Intoxication of Crotalaria pallida seeds to growing broiler chicks

The adverse effects of feeding Crotalaria pallida (CP) seeds to chicks was investigated in a 21-day randomized trial of 4 dietary treatments (control, 1,2 and 3% ground CP seeds). Mortality rates in birds fed 0, 1, 2, and 3% dietary CP were 0, 2.1, 6.2, and 16.7%, respectively. Body weight gain and feed efficiency were adversely affected by all levels of inclusion of CP seeds, but feed intake was decreased only by dietary levels of 2 and 3%. Dietary CP of 2 and 3% increased the relative weight of lung, heart and spleen. Relative liver weight was increased by 2% dietary CP, but decreased by 3% CP. At day 14, serum GGT was increased by 2 and 3% dietary CP; serum ALT was significantly increased by 3% CP. No differences in ALT, AST or GGT were observed at day 21. Dietary levels equal to or greater than 1% CP are toxic for growing broiler chicks.

Assessing changes in Cd phytoavailability to tomato in amended calcareous soils

A plot study was conducted to assess changes in Cd phytoavailability to a tomato cultivar in an agricultural soil in Southeastern Spain amended in two different ways (A and B), under controlled conditions. The experimental soil corresponded to a fine-loamy carbonatic thermic Calcidic Haploxeroll (Soil Survey Staff, Keys to Soil Taxonomy, eighth ed., USDA, Washington, 1998). (A) Soil was amended with a single application of sewage sludge from a municipal source that had a total Cd concentration of 0.5 mg kg(-1) at a rate that represented a final average concentration in the mixture of soil and sludge of less than 50 microg Cd kg(-1). (B) The amendment consisted of the addition of a mineral fertiliser with the same amount of NPK as in the sewage sludge application. The final levels of Cd were supposed to be negligible. A plot series without amendments was also performed (C). DTPA plus triethanolamine, and ammonium acetate extractable fractions in soils were analysed for all the plots. The time-dependent Cd accumulation in different parts of the tomato plants was studied by means of a Cd salt treatment. For each block (A-C) four levels of Cd (0, 3, 30, and 100 mg kg(-1)) were added as CdCl2. There was a significant increase in plant Cd after the initial cropping. Tomato stems, leaves and fruits were analysed separately for Cd determination. Differential Cd distribution and accumulation in tomato parts was detected.

Contribution of engineered electrostatic interactions to the stability of cytosolic malate dehydrogenase

Protein engineering is a promising tool to obtain stable proteins. Comparison between homologous thermophilic and mesophilic enzymes from a given structural family can reveal structural features responsible for the enhanced stability of thermophilic proteins. Structures from pig heart cytosolic and Thermus flavus malate dehydrogenases (cMDH, Tf MDH), two proteins showing a 55% sequence homology, were compared with the aim of increasing cMDH stability using features from the Thermus flavus enzyme. Three potential salt bridges from Tf MDH were selected on the basis of their location in the protein (surface R176-D200, inter-subunit E57-K168 and intrasubunit R149-E275) and implemented on cMDH using site-directed mutagenesis. Mutants containing E275 were not produced in any detectable amount, which shows that the energy penalty of introducing a charge imbalance in a region that was not exposed to solvent was too unfavourable to allow proper folding of the protein. The salt bridge R149-E275, if formed, would not enhance stability enough to overcome this effect. The remaining mutants were expressed and active and no differences from wild-type other than stability were found. Of the mutants assayed, Q57E/L168K led to a stability increase of 0.4 kcal/mol, as determined by either guanidinium chloride denaturalization or thermal inactivation experiments. This results in a 15 degrees C shift in the optimal temperature, thus confirming that the inter-subunit salt bridge initially present in the T.flavus enzyme was formed in the cMDH structure and that the extra energy obtained is transformed into an increase in protein stability. These results indicate that the use of structural features of thermophilic enzymes, revealed by a detailed comparison of three-dimensional structures, is a valid strategy to improve the stability of mesophilic malate dehydrogenases.

