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D R Benson

Publications and source records attributed to D R Benson.

At least 55 records · Page 3Linked to original sources
PubMed1993

Close linkage of genes encoding glutamine synthetases I and II in Frankia alni CpI1.

Frankia alni CpI1 has two glutamine synthetases (GSs), GSI and GSII. The GSI gene (glnA) was isolated from a cosmid library of F. alni CpI1 DNA by heterologous probing with glnA from Streptomyces coelicolor. The glnA gene was shown to be located upstream of the GSII gene (glnII) by DNA-DNA hybridization. The nucleotide sequences of the 1,422-bp CpI1 glnA gene and of the 449-bp intervening region between glnA and glnII were determined, and the glnA amino acid sequence was deduced. In common with GSIs from other organisms, CpI1 GSI contains five conserved regions near the active site and a conserved tyrosine at the adenylylation site. F. alni CpI1 glnA complemented the glutamine growth requirement of the Escherichia coli glnA deletion strain YMC11 but only when expressed from an E. coli lac promoter. While the functional significance of maintaining two GSs adjacent to one another remains unclear, this arrangement in F. alni provides support for the recently proposed origin of GSI and GSII as resulting from a gene duplication early in the evolution of life.

Actinomycetales↗
PubMed1993

Biology of Frankia strains, actinomycete symbionts of actinorhizal plants.

Frankia strains are N2-fixing actinomycetes whose isolation and cultivation were first reported in 1978. They induce N2-fixing root nodules on diverse nonleguminous (actinorhizal) plants that are important in ecological successions and in land reclamation and remediation. The genus Frankia encompasses a diverse group of soil actinomycetes that have in common the formation of multilocular sporangia, filamentous growth, and nitrogenase-containing vesicles enveloped in multilaminated lipid envelopes. The relatively constant morphology of vesicles in culture is modified by plant interactions in symbiosis to give a diverse array of vesicles shapes. Recent studies of the genetics and molecular genetics of these organisms have begun to provide new insights into higher-plant-bacterium interactions that lead to productive N2-fixing symbioses. Sufficient information about the relationship of Frankia strains to other bacteria, and to each other, is now available to warrant the creation of some species based on phenotypic and genetic criteria.

Actinomycetales↗
PubMed1993

Early failure of short-segment pedicle instrumentation for thoracolumbar fractures. A preliminary report.

The results after treatment of fifty-two lumbar and thoracolumbar fractures with Cotrel-Dubousset instrumentation were reviewed as part of an ongoing study. Nineteen patients (average duration of follow-up, fifteen months) had been managed with short-segment pedicle-screw instrumentation. This preliminary report outlines the complications and pitfalls identified during the initial healing phase in this subgroup of patients. There were no neurological or vascular injuries due to placement of the pedicle screws, but ten patients had some form of failure of the fixation during the early period of healing. Failure of the fixation was manifested in three ways: progressive kyphosis secondary to the bending of screws (six patients), kyphosis secondary to osseous collapse or vertebral translation without bending of the hardware (three patients), and segmental kyphosis after a caudad screw in the lumbar construct broke (one patient, who had had a combined instrumentation for multiple fractures). Untreated anterior instability, and pre-stressing of the screws when the rods were contoured in situ, resulted in a high rate of failure. The high rate of failure of the hardware associated with this fixation construct suggests that posterior screw fixation alone may not be adequate when Cotrel-Dubousset instrumentation is used for short-segment lumbar arthrodeses. Bent screws or measurable kyphosis did not always herald a clinical failure, but patients who had progressive kyphosis of more than 10 degrees had substantially more pain than did those who had little or no progression. The results reported here are preliminary, and speculation as to the importance of these findings and as to the long-term outcome in these patients would be premature.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Cloning and expression of Trypanosoma cruzi ribosomal protein P0 and epitope analysis of anti-P0 autoantibodies in Chagas' disease patients.

Chagas' disease, caused by the intracellular protozoan parasite Trypanosoma cruzi, is a major cause of heart failure in endemic areas. Antigenic mimicry by T. cruzi antigens sharing epitopes with host macromolecules has been implicated in the pathogenesis which is thought to have a significant autoimmune component. We report herein on the cloning and characterization of a full-length cDNA from a T. cruzi expression library encoding a protein, TcP0, that is homologous to the human 38-kD ribosomal phosphoprotein HuP0. The T. cruzi P0 protein shows a clustering of residues that are evolutionarily conserved in higher eukaryotes. This includes an alanine- and glycine-rich region adjacent to a highly charged COOH terminus. This "hallmark" domain is the basis of the crossreactivity of the highly immunogenic eukaryotic P protein family. We found that T. cruzi-infected individuals have antibodies reacting with host (self) P proteins, as well as with recombinant TcP0. Deletion of the six carboxy-terminal amino acids abolished the reactivity of the T. cruzi infection sera with TcP0. This is similar to the specificity of anti-P autoantibodies described for a subset of patients with systemic lupus erythematosus (SLE) (Elkon, K., E. Bonfa, R. Llovet, W. Danho, H. Weissbach, and N. Brot. 1988. Proc. Natl. Acad. Sci. USA. 85:5186). These results suggest that T. cruzi P proteins may contribute to the development of autoreactive antibodies in Chagas' disease, and that the underlying mechanisms of anti-P autoantibody may be similar in Chagas' and SLE patients. This study represents the first definitive report of the cloning of a full-length T. cruzi antigen that mimics a characterized host homologue in structure, function, and shared antigenicity.

