynebacterium species and other coryneforms.

The Rapid CORYNE system for identification of aerobic, nonsporeforming, gram-positive rods was evaluated according to the manufacturer's instructions with 177 organisms. After inoculation with a heavy suspension of growth, strips containing 20 cupules were incubated for 24 h, reagents were added, and the results of 21 biochemical reactions were recorded as numerical profiles. The strains consisted of pathogenic species of the genus Corynebacterium, primarily C. diphtheriae (n = 29), opportunistic species of Corynebacterium including C. jeikeium (n = 75), recognized species of non-corynebacteria such as Gardnerella and Arcanobacterium (n = 51), and Centers for Disease Control (CDC) coryneform groups (n = 22). Results from single tests read after 24 h yielded correct identifications to species level with no additional tests for 26 (89.7%) of the pathogenic species; 64 (85.3%) of the opportunistic organisms; 51 (100%) of the non-corynebacteria, and 8 (36.4%) of the CDC coryneform groups. Supplemental tests produced the correct identification for three additional pathogenic isolates (100% total) and four additional isolates from the opportunistic species (90.6% total). Twelve of the 15 isolates not identified by the system were in the CDC coryneform groups. Four of the six misidentified and one of the unidentified isolates were C. matruchotii, which was not included in the data base. The system is an excellent rapid alternative to conventional biochemical tests.

Actinomycetales↗
PubMed1991

Identification of the midbrain locomotor region and its relation to descending locomotor pathways in the Atlantic stingray, Dasyatis sabina.

The midbrain locomotor region (MLR) in the Atlantic stingray, Dasyatis sabina, was identified and characterized. Stimulation (50-100 microA, 60 Hz) of the midbrain in decerebrated, paralyzed animals was used to elicit locomotion monitored as alternating activity in nerves innervating an antagonist pair of elevator and depressor muscles. Effective sites for evoking locomotion in the midbrain included parts of several nuclei: the caudal portion of the interstitial nucleus of the medial longitudinal fasciculus and the caudomedial parts of the cuneiform and subcuneiform nuclei. This region did not include the red nucleus, any parts of the optic tectum or the medial or lateral mesencephalic nuclei. Electrical stimulation in the MLR evokes locomotion in either the ipsi- or contralateral pectoral fin, whereas stimulation in the medullary reticular formation evokes locomotion only in the contralateral fin. Lesion experiments were performed to identify the location of descending pathways from the midbrain to the medullary reticular formation. To abolish locomotion evoked by electrical stimulation in the MLR, the medial reticular formation in the rostral medulla had to be lesioned bilaterally, or the ipsilateral medial medullary reticular formation and fibers projecting from the MLR to the contralateral midbrain had to be disrupted. Injections of HRP into the magnocellular/gigantocellular reticular formation confirmed that this area received bilateral projections from the MLR. The MLR of the Atlantic stingray appears to be similar to the lateral component of the mammalian MLR and to the MLR in other non-mammalian vertebrates.

Animals↗
PubMed1991

Manmade disasters.

A disaster that produces a multitude of patients may severely stress a community's health-care system, from the EMS system to the hospitals. Physicians involved in such an event must realize that they will have to change their normal mode of delivering care, having to make decisions with less than the normal amount of information, and doing the most good for the most salvageable patients. Some understanding of and appreciation for the unique problems that face emergency personnel in the field are important for physicians who do not normally interact with fire and EMS personnel, because it will allow them to realize that they are not alone in the chaos of a disaster. Many manmade disasters produce patients with medical or surgical problems with which one is familiar, the only difference being the sheer number of patients. Other manmade disasters, however, most notably those involving hazardous materials and radioactive materials, are capable of producing patients who not only have unfamiliar medical problems but also have problems about which little information is readily available in the medical literature. Hospital physicians can do much to prepare themselves for these eventualities. Discussion and planning should be done among separate staffs (ICU, operating suite, emergency department), as well as among staff of the various disciplines so they can interact more effectively when a disaster occurs. Local disaster planners should receive input from hospital staffs so hospital capabilities are known and the field operation can mesh well with the hospital's operation.

