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111.
Spinalona anophtalma n. gen. n. sp. is describedon parthenogenetic and ephippial females andmales from material collected in a temporary lagoonlocated in the Neovolcanic Province from Mexico at analtitude of 2507 m above sea level. It ischaracterized by a strong armature of the antenna,postabdomen and postabdominal claw, no compound eyeor ocellus, the exopod of thoracic limb IIIwith only four setae and that of P5 with only three setae.This new taxon has no relationwith blind Alona from hypogean habitats. 相似文献
112.
Speciation in monogonont rotifers 总被引:7,自引:4,他引:3
Monogonont rotifers are cyclical parthenogens livingin limnic habitats with considerable seasonalvariation and often with island-like features. Theoccurrence of bisexual reproduction in these organismsmakes it feasible to define fields for generecombination, i.e. biological species. In thispaper, we analyze the structure of the diversity inmonogonont rotifers using several data sets: taxonomicand intraspecific diversity as reported inidentification keys, morphological variation reportedin ecological studies, and allozyme and matingbehavior patterns. Our analysis suggests that siblingspecies may be frequent in rotifers. Monogonontrotifers seem to meet conditions for an activespeciation, which might be particularly promoted byseasonal specialization and timing of bisexualreproduction. 相似文献
113.
Identification and Characterization of a New Serotonergic Recognition Site with High Affinity for 5-Carboxamidotryptamine in Mammalian Brain 总被引:1,自引:0,他引:1
Ma. Elena Castro Tamara Romón Ma. Josefa Castillo Elena del Olmo Angel Pazos Carmen del Arco 《Journal of neurochemistry》1997,69(5):2123-2131
Abstract: We analyzed the existence of an additional serotonin (5-HT) receptor subtype, sensitive to 5-carboxamidotryptamine, in the mammalian brain. Radioligand binding studies with [3 H]5-HT were carried out in rat, guinea pig, and human brain membranes, in the presence of unlabeled drugs to mask the binding to all known 5-HT receptors, with the exception of 5-HT1E sites. Under these conditions, unlabeled 5-carboxamidotryptamine still showed a biphasic competition curve with a nanomolar affinity component. Saturation studies with 5-[3 H]carboxamidotryptamine were carried out in the presence of (±)-8-hydroxy-2-(di- n -propylamino)tetralin, mesulergine, and ergotamine, to mask the binding to all receptors known to be labeled by 5-carboxamidotryptamine. These studies showed the existence in cortex and hippocampus from guinea pig and human brain of a remaining binding site with high affinity ( pK D = 7.8–8.1) and a unique pharmacological profile. 5-HT and 5-carboxamidotryptamine showed nanomolar affinity, whereas 5-methoxytryptamine recognized this binding site with intermediate affinity. Other drugs exhibited low or very low potency in inhibiting this binding. The addition of 5'-guanylylimidodiphosphate significantly reduced the number of binding sites labeled by 5-[3 H]carboxamidotryptamine, in the presence of the masking drugs described above, indicating the interaction with a GTP-binding protein. Preliminary autoradiographic studies in human brain appear to indicate that this 5-HT binding site is present in areas such as the globus pallidus, neocortex, and hippocampus, among others. 相似文献
114.
Koulouris Nickolaos G.; Dimopoulou Ioanna; Valta Paivi; Finkelstein Richard; Cosio Manuel G.; Milic-Emili J. 《Journal of applied physiology》1997,82(3):723-731
Koulouris, Nickolaos G., Ioanna Dimopoulou, PäiviValta, Richard Finkelstein, Manuel G. Cosio, and J. Milic-Emili.Detection of expiratory flow limitation during exercise in COPDpatients. J. Appl. Physiol. 82(3):723-731, 1997.The negative expiratory pressure (NEP) method wasused to detect expiratory flow limitation at rest and at differentexercise levels in 4 normal subjects and 14 patients with chronicobstructive pulmonary disease (COPD). This method does not requireperformance of forced expirations, nor does it require use of bodyplethysmography. It consists in applying negative pressure (5cmH2O) at the mouth during early expiration and comparing the flow-volume curve of the ensuing expiration with that of the preceding control breath. Subjects in whomapplication of NEP does not elicit an increase in flow during part orall of the tidal expiration are considered flow limited. The fournormal subjects were not flow limited up to 90% of maximal exercisepower output(max).Five COPD patients were flow limited at rest, 9 were flow limited atone-third max, and 12 were flow limited at two-thirdsmax. Whereasin all patients who were flow limited at rest the maximalO2 uptake was below the normallimits, this was not the case in most of the other patients. Inconclusion, NEP provides a rapid and reliable method to detectexpiratory flow limitation at rest and during exercise. 相似文献
115.
