RESUMEN
AIMS: To isolate and identify endophytic nitrogen-fixing bacteria in sugarcane growing in Cuba without chemical fertilizers. METHODS AND RESULTS: Two N2-fixing isolates, 9C and T2, were obtained from surface-sterilized stems and roots, respectively, of sugarcane variety ML3-18. Both isolates showed acetylene reduction and H2 production in nitrogen-free media. Nitrogenase activity measured by H2 production was about 15 times higher for isolate 9C than for T2 or for Gluconoacetobacter diazotrophicus (PAL-5 standard strain, ATCC 49037). The nifH gene segment was amplified from both isolates using specific primers. Classification of both T2 and 9C was made on the basis of morphological, biochemical, PCR tests and 16S rDNA sequence analysis. CONCLUSIONS: Isolate 9C was identified as a Pantoea species from its 16S rDNA, but showed considerable differences in physiological properties from previously reported species of this genus. For example, 9C can be cultured over a wide range of temperature, pH and salt concentration, and showed high H2 production (up to 67.7 nmol H2 h(-1) 10(10) cell(-1)). Isolate T2 was a strain of Gluconacetobacter diazotrophicus. SIGNIFICANCE AND IMPACT OF THE STUDY: A new N2-fixing endophyte, i.e. Pantoea, able to produce H2 and to grow in a wide range of conditions, was isolated from sugarcane stem tissue and characterized. The strain with these attributes may well be valuable for agriculture.
Asunto(s)
Gluconacetobacter/aislamiento & purificación , Fijación del Nitrógeno/fisiología , Pantoea/aislamiento & purificación , Saccharum/microbiología , Cuba , Medios de Cultivo , ADN Bacteriano/genética , Gluconacetobacter/genética , Gluconacetobacter/crecimiento & desarrollo , Hidrógeno/metabolismo , Concentración de Iones de Hidrógeno , Nitrogenasa/metabolismo , Pantoea/genética , Pantoea/crecimiento & desarrollo , ARN Bacteriano/genética , ARN Ribosómico 16S/genética , ARN Ribosómico 23S/genética , Microbiología del Suelo , TemperaturaRESUMEN
A series of 2-piperazinylbenzimidazole derivatives were prepared and evaluated as 5-HT3 receptor antagonists. Their 5-HT3 receptor affinities were evaluated by radioligand binding assays, and their abilities to inhibit the 5-HT-induced Bezold-Jarisch reflex in anesthetized rats were determined. Compound 7e (lerisetron, pKi = 9.2) exhibited higher affinity for the 5-HT3 receptor than did tropisetron and granisetron, while compound 7q (pKi = 7.5) had very low affinity for this receptor, showing that substitution on the N1 atom of the benzimidazole ring is essential for affinity and activity. The effect of substitution on the aromatic ring of benzimidazole by several substituents in different positions is also discussed. A strong correlation between the 5-HT3 antagonistic activity of the studied compounds and the position of substitution on the aromatic ring was established. Thus, while the 4-methoxy derivative 7m showed weak affinity for the 5-HT3 receptor (pKi = 6.7), the 7-methoxy derivative 7n exhibited the highest affinity (pKi = 9.4). Compounds 7e and 7n are now under further investigation as drugs for the treatment of nausea and emesis evoked by cancer chemotherapy and radiation.
Asunto(s)
Bencimidazoles/química , Piperazinas/química , Piperidinas , Antagonistas de la Serotonina/síntesis química , Animales , Cobayas , Indazoles/metabolismo , Masculino , Modelos Químicos , Ratas , Ratas Wistar , Receptor de Serotonina 5-HT2A , Receptores de Serotonina/metabolismo , Receptores de Serotonina 5-HT1 , Receptores de Serotonina 5-HT3 , Receptores de Serotonina 5-HT4 , Antagonistas de la Serotonina/farmacología , Tropanos/metabolismoRESUMEN
The intercellular spaces of sugarcane (Saccharum officinarum L.) stem parenchyma are filled with solution (determined by cryoscanning microscopy), which can be removed aseptically by centrifugation. It contained 12% sucrose (Suc; pH 5.5.) and yielded pure cultures of an acid-producing bacterium (approximately 104 bacteria/mL extracted fluid) on N-poor medium containing 10% Suc (pH 5.5). This bacterium was identical with the type culture of Acetobacter diazotrophicus, a recently discovered N2-fixing bacterium specific to sugarcane, with respect to nine biochemical and morphological characteristics, including acetylene reduction in air. Similar bacteria were observed in situ in the intercellular spaces. This demonstrates the presence of an N2-fixing endophyte living in apoplastic fluid of plant tissue and also that the fluid approximates the composition of the endophytes's optimal culture medium. The apoplastic fluid occupied 3% of the stem volume; this approximates 3 tons of fluid/ha of the crop. This endogenous culture broth consisting of substrate and N2-fixing bacteria may be enough volume to account for earlier reports that some cultivars of sugarcane are independent of N fertilizers. It is suggested that genetic manipulation of apoplastic fluid composition may facilitate the establishment of similar symbioses with endophytic bacteria in other crop plants.
RESUMEN
Two patients with chronic lymphocytic leukemia of T-cell immunological origin are studied. One case was of the prolymphocytic variety, and the other corresponded to the "classical" type of chronic T-cell lymphocytic leukemia. From a morphological point of view what stood out was the hyperchromatic aspect of the cytoplasm of the lymphocytic proliferation. The high increase of acid hydrolases localized preferentially in the centrosomic area was the main cytochemical characteristic. Isoenzymatic study of leukocytic acid phosphatase showed a noticeable increase of band 3 and the absence of supernumerary band 3b. Immunological analysis revealed a significant decrease of the surface immunoglobulins and a rise in absolute terms in the number of lymphocytes forming spontaneous rosettes. In the case of the prolymphocytic variety what was particularly noticeable was the great number of lymphocytes bearing complement receptors. The combination of cytomorphologic, isoenzymatic and immunological data make it possible to differentiate between lymphoproliferative diseases of T and B-cell origin at the present time.