Relationships between inhibition constants, inhibitor concentrations for 50% inhibition and types of inhibition: new ways of analysing data

The concentration of an inhibitor that decreases the rate of an enzyme-catalysed reaction by 50%, symbolized i(0.5), is often used in pharmacological studies to characterize inhibitors. It can be estimated from the common inhibition plots used in biochemistry by means of the fact that the extrapolated inhibitor concentration at which the rate becomes infinite is equal to -i(0.5). This method is, in principle, more accurate than comparing the rates at various different inhibitor concentrations, and inferring the value of i(0.5) by interpolation. Its reciprocal, 1/i(0.5), is linearly dependent on v(0)/V, the uninhibited rate divided by the limiting rate, and the extrapolated value of v(0)/V at which 1/i(0.5) is zero allows the type of inhibition to be characterized: this value is 1 if the inhibition is strictly competitive; greater than 1 if the inhibition is mixed with a predominantly competitive component; infinite (i.e. 1/i(0.5) does not vary with v(0)/V) if the inhibition is pure non-competitive (i.e. mixed with competitive and uncompetitive components equal); negative if the inhibition is mixed with a predominantly uncompetitive component; and zero if it is strictly uncompetitive. The type of analysis proposed has been tested experimentally by examining inhibition of lactate dehydrogenase by oxalate (an uncompetitive inhibitor with respect to pyruvate) and oxamate (a competitive inhibitor with respect to pyruvate), and of cytosolic malate dehydrogenase by hydroxymalonate (a mixed inhibitor with respect to oxaloacetate). In all cases there is excellent agreement between theory and experiment.

LYT1 protein is required for efficient in vitro infection by Trypanosoma cruzi

Trypanosoma cruzi invasion of host cells involves several discrete steps: attachment, parasite internalization mediated by recruitment and fusion of host cell lysosomes, and escape from the parasitophorous vacuole to liberate amastigotes to multiply freely in the cytosol. This report describes the initial characterization of the LYT1 gene and the demonstration that the gene product is involved in cell lysis and infectivity. Mutational analysis demonstrated that deletion of LYT1 resulted in attenuation of infection, which was associated with diminished hemolytic activity. Reintroduction of LYT1 restored infectivity in null mutants, confirming the critical role of LYT1 in infection. Additionally, in vitro stage transition experiments with LYT1-deficient lines showed that these parasites converted to extracellular amastigote-like cells and metacyclic trypomastigotes more rapidly than wild-type parasites, suggesting that the diminished infectivity was not a result of the LYT1 deficiency that affected the parasite's ability to complete the life cycle.

DDP1, a heterochromatin-associated multi-KH-domain protein of Drosophila melanogaster, interacts specifically with centromeric satellite DNA sequences

DDP1 is a single-stranded nucleic acid binding protein of Drosophila melanogaster that associates with pericentric heterochromatin. DDP1 contains 15 consecutive KH domains and is homologous to the highly conserved vigilin proteins that, in Saccharomyces cerevisiae, are involved in the control of cell ploidy. DDP1 was identified and purified on the basis of its binding to the pyrimidine-rich C strand of the centromeric Drosophila dodeca-satellite. Here, the interaction of DDP1 with the dodeca-satellite C strand was analyzed in detail. This interaction is sequence specific. In particular, a guanine residue which is highly conserved in natural dodeca-satellite sequences was found to be essential for the efficient binding of DDP1. DDP1 binding was also found to be strongly influenced by the length and extent of secondary structure of the DNA substrate. Efficient DDP1 binding required a minimal length of about 75 to 100 nucleotides and was facilitated by the lack of secondary structure of the substrate. DDP1 also showed a significant affinity for the unstructured pyrimidine-rich strand of the most abundant centromeric Drosophila AAGAG satellite. The stoichiometry of the complexes formed with the dodeca-satellite C strand suggests that, in DDP1, the 15 consecutive KH domains are organized such that they define two nucleic acid binding surfaces. These results are discussed in the context of the possible contribution of DDP1 to heterochromatin organization and function.

Low-flow anesthesia and reduced animal size increase carboxyhemoglobin levels in swine during desflurane and isoflurane breakdown in dried soda lime

After institutional approval, we studied the effect of animal size, anesthetic concentration, and fresh gas flow (FGF) rate on inspired carbon monoxide (CO) and carboxyhemoglobin (COHb) during anesthesia in swine, using soda lime previously dried to 1 +/- 0.1% water content. To ascertain the effect of anesthesia, eight adult pigs were anesthetized with either 1 minimum alveolar anesthetic concentration (MAC) desflurane or isoflurane and, to characterize the effect of the FGF rate, it was doubled in four pigs. To determine the effect of animal size, four small and four large pigs received 1 MAC desflurane or isoflurane, and to determine the effect of the anesthetic concentration, a group of four swine was exposed to 0.5 MAC. CO and COHb concentrations were larger with desflurane (5500 +/- 980 ppm and 57.90% +/- 0.50%, respectively) than with isoflurane (800 ppm and 17.8% +/- 2.14%, respectively), especially in the small animals. Increasing the FGF rate significantly reduced peak CO and COHb concentrations resulting from both anesthetics; however, when each anesthetic was reduced to 0.5 MAC, the concentrations obtained were similar. We conclude that CO intoxication is more severe with desflurane than with isoflurane, that small animals are at higher risk for CO poisoning, and that low FGF can increase COHb concentrations.

