RESUMEN
AIMS: To determine the effects of carbohydrates on Bacillus cereus ATCC14579(T) anaerobic metabolism and enterotoxin production in amino acids rich medium. METHODS AND RESULTS: Bacillus cereus anaerobic growth on different carbohydrates (glucose, fructose, sucrose or glucose-fructose mixture) was examined in synthetic mMOD medium under continuous cultures (mu = 0.2 h(-1)). Fermentation end-products, flux partitioning at each key branch points of the mixed acid pathway and consumption or production of amino acids were determined. On both fructose and sucrose, ATP production was favoured via acetate production from acetyl-CoA. In addition, amino acids present in the growth medium showed significant variations with high consumption of serine and net production of glutamate and alanine on some or all sugars. Enterotoxins Hbl and Nhe production was high during growth on fructose (or mixtures involving a fructose moiety). CONCLUSIONS: Fructose was identified as a key sugar influencing anaerobic metabolism and toxin production of B. cereus. SIGNIFICANCE AND IMPACT OF THE STUDY: The physiological differences associated with the fermentation of the various carbohydrates clearly modify toxinogenesis indicating that the risk of foodborne pathogens is to some extent dependent upon the prevailing nutritional environment.
Asunto(s)
Aminoácidos/metabolismo , Bacillus cereus/efectos de los fármacos , Carbohidratos/farmacología , Enterotoxinas/biosíntesis , Adenosina Trifosfato/metabolismo , Alanina/metabolismo , Bacillus cereus/genética , Bacillus cereus/crecimiento & desarrollo , Bacillus cereus/metabolismo , Medios de Cultivo/química , Medios de Cultivo/farmacología , Fermentación , Fructosa/metabolismo , Fructosa/farmacología , Glucosa/metabolismo , Glucosa/farmacología , Ácido Glutámico/metabolismo , Reacción en Cadena de la Polimerasa/métodos , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , Serina/metabolismoRESUMEN
Eukaryotic tRNAs are transcribed as precursors. A 5'-end leader and 3'-end trailer are endonucleolytically removed by RNase P and 3'-tRNase before 3'-end CCA addition, aminoacylation, nuclear export and translation. 3'-End -CC can be a 3'-tRNase anti-determinant with the ability to prevent mature tRNA from recycling through 3'-tRNase. Twenty-two tRNAs punctuate the two rRNAs and 13 mRNAs in long, bidirectional mitochondrial transcripts. Accurate mitochondrial gene expression thus depends on endonucleolytic excision of tRNAs. Various mitochondrial diseases and syndromes could arise from defective tRNA end processing. The U7445C substitution in the human mitochondrial L-strand transcript (U74C directly following the discriminator base of tRNA(Ser(UCN))) causes non-syndromic deafness. The sequence of the precursor (G/UCU) becomes G/CCU, resembling a 3'-tRNase anti-determinant. We demonstrate that a tRNA(Ser(UCN)) precursor with the U7445C substitution cannot be processed in vitro by 3'-tRNase from human mitochondria. A 3'-end processing defect in this tRNA precursor could thus be responsible for mitochondrial disease.
Asunto(s)
Sordera/genética , Enfermedades Mitocondriales/genética , Mutación Puntual/genética , Procesamiento de Término de ARN 3' , Precursores del ARN/metabolismo , ARN de Transferencia de Serina/metabolismo , ARN/metabolismo , Secuencia de Bases , Extractos Celulares , Sordera/enzimología , Endorribonucleasas/metabolismo , Células HeLa , Humanos , Mitocondrias/genética , Enfermedades Mitocondriales/enzimología , Modelos Genéticos , Conformación de Ácido Nucleico , ARN/química , ARN/genética , Precursores del ARN/química , Precursores del ARN/genética , ARN Catalítico/metabolismo , ARN Mitocondrial , ARN de Transferencia de Serina/química , ARN de Transferencia de Serina/genética , Ribonucleasa P , Especificidad por Sustrato , Moldes GenéticosRESUMEN
Current recommendations for mechanical ventilation in the acute respiratory distress syndrome (ARDS) include the use of small tidal volumes (VT), even at the cost of respiratory acidosis. We evaluated the effects of this permissive hypercapnia on pulmonary gas exchange with the multiple inert gas elimination technique (MIGET) in eight patients with ARDS. After making baseline measurements, we induced permissive hypercapnia by reducing VT from 10 +/- 2 ml/kg to 6 +/- 1 ml/kg (mean +/- SEM) at constant positive end-expiratory pressure. After restoration of initial VT, we infused dobutamine to increase cardiac output (Q) by the same amount as with hypercapnia. Permissive hypercapnia increased Q by an average of 1.4 L. min(-)(1). m(2), decreased arterial oxygen tension from 109 +/- 10 mm Hg to 92 +/- 11 mm Hg (p < 0.05), markedly increased true shunt (Q S/Q T), from 32 +/- 6% to 48 +/- 5% (p < 0.0001), and had no effect on the dispersion of VA/Q.VA/Q. On reinstatement of baseline V T with maintenance of a high Q, Q S/Q T remained increased, to 38 +/- 6% (p < 0.05), and Pa(O(2 ))remained decreased, to 93 +/- 4 mm Hg (p < 0. 05). These results agreed with effects of changes in VT and Q predicted by the mathematical lung model of the MIGET. We conclude that permissive hypercapnia increases pulmonary shunt, and that deterioration in gas exchange is explained by the combined effects of increased Q and decreased alveolar ventilation.
