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A Lagares

Publications and source records attributed to A Lagares.

49 records · Page 3Linked to original sources
PubMed1999

Cerebral aneurysm rupture after r-TPA thrombolysis for acute myocardial infarction.

BACKGROUND: Intracranial hemorrhage is the most dreaded risk of thrombolytic therapy for acute myocardial infarction because of the high mortality and disability rates associated with this complication. Brain structural lesions may predispose a patient to bleeding. To date, aneurysm rupture has not been described as a complication of such therapy. CASE DESCRIPTION: A 66-year-old hypertensive woman was admitted because of chest pain. Myocardial infarction was diagnosed and fibrinolytic therapy with recombinant tissue plasminogen activator (r-TPA) was initiated. Eight hours after admission she became unconscious. Brain computed tomography scan showed subarachnoid hemorrhage, and a cerebral arteriography showed an anterior communicating artery aneurysm. Because of her poor clinical condition treatment was postponed. Death occurred 7 days later because of multiorgan failure. CONCLUSIONS: Cerebral aneurysms should be considered as a possible contributing factor to intracranial bleeding after thrombolytic therapy.

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PubMed1999

Isolation and characterization of alfalfa-nodulating rhizobia present in acidic soils of central argentina and uruguay

We describe the isolation and characterization of alfalfa-nodulating rhizobia from acid soils of different locations in Central Argentina and Uruguay. A collection of 465 isolates was assembled, and the rhizobia were characterized for acid tolerance. Growth tests revealed the existence of 15 acid-tolerant (AT) isolates which were able to grow at pH 5.0 and formed nodules in alfalfa with a low rate of nitrogen fixation. Analysis of those isolates, including partial sequencing of the genes encoding 16S rRNA and genomic PCR-fingerprinting with MBOREP1 and BOXC1 primers, demonstrated that the new isolates share a genetic background closely related to that of the previously reported Rhizobium sp. Or191 recovered from an acid soil in Oregon (B. D. Eardly, J. P. Young, and R. K. Selander, Appl. Environ. Microbiol. 58:1809-1815, 1992). Growth curves, melanin production, temperature tolerance, and megaplasmid profiles of the AT isolates were all coincident with these characteristics in strain Or191. In addition to the ability of all of these strains to nodulate alfalfa (Medicago sativa) inefficiently, the AT isolates also nodulated the common bean and Leucaena leucocephala, showing an extended host range for nodulation of legumes. In alfalfa, the time course of nodule formation by the AT isolate LPU 83 showed a continued nodulation restricted to the emerging secondary roots, which was probably related to the low rate of nitrogen fixation by the largely ineffective nodules. Results demonstrate the complexity of the rhizobial populations present in the acidic soils represented by a main group of N2-fixing rhizobia and a second group of ineffective and less-predominant isolates related to the AT strain Or191.

Journal Article↗
PubMed1996

A stereological analysis of the numerical distribution of neurons in dorsal root ganglia C4-T2 in adult macaque monkeys.

The numbers of neurons in dorsal root ganglia C4-T2 of adult monkeys (M. nemestrina) were estimated in celloidin-embedded material by means of the optical fractionator, a stereological procedures that combines the optical disector with a fractionator sampling scheme. On each side, counts of A-type, B-type, and total neurons were performed for the whole set of ganglia, as well as separately for ganglia C7, C8, and T1. Sampling and counting in this study were carried out with the help of an interactive computer system, the test grids being provided by the GRID general stereological software package (Olympus Denmark). The precision of the estimates for each animal was evaluated by computing the coefficient of error, which was kept at or below 0.10. The mean number of neurons on each side of the C4 - T2 set was 236,500 with a coefficient of variation among animals (CV) of 0.13. Of these neurons, 42% were A-type and 56% were B-type. Mean left-right differences among animals were below 1%, with low variability (CV = 0.07). The mean numbers of neurons in ganglia C7, C8, and T1 were, respectively, 46,000 (CV = 0.20), 51,000 (CV = 0.18), and 41,000 (CV = 0.22). Mean side differences for individual ganglia were 17%, 16%, and 12%, respectively, with high variability among animals. Intraanimal side differences were low for the whole set of ganglia (4%), as well as for the C7-T1 group (5%), but increased substantially when ganglia were considered separately (up to 17% on average in C7) or even in pairs of adjacent ganglia. These findings provide a quantitative frame for developmental or lesion studies in the peripheral somatosensory system of macaques, and warn against using single ganglia in studies requiring quantitative side comparisons.

Animals↗
PubMed1995

Early Interactions of Rhizobium leguminosarum bv. phaseoli and Bean Roots: Specificity in the Process of Adsorption and Its Requirement of Ca(sup2+) and Mg(sup2+) Ions.