IMPLICATIONS

The present study shows that the use of desflurane with desiccated carbon dioxide absorbents in pediatric anesthesia can produce a dangerous carbon dioxide intoxication, especially with low-flow anesthesia.

[Strains of ganciclovir-resistant cytomegalovirus]

BACKGROUND

In countries where the resistance of cytomegalovirus to ganciclovir has been studied, strains resistant to therapeutic doses of this drug have been isolated. When a change in treatment has been impossible the patient has shown bad clinical evolution. The aim of this study was to investigate the presence of these strains in our medium, observe whether the resistances appear in patients previously treated with ganciclovir and determine its implication in the evolution of cytomegalovirus infection.

PATIENTS AND METHODS

One hundred twenty-three stains of cytomegalovirus, isolated during the period 1990-1998, corresponding to the following 94 patients were studied: 17 breast feeding children of healthy parents who were negative controls (sensitive strains), 43 organ transplant recipients, 29 AIDS patients, 2 with other immunodeficiencies and 3 children with intrauterine infection. Seventeen patients were studied due to the insidious course of the infection despite treatment. The remaining were random. The technique used was that of growth inhibition of the strains seeded on different gradients of ganciclovir: 0, 1, 5, 10 and 20 microM. The inoculate consisted in a cellular suspension evaluated according to the degree of viral growth. The strains presenting an inhibitory doses 50% (ID 50%) greater than 10 microM were considered as resistant.

RESULTS

Eighty-two strains presented an ID 50% lower than 5 microM, 24 from 5 to 10 microM and in the 17 remaining strains, corresponding to 12 patients, the ID 50% was greater than 10 microM. The evolution of these latter 12 patients with strains considered to be resistant to ganciclovir was of death in 8. All were immunodepressed and with a history of having previously received ganciclovir. Another currently has a chronic evolution and the three remaining patients, who presented better immunity, became cured. All patients has a chronic evolution and the three remaining patients, who presented better immunity, became cured. All patients had undergone previous treatment with ganciclovir except two: one patient with Wegener disease treated with acyclovir 15 days before, and the other was an infant of an HIV positive mother who had received the drug.

CONCLUSIONS

The presence of cytomegalovirus strains resistant to ganciclovir was confirmed in our patients. The previous use of ganciclovir and, in one case of acyclovir, appears to be implicated in the appearance of resistance. The evolution of the immunodepressed patients with infection by resistant strains was mortal except when their immunity was improved.

DDP1, a single-stranded nucleic acid-binding protein of Drosophila, associates with pericentric heterochromatin and is functionally homologous to the yeast Scp160p, which is involved in the control of cell ploidy

The centromeric dodeca-satellite of Drosophila forms altered DNA structures in vitro in which its purine-rich strand (G-strand) forms stable fold-back structures, while the complementary C-strand remains unstructured. In this paper, the purification and characterization of DDP1, a single-stranded DNA-binding protein of high molecular mass (160 kDa) that specifically binds the unstructured dodeca-satellite C-strand, is presented. In polytene chromosomes, DDP1 is found located at the chromocentre associated with the pericentric heterochromatin but its distribution is not constrained to the dodeca-satellite sequences. DDP1 also localizes to heterochromatin in interphase nuclei of larval neuroblasts. During embryo development, DDP1 becomes nuclear after cellularization, when heterochromatin is fully organized, being also associated with the condensed mitotic chromosomes. In addition to its localization at the chromocentre, in polytene chromosomes, DDP1 is also detected at several sites in the euchromatic arms co-localizing with the heterochromatin protein HP1. DDP1 is a multi-KH domain protein homologous to the yeast Scp160 protein that is involved in the control of cell ploidy. Expression of DDP1 complements a Deltascp160 deletion in yeast. These results are discussed in view of the possible contribution of DNA structure to the structural organization of pericentric heterochromatin.