Asunto(s)
Hipercapnia/fisiopatología , Intercambio Gaseoso Pulmonar , Síndrome de Dificultad Respiratoria/fisiopatología , Adolescente , Adulto , Anciano , Gasto Cardíaco , Femenino , Humanos , Hipercapnia/complicaciones , Masculino , Persona de Mediana Edad , Síndrome de Dificultad Respiratoria/complicacionesRESUMEN
A small surgical lesion of the parietal cortex induces an increase in the expression of several messenger RNAs varying from 172 to 980% in the entire homolateral cerebral cortex, as detected by quantitative in situ hybridization histochemistry. The messenger RNAs encoding the immediate early genes of the leucine zipper family (c-fos, c-jun, jun-B), the Zinc finger family (zif268), the glucocorticoid receptor family (NGFI-B) and the interferon family (PC4) are increased within 2 h after the lesion and return to normal levels at 6 h. The messenger RNAs encoding cholecystokinin, neuropeptide Y, somatostatin and the synthetizing enzyme of the neurotransmitter GABA, glutamate decarboxylase, are elevated within one day and return to normal levels after six days. An intraperitoneal injection of the N-methyl-D-aspartate receptor antagonist dizocilpine maleate, 30 min before surgery, prevented either the induction of immediate early gene expression or the increase of neuropeptide and glutamate decarboxylase messenger RNA expression. This study demonstrates that a minimal cortical lesion induces extensive changes in gene expression and that the mechanism(s) leading to these changes involves the action of glutamate at the N-methyl-D-aspartate receptor. These modifications may be of importance in explaining diffuse changes not related to neuronal circuitry in several conditions.
Asunto(s)
Corteza Cerebral/metabolismo , Maleato de Dizocilpina/farmacología , Genes Inmediatos-Precoces , Genes fos , Genes jun , Glutamatos/fisiología , Proteínas Inmediatas-Precoces , N-Metilaspartato/antagonistas & inhibidores , Proteínas del Tejido Nervioso/biosíntesis , Neurotransmisores/biosíntesis , Lóbulo Parietal/lesiones , Animales , Infarto Cerebral/fisiopatología , Colecistoquinina/biosíntesis , Colecistoquinina/genética , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/genética , Proteína 1 de la Respuesta de Crecimiento Precoz , Femenino , Regulación de la Expresión Génica , Glutamato Descarboxilasa/biosíntesis , Glutamato Descarboxilasa/genética , Ácido Glutámico , Leucina Zippers/genética , Proteínas de la Membrana/biosíntesis , Proteínas de la Membrana/genética , Proteínas del Tejido Nervioso/genética , Neuropéptido Y/biosíntesis , Neuropéptido Y/genética , Miembro 1 del Grupo A de la Subfamilia 4 de Receptores Nucleares , Ratas , Ratas Wistar , Receptores Citoplasmáticos y Nucleares , Receptores de Esteroides , Somatostatina/biosíntesis , Somatostatina/genética , Factores de Tiempo , Factores de Transcripción/biosíntesis , Factores de Transcripción/genética , Dedos de Zinc/genéticaRESUMEN
RDC8 has been recently cloned and characterized as an adenosine A2 receptor. This receptor is expressed exclusively by medium-sized neurons of the striatum as demonstrated by in situ hybridization. We have now studied the relationship of this receptor with three major components of the rat caudate-putamen: enkephalin, substance P, and choline acetyltransferase. Our results demonstrate that the adenosine A2 receptor is expressed exclusively by the enkephalinergic striatal subpopulation but not by the substance P-containing or cholinergic neurons.