Roots of Phaseolus vulgaris L. were incubated with dilute suspensions (1 x 10(sup3) to 3 x 10(sup3) bacteria ml(sup-1)) of an antibiotic-resistant indicator strain of Rhizobium leguminosarum bv. phaseoli in mineral medium and washed four times by a standardized procedure prior to quantitation of adsorption (G. Caetano-Anolles and G. Favelukes, Appl. Environ. Microbiol. 52:371-376, 1986). The population of rhizobia remaining adsorbed on roots after washing was homogeneous, as indicated by the first-order course of its desorption by hydrodynamic shear. Rhizobia were maximally active for adsorption in the early stationary phase of growth. The process leading to adsorption was rapid, without an initial lag, and slowed down after 1 h. Adsorption of the indicator strain at 10(sup3) bacteria ml(sup-1) was inhibited to different extents in the presence of 10(sup3) to 10(sup8) antibiotic-sensitive competitor rhizobia ml(sup-1). After a steep rise above 10(sup4) bacteria ml(sup-1), inhibition by heterologous competitors in the concentration range of 10(sup5) to 10(sup7) bacteria ml(sup-1) was markedly less than by homologous strains, while at 10(sup8) bacteria ml(sup-1) it approached the high level of inhibition by the latter. At 10(sup7) bacteria ml(sup-1), all of the heterologous strains tested were consistently less inhibitory than homologous competitors (P < 0.001). These differences in competitive behavior indicate that in the process of adsorption of R. leguminosarum bv. phaseoli to its host bean roots, different modes of adsorption occur and that some of these modes are specific for the microsymbiont (as previously reported for the alfalfa system [G. Caetano-Anolles and G. Favelukes, Appl. Environ. Microbiol. 52:377-381, 1986]). Moreover, whereas the nonspecific process occurred either in the absence or in the presence of Ca(sup2+) and Mg(sup2+) ions, expression of specificity was totally dependent on the presence of those cations. R. leguminosarum bv. phaseoli bacteria adsorbed in the presence of Ca(sup2+) and Mg(sup2+) were more resistant to desorption by shear forces than were rhizobia adsorbed in their absence. These results indicate that (i) symbiotic specificity in the P. vulgaris-R. leguminosarum bv. phaseoli system is expressed already during the early process of rhizobial adsorption to roots, (ii) Ca(sup2+) and Mg(sup2+) ions are required by R. leguminosarum bv. phaseoli for that specificity, and (iii) those cations cause tighter binding of rhizobia to roots.

Journal Article↗
PubMed1992

A Rhizobium meliloti lipopolysaccharide mutant altered in competitiveness for nodulation of alfalfa.

A transposon Tn5-induced mutant of Rhizobium meliloti Rm2011, designated Rm6963, showed a rough colony morphology on rich and minimal media and an altered lipopolysaccharide (LPS). Major differences from the wild-type LPS were observed in (i) hexose and 2-keto-3-deoxyoctonate elution profiles of crude phenol extracts chromatographed in Sepharose CL-4B, (ii) silver-stained sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis patterns of crude and purified LPS fractions, and (iii) immunoreactivities otherwise present in purified LPS of the parental strain Rm2011. In addition, Rm6963 lost the ability to grow in Luria-Bertani medium containing the hydrophobic compounds sodium deoxycholate or SDS and showed a decrease in survival in TY medium supplemented with high calcium concentrations. The mutant also had altered symbiotic properties. Rm6963 formed nodules that fixed nitrogen but showed a delayed or even reduced ability to nodulate the primary root of alfalfa without showing changes in the position of nodule distribution profiles along the roots. Furthermore, 2 to 3 weeks after inoculation, plants nodulated by Rm6963 were smaller than control plants inoculated with wild-type bacteria in correlation with a transient decrease in nitrogen fixation. In most experiments, the plants recovered later by expressing a full nitrogen-fixing phenotype and developing an abnormally high number of small nodules in lateral roots after 1 month. Rm6963 was also deficient in the ability to compete for nodulation. In coinoculation experiments with equal bacterial numbers of both mutant and wild-type rhizobia, only the parent was recovered from the uppermost root nodules. A strain ratio of approximately 100 to 1 favoring the mutant was necessary to obtain an equal ratio (1:1) of nodule occupancy. These results show that alterations in Rm6963 which include LPS changes lead to an altered symbiotic phenotype during the association with alfalfa that affects the timing of nodule emergence, the progress of nitrogen fixation, and the strain competitiveness for nodulation.

Calcium↗
PubMed1990

Rhizobium meliloti exopolysaccharide Mutants Elicit Feedback Regulation of Nodule Formation in Alfalfa.

