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R López

Publications and source records attributed to R López.

At least 127 records · Page 7Linked to original sources
PubMed1998

Characterization of IS1515, a functional insertion sequence in Streptococcus pneumoniae.

We describe the characterization of a new insertion sequence, IS1515, identified in the genome of Streptococcus pneumoniae I41R, an unencapsulated mutant isolated many years ago (R. Austrian, H. P. Bernheimer, E. E. B. Smith, and G. T. Mills, J. Exp. Med. 110:585-602, 1959). A copy of this element located in the cap1EI41R gene was sequenced. The 871-bp-long IS1515 element possesses 12-bp perfect inverted repeats and generates a 3-bp target duplication upon insertion. The IS encodes a protein of 271 amino acid residues similar to the putative transposases of other insertion sequences, namely IS1381 from S. pneumoniae, ISL2 from Lactobacillus helveticus, IS702 from the cyanobacterium Calothrix sp. strain PCC 7601, and IS112 from Streptomyces albus G. IS1515 appears to be present in the genome of most type 1 pneumococci in a maximum of 13 copies, although it has also been found in the chromosome of pneumococcal isolates belonging to other serotypes. We have found that the unencapsulated phenotype of strain 141R is the result of both the presence of an IS1515 copy and a frameshift mutation in the cap1EI41R gene. Precise excision of the IS was observed in the type 1 encapsulated transformants isolated in experiments designed to repair the frameshift. These results reveal that IS1515 behaves quite differently from other previously described pneumococcal insertion sequences. Several copies of IS1515 were also able to excise and move to another locations in the chromosome of S. pneumoniae. To our knowledge, this is the first report of a functional IS in pneumococcus.

Amino Acid Sequence↗
PubMed1998

Pneumococcal bacteriophage Cp-1 encodes its own protease essential for phage maturation.

The major capsid protein of the pneumococcal phage Cp-1 that accounts for 90% of the total protein found in the purified virions is synthesized by posttranslational processing of the product of the open reading frame (ORF) orf9. Cloning of different ORFs of the Cp-1 genome in Escherichia coli and Streptococcus pneumoniae combined with Western blot analysis of the expressed products led to the conclusion that the product of orf13 is an endoprotease that cleaves off the first 48 amino acid residues of the major head protein. This protease appears to be a key enzyme in the morphopoietic pathway of the Cp-1 phage head. To our knowledge, this is the first case of a bacteriophage infecting gram-positive bacteria that encodes a protease involved in phage maturation.

DNA-Binding Proteins↗
PubMed1998

Effect of discontinuing prophylaxis with norfloxacin in patients with hematologic malignancies and severe neutropenia. A matched case-control study of the effect on infectious morbidity.

The use of fluorinated quinolones for prophylaxis of infections in neutropenic cancer patients has led to a reduction of infections with gram-negative enteric bacilli, but there is concern about the emergence of antibiotic-resistant entero-bacterial infections and a rise of gram-positive bacteremias. Due to these concerns, in mid-1995 the use of prophylactic norfloxacin was discontinued in our unit. In order to evaluate the impact of this measure on the infectious morbidity in our unit, 91 severe neutropenic episodes in 58 patients with hematologic malignancies who did not receive norfloxacin prophylaxis (NO group) were closely matched to 91 episodes in 60 patients who received norfloxacin prophylaxis (NORFLO group). There were no differences in the incidence of febrile neutropenia, fever of unknown origin or bacteremia during the first febrile episode. There was a trend for a higher rate of coagulase-negative staphylococcal bacteremia in the NORFLO group (5 vs. 11 cases in the NO and NORFLO groups, respectively, p = NS). Enterobacterial bloodstream infections were more frequent in the NO group (13 vs. 2 cases, respectively, p = 0.01), especially Escherichia coli (9 vs. 1 case, respectively, p = 0.01). Twelve of 13 enterobacterial isolates in the NO group were sensitive to the fluoroquinolones vs. 0/2 in the NORFLO group (p = 0.07). We conclude that the abrupt discontinuation of norfloxacin prophylaxis in our ward led to a rapid increase in the rate of fluoroquinolone-susceptible enterobacterial infections, with a scarce impact on infectious morbidity. This suggests that the selection of resistant flora in an inpatient ward by prophylactic antimicrobials may be reversible following the discontinuation of the prophylactic agent(s).

Adolescent↗
PubMed1998

[Iron deficiency and pica].

