Search PubMed⌕ Search

Biomedical subjects

I Bonilla

Publications and source records attributed to I Bonilla.

32 records · Page 2Linked to original sources
PubMed1997

The aberrant cell walls of boron-deficient bean root nodules have no covalently bound hydroxyproline-/proline-rich proteins.

B-deficient bean (Phaseolus vulgaris L.) nodules examined by light microscopy showed dramatic anatomical changes, mainly in the parenchyma region. Western analysis of total nodule extracts examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that one 116-kD polypeptide was recognized by antibodies raised against hydroxyproline-rich glycoproteins (HRGPs) from the soybean (Glycine max) seed coat. A protein with a comparable molecular mass of 116 kD was purified from the cell walls of soybean root nodules. The amino acid composition of this protein is similar to the early nodulin (ENOD2) gene. Immunoprecipitation of the soybean ENOD2 in vitro translation product showed that the soybean seed coat anti-HRGP antibodies recognized this early nodulin. Furthermore, we used these antibodies to localize the ENOD2 homolog in bean nodules. Immunocytochemistry revealed that in B-deficient nodules ENOD2 was absent in the walls of the nodule parenchyma. The absence of ENOD2 in B-deficient nodules was corroborated by performing hydroxyproline assays. Northern analysis showed that ENOD2 mRNA is present in B-deficient nodules; therefore, the accumulation of ENOD2 is not affected by B deficiency, but its assembly into the cell wall is. B-deficient nodules fix much less N2 than control nodules, probably because the nodule parenchyma is no longer an effective O2 barrier.

Boron↗
PubMed1995

Ionic Stress and Osmotic Pressure Induce Different Alterations in the Lipopolysaccharide of a Rhizobium meliloti Strain.

A halotolerant strain of Rhizobium meliloti was isolated from nodules of a Melilotus plant growing in a salt marsh in Donana National Park (southwest Spain). This strain, EFB1, is able to grow at NaCl concentrations of up to 500 mM, and no effect on growth is produced by 300 mM NaCl. EFB1 showed alterations on its lipopolysaccharide (LPS) structure that can be related to salt stress: (i) silver-stained electrophoretic profiles showed a different mobility that was dependent on ionic stress but not on osmotic pressure, and (ii) a monoclonal antibody, JIM 40, recognized changes in LPS that were dependent on osmotic stress. Both modifications on LPS may form part of the adaptive mechanism of this bacterium for saline environments.

Journal Article↗
PubMed1991

Binding of cadmium by cyanobacterial growth media: free ion concentration as a toxicity index to the cyanobacterium Nostoc UAM 208.

A quantitative study of cadmium binding to three different growth media for nitrogen-fixing cyanobacteria was done with the aid of a solid state ion-specific electrode. Kratz and Myers modified medium and Arnon medium bound large amounts of Cd2+, BG11o medium had less binding capacity. Of the media components, phosphate ion showed the greatest ability to bind Cd2+. Different pHs, the size of cell inoculum and two buffers (Tricine and HEPES, 25 mM) also changed the availability of free cadmium ion in solution. The effect of free Cd2+ ion towards the cyanobacterium Nostoc UAM 208, isolated from a heavy metal polluted environment, also was tested. The effective concentration affecting 50% of population (EC50), at 120 h of exposure, was less for nitrogenase activity (0.26 microgram/mL) than for growth (0.55 microgram/mL), suggesting that this enzyme activity is more sensitive to cadmium than growth. Furthermore, cadmium toxicity was influenced by the addition of buffers to the growth medium. In the presence of buffer, Tricine (25 mM), growth and nitrogenase activity was reduced by 50% at a total cadmium concentration of about 115 micrograms/mL, although no free ion was detected in this case. These results suggest that although generally cadmium toxicity is a function of free metal ion concentration, this can also vary in the presence of complexing agents.

Cadmium↗
PubMed1990

Effect of Boron Deficiency on Photosynthesis and Reductant Sources and Their Relationship with Nitrogenase Activity in Anabaena PCC 7119.