Nodule formation by wild-type Rhizobium meliloti is strongly suppressed in younger parts of alfalfa (Medicago sativum L.) root systems as a feedback response to development of the first nodules (G Caetano-Anollés, WD Bauer [1988] Planta 175: 546-557). Mutants of R. meliloti deficient in exopolysaccharide synthesis can induce the formation of organized nodular structures (pseudonodules) on alfalfa roots but are defective in their ability to invade and multiply within host tissues. The formation of empty pseudonodules by exo mutants was found to elicit a feedback suppression of nodule formation similar to that elicited by the wild-type bacteria. Inoculation of an exo mutant onto one side of a split-root system 24 hours before inoculation of the second side with wild-type cells suppressed wild-type nodule formation on the second side in proportion to the extent of pseudonodule formation by the exo mutants. The formation of pseudonodules is thus sufficient to elicit systemic feedback control of nodulation in the host root system: infection thread development and internal proliferation of the bacteria are not required for elicitation of feedback. Pseudonodule formation by the exo mutants was found to be strongly suppressed in split-root systems by prior inoculation on the opposite side with the wild type. Thus, feedback control elicited by the wild-type inhibits Rhizobium-induced redifferentiation of host root cells.

Journal Article↗
PubMedDate not supplied

Release of lipopolysaccharide during Bordetella pertussis growth.

The effect of the addition of (2,6-O-dimethyl)-beta-cyclodextrin (Me beta CD) during growth of Bordetella pertussis in synthetic Stainer-Scholte liquid medium (SS) on lipopolysaccharide (LPS; endotoxin) release was investigated. The Me beta CD concentration used (3 mg/ml) was chosen according to the optimal level found in previous studies to enhance major soluble antigen production. The profiles in SDS-PAGE (sodium dodecyl sulphate/polyacrylamide gel electrophoresis) of LPS extracted from cells grown in SS and SS + Me beta CD media revealed similar patterns. Although the LPS content of whole cells decreased during cell growth, yields obtained at different growth periods in cyclodextrin medium were lower than those corresponding to SS medium alone. Consequently, the level of LPS released in supernatants of both media increased during cellular growth. This amount of free LPS was higher in the cyclodextrin liquid medium and became significant at the beginning of the stationary growth phase. Binding of cyclodextrin to pertussis cells could account for the data obtained. Similar results were obtained with all species of the genus Bordetella.

Bacterial Outer Membrane Proteins↗
PubMedDate not supplied

[Bilateral thalamic gliomas: report of a case with cognitive impairment].

INTRODUCTION: Bilateral thalamic tumours are very rare and have been recently identified as a subgroup of thalamic neoplasms due to their characteristic clinical presentation, with behavioural and memory disorders and without sensory or motor changes. We describe a patient who presented with mood and behaviour changes due to a bilateral thalamic glioma, discuss the literature related to these rare neoplasms and review the anatomical bases of their particular clinical presentation. CASE REPORT: A 67-year-old woman consulted because of behavioural changes and frequent forgetfulness. Neurological examination was normal except from a deficit in the retention of words and numbers. MR images revealed bilateral thalamic swelling by a isointense in T1, hyperintense in T2 and protonic density mass that did not enhance. The tumour was diagnosed as an astrocytoma by stereotactic biopsy. She continued to deteriorate and a year after diagnosis she was bedridden and with a severe dementia. CONCLUSION: Bithalamic tumors, as other lesions that affect the thalamus bilaterally, characteristically present with mood and behaviour changes and memory impairment.

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PubMedDate not supplied

[Guillain-Barre syndrome following resection of glioblastoma multiforme].

INTRODUCTION: Guillain-Barre syndrome (GBS) is an acute demyelinating polyneuropathy characterised by progressive muscular weakness and areflexia. Although the pathogenesis is uncertain, it is probably secondary to an aberrant immunological response to components of the peripheral nervous system. GBS has been linked to bacterial or viral infections, systemic diseases, neoplasias, pregnancy, traumatic injuries or organ transplant. An association with intracranial surgery has been reported, but this is exceptional. CASE REPORT: We report the case of a 67-year-old male submitted to surgical intervention due to a right-side occipital-parietal glioblastoma. The patient was well until ten days after the intervention, when he presented a rapidly progressive are flexive paraparesis with an ascending course. A spinal tap revealed cerebrospinal liquid with an elevated protein level and albuminocytologic dissociation. The electromyogram study and lumbar magnetic resonance with contrast confirmed the suspected diagnosis of GBS. After establishing treatment with immunoglobulins the patient progressed well and recovered quickly and completely from the paresis. CONCLUSIONS: GBS may appear after intracranial surgery and make it more difficult to reach a differential diagnosis with other entities. To optimise the prognosis, treatment must begin as early as possible. Intravenous immunomodulation with immunoglobulins or plasma exchange are effective in shortening the course of the disease.

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