PURPOSE: To study the relationship between pica and iron-lack anaemia in a series of iron-deficiency patients in order to establish the pathogenesis of such relationship. PATIENTS AND METHODS: Four-hundred and thirty-three patients were analysed. Pica was studied by introducing certain diet queries into the clinical history. All patients received oral iron and were periodically controlled with the usual clinico-haematological procedures. RESULTS: Pica was present in 23 patients (5.3%). Eight nourishing (namely, coffee grains, almonds, chocolate, ice, lettuce, carrots, sunflower seeds and bread) and 2 non-nourishing (clay and paper) substances were involved. A second episode of pica appeared in 9 cases upon relapsing of iron deficiency. Both anaemia and pica were cured by etiologic and substitutive therapy in all instances. No clear correlation was found with either socio-economic status or pathogenetic causes of iron deficiency and pica, and no haematological differences were seen between patients with pica and those without this alteration. CONCLUSIONS: (1) The pathogenesis of pica is unclear, although it appears unrelated to the degree of iron deficiency. (2) According to the findings in this series, pica seems a consequence of iron deficiency rather than its cause. (3) Adequate therapy can cure both conditions, although pica may reappear upon relapse of iron deficiency.

Adolescent↗
PubMed1998

[The use of anorectal manometry and dynamic proctography in patients for diagnosis of solitary rectal ulcer syndrome].

BACKGROUND: Solitary rectal ulcer syndrome is caused by rectal prolapse and/or anismus. The diagnosis by physical examination, or using endoscopy or radiology alone is difficult. AIM: To evaluate the diagnostic utility of videoproctography and anorectal manometry in solitary rectal ulcer syndrome. PATIENTS AND METHODS: We studied six patients (5 women/1 man; 21-66 years) with rectal lesions suggestive of solitary rectal ulcer. By videoproctography, we measured the changes in the anorectal angle and the shape of the rectal wall during voiding. By manometry, we measured the resting pressure of the anal canal, and the pressure during maximal voluntary contraction and during straining. RESULTS: Proctography showed a rectal prolapse in 5 patients (non-exteriorized in 4). Both manometry and proctography demonstrated the normal relaxation of puborectalis and external sphincter during straining in 4 patients, manometry found sphincteric weakness in two of these patients. Both manometry and proctography evidenced anismus in a patient with rectal prolapse. CONCLUSION: The high prevalence of rectal prolapse in our patients allows us to recommend proctography in patients with morphological lesions suggestive of solitary rectal ulcer. The manometric examination identifies patients at risk of developing incontinence. Both techniques contribute to ascertain the presence of anismus and are indispensable in the selection of the adequate treatment for patients with solitary rectal ulcer.

Adult↗
PubMed1998

[Cardiorespiratory failure and diabetic autonomic neuropathy: a case report].

Advanced autonomic neuropathy in diabetic patients is associated with homeostatic cardiovascular response. Sympathetic compensation diminishes and the organism becomes more susceptible to the depressant effect of certain drugs. The incidence of undesirable cardiovascular effects (bradycardia, hypotension and sudden heart failure) during anesthesia is higher in such patients. We report the case of a woman with diabetes who suffered two episodes of sudden heart failure after brachial plexus block through the axilla, followed one year later by sudden heart failure during general anesthesia for kidney transplantation. The possible contributing mechanisms are described.

Adult↗
PubMed1998

[Spontaneous chagasic peritonitis in a patient with AIDS].

An AIDS-Chagas association has been extensively reported in the literature specially in cardiac and cerebral localizations. A case is presented of a 36 year old male patient with a diagnosis of AIDS and positive serology for Chagas, as well as chronic hepatopathy and CD4 cell count of 31. While in the hospital he developed ascitis which revealed the presence of numerous tripomastigote forms of T. cruzi in the ascitic fluid. This clinical presentation of Chagasic reactivation has not been reported in the literature.

Acquired Immunodeficiency Syndrome↗
PubMed1998

[Drug allergy in a population of surgical patients].