Amino Acid Sequence↗
PubMed1992

Efficacy of laser punctal occlusion.

Dry eye is a common problem and in its more severe form may be treated with punctal occlusion. Photothermal coagulation of the puncta with the argon laser has recently been advocated to occlude the lacrimal puncta. Its long-term efficacy has not been investigated. The authors examined 22 puncta that had been occluded with the argon laser an average of 16 months before this study. Of the 22 puncta, 19 (86%) were patent. The results of our retrospective studies suggest that argon laser punctal occlusion is not an efficacious method for producing long-term punctal closure. The authors also used an animal model to investigate the effect on tissue of thermal cauterization and argon laser photothermal coagulation and found that thermal cauterization resulted in more widespread coagulative necrosis.

Adult↗
PubMed1992

Unstable thoracolumbar and lumbar burst fractures treated with the AO fixateur interne.

Twenty-five consecutive patients with unstable thoracolumbar and lumbar burst fractures were surgically treated with the AO Fixateur Interne (Synthes USA, 1690 Russell Rd., Paoli, PA). Indications for surgery included a progressive neurologic deficit, spinal canal compromise greater than 50%, vertebral body collapse greater than 50%, or sagittal angulation greater than 20 degrees. Twenty males and five females ranging in age from 16 to 60 years (average 31) were treated surgically and prospectively followed. Twenty-one fractures occurred at the thoracolumbar junction (T10-L2) and 4 in the lumbar spine (L3-5). Twenty-four patients were followed for a minimum of 12 months, ranging from 12 to 38 months (average 22); one patient was lost to follow-up after 1 month postoperatively. Preoperatively, 12 patients had partial neurologic deficits; postoperatively, 11 improved at least 1 Frankel grade. Preoperatively, the 12 patients with partial neurologic deficits averaged 45 points (range 24-49) on the lower extremity motor index scale. After surgery, these patients improved an average of five points (range 1-23) on the motor index scale. Both patients with complete spinal cord injuries remained unchanged neurologically postoperatively; no patients deteriorated neurologically after surgery. The average preoperative sagittal kyphosis at the fracture site was +16 degrees (range +10 degrees to +31 degrees); the immediate postoperative sagittal angular correction averaged -4 degrees (lordosis) and ranged from +12 degrees (kyphosis) to -26 degrees (lordosis). At last follow-up, the sagittal angular correction remained unchanged in three patients and decreased in 21 patients to an average of +5 degrees (range +37 degrees to -14 degrees).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Scanning electron and light microscopic study of microbial succession on bethlehem st. Nectaire cheese.

St. Nectaire cheese is a semisoft cheese of French origin that, along with Brie and Camembert cheeses, belongs to the class of surface mold-ripened cheese. The surface microorganisms that develop on the cheese rind during ripening impart a distinctive aroma and flavor to this class of cheese. We have documented the sequential appearance of microorganisms on the cheese rind and in the curd over a 60-day ripening period. Scanning electron microscopy was used to visualize the development of surface fungi and bacteria. Light microscopy of stained paraffin sections was used to study cross sections through the rind. We also monitored the development of bacterial and yeast populations in and the pH of the curd and rind. The earliest stage of ripening (0 to 2 days) is dominated by the lactic acid bacterium Streptococcus cremoris and multilateral budding yeasts, primarily Debaryomyces and Torulopsis species. Geotrichum candidum follows closely, and then zygomycetes of the genus Mucor develop at day 4 of ripening. At day 20, the deuteromycete Trichothecium roseum appears. From day 20 until the end of the ripening process, coryneforms of the genera Brevibacterium and Arthrobacter can be seen near the surface of the cheese rind among fungal hyphae and yeast cells.

Journal Article↗
PubMed1991

Spinal canal decompression in traumatic thoracolumbar burst fractures: posterior distraction rods versus transpedicular screw fixation.