[Rol of thallium-201/gallium-67 cerebral tomogammography in the differential diagnosis of cerebral space occupying lesions]

INTRODUCTION

Central nervous system (CNS) neoplasms are 10% of all tumors. A metastasis of an unknown primary neoplasm should be suspected in an adult with a cerebral tumor. In this location, the origin of most of metastases (62%) is lung, breast, skin and kidney. However, a differentiation of CNS focal infection and brain tumor, based on clinical status and morphologic imaging, may be difficult. A positive Tl-201 next to a negative Ga-67 SPECT brain scans is entirely in accord with brain metastatic tumor.

CLINICAL CASE

A 72-year-old man, with history of excised bladder cancer, was admitted for neurological symptoms associated with a left occipital mass demonstrated by cranial CT and brain MRI. Clinicoradiological findings suggested a neoplastic process. Two cerebral biopsies just showed inflammatory cells. Tl-201 and Ga-67 SPECT brain scans were performed and their findings, an abnormal uptake of Tl-201 in the left occipital cortex and a negative Ga-67 scan, favored a neoplastic process. Radical exeresis of the lesion showed a metastatic adenosquamous carcinoma of probably lung origin.

CONCLUSION

Tl-201 in addition to Ga-67 brain SPECT scans are a valuable tool for differential diagnosis between cerebral infection and brain tumour in patients with a sole cerebral mass lesion, especially when clinicoradiological findings and biopsy results are conflicting.

Structural basis of substrate specificity in malate dehydrogenases: crystal structure of a ternary complex of porcine cytoplasmic malate dehydrogenase, alpha-ketomalonate and tetrahydoNAD

The structural basis for the extreme discrimination achieved by malate dehydrogenases between a variety of closely related substrates encountered within the cell has been difficult to assess because of the lack of an appropriate catalytically competent structure of the enzyme. Here, we have determined the crystal structure of a ternary complex of porcine cytoplasmic malate dehydrogenase with the alternative substrate alpha-ketomalonate and the coenzyme analogue 1,4,5,6-tetrahydronicotinamide. Both subunits of the dimeric porcine heart, and from the prokaryotes Escherichia coli and Thermus flavus. However, large changes are noted around the active site, where a mobile loop now closes to bring key residues into contact with the substrate. This observation substantiates a postulated mechanism in which the enzyme achieves high levels of substrate discrimination through charge balancing in the active site. As the activated cofactor/substrate complex has a net negative charge, a positive counter-charge is provided by a conserved arginine in the active site loop. The enzyme must, however, also discriminate against smaller substrates, such as pyruvate. The structure shows in the closed (loop down) catalytically competent complex two arginine residues (91 and 97) are driven into close proximity. Without the complimentary, negative charge of the substrate side-chain of oxaloacetate or alpha-ketomalonate, charge repulsion would resist formation production of this catalytically productive conformation, hence minimising the effectiveness of pyruvate as a substrate. By this mechanism, malate dehydrogenase uses charge balancing to achieve fivefold orders of magnitude in discrimination between potential substrates.

Enhancement of resistance in mice treated with Lactobacillus casei: effect on Trichinella spiralis infection

The ability of viable Lactobacillus casei, administered by an intraperitoneal route, to induce resistance in mice against Trichinella spiralis infection was tested. The percent reduction of adult worms in the intestine 5 days after T. spiralis infection observed in L. casei-treated animals, compared with those of the control group, fluctuated between 70.9 and 88.5%; reductions of larvae per gram of muscle tissue, evaluated at 30 days after infection, varied from 46.6 to 84.4% in L. casei-treated mice compared with controls. At 5 days after infection, intestinal villus height was shorter in T. spiralis-infected animals than in L. casei-treated or uninfected mice. There were fewer mast cells/crypt unit in L. casei-treated and uninfected mice than in T. spiralis-infected animals. Lactobacilli-treated mice showed twice as many mononuclear cells/crypt unit as T. spiralis-infected animals. The IFN-gamma serum level was higher in L. casei-treated animals at the time of worm challenge as compared with T. spiralis-infected or uninfected mice. The results indicate that: (1) L. casei increased resistance that acted against T. spiralis infection in mice, (2) this resistance apparently was directed against adult worms in the intestine.

[Swallowing changes in cerebrovascular accidents: incidence, natural history, and repercussions on the nutritional status, morbidity, and mortality]

OBJECTIVE

To determine the frequency of dysphagia in CVA, its natural history and value as a risk factor of respiratory infection, malnutrition and death.