OBJECTIVES: To determine the prevalence of drug allergies in a population of surgical patients. To establish a clinical classification of events as being very or not very likely to be allergic reactions. To detect which drug groups are associated with greater incidence of anaphylactic reaction and to analyze the severity of such reactions. PATIENTS AND METHODS: Epidemiological study. During a preoperative interview, patients were asked if they were aware of the existence of any episode of allergy to drugs. If a patient answered yes, a specific data collection questionnaire on allergies was completed. Based on signs and symptoms described by the patient, reactions were classified as indicating high likelihood of allergy, low likelihood of allergy, or as being of unknown origin. RESULTS: We questioned 1,218 patients (754 women/464 men), of whom 159 (13.05%) reported being allergic to drugs. The total number of drugs employed was 212 (1.34 drugs/patient). Antibiotics (54.7%), nonsteroidal anti-inflammatory drugs (NSAIDs) (19.3%), radiological contrast media (6.1%) and local anesthetics (4.7%) were the substance groups most often mentioned. We classified 74.5% of the reactions as indicating high likelihood of allergy, 19.8% as indicating low likelihood, and 5.6% to be of unknown origin. The skin was involved in 72.1% of the reactions that were highly likely to have been caused by allergy; 6.9% of these reactions involved the respiratory tract, 4.4% the circulatory system, 12% the skin plus respiratory tract, and 4.4% the skin plus respiratory and circulatory systems. The most severe reactions (16.4%) were associated with radiological contrast media (36.4%), NSAIDs (33.3%) and intravenous administration (38.1%). Signs of latex allergy were seen in 0.4% and signs of allergy to hair dyes in 0.9%. All allergy tests were negative in all these patients. CONCLUSIONS: Drug allergy is reported by 13% of patients. It is highly likely that 74.5% of reactions are due to allergy. Antibiotics are the most frequently implicated drugs, followed by NSAIDs. The most serious reactions are caused by radiological contrast media and NSAIDs. Intravenous administration causes the most serious reactions.

Adolescent↗
PubMed1997

Ecology of inoculated and spontaneous fermentations in Rioja (Spain) musts, examined by mitochondrial DNA restriction analysis.

Analysis of mitochondrial DNA restriction patterns was used to study the introduction of a selected strain of Saccharomyces cerevisiae for fermentation of non-sterile musts of La Rioja (Spain). All of the isolates from the inoculated musts showed the restriction pattern of the selected strain. The same technique was used to study the spontaneous fermentation of musts, showing that a few strains were responsible for the fermentations. One of the strains identified from the spontaneous fermentations had been identified in a previous vintage.

Animals↗
PubMed1997

A Streptomyces fradiae protease dissociates structurally preserved neurons and glial cells from the embryonic and adult central nervous system of vertebrates.

Nerve cell dissociation has become a key procedural tool in the implementation of a number of techniques in cellular and molecular neurobiology. We report that a protease preparation from Streptomyces fradiae (henceforth SF-protease) dissociates viable and morphologically identifiable embryonic and mature neurons and glial cells from the central nervous system of chick and rat, when used under strictly controlled conditions. Typical dendritic and axonal growth cones, with their lamellipodia and filopodia, are seen in many neuroblast types - growth cones in the case of embryonic glial cells and even the thinnest processes of some cells, such as the microvilli of adult chick retinal Müller (glial) cells, or the cilia of photoreceptors appear intact. Our results suggest that the SF-protease releases cells from tissue in a way that ensures the continuity of the plasma membrane and cuts through the transmembrane attachment systems (either cell-cell or cell-extracellular matrix) without compromising the cytoskeletal integrity underlying native cell shape.

Animals↗
PubMed1997

Molecular biology of the capsular genes of Streptococcus pneumoniae.

The polysaccharide capsule of Streptococcus pneumoniae is the main virulence factor of this microorganism. Although the study of the genes responsible for the synthesis of the pneumococcal capsule enabled genetic and molecular analysis, the precise structure, organization, and functioning of these genes have only been investigated very recently. The genes implicated in the production of the type 3 capsule have been sequenced, expressed and their corresponding products biochemically characterized. In addition, partial information on the genes responsible for the biosynthesis of the capsules of pneumococcal types 1, 14 or 19 F is currently available.

Bacterial Capsules↗
PubMed1997

Angiotensin converting enzyme inhibition corrects Na+/H+ exchanger overactivity in essential hypertension.

In this study, we investigated whether antihypertensive treatment with the angiotensin converting enzyme inhibitor quinapril modifies Na+/H+ exchanger activity or NHE-1 (isoform of the exchanger) mRNA expression in lymphocytes from patients with essential hypertension. Thirty-three hypertensive patients and 27 normotensive subjects were studied. Maximal sodium-proton exchange activity was determined by acidifying cell pH and measuring the initial rate of the net sodium-dependent proton efflux driven by an outward proton gradient. The transcript level of NHE-1 was measured by reverse transcription-polymerase chain reaction in comparison with a constitutively expressed reference gene (beta-actin). With the 100% confidence (upper) limit of the normotensive population as a cutoff point, a subgroup of 11 hypertensive patients had an abnormally high lymphocyte Na+/H+ exchange activity (group A). The activity of the exchanger was within the normal range in the remaining patients (group B). After 6 months of quinapril treatment the activity of the exchanger decreased to normal values (P < .001) in patients from group A, but remained unchanged in patients from group B. The NHE-1 mRNA expression was not modified with treatment neither in patients from the group A, nor in patients from the group B. These results suggest that chronic angiotensin enzyme inhibition with quinapril abolishes Na+/H+ exchange overactivity present in lymphocytes from a subgroup of hypertensive patients. This effect appears to be independent of changes in the expression of the mRNA encoding for the NHE-1 isoform of the exchanger.