Although the benefit of spinal canal decompression of traumatic thoracolumbar burst fractures is controversial, it remains a desirable procedure, as many reports describe improved neurologic outcome with spinal canal reconstruction. The optimal type of posterior instrumentation for reconstructing the spinal canal is unclear. This study focused on the efficacy of posterior distraction rods versus transpedicular screw fixation implants in decompressing the spinal canal and on the relationship between the amount of canal decompression and subsequent neurologic recovery. A medical records review was conducted to identify all patients surgically treated for traumatic burst fractures of the thoracolumbar spine from January 1, 1987 to June 30, 1989. Sixty-seven patients were selected by this review, and, of these, 30 had had both preoperative and postoperative CT scans. We could find no bias among patients who received both preoperative and postoperative CT scans as compared to those who did not, therefore the 30 patients were considered to be a random sample of the total population of 67. A retrospective study was then conducted on the 30 patients with surgically treated burst fractures--15 treated with posterior distraction rods and 15 treated with AO Fixator Interne transpedicular screw fixation implants. Preoperative and postoperative spinal canal cross-sectional areas were measured directly from the scaled CT scans. The area of most severe compromise was compared with an internal standard defined as the next, caudal, uncompromised spinal level, and the percentage of preoperative and postoperative canal compromise was calculated.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Biomechanics of cervical spine internal fixation.

Recent advances in the area of cervical spine internal fixation have resulted in important additions to the armamentarium of the spine surgery. However, a sophisticated knowledge of the biomechanics of these devices is important. This article discusses the biomechanics of odontoid screws, anterior cervical plates, posterior cervical plates, and posterior C1-C2 screw arthrodesis. It is hoped that this information will aid in implant selection.

Biomechanical Phenomena↗
PubMed1991

Isolation and structure of the lipid envelopes from the nitrogen-fixing vesicles of Frankia sp. strain CpI1.

Frankia vesicles are differentiated during nitrogen starvation; they contain nitrogenase whether produced by free-living frankiae or by frankiae in actinorhizal root nodules. Vesicles are surrounded by envelopes of several monolayers of uncharacterized lipid. It has been suggested that the envelope limits diffusion of O2 into the vesicle cytoplasm, thereby preventing inactivation of nitrogenase. Whole vesicles were prepared on sucrose gradients and sonicated, and vesicle envelopes were isolated on top of a cushion of 40% sucrose. Transmission electron microscopy of potassium permanganate-fixed envelopes confirmed the purity of these preparations. Only the outer and inner envelope layers were visible in permanganate-fixed intact vesicles; the laminae were not visible in aldehyde-osmium-fixed, lead citrate-uranyl acetate-stained whole vesicles. However, the laminated nature of the envelope was clearly evident in sonicated vesicles and in envelope fragments fixed with KMnO4. The observations indicate that partial disruption of the vesicle envelope enables its visualization with permanganate fixation, and these observations open the way for further studies on the relationship of the vesicle surface to environmental conditions.

Actinomycetales↗
PubMed1990

Dural tears associated with lumbar burst fractures.

A retrospective review of 817 spinal fracture patients revealed a 7.7% (20 of 258) incidence of dural tears in surgically treated patients. Dural tears were most common in the lumbar burst fractures (10 of 85). Twenty-five percent of patients with lumbar spine burst fractures and a neurologic deficit had a dural tear requiring repair. Eighty-six percent of patients with lumbar burst injuries and dural tears had a neurologic deficit. An initial posterior approach with inspection of the dura and stabilization of the fracture is recommended when treating lumbar burst fractures with a neural deficit.

Dura Mater↗
PubMed1990

Enzymes of ammonia assimilation in hyphae and vesicles of Frankia sp. strain CpI1.

Frankia spp. are filamentous actinomycetes that fix N2 in culture and in actinorhizal root nodules. In combined nitrogen-depleted aerobic environments, nitrogenase is restricted to thick-walled spherical structures, Frankia vesicles, that are formed on short stalks along the vegetative hyphae. The activities of the NH4(+)-assimilating enzymes (glutamine synthetase [GS], glutamate synthase, glutamate dehydrogenase, and alanine dehydrogenase) were determined in cells grown on NH4+ and N2 and in vesicles and hyphae from N2-fixing cultures separated on sucrose gradients. The two frankial GSs, GSI and GSII, were present in vesicles at levels similar to those detected in vegetative hyphae from N2-fixing cultures as shown by enzyme assay and two-dimensional polyacrylamide gel electrophoresis. Glutamate synthase, glutamate dehydrogenase, and alanine dehydrogenase activities were restricted to the vegetative hyphae. Vesicles apparently lack a complete pathway for assimilating ammonia beyond the glutamine stage.

Actinomycetales↗
PubMed1990

Molecular cloning, sequencing, and expression of the glutamine synthetase II (glnII) gene from the actinomycete root nodule symbiont Frankia sp. strain CpI1.

