Archivos de biologia y medicina experimentales最新文献

The contributions of the peripheral arterial chemoreceptors to the tonic and phasic reflex ventilatory regulation were studied in spontaneously breathing pentobarbitone anesthetized adult cats. The chemosensory drive during eucapnic normoxia was inferred from the transient ventilatory effects induced by anesthetic blockade of the buffer nerves. Aortic nerves block did not modify ventilation. Carotid nerves block provoked transient ventilatory depression, decreasing VT by 46% and fR by 26%, followed by recovery to steady-state values in VT, fR and PETCO2. Changes in PETCO2 were correlated with those in VT, but not with those in fR. The ventilatory effects of blocking a given carotid nerve were more intense when the contralateral carotid nerve was already blocked. This effect may be an expression of hypoadditive interactions between carotid nerves inputs with respect to chemosensory drive of ventilation. Analysis of the dose-response curves for the ventilatory reflexes evoked by NaCN i.v., before and after blockade of the buffer nerves, revealed major contributions of the carotid nerves, with small contributions of the aortic nerves to the those responses to high doses of NaCN. The contributions of each carotid nerve to the tonic chemosensory drive and to the phasic ventilatory chemoreflexes were highly correlated (rs = 0.90; p less than 0.01). We propose that a family of modulatory functions may describe the effects exerted by the peripheral arterial chemoreceptors upon the tonic ventilatory drive in normoxia and the phasic reflex responses evoked by hypoxia. While the carotid nerves mediated modulation is evident in normoxia, that provided by both aortic nerves is only expressed during pronounced hypoxia.

Myths and facts concerning the heredity of human alcohol abuse are discussed in this article. Familial aggregation, adoption studies, twin concordances, marker gene associations and, finally, recent biochemical and genetic evidence are examined critically. It is concluded that with the exception of a possible protective action of the ALDH2 gene in Japanese there is a lack of clear cut evidence with respect to the direct participation of genetic factors in human alcoholism.

This article reviews methods based on direct observation of proton NMR in macromolecules containing 13C or 15N labels. The resonances and Overhauser effects of protons attached to the labels can be edited or filtered from the remaining overlapping resonances. This leads to simplification of the spectra when labels are incorporated selectively. In 2D and related methods the label's chemical shift provides a second dimension which is useful for spectral differentiation and identification. The methods are useful for larger proteins and we describe our progress on studies of T4 lysozyme, mass 18.7 kD, in which we have already identified a large number of resonances.

Secondary structure predictions on nine snake venom phospholipases A2 by the Chou and Fasman and Cid et al. prediction methods, have led to the location of two possible "toxic sites", responsible for the neurotoxic and myotoxic action of the basic snake venom PLA2, respectively. The accessibility to the neurotoxic site is blocked by the presence of a small helical structure (helix D in the bovine PLA2). The role of lysine residues is found to be decisive in the venom's toxicity.

To study the relationship between the exchangeable GTP binding site (E-site) and the high affinity metal binding site we synthesized P3-fluoro P1-5'-guanosine tripaosphate (GTP(gamma F), an analog of GTP. Our results show that this analog binds to the exchangeable GTP binding site of calf brain tubulin. The values of the dissociation constant and the stoichiometry of the GTP(gamma F)-Mn(II) complex as determined by EPR spectroscopy were 1.64 x 10(-4) M and one mole of manganese per mole of nucleotide, respectively. The distance separating the high-affinity binding site for the divalent metal ion and the exchangeable nucleotide binding site was evaluated by using high-resolution 19F-NMR. The 31P- and 19F-NMR spectra of GTP(gamma F) were studied, both the fluorine and the gamma-phosphate were split in a doublet with a coupling constant of 936 Hz. Tubulin purified by the method of Weisenberg (Weisenberg, R.C., and Timashef, S.N. (1970) Biochemistry 9, 4110-4116) was treated with colchicine to stabilize it, GTP(gamma F) was added and the 254.1 MHz 19fluorine relaxation rates measured within the first four hours. Longitudinal and transversal relaxation rates were determined in the presence of colchicine-tubulin-Mn(II), (paramagnetic complex), or the ternary complex with magnesium (diamagnetic complex). The analysis of the temperature-dependent relaxation data indicates that the metal and the exchangeable nucleotide binding sites are separated by a maximal distance of 6 at 35 degrees C, to 8.1 A at 12 degrees C.

The author proposes: 1. That a lineage of living systems is constituted by the reproductive conservation of a manner of living under the form of an ontogenic phenotype. 2. That language is a manner of living in recurrent consensual coordinations of consensual coordinations of actions. 3. That the human manner of living entails among other things, a braiding of languaging and emotioning that we call conversation. 4. That human beings arise in the history of bipedal primates with the origin of language, and the constitution of a lineage defined by the conservation of an ontogenic phenotype that includes conversations as part of it. 5. That the magnitude of the involvement of the brain and anatomy of the larynx and face in speech as our main manner of languaging indicate that language cannot have arisen later than two to three millions year ago. 6. That rationally pertains to the operational coherences of languaging and that different rational domains are constituted by different basic notions that are accepted a priori. That is, on preference. 7. That responsibility and freedom are a function of our awareness of the participation of our emotions (preferences) in the constitution of the rational domains in which we operate.

The distribution of intermediate filaments in toad and frog urinary bladder was studied on frozen sections by indirect immunofluorescence microscopy using specific antiprekeratin antibodies. Our results show that in both species, epithelial cells lining the urinary bladder are very rich in cytokeratin, organized as a filamentous network. In granular cells, the most abundant cells facing the urinary lumen, vasopressin promotes fusion of the membranous tubular structures located in the luminal cytoplasm with the apical cell membrane. A role for intermediate filaments in the membrane rearragements induced by vasopressin in these cells, is proposed.

The interaction between trophoblastic and maternal cells was analysed by electron microscopy on days 6, 7 and 8 of pregnancy, in the mouse. Special emphasis was given to phagocytic activity and invasiveness by the trophoblast. On the sixth day of pregnancy, the trophoblast cells are in contact with the epithelial cells of the implantation crypt, with the basal lamina of the crypt, and with cells of the antimesometrial decidua. On the seventh and eighth days of pregnancy, the trophoblastic cells interact with those of the antimesometrial decidua. The giant trophoblastic cells engulf epithelial cells, maternal blood cells and decidual cells although the pattern of phagocytosis of these structures differs. Both whole epithelial cells and blood cells were ingested. The epithelial cells were deteriorated whereas the blood cells had a normal morphology; the decidual cells were ingested following a severe process of deterioration. Processes of trophoblastic cells interposed between the epithelium of the implantation crypt and its basal lamina seem to contribute to the displacement of the epithelial cells. The invasion of the endometrium by the trophoblast begins with the penetration by processes of trophoblastic cells between the decidual cells. The contact between the surface of both cell types may be very close: adherens type junctions and focal contacts are formed between trophoblastic cells and healthy decidual cells. Trophoblastic cells ingest deteriorated or fragmented cells and gradually occupy the spaces left by the latter.