Adult↗
PubMed1997

Molecular organization of the genes required for the synthesis of type 1 capsular polysaccharide of Streptococcus pneumoniae: formation of binary encapsulated pneumococci and identification of cryptic dTDP-rhamnose biosynthesis genes.

We report here the molecular organization of the capsular locus (cap1) of the type 1 pneumococcus. This locus is located between dexB and aliA and flanked by IS1167 insertion elements. Sequence analysis showed that the cluster contains 11 genes (cap1A to cap1K), which are apparently arranged as a single transcriptional unit. The presence of a functional promoter (cap1p) located upstream of cap1A has been demonstrated and the transcription start point was mapped by primer-extension analysis. A 14.3 kb fragment containing the genes cap1ABCDEFGHIJK and including cap1p was sufficient to allow the synthesis of a type 1 capsule in Streptococcus pneumoniae. An internal deletion of cap1E leads to an unencapsulated phenotype demonstrating that this gene is essential for capsular production. The cap1K gene has been expressed in Escherichia coli resulting in UDP-glucose dehydrogenase (UDP-GlcDH) activity. Moreover, this gene was able to restore the synthesis of type 3 capsule when cloned into a plasmid and introduced by transformation into S. pneumoniae cap3A mutants deficient in UDP-GlcDH. In marked contrast with what was previously thought, recombination between cap1K and cap3A does occur. We provide data on the molecular mechanism that leads to the formation of binary encapsulated pneumococcal cells, i.e. strains that simultaneously produce type 1 and type 3 capsules. Downstream of cap1K, one truncated and three complete open reading frames homologous to those involved in the biosynthesis of dTDP-rhamnose, a monosaccharide that does not participate in the formation of type 1 polysaccharide, have been identified in all the clinical strains of type 1 pneumococcus tested. Our results provide new insights into the generation of capsule diversity in pneumococci.

Bacterial Capsules↗
PubMed1997

The lytic enzyme of the pneumococcal phage Dp-1: a chimeric lysin of intergeneric origin.

We have localized, cloned and characterized the genes coding for the lytic system of the pneumococcal phage Dp-1. The lytic enzyme of this phage (Pal), previously identified as an N-acetyl-muramoyl-L-alanine amidase, shows a modular organization similar to that described for the lytic enzymes of Streptococcus pneumoniae and its bacteriophages. The construction of chimeric enzymes between pneumococcus and bacteria (or phages) that belong to different Gram-positive families has shown that the interchange of functional domains switches enzyme specificity. Interestingly, Pal appears to be a natural chimeric enzyme of intergeneric origin, that is the N-terminal domain was highly similar to that of the murein hydrolase coded by a gene found in the phage BK5-T that infects Lactococcus lactis, whereas the C-terminal domain was homologous to those found in the lytic enzymes of the pneumococcal system that is responsible for the binding to the choline residues present in the cell wall substrate. Biochemical analysis of Pal revealed that this enzyme shares important properties with those of the major LytA101 autolysin found in an atypical, clinical pneumococcal isolate. These peculiar characteristics have been ascribed to a modified C-terminal domain. The natural chimeric enzyme described here provides further support for the theory of modular evolution of proteins and its characteristics also furnish interesting clues on the molecular mechanisms involved in the more invasive types of atypical pneumococci.

Amino Acid Sequence↗
PubMed1997

Bacteriophages of Streptococcus pneumoniae: a molecular approach.

