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Biomedical subjects

J Calvete

Publications and source records attributed to J Calvete.

25 records · Page 2Linked to original sources
PubMed1990

Complete localization of the disulfide bridges and glycosylation sites in boar sperm acrosin.

Acrosin is a disulfide-bonded two-chain glycoprotein, which belongs to the serine proteinase family and which plays a central role in mammalian fertilization. The amino acid sequence of acrosin from different species has been recently derived by cDNA analysis. Boar sperm acrosin contains twelve cysteine residues forming two interchain and 4 intrachain disulfide bonds. Protein-chemical and mass-spectroscopic analyses of fragments and subfragments obtained by proteolytic and chemical degradation of the isolated protein allowed the unambiguous localization of all disulfide bridges and glycosylation points in boar acrosin. The 12 cysteines and the glycosylated asparagines in the porcine enzyme are absolutely conserved in number and position within all known acrosin sequences. Thus, the disulfide bond and glycosylation patterns outlined here are conserved during evolution and may be important for enzyme function.

Acrosin↗
PubMed1985

Human vascular smooth muscle responses mediated by alpha 2 mechanisms in vivo and in vitro.

The effects of compounds with alpha 2-agonist and alpha 2-antagonist properties on human forearm blood flow and on isolated human arterial segments have been studied. The findings from these studies in vivo and in vitro did not provide evidence in support of the hypothesis that postsynaptic alpha 2-receptors mediate smooth muscle contraction in the tissues under investigation. The constriction of the forearm vascular bed in response to low intra-arterial doses of idazoxan (RX 781094), an alpha 2-antagonist, provides evidence for a physiological role for a presynaptic alpha 2 autoregulatory mechanism. The variability of the forearm vascular responses to higher doses of idazoxan highlights the pitfalls that may have misled previous authors in their interpretation of the results of similar studies. A U-shaped dose-response curve to compounds with mixed alpha 2- and alpha 1-antagonist properties may be constructed, which emphasizes the importance of the dose-dependent selectivity of these antagonists at alpha 2- and alpha 1-receptors. The effect of idazoxan on the responses of arterial segments in vitro to exogenous catecholamines was dependent on the integrity of the endothelium, and provides evidence that alpha 2-receptors may mediate release of the endothelium-derived relaxing factor.

Adrenergic alpha-Agonists↗
PubMed1985

In vivo and in vitro studies of alpha 2-adrenoceptor responses in human vascular smooth muscle.

To assess the role of alpha 2-receptor mechanisms in the control of vascular tone in humans, the pharmacological activities of RX 781094, an alpha 2-antagonist, and UK 14304, an alpha 2-agonist, have been investigated with the additional use of an alpha 1-antagonist, doxazosin. The effects of these agents on human forearm blood flow have been studied. In addition, some preliminary observations on the effects of these alpha 2-selective agents on isolated human arterial segments have been made. The alpha 2 agonist, UK 14304, produced a dose-dependent reduction in forearm blood flow, but the antagonism of this response by both doxazosin and RX 781094 at a dose which must be regarded as nonselective casts doubt on the hypothesis that alpha 2-receptors may be located postsynaptically in human vascular smooth muscle. These observations may be explained by UK 14304 having partial alpha 1-agonist activity. RX 781094 infused at low doses produced a dose-dependent reduction in forearm blood flow, which is interpreted as evidence for a presynaptic alpha 2 autoregulatory mechanism in the vasculature. Observations on isolated arterial segments (mesenteric, renal, splenic, gastric, and brachial) obtained during surgical procedures and mounted under tension in tissue baths did not provide evidence for a postsynaptic alpha 2-receptor mediating vasoconstriction. In contrast, the potentiation of the adrenaline response in the presence of the alpha 2 antagonist, RX 781094, supports the possibility that, in humans, an extrajunctional alpha 2-receptor may serve as the adrenergic mechanism for the release of an endothelial derived relaxing factor.

Adult↗
PubMedDate not supplied

Primary structure of rat liver L-threonine deaminase.

The primary structure of rat liver L-threonine deaminase has been studied utilizing a highly purified preparation (S.A. = 940 U/mg protein) obtained from Wistar male rats. These data have been compared with the predicted sequences obtained by other Authors, showing a considerable concordance with the Noda's prediction and difference with the Ogawa's results. The FAB-MS analysis has demonstrated the presence of an acetyl group as blocking agent on the N-terminal alanine.

Amino Acid Sequence↗
PubMedDate not supplied

Amino acid sequence around the pyridoxal 5'-phosphate binding site of rat liver L-threonine deaminase.

Rat liver L-threonine deaminase is a pyridoxal 5'-phosphate dependent enzyme. In the present study we have studied the amino acid sequence composition of the peptide surrounding the coenzyme binding lysine at the active site of the native enzyme. We have also examined the homology between this peptide and the analogue forms of L-threonine deaminase from different sources.

Amino Acid Sequence↗
PubMedDate not supplied

[Intestinal complications from vascular prostheses].

Secondary FAE is a rare complication, usually located at the duodenum. The typical clinical presentation is like a digestive hemorrhage or a sepsis. We report two cases of FAE with atypical manifestations. The first case presented a lower digestive hemorrhage produced by the fistulization to the sigma. The second case appeared like an intestinal obliteration caused by the full emigration of a prosthesis to the jejunum. We wish to remark the importance of the clinical suspicion of a FAE (Key of diagnosis), and the sparing relevance of the complementary examinations and the urgency of a surgical treatment in order to avoid the high rate of morbi-mortality associated with this complication.

Blood Vessel Prosthesis↗