In common with other plant symbionts, Frankia spp., the actinomycete N2-fixing symbionts of certain nonleguminous woody plants, synthesize two glutamine synthetases, GSI and GSII. DNA encoding the Bradyrhizobium japonicum gene for GSII (glnII) hybridized to DNA from three Frankia strains. B. japonicum glnII was used as a probe to clone the glnII gene from a size-selected KpnI library of Frankia strain CpI1 DNA. The region corresponding to the Frankia sp. strain CpI1 glnII gene was sequenced, and the amino acid sequence was compared with that of the GS gene from the pea and glnII from B. japonicum. The Frankia glnII gene product has a high degree of similarity with both GSII from B. japonicum and GS from pea, although the sequence was about equally similar to both the bacterial and eucaryotic proteins. The Frankia glnII gene was also capable of complementing an Escherichia coli delta glnA mutant when transcribed from the vector lac promoter, but not when transcribed from the Frankia promoter. GSII produced in E. coli was heat labile, like the enzyme produced in Frankia sp. strain CpI1 but unlike the wild-type E. coli enzyme.

Actinomycetales↗
PubMed1990

Non-contiguous spinal fractures.

A retrospective review of 817 spinal fracture patients revealed a 6.4% (52/817) incidence of non-contiguous spine fractures. Seventy-three per cent of the non-contiguous injuries were comprised of combinations of injuries in the cervical and thoracic regions or in the thoracic and lumbar regions. Forty-five per cent of fractures were a combination of compression fractures, 40% a combination of a compression fracture and a major spine fracture (i.e., one more likely to cause a neurologic deficit), and 15% a combination of major fractures.

Fractures, Bone↗
PubMed1989

Differences in fatty acid composition between vegetative cells and N(2)-fixing vesicles of Frankia sp. strain CpI1.

When growing on N(2), actinomycetes from the genus Frankia form multicellular structures that contain nitrogenase. The structures are referred to as vesicles and are indistinguishable from vesicles formed when Frankia sp. are in root-nodule symbioses. Vesicles isolated from N(2)-grown cells of Frankia sp. strain CpI1 had a significantly higher amount and different composition of fatty acids than did vegetative cells recovered from NH(4) (+)-containing medium. Lipids from vesicles, whole cells grown on N(2), and whole cells grown on NH(4) (+) were fractionated by silicic acid chromatography into neutral lipids, glycolipids, and polar lipids. The fatty acids were transesterified by methanolysis and analyzed by gas chromatography and mass spectrometry. Vesicles had considerably higher amounts of fatty acids in the neutral and glycolipid fractions but lower amounts of polar lipid fatty acids than did vegetative cells. Polar lipids from vesicles had a higher proportion of mono-unsaturated and cyclopropane fatty acids and a lower proportion of isobranched fatty acids than did polar lipids from NH(4) (+)-grown or N(2)-grown cells. The neutral lipid and glycolipid fractions contained several long-chain compounds with molecular ions at m/z 408 and 410. The proportions of these compounds were significantly higher in the lipids from vesicles than from vegetative cells. These results suggest that lipids in vesicles might be involved in the protection of nitrogenase from O(2) and suggest a parallel with the glycolipids involved in protecting nitrogenase from O(2) in the cyanobacterial heterocysts.

Journal Article↗
PubMed1989

Somatosensory evoked potentials for orthopaedic spine trauma.

Monitoring somatosensory evoked potentials (SSEPs) for intraoperative assessment of spinal cord activity provides a reliable and valid measure of sensory function during manipulation of structures placing cord function at risk. We describe a multichannel technique with artifact reductions that has proved successful in 415 spine cases including 146 posttraumatic injuries. Accurate prediction of sensory function in near or at 100% of cases is possible. No patient has recovered with less than the predicted sensory function. Statistics and cases are presented. A professional-level consultant role for SSEP monitoring is suggested as necessary for valid use of the technique.

Adult↗
PubMed1989

Intraoperative ultrasonography for reduction of thoracolumbar burst fractures.

The purpose of this study was to determine the efficacy of intraoperative ultrasound monitoring in the reduction and stabilization of thoracolumbar burst fractures of the spine. Thirty-one patients underwent a posterior approach for reduction and stabilization of a thoracolumbar burst fracture, with complete follow-up available on 26. Intraoperative real-time sonography was used for monitoring retropulsed fragments during distraction and fracture impaction. Computed tomography was used to compare preoperative canal compromise and postoperative reduction. Average canal compromise preoperatively was 66.5%, and the average canal compromise postoperatively was 18.7%. Neurologic function was not changed in 16, improved in ten, and worsened in none. Average hospital stay was 21.6 days. No complications were directly attributable to the use of the ultrasound. The authors believe that ultrasonography provides a safe and accurate method of intraoperatively evaluating reduction of burst fracture of the thoracolumbar spine from the posterior approach.

Follow-Up Studies↗