Chemical Warfare↗
PubMed1990

Locomotion evoked by stimulation of the brain stem in the Atlantic stingray, Dasyatis sabina.

The primary pathway descending to the spinal cord to initiate locomotion in the stingray is located in the intermediate to ventral portion of the lateral funiculus; a second pathway is located in the dorsolateral funiculus. The goal of this study was to identify the origins of these pathways in the rhombencephalic reticular formation (RF). To do this we used microstimulation of the RF in conjunction with selective lesions of the brain stem and spinal cord. In some animals microinjections of excitatory amino acids were used to avoid stimulating axons of passage. Locomotion in the contralateral pectoral fin was evoked by microstimulation of the dorsal and ventral reticular nuclei, the middle and superior RF, and the ventral portion of the lateral RF. The regions from which locomotion was evoked by chemical stimulation were more restricted and included the rostral dorsal reticular nucleus, the middle RF, and the adjacent ventral lateral RF. This area encompasses the magnocellular RF and coincides with the distribution of numerous reticulospinal cells that project ipsilaterally into the ventral half of the lateral funiculus. Our results indicate, then, that locomotion in the stingray is mediated primarily by a pathway originating in the magnocellular RF that descends ipsilaterally in the ventral half of the lateral funiculus to elicit swimming in the contralateral pectoral fin. We suggest that this primary pathway is specifically associated with the control of locomotion. We also demonstrated that locomotion can be evoked independently from the lateral RF, but is probably mediated by an indirect pathway relaying near the spinomedullary junction or in the rostral spinal cord.

Animals↗
PubMed1989

SARA (Superfund Amendments and Reauthorization Act), Title III: implications for emergency physicians.

Practically every community has one or more industries that use or produce hazardous chemicals. The release of these chemicals into that community's environment has the potential of causing serious health problems. Previously, physicians have not had information about what hazardous chemicals were in their community or a warning that release of a hazardous chemical had occurred. The Emergency Planning and Community Right-to-Know Act of 1986, known as Title III of the Superfund Amendments and Reauthorization Act (SARA), now mandates that every facility using, storing, or manufacturing hazardous chemicals make public its inventory and report every release of a hazardous chemical to public officials and health personnel. Every facility also must cooperate with physicians who are treating victims of exposure. Emergency physicians, both in their role in their community's emergency medical services system and as physicians in emergency departments, will soon be involved in many aspects of SARA's numerous ramifications. This report is intended to familiarize the emergency physician with the basic components of Title III of SARA.

Accidents, Occupational↗
PubMed1988

Role of pediatricians in disasters and mass casualty incidents.

In disaster planning, the role of the specialist is often overlooked. That role, for the pediatrician, entails being familiar with hospital and community disaster plans and agreeing to take part in implementation of those plans by: (1) before a disaster, teaching special pediatric emergency techniques to emergency medical technicians and paramedics, being sure that pediatric supplies and equipment are available in ambulances, checking to see that pediatric needs have been considered in designated evacuation shelters, and, for disasters occurring in one's own hospital, being sure that evacuation routes are known and that means of notifying parents have been set up; (2) during a disaster, helping to determine which pediatric patients can be discharged from the hospital or transferred to another hospital if beds are needed for accident victims, and being available as needed according to the plans; and (3) after a disaster, counseling parents and children on how to cope with the stress and fear of having been involved in a disaster. The emergency pediatrician active in disaster planning has a responsibility to see that the services of pediatricians in general practice are incorporated into those plans.

Child↗
PubMed1986

Chromatophore motoneurons in the brain of the squid, Lolliguncula brevis: an HRP study.