We have characterized four families of pneumococcal phages with remarkable morphologic and physiological differences. Dp-1 and Cp-1 are lytic phages, whereas HB-3 and EJ-1 are temperate phages. Interestingly, Cp-1 and HB-3 have a terminal protein covalently linked to the 5' ends of their lineal DNAs. In the case of Dp-1, we have found that the choline residues of the teichoic acid were essential components of the phage receptors. We have also developed a transfection system using mature DNAs from Dp-4 and Cp-1. In the later case, the transfecting activity of the DNA was destroyed by treatment with proteolytic enzymes, a feature also shared by the genomes of several small Bacillus phages. DNA replication was investigated in the case of Dp-4 and Cp-1 phages. The terminal protein linked to Cp-1 DNA plays a key role in the peculiar mechanism of DNA replication that has been coined as protein-priming. Recently, the linear 19,345-bp double-stranded DNA of Cp-1 has been completely sequenced, several of its gene products have been analyzed, and a complete transcriptional map has been ellaborated. Most of the pneumococcal lysins exhibit an absolute dependence of the presence of choline in the cell wall substrate for activity, and phage lysis requires, as reported for other systems, the action of a second phage-encoded protein, the holin, which presumably forms some kind of lesion in the membrane. The two lytic gene cassettes, from EJ-1 and Cp-1 phages, have been cloned and expressed in heterologous and homologous systems. The finding that some lysogenic strains of Streptococcus pneumoniae harbor phage remnants has provided important clues on the interchanges between phage and bacteria and supports the view of the chimeric origin of phages.

DNA Replication↗
PubMed1997

The pneumococcal cell wall degrading enzymes: a modular design to create new lysins?

Autolysins are enzymes that degrade different bonds in the peptidoglycan and, eventually, cause the lysis and death of the cell. Streptococcus pneumoniae contains a powerful autolytic enzyme that has been characterized as an N-acetylmuramoyl-L-alanine amidase. We have cloned the lytA gene coding for this amidase and studied in depth the genetics and expression of this gene, which represented the first molecular analysis of a bacterial autolysin. Two observations have been fundamental in revealing further knowledge on the lytic systems of pneumococcus: (a) The well-documented dependence of the pneumococcal autolysin on the presence of choline in the cell wall for activity, and (b) the early observation that most pneumococcal phages also required the presence of this amino-alcohol in the growth medium to achieve a successful liberation of the phage progeny. We concluded that choline would serve as an element of strong selective pressure to preserve certain structures of the host and phage lytic enzymes which should lead to sequence homologies. We constructed active chimeras between the lytic enzymes of S. pneumoniae and its bacteriophages using genes that share sequence homology as well as genes that completely lack homologous regions. In this way, we demonstrated that the pneumococcal lytic enzymes are the result of the fusion of two independent functional modules where the carboxy-terminal domain might be responsible for the specific recognition of choline-containing cell walls whereas the active center of these enzymes should be localized in the N-terminal part of the protein. The modular design postulated for the pneumococcal lysins seems to be a widespread model for many types of microbial proteins and the construction of functional chimeric proteins between the lytic enzymes of pneumococcus and those of several gram-positive microorganisms, like Clostridium acetobutylicum or Lactococcus lactis, provided interesting clues on the modular evolution of proteins. The study of several genes coding for the lytic enzymes of temperate phages of pneumococcus also highlighted on some evolutionary relationships between microorganisms. We suggest that lysogenic relationships may represent a common mechanism by which pathogenic organisms like pneumococcus should undergo a rapid adaptation to an evolving environment.

Bacteriolysis↗
PubMed1997

A functional analysis of the Streptococcus pneumoniae genes involved in the synthesis of type 1 and type 3 capsular polysaccharides.

Type 3 pneumococci produce a capsule composed of cellobiuronic acid units connected in a beta (1-->3) linkage. Cellobiuronic acid is a disaccharide consisting of D-glucuronic acid (GlcA) beta (1-->4) linked to D-glucose (Glc). The genes implicated in the biosynthesis of the type 3 capsule have been cloned, expressed, and biochemically characterized. The three type 3-specific genes--designated as cap3ABC--are transcribed together. However, the two complete open reading frames located upstream of cap3A are not transcribed and, consequently, are not required for capsule formation. The promoter of the cap3 operon was localized by primer extension analysis. The products of cap3A, cap3B, and cap3C were biochemically characterized as a UDP-Glc dehydrogenase, the type 3 polysaccharide synthase, and a Glc-1-P uridyltransferase, respectively. The Cap3B synthase was expressed in Escherichia coli, and pneumococcal type 3 polysaccharide was synthesized in this heterologous system. When a recombinant plasmid (pLSE3B) containing cap3B was introduced by transformation into encapsulated pneumococci of types 1, 2, 5, or 8, the lincomycin-resistant transformants displayed a binary type of capsule, this is, they showed a type 3 capsule in addition to that of the recipient type. Unencapsulated (S2) laboratory strains of S. pneumoniae also synthesized a type 3 capsule when transformed with pLSE3B. On the other hand, we have cloned and sequenced seven type 1-specific genes (designated as cap1A-G), and their functions have been preliminarily assigned based on sequence similarities.

Amino Acid Sequence↗