PATIENTS AND METHODS

A prospective study was made of 187 consecutive patients with cerebrovascular accidents (CVA). A standardized test for dysphagia was done during the first two days of the illness and repeated three days a week. The levels of urea, total proteins and albumin were determined on admission and on discharge. The patients were questioned by phone after 6 months.

RESULTS

There was dysphagia of liquids in 36.4% of the patients. The incidence of dysphagia for semisolids was of the same frequency but more severe. Coma was the cause of inability to swallow in 25.7% of the patients. During their stay in hospital one third of the patients with dysphagia died, one third became normal and one third still had dysphagia when they were discharged. After one week, one, three and six months respectively, the cure rate for dysphagia was 29.4%, 4.1%, 55.9% and 55.9%, and survival 83.8%, 67.6%, 61.8% and 60.3%. Thus after 6 months only 3 patients (4.4%) were alive and dysphagic. Half of the 'cures' occurred in the first week, and none occurred after more than 77 days. As compared to the non-dysphagic patients, the dysphagic patients had 10 times more risk of respiratory infection, 18 times higher risk of death, greater loss of albumin and less loss of urea.

CONCLUSIONS

There is a high prevalence of dysphagia in CVA and although functional prognosis is not unfavorable, respiratory infections, malnutrition and death are frequent.

Uptake of I-131 in the biliary tract: a potential cause of a false-positive result of scintiscan

Focal uptake of I-131 in the region of the liver was seen on whole-body scans in a 22-year-old asymptomatic woman who had invasive papillary cancer. Hepatic metastases were unlikely because of the clinical risk factors, and a CT scan of the liver was normal. By superimposing the I-131 scintiscan and a hepatobiliary scan, the site of the uptake was shown to be in the biliary tract, and it had migrated to the gallbladder on more delayed images. No pathologic cause was found.

[Report on the activity of the blood bank accreditation program (1987-1995)]

PURPOSE

To show the incidence of the deficiencies detected in the Blood Banks for the accreditation by the Transfusion Accreditation Committee (CAT), previously named PABAS.

MATERIALS AND METHODS

Analysis of the reports of the accreditation of 85 Blood Banks made by the PABAS during the period 1987-1995.

RESULTS

Eighty-five (20.8%) of the 407 Community Blood Centers, Hospital-Based Blood Banks and Transfusional Services of Spain had been surveyed. There were 244 deficiencies, of which 31 (12.7%) were of the equipment, 114 (46.7%) of the procedures used, and 99 (40.6%) of the documentation. The activities with more incidence of faults were: Control of the temperatures of the storage of units 53 (21.7%), label of the components 38 (15.5%), quality system of the institution surveyed 32 (13.1%), transfusional procedures 30 (12.3%), and on the procedure of the selection of donors 29 (11.9%). By contrary, the areas of work with fewer incidences of faults were those related with the collection of the blood and components 10 (4.1%) and the laboratory 14 (5.7%).

CONCLUSIONS

Low percentage of the Community Blood Centers, Hospital-Based Blood Banks and Transfusional Services, which ask to be accredited by the Transfusion Accreditation Committee. The 83.7% of the errors detected are of the procedures and documentation, which could be easily corrected by the training and continuous improving of the quality, and without need of new inversions in equipment.

Tandem 5'-GA:GA-3' mismatches account for the high stability of the fold-back structures formed by the centromeric Drosophila dodeca-satellite

The centromeric dodeca-satellite of Drosophila forms unusual DNA structures in which its purine-rich strand (GTACGGGACCGA)n folds into very stable intramolecular hairpins. These intramolecular hairpins contain groups of tandem 5'-GA:GA-3' mismatches that, as judged by gel electrophoresis analysis and UV-melting studies, have a determinant contribution to their stability. Duplexes of the dodeca-satellite purine-rich strand, carrying tandem 5'-GA:GA-3' mismatches, are as stable as equivalent fully Watson-Crick duplexes containing tandem 5'-TA:TA-3' Watson-Crick pairs in place of the non-Watson-Crick G.A pairs. On the other hand, duplexes carrying any of the other three possible tandem combinations of purine.purine mismatches, including G.A pairs on the opposite orientation 5'-AG:AG-3', are very unstable. The high stability of the dodeca-satellite hairplus suggests that the tandem G.A pairs are on the sheared configuration although they are found within the less favourable 5'-G-(G-A)-C-3' sequence context. Other centromeres DNA sequences, including the AAGAG satellite of Drosophila and the mammalian CENP-B box sequence, have the potential of forming intramolecular hairpins stabilised by similar purine.purine interactions.