The location of the motoneuron somata controlling activity of the chromatophore muscles was studied in the squid Lolliguncula brevis. Retrograde transport of horseradish peroxidase from injection sites in the skin or in the mantle muscle established that the chromatophore motoneurons are situated in the subesophageal mass of the brain while at least some of the mantle muscle motoneurons are in the stellate ganglia. Motoneurons to chromatophores in the mantle have their somata in the posterior subesophageal mass, mainly in the chromatophore or fin lobes. Motoneurons to chromatophores in the head are located in the anterior pedal lobes and those to the chromatophores in the arms project mainly from the anterior chromatophore lobes. However, some neurons in the posterior chromatophore lobes project to the head or arm regions. A few cells in both the anterior and posterior chromatophore lobes project contralaterally. Somata in other lobes of the subesophageal mass are also labelled by injections in the skin or in the mantle muscle. Evidence presented here suggests that some of the neurons labelled outside the chromatophore lobes are chromatophore motoneurons.

Animals↗
PubMed1985

Tonic descending inhibition in the stingray's spinal cord.

Reflexes elicited by peripheral nerve stimulation were compared in decerebrated stingrays with the spinal cord intact, after a lesion of the dorsal spinal cord and after spinal transection. Reflexes elicited in decerebrated stingrays are tonically inhibited. Lesions of the dorsal spinal cord release this tonic descending inhibition. The tonic descending inhibitory system in stingrays is comparable to that of mammals.

Animals↗
PubMed1985

Funicular trajectories of brainstem neurons projecting to the lumbar spinal cord in the monkey (Macaca fascicularis): a retrograde labeling study.

Brainstem nuclei projecting to the lumbar spinal cord in the monkey were identified by using horseradish peroxidase and the fluorescent dye granular blue. These retrogradely transported tracers were used in fluid and/or gel forms to determine the funicular trajectories of the brainstem-spinal projections. The major descending components of the dorsal funiculus arose from the n. gracilis, n. cuneatus, and the n. of the solitary tract. Major components of the dorsolateral funiculus (DLF) came from the raphe complex, medullary and pontine reticular formation, locus coeruleus, Edinger-Westphal n., and red n. Other nuclei giving rise to minor contributions to the DLF included n. gracilis, n. cuneatus, n. of the solitary tract, medial and spinal vestibular n., subcoeruleus, periaqueductal gray, interstitial n. of Cajal, n. of Darkschewitsch, and the anteromedian n. The major components of ventral cord paths (ventrolateral and ventral funiculi) arose from the raphe complex, the medullary and pontine reticular formation, lateral and spinal vestibular n., and the coerulean complex. Minor contributions to the ventral paths descended from the dorsal motor n. of X, n. of the solitary tract, medial vestibular n., paralemniscal reticular formation, dorsal parabrachial n., n. cuneiformis, periaqueductal gray, Kölliker-Fuse n., and red n. The possible functional implications of the funicular distribution of these descending pathways are discussed from the perspective of descending inhibition and pain modulation.

Afferent Pathways↗
PubMed1984

The descending and intrinsic serotoninergic innervation of an elasmobranch spinal cord.

The descending and the intrinsic components of the serotoninergic (5HT) innervation of the Atlantic stingray spinal cord were described by comparing the distributions of neuronal elements exhibiting 5HT-like immunoreactivity (peroxidase-antiperoxidase method) in sections caudal and rostral to spinal transections. The cells of origin of the descending 5HT system were located with a double labeling method for both retrogradely transported horseradish peroxidase (HRP) and 5HT staining. The descending system provides virtually the entire 5HT innervation of the dorsal horn, the intermediate zone, and the dorsal and lateral portions of the ventral horn. Fibers of the descending 5HT system course in the lateral funiculus, the dorsal portion of the ventral funiculus, and in the submeningeal zones of the dorsal and lateral aspects of the spinal cord. This projection primarily originates from the 5HT cell groups of the caudal rhombencephalon (groups II and III; Ritchie et al., '83), with a minor contribution from group IV in the rostral rhombencephalon. The organization of the descending 5HT system in stingrays is remarkably similar to that of mammals. The intrinsic spinal 5HT system consists of cells distributed in the ventromedial spinal cord that have processes extending longitudinally in a ventral submeningeal fiber network. Fibers were traced from the submeningeal system to the ventral horn, where varicose processes were restricted largely to the neuropil ventral to the somata of the fin motoneurons. The existence of a well-defined intrinsic 5HT system in stingrays supports the hypothesis that such a system exists in the spinal cords of a variety of vertebrates.

Animals↗