116.
Plasmid rolling circle replication and its control 总被引:10,自引:0,他引:10
Manuel Espinosa Gloria del Solar Fernando Rojo Juan C. Alonso 《FEMS microbiology letters》1995,130(2-3):111-120
Abstract This review summarises current information on rolling circle replicating plasmids originally isolated from Gram-positive bacteria with a low guanine and cytosine content in their DNA. It focuses on the peculiar biological features of these small, high copy number plasmids that replicate via an asymmetric RC mechanism. The regulation of plasmid copy number is also discussed. 相似文献
117.
Gonzalo Bonelo Manuel Megías Dr. Antonio Ventosa Joaquín J. Nieto Francisco Ruiz-Berraquero 《Current microbiology》1984,11(3):165-169
Compared withEscherichia coli, Halobacterium mediterranei was highly resistant to the lethal effect of N-methyl-N-nitro-N-nitrosoguanidine (nitrosoguanidine), but it was sensitive to the mutagenic action of this chemical agent. Nitrosoguanidine at 500 g ml–1 gave a cell survival level between 1% and 10%, and this allowed us to obtain more Josamycin-resistant mutants compared with lower concentrations, which gave higher survival rates but fewer mutants. The efficiency of the mutagenicity obtained with the nitrosoguanidine treatment was examined under a variety of conditions. The optimal conditions for obtaining Josamycinresistant mutants were achieved by exposing, in darkness and without shaking, a suspension of about 108 log-phase cells to 500 g nitrosoguanidine in 1 ml of 50 mM modified saline Tris-maleate buffer at pH 7.5, or in 1 ml of 5 mM modified saline Tris-citrate-maleate for 30 min at 37°C. 相似文献
118.
119.
Inducer T lymphocytes synthesize and secrete peptides that stimulate growth and differentiation of many cell types, including lymphocytes and monocytes that kill foreign organisms, B lymphocytes, mast cells and hematopoietic precursor cells. To define these inducer molecules more precisely, we have generated clones of these T cells as a source of homogeneous material for biochemical analysis. These clones synthesize peptides that stimulate T and B cells to divide and that also induce the latter cells to secrete immunoglobulin. Inducer cells synthesize a 14 kilodalton growth polypeptide that stimulates T and B lymphocytes, as well as other cell types, to divide. This 14 kilodalton peptide is normally associated with different, larger peptides that appear to focus its mitogenic activity to one or another target cell. 相似文献
120.
The incorporation of3H-thymidine into DNA in the brains of the 17-day and 20-day old rat fetuses was significantly reduced by maternal zinc restriction
during pregnancy. The activity of the enzyme thymidine kinase (EC 2.7.1.21) was similarly reduced in the zine-deprived fetal
brains on days 14 and 20 of gestation, but not on day 17. Fetal brain alkaline phosphatase (EC 3.1.3.1) was significantly
depressed by maternal zinc deprivation on days 17 and 20 of pregnancy.
The data suggest an association between thymidine kinase and the reduced incorporation of3H-thymidine into DNA in the brains of 20-day old fetuses but not in animals on day 17. Alkaline phosphatase was however depressed
at this stage.
The suggestion is made that because of the complexity of brain development, future biochemical studies in this area should
concern specific structures in the brain at particular critical stages during neurogenesis. 相似文献