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R M Lehman

Publications and source records attributed to R M Lehman.

At least 19 recordsLinked to original sources
PubMed2001

Attached and unattached bacterial communities in a 120-meter corehole in an acidic, crystalline rock aquifer.

The bacteria colonizing geologic core sections (attached) were contrasted with those found suspended in the groundwater (unattached) by examining the microbiology of 16 depth-paired core and groundwater samples using a suite of culture-independent and culture-dependent analyses. One hundred twenty-two meters was continuously cored from a buried chalcopyrite ore hosted in a biotite-quartz-monzonite porphyry at the Mineral Park Mine near Kingman, Ariz. Every fourth 1.5-m core was acquired using microbiologically defensible methods, and these core sections were aseptically processed for characterization of the attached bacteria. Groundwater samples containing unattached bacteria were collected from the uncased corehole at depth intervals corresponding to the individual cores using an inflatable straddle packer sampler. The groundwater was acidic (pH 2.8 to 5.0), with low levels of dissolved oxygen and high concentrations of sulfate and metals, including ferrous iron. Total numbers of attached cells were less than 10(5) cells g of core material(-1) while unattached cells numbered about 10(5) cells ml of groundwater(-1). Attached and unattached acidophilic heterotrophs were observed throughout the depth profile. In contrast, acidophilic chemolithotrophs were not found attached to the rock but were commonly observed in the groundwater. Attached communities were composed of low numbers (<40 CFU g(-1)) of neutrophilic heterotrophs that exhibited a high degree of morphologic diversity, while unattached communities contained higher numbers (ca. 10(3) CFU ml(-1)) of neutrophilic heterotrophs of limited diversity. Sulfate-reducing bacteria were restricted to the deepest samples of both core and groundwater. 16S ribosomal DNA sequence analysis of attached, acidophilic isolates indicated that organisms closely related to heterotrophic, acidophilic mesophiles such as Acidiphilium organovorum and, surprisingly, to the moderately thermophilic Alicyclobacillus acidocaldarius were present. The results indicate that viable (but possibly inactive) microorganisms were present in the buried ore and that there was substantial distinction in biomass and physiological capabilities between attached and unattached populations.

Colony Count, Microbial↗
PubMed2001

Attached and unattached microbial communities in a simulated basalt aquifer under fracture- and porous-flow conditions.

Bench scale column studies were used to examine the partitioning of microorganisms between groundwater and a geologic medium and to examine the effect of hydrogeology (i.e., porous- versus fracture-flow) on organism partitioning. Replicated columns were constructed with intact basalt core segments that contained natural fractures and with the same basalt crushed into particles. The columns were perfused with groundwater, and upon reaching a steady state, the columns were sacrificed and the attached and unattached communities were analyzed by multiple approaches. The analyses included the total number of cells, the phylogenetic affiliation of the cells (i.e., the alpha, beta, and gamma subclasses of the class Proteobacteria and gram positives with high G+C DNA content) by fluorescent in situ hybridization (FISH), number and taxonomic affiliation by fatty acid methyl ester profiles of culturable heterotrophs, most-probable-number estimates of methanotrophs and phenol oxidizers, and whole-community sole carbon source utilization patterns from Biolog GN microplates. In the packed columns, about 99% of the total biomass (per cubic centimeter of porous medium) was attached to the geologic medium. Lack of equitable units precluded a comparison of attached and unattached biomasses in the fractured columns where the attached biomass was expressed per unit of surface area. Compositional differences in the attached and unattached communities were evidenced by (i) the recovery of Pseudomonas stutzeri, an Enterococcus sp., and Bacillus psychrophilus from the groundwater and not from the basalt, (ii) differences between community carbon source utilization patterns, and (iii) the relative abundances of different phylogenetic groups estimated by FISH in both column types. In the packed columns, attached communities were depleted of members of the alpha- and beta-Proteobacteria subclasses in comparison to those in the corresponding groundwater. In the fractured columns, attached communities were enriched in gram-positive Bacteria and gamma-Proteobacteria and depleted of beta-Proteobacteria, in comparison to those in the corresponding groundwater. Segregation of populations and their activities, possibly modified by attachment to geologic media, may influence contaminant fate and transport in the subsurface and impact other in situ applications.

Colony Count, Microbial↗
PubMed2000

Comparison of 3-D stereoscopic MR imaging with pre and post lesion recording in pallidotomy.

OBJECTIVES: A quantitative on-line analysis of electrical activity in the pallidum of Parkinsonian patients has been developed to determine the focal point of lesioning. Additional recordings are made after the lesioning, to assess residual neural activity. A 3-D volume stereoscopic image system is proposed to display the complex anatomy and to superimpose the electrophysiological data into this system. The purpose of this study is to understand the complex pathophysiology in real-time anatomic/image space and determine the location and effect of lesioning residual energy sites. MATERIAL AND METHODS: Thirty patients undergoing 41 pallidotomies are presented. Neuronal activity from the pallidum is recorded using a semi-microelectrode. Based on this activity, lesioning is performed. Post-lesion recordings are made to determine the necessity of additional lesioning. 3-D volume MR images are acquired pre and postoperatively and compared for accuracy of lesion sites. A 3-D stereoscopic image system has been developed to depict basal ganglia geometry in the last 5 patients. Electrophysiological data are superimposed on this image system to show the surgeon the virtual position of the electrode tip. RESULTS: A stereoscopic 3-D volume MR image system has been developed. This system more efficiently and accurately visualizes and records the coordinates of high neural activity in the pallidum and post lesion residual activity. Post-lesion power analysis was carried out in 30 patients. Additional lesions were indicated in 8 and different trajectories in 6. CONCLUSION: Real-time visualization of neural recording, both pre and post-lesioning during pallidotomy, facilitates the surgeon's understanding of the spatiotemporal relationships of pathophysiological properties within the globus pallidus.