Nitrogenase activity of Anabaena PCC 7119 is inhibited under conditions of boron deficiency. To elucidate the mechanisms of this inhibition, this study examined how the deficiency of boron affected photosynthesis, photosynthetic pigments, the enzymes of the oxidative pentose phosphate pathway, and respiration of Anabaena PCC 7119 cultures. After 24 to 48 hours of boron deficiency, reductions in photosynthetic O(2) evolution and in CO(2) fixation were observed. At the same time, the activities of oxidative pentose phosphate pathway enzymes and respiration increased significantly with boron deficiency. No change was observed in these processes when assays were performed after 4 to 6 hours of deficiency, a time at which nitrogenase activity was severely inhibited. These results suggest that the requirement for boron in N(2) fixation is independent of its effects on photosynthesis and reductant supply.

Journal Article↗
PubMed1990

Boron requirement in cyanobacteria : its possible role in the early evolution of photosynthetic organisms.

The effect of boron on heterocystous and nonheterocystous dinitrogen fixing Cyanobacteria was examined. The absence of boron in culture media inhibited growth and nitrogenase activity in Nodularia sp., Chlorogloeopsis sp., and Nostoc sp. cultures. Examinations of boron-deficient cultures showed changes in heterocyst morphology. However, cultures of nonheterocystous Cyanobacteria, Gloeothece sp. and Plectonema sp., grown in the absence of boron did not show any alteration in growth or nitrogenase activity. These results suggest a requirement of boron only by heterocystous Cyanobacteria. A possible role for this element in the early evolution of photosynthetic organisms is proposed.

Journal Article↗
PubMed1988

Boron Protection for O(2) Diffusion in Heterocysts of Anabaena sp. PCC 7119.

The effect of boron on nitrogenase activity has been studied. When cells were dependent on N(2) fixation, the lack of boron inhibited nitrogenase activity. However, under anaerobic conditions or in the presence of Na-dithionite this effect was not observed. Nitrogenase synthesis was not affected by boron deficiency. Similarly, the heterocyst number was not altered. Examination of boron-deficient cultures showed, however, some dramatic changes in heterocyst morphology. The increased activity of those enzymes related to the maintaining of the low intracellular level of toxic oxygen species (superoxide dismutase, catalase, and peroxidase) support our hypothesis of the role of boron in heterocyst envelope stabilization.

Journal Article↗
PubMed1986

Essentiality of Boron for Dinitrogen Fixation in Anabaena sp. PCC 7119.

The relationship between the requirement for boron and the form of N supplied in nutrient media to cyanobacterium Anabaena sp. PCC 7119 was investigated. When cells were grown in a medium which contained nitrate or ammonium-N, boron deficiency in the nutrient media did not inhibit growth or change cell composition. However, when cells were dependent on N(2) fixation, the lack of boron inhibited growth (i.e. growth ceased after 96 hours under these conditions). Additionally, boron-deficient cells showed a significant decrease in their content of phycobiliproteins and chlorophyll and accumulated carbohydrates within 24 hours of removing boron from the nutrient media. Inhibition of photosynthetic O(2) evolution accompanied the decrease in photosynthetic pigments. Boron deficiency symptoms were relieved when either boron or combined N was added to boron-deficient cultures. The degree of recovery depended upon the age of the cultures. Assays of nitrogenase activity showed that, after 2 hours of growth, nitrogenase activity of boron-deficient cells was inhibited by 40%. After 24 hours a total inactivation of nitrogenase activity was observed in boron-deficient cells. These results strongly suggest an involvement of boron in N(2) fixation in cyanobacteria.

Journal Article↗
PubMed1980

[A rare case of silent cholinesterase genetic variant (author's transl)].

Some patients present prolonged apnea following the administration of succinylcholine because of substantial portion of plasma cholinesterase (the enzyme responsible for the hydrolysis of this muscle relaxant) is present as an atypical variant. Up to the present four types of cholinesterase genes are known which combination can cause apnea to a greater or less extent. Silent homozygous EsEs present apnea of greatest duration due to the complete absence of cholinesterase activity. The case reported belongs to a family of four members and is an example of this extremely uncommon genetic variant, with a frequency of 1/170.000. To determine total cholinesterase activity genetic typing of the whole family was carried out utilizing the spectrophotometric technique of Szasz and Knedel with butirylthiocholine iodide as substrate. Inhibition studies were performed using benzoylcholine and dibucaine, sodium fluoride, scholine, and sodium chloride as inhibitors.

Adolescent↗