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C Orozco

Publications and source records attributed to C Orozco.

7 recordsLinked to original sources
PubMed1991

Identification of molecules involved in the 'early pregnancy factor' phenomenon.

An isolated preparation from ovine placental extracts which was active in the rosette inhibition assay mimicking the activity of the so-called 'early pregnancy factor' (EPF) has been shown to contain a 12 kDa polypeptide which could be partially resolved from low-molecular-weight active moieties. N-terminal amino acid sequence analysis of the polypeptide indicated that it was ovine thioredoxin, an identification confirmed by isolation and complete sequence analysis of the corresponding cDNA. The cDNA for human thioredoxin was expressed in Escherichia coli and the recombinant protein isolated and purified. Pure recombinant thioredoxin alone did not induce the expression of increased rosette inhibition titres (RITs) when tested in the rosette inhibition assay; but, when tested in combination with cell stimuli such as platelet-activating factor (PAF) or serum, it allowed the expression of increased RITs where none was achieved in its absence. Thioredoxin acted in the assay to reverse a refractory state normally induced by these stimuli, allowing lipoxygenase-dependent moieties also induced by the stimuli to exert their effects, resulting in the expression of increased RITs. Antibodies to recombinant thioredoxin removed from pregnancy sera the capacity to induce increased RITs, i.e. to express EPF activity, thus establishing a role for thioredoxin or thioredoxin-like proteins and associated molecules in the mechanisms which allow pregnancy sera to induce increased RITs. Based on a consideration of these and other results, a new model for the study of the EPF phenomenon is presented and discussed.

Amino Acid Sequence↗
PubMed1990

Leukotrienes are active in the rosette inhibition assay mimicking the action of 'early pregnancy factor'.

Lipoxygenase metabolites have been found to be active in the rosette inhibition assay by inducing increased rosette inhibition titres. Leukotrienes B4, C4, D4 and E4 were identified as possessing this activity. The cycloxygenase products, prostaglandins E2, D2 and F2 alpha had no such activity; however, prostaglandin E2 and to a lesser degree prostaglandin D2 could counteract the activity of the leukotrienes in this assay. The identified leukotrienes are the first characterised molecules known to display activity in the assay. In this respect they mimic the action of early pregnancy serum, an action ascribed to a so called 'early pregnancy factor'.

Animals↗
PubMed1990

Platelet-activating factor and serum components from oestrous mice co-operate to mimic the activity of 'early pregnancy factor' in the rosette inhibition assay.

When male mouse spleen cells were incubated with a combination of platelet activating factor (PAF, 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) and sera from female mice in oestrus, the cells displayed a markedly increased rosette inhibition titre (RIT) when subsequently tested in the rosette inhibition assay. Neither PAF nor oestrous mouse sera alone could induce this effect, the combined action was required. Lyso-PAF could not substitute for the PAF, nor could male mouse sera nor the sera from females in dioestrus or metoestrus substitute for the oestrous mouse serum requirement. Pro-oestrous mouse sera could replace oestrous mouse sera but were less effective in their dose-responses. Studies on the mechanism of action of the PAF and oestrous mouse serum components suggested that the PAF stimulated the production and release of soluble factors (termed S2 factors) which by themselves could induce increased RIT values when applied to fresh spleen cells. The PAF-stimulated cell populations were rendered refractory to the action of these S2 factors and did not display increased RIT values, unless oestrous mouse serum was added. This serum acted to reverse the refractory state, allowing the S2 factors to exert their effect, and so cells treated with PAF and oestrous mouse serum displayed increased RIT values.

Animals↗
PubMed1990

Partial characterization of the PAF-induced soluble factors which mimic the activity of 'early pregnancy factor'.

Platelet-activating factor (PAF) stimulated mouse spleen cells to release soluble factors (termed S2 factors) which were capable of inducing increased rosette inhibition titres when applied to fresh mouse spleen cells in the rosette inhibition assay. In this ability the S2 factors mimic that of pregnancy serum, an action previously ascribed to 'early pregnancy factor'. The PAF-stimulated production of these S2 factors was not influenced by inhibitors of cyclooxygenase metabolism, but was completely inhibited by the lipoxygenase inhibitors, diethyl carbamazine and nordihydroguaiaretic acid. The S2 factors had a lipid-like character in that they were extractable in organic solvents. The calcium ionophore A23187 also stimulated the production of these factors which may well be products of the lipoxygenase pathway of arachidonic acid metabolism.

Animals↗
PubMed1986

Single calcium channels in native sarcoplasmic reticulum membranes from skeletal muscle.

Electrical properties of native sarcoplasmic reticulum membranes from rabbit skeletal muscle were investigated using the patch-clamp technique. Bilayers were assembled at the tip of patch pipettes from monolayers formed at the air-water interface of sarcoplasmic reticulum membrane suspensions. The membranes were found to contain a spontaneously active cation channel of small conductance (5 pS in 200 mM CaCl2, symmetrical solutions) that was selective for Ca2+ and Ba2+. Between 50 and 200 mM CaCl2 (symmetrical) the increase in conductance as a function of [Ca2+] fit a hyperbola (K0.5, 83 mM, and gamma max, 7.9 pS) that extrapolated to a single-channel conductance of 0.5 pS at physiological Ca2+ levels. The channel opened in bursts followed by long silent periods of up to a minute. During a burst the channel fluctuated very rapidly with time constants in the millisecond range. The mean burst duration was voltage dependent, increasing from 1.8 s at a pipette voltage of +60 mV to 4.1 s at +80 mV. Over this range, burst frequency decreased with increasing voltage such that the fraction of time spent in the open state (fb) remained constant. Application of 1.6 mM caffeine resulted in activation of the channel that appeared as an increase in mean burst duration. In contrast, 50 microM dantrolene significantly decreased burst frequency, whereas 10 microM nitrendipine had no effect. The functional and pharmacological properties of this Ca2+ channel suggest that it may be important in mediating Ca2+ release from the sarcoplasmic reticulum during excitation-contraction coupling.

Animals↗
PubMed1975

On the role of catecholamines in the humoral modulation of the electrocortical activity in the cat.

By using the mescaline or the strychnine spikes as indicators of electrocortical activity it was found that they are increased in size by some catecholamines topically applied. These spikes showed late and long-lasting changes after somatic, as well as after autonomic afferent stimulation. The latter induced by cyanide, light asphyxia, intravenous injections of adrenaline or noradrenaline, and after a small dose of 6-hydroxydopamine. After a dose of this last substance, high enough to deplete the catecholamines of the brain, the late increase in amplitude of the cortical potentials observed following afferent stimulation disappeared leaving a long lasting reduction in that amplitude. The hypothesis is presented that the noradrenaline liberated by the adrenergic nerve fibers reaching the upper layers of the cortex acts on the nonsynaptic dendritic membranes modulating their activity in a humoral-like way. The pattern of this facilitating effect has a different temporal course and is longer lasting than that which is to be expectec only by the arrival of impulses at the cortex during the persistence of the neuronal activation induced by the information input to the CNS.

Animals↗