Adult↗
PubMed2000

BASIC program for reduction of data from community-level physiological profiling using biolog microplates: rationale and critical interpretation of data.

A BASIC program is offered that reduces data resulting from mixed-species inoculations into Biolog microplates. The procedures of the program are supported by a critical review of the literature relating to Biolog data reduction. The availability of standardized, accelerated data reduction protocols will facilitate study comparisons and allow efficient evaluation of new data reduction approaches.

Bacteria↗
PubMed2000

Quantitative on-line analysis of physiological data for lesion placement in pallidotomy.

A computerized method of determining the focal point of electrical activity in the pallidum of parkinsonian patients was developed using on-line quantitative physiological data analysis. Thirty patients in a series of 70 were studied in depth. Neuronal activity was recorded from the pallidum using a semi-microelectrode. The signal is inspected visually while its average power, characteristic frequency and complexity are computed. The target locus was indicated by the highest level of global activity in the vicinity of the electrode (signal power maximum), maximal signal complexity and minimal characteristic frequency. Most often, the vertical coordinate required correction. The postoperative clinical and imaging results have indicated the effectiveness of this method.

Adult↗
PubMed1999

Electrophysiological recordings in pallidotomy localized to 3D stereoscopic imaging.

A quantitative on-line analysis of electrical activity in the pallidum of Parkinsonian patients has been developed to determine the focal point of lesioning. A 3D volume image system has been developed to display basal ganglia anatomy and coregister the electrophysiological data within the globus pallidus. Thirty patients undergoing 41 pallidotomies are presented. Neuronal activity from the pallidum is recorded using a semi-microelectrode. Based on this activity, lesioning is performed. Postlesion recordings are made to determine the necessity of additional lesioning. A stereoscopic 3D volume MR image system has been developed that along with on-line signal processing allows visualization of high neural activity in the pallidum and postlesion residual activity.

Action Potentials↗
PubMed1997

Frameless 3D volume registration of MR data sets for stereotactic pallidotomy.

Frameless 3D volume registration of Magnetic Resonance (MR) and computed (CT) data sets has been described by Kummar et al. [11]. Its use in 3D volume registration for stereotactic planning in patients undergoing pallidotomy is presented. Pre-operative examinations with the stereotactic frame and postoperative examinations without the stereotactic frame can be co-registered and reviewed for accuracy of planned and lesional coordinates.

Brain Mapping↗
PubMed1997

Anterior approach to the cervicothoracic junction: an anatomic dissection.

The anterior surgical approach to the cervicothoracic spine presents a challenge to the spine surgeon. To adequately explore the anterior spine from C4 to T4 requires a midsternotomy with extended anterior cervical incision. This approach most adequately provides the extensive cranial-caudal exposure required in dealing with tumors at the cervicothoracic junction. Our surgical experience with five patients harboring tumors in this area of the spine has led us to reflect on the anatomy of the exposure and the corridors of approach at various levels of the cervicothoracic junction. Cadaver dissection and demonstration of the anatomic structures encountered in this exposure and the spinal subdivisions created by these various neurovascular structures will be presented. The anatomy, so demonstrated, will be correlated with the clinical cases.

Anatomy, Artistic↗
PubMed1995

Partial seizures with onset in central area: use of the callosal grid system for localization.

Focal seizures arising in the central area require precise anatomic and physiologic mapping of ictal onset. The central sulcus is identified by the callosal grid system whose mid-vertical plane identifies the central sulcus inferiority where the central artery passes into the central sulcus. 5 patients with intractable seizures of central origin where localized with this method. Extent of resection was confirmed on postoperative NRI. The subdural grid was accurately placed on the central sulcus, confirmed by electrophysiologic means. Grid planes compartmentalized ictal onset, and post-operative resection correlated precisely. All patients are seizure-free. Seizures arising in the central area, precisely located, can be treated with good to excellent results. Localization of onset is facilitated by use of the callosal grid system, and allows superimposition of pre-, intra- and post-operative anatomic and physiologic data.

Adolescent↗
PubMed1994

Peri- and postoperative magnetic resonance imaging localization of pallidotomy.

Postoperative magnetic resonance imaging (MRI) of basal ganglia functional lesions illustrates the accuracy of preoperative target localization. The technique of perioperative MRI and CT localization for pallidotomy will be discussed and correlated with the center of the lesion on postoperative standard MRI as well as three-dimensional (3-D) volume acquisition of image. Using a 1.5-tesla Signa system, a conventional acquisition of 128-slice, 256 x 256 matrix spoiled grass (SPGR) images were used for 3-D reformation. This allowed approximately 1 x 1 x 2 mm resolution over a 24-cm field of view in a T-1-weighted image. The display affords a volumetric analysis of the anatomic location and relation of the post-ventral pallidotomy to adjacent structures. Accuracy lesion placement based on perioperative MR coordinates and revealed on postoperative images is confirmed. The volume of the lesion as well as its location are factors that affect clinical outcome.

Basal Ganglia↗