Browsing by Author "FERNANDEZ, E"
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- ItemANDROGENS AND EFFECTS OF OPIOIDS AND CATECHOLAMINES ON THE SMOOTH-MUSCLE OF THE RAT VAS-DEFERENS(1985) MIRANDA, H; PEREZ, E; FERNANDEZ, E; ROSSELOT, F; VERGARA, JF; WOLSTENHOLME, WW; ZUAZO, AIn the neuronal electrically stimulated vas deferens of the rat, the responses evoked by morphine, .beta.-endorphin and catecholamines were studied. The tissue was obtained from rats at various times (7-60 days) following castration, adrenalectomy and castration with adrenalectomy. Pharmacological data are presented which verify an increased responsiveness to morphine after castration with or without adrenalectomy. Decreased responsiveness was observed after adrenalectomy alone. Decreased responsiveness of the vas deferens to catecholamines was observed after castration, adrenalectomy and castration with adrenalectomy. Since the responsiveness of the electrically stimulated vas deferens to .beta.-endorphin was unchanged by this treatment (castration, adrenalectomy), the .epsilon.-opioid receptor may be unaffected by androgens.
- ItemBIOGENIC-AMINES AND BETA-ENDORPHIN RESPONSES IN THE RAT VAS-DEFERENS(1982) MIRANDA, H; VERGARA, JF; ROSSELOT, F; FERNANDEZ, EActivation of opioid peptide receptors by .beta.-endorphin results in a change of bioamines in peripheral tissues. The action of .beta.-endorphin on the smooth muscle of the isolated rat vas deferens may be independent of catecholaminergic, cholinergic and tryptaminergic neurotransmission. The action may involve a specific opioid .epsilon.-receptor having a high degree of affinity for .beta.-endorphin.
- ItemHIGH POTASSIUM CONCENTRATION IMPROVES THE RATE OF ACROSOME REACTION IN HUMAN-SPERMATOZOA(1988) ROBLERO, L; FERNANDEZ, E; GUADARRAMA, A; ZEGERSHOCHSCHILD, F; ORTIZ, MEProgressively motile spermatozoa recovered by swim-up method from semen of two fertile men were inoculated for 24 hours in culture media containing either 4.7, 15, or 25 mM of potassium (K). Aliquots of each culture condition were obtained at 0, 1, 5, 10, and 24 hours of incubation for the assessment of progressive motility, percentage of dead spermatozoa, and percentage of acrosome reaction (AR), as measured by triple-stain technique. A total of ten experiments including each K concentration were analyzed. The results of this study showed no effect of K concentration on the percentage of progressively motile spermatozoa, irrespective of the time of incubation. The percentage of live spermatozoa was significantly greater in culture medium containing 25 mM K (P < 0.05). There was a greater percentage of reacted spermatozoa with 25 mM K, as compared with 4.7 and 15 mM (P < 0.05). Furthermore, the time taken to acheive 20% of AR was 2 hours at 25 mM K compared with 10.9 hours at 4.7 mM K.
- ItemMANY-BODY EFFECTS IN A QUANTUM FREE-ELECTRON LASER MODEL(1987) FERNANDEZ, E; ORSZAG, M
- ItemNETWORK EQUILIBRIUM-MODELS WITH COMBINED MODES(INFORMS, 1994) FERNANDEZ, E; DECEA, J; FLORIAN, M; CABRERA, EMany trips in urban areas are taken by using more than one mode, such as the so called ''kiss'n ride'' or ''park'n ride'' trips; the first part of the trip is taken by the private care and then completed by taking one or more transit modes. We present in this paper several approaches to formulating network equilibrium models with combined modes. One of these approaches results in a new network equilibrium model, where the combined mode is considered as a distinct alternative in a demand model, and the network flows are suitably modelled on different modal subnetworks. The mathematical structure of the model is analysed and solution algorithms are outlined.
- ItemOPERATORS-USERS EQUILIBRIUM-MODEL IN A PARTIALLY REGULATED TRANSIT SYSTEM(OPERATIONS RESEARCH SOC AMER, 1992) FERNANDEZ, E; MARCOTTE, PWe present two formulations of a model for finding equilibrium passenger and operator flows in a partially regulated transit system where bus operators are free to choose the routes on which they offer public transport services. The transit fares are assumed fixed and known. The model offers a detailed representation of the transit system network and of the transit users behavior. Congestion effects are also considered as a consequence of the operation of cars and buses over a common road network. Two algorithmic solution approaches are investigated.
- ItemPOST-OVULATORY AGING OF HUMAN OVA .1. LIGHT MICROSCOPIC OBSERVATIONS(1982) ORTIZ, ME; SALVATIERRA, AM; LOPEZ, J; FERNANDEZ, E; CROXATTO, HBThe morphologic changes undergone by the human secondary oocyte following ovulation were assessed by light microscopy in 57 specimens recovered from the Fallopian tube and endometrial cavity between 24 and 144 h after the luteinizing hormone [LH] peak in plasma. Ova recovered shortly after ovulation were surrounded by a large cumulus mass comprising .apprx. 20,000 follicular cells. Whenever it was possible to perform a detailed observation of the perivitelline space in these ova, the presence of a polar body was recognized. The oocyte usually occupied an excentric position within the cumulus. Ovum denudation appeared to proceed by breakdown of the cumulus into fragments and release of the oocyte with a small number of cells attached to the zona. As a consequence of this process, the oocyte, surrounded by a few layers of the cells, frequently coexisted with large fragments of the cumulus. Progress of ovum denudation was time dependent and proceeded at a relatively slow pace. Some uterine ova still had cells attached to the zona. At 96 h after the LH peak 40% of the ova underwent fragmentation of the cytoplasm giving rise to anucleated pieces of varying sizes. The dimensions of the zona pellucida and ooplasm presented wide individual variations as well as some time related changes. The mean external diameter of the zona .+-. SD of 43 ova was 161.6 .+-. 14.6 .mu.m. The occurrence of denudation and cytoplasmic fragmentation were more clearly related to the postovulatory age of the ovum than to the site of recovery. The rate of denudation of human oocytes seems to proceed at a much lower speed in comparison with small mammals currently used as laboratory animals.
- ItemTRANSIT ASSIGNMENT FOR CONGESTED PUBLIC TRANSPORT-SYSTEMS - AN EQUILIBRIUM-MODEL(1993) DECEA, J; FERNANDEZ, EWe propose a new formulation for the assignment problem over congested transit networks. The congestion effects due to insufficient capacity of system elements (transit lines) are considered to be concentrated at transit stops. Waiting times on access links are therefore dependent on passenger flows. A special formulation of the transit network is used in order to model correctly the congestion effects. Finally, algorithms for solution are analyzed.