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Biomedical subjects

A Gual

Publications and source records attributed to A Gual.

At least 37 records · Page 2Linked to original sources
PubMed1997

Effects of time of storage, albumin, and osmolality changes on outflow facility (C) of bovine anterior segment in vitro.

PURPOSE: To analyze the influence of time of storage, the presence of albumin at physiological concentrations, and the perfusion with anisosmotic media on the aqueous humor outflow facility (C) of isolated bovine anterior segments (AS). METHODS: Anterior segments dissected from cow eyes were perfused at a constant pressure of 10 mm Hg with Dulbecco's modified Eagle's medium (DMEM; osmolality 300 mOsm/kg), with hyposmotic media (150, 210, and 270 mOsm/kg), or with hyperosmotic media (360, 420, and 480 mOsm/kg). Outflow facility was calculated every 5 seconds as the ratio between average inflow from the reservoir (in microliters per minute) and the perfusion pressure (in millimeters of mercury). Three groups were studied: a 0-hour group, with AS perfused with DMEM 1 to 3 hours after enucleation; a 0-hour alb-group, with AS perfused with DMEM plus 0.1 mg/ml albumin 1 to 3 hours after enucleation; and a 24-hour group, with AS perfused after storage for 24 hours in DMEM. In the 0-hour groups, perfusion with increasingly hyposmotic or hyperosmotic media was also made in 30-minute steps, followed by a return to isosmotic medium for 90 minutes. RESULTS: Perfusion of AS with DMEM for 9 hours caused a progressive increase in C that was statistically significant at 225 minutes in the 0-hour group perfused with DMEM and at 195 minutes in the 24-hour group perfused with DMEM. The 0-hour alb-group perfused with DMEM did not show changes in C throughout the 9-hour perfusion period. Perfusion with increasingly hyposmotic media induced a progressive decrease in C that did not recover on return to isotonic medium. Hyperosmotic media caused a progressive increase in C that returned to control values when isotonic medium was again perfused. CONCLUSIONS: Preservation of tissue for C measurements is best achieved with short storage time (1 to 3 hours). Physiological concentrations of albumin (0.1 mg/ml) prevent development of washout, suggesting that albumin or an albumin-bound factor in aqueous humor may play a role in the maintenance of outflow resistance. Outflow facility also may be influenced by volume changes in the trabecular meshwork.

Animals↗
PubMed1995

Mathematical analysis of epidural space location.

BACKGROUND: The location of epidural space for local anaesthetic injection can be difficult. The aim of this study was to define the mathematical function of the pressure changes in the syringe during puncture of the epidural space. Knowledge of pressure changes might be of help to the anesthetist who attempts to ascertain the location of the needle, and it is essential to the design of a device with which to locate epidural space. METHODS: Epidural punctures were performed in 20 patients, using an 18-Tuohy needle connected to a 10 ml syringe. The epidural space was located by the loss of resistance technique. Pressure variations within the injection system during epidural puncture were measured and digitized at 250 Hz. Pressure curves were analyzed for amplitude and rate of a decay after entry of the needle into the epidural space. RESULTS: Pressure increased as the needle passed through skin, subcutaneous fat and muscle. The maximal pressure was observed when the needle perforated the ligamentum flavum (689 +/- 124 cm H2O). When the needle entered the epidural space, an exponential decrease in pressure was observed in all patients (R2 = 0.99; tau = 2.1 +/- 0.9 seconds). End-residual pressure was 22 +/- 12 cm H2O. The change in pressure observed when the needle entered the epidural space fitted a negative exponential function (y = e-x/2.08). CONCLUSIONS: Pressures within the injection system for epidural puncture can reach 1100 cm H2O. Location of the epidural space is characterized by an exponential decay to and end-residual pressure below 50 cm H2O, with a constant time of approximately 2 seconds.

Adolescent↗
PubMed1995

Sensory receptors in the anterior uvea of the cat's eye. An in vitro study.

PURPOSE: To identify electrophysiologically the functional types of sensory fibers innervating the iris and the ciliary body of the cat's eye. METHODS: The uveal tract tract of cat's eye was excised and placed in a superfusion chamber. Recordings were made from single afferent units of ciliary nerve branches responding to mechanical stimulation of the iridal surface, the ciliary body, and the choroid with a nylon filament or a glass rod. Chemical sensitivity was explored by applying acetic acid, hypertonic NaCl, and bradykinin. Warm (60 degrees C) and cold (4 degrees C) saline and a servocontrolled thermode were used for thermal stimulation. RESULTS: Thirty per cent of the studied population of sensory units (n = 95) were spontaneously active when the recording was started. Approximately 30% of the fibers conducted in the lowest range of the A-delta group; the remaining 70% were C fibers. Sustained mechanical stimulation of the receptive area elicited a tonic response in approximately 60% of the units, and a phasic response in the remaining 40%. Exposure of the receptive field of mechanosensitive fibers to 600 mM NaCl evoked a long-lasting discharge in 50% of the units; application of 1 to 10 mM acetic acid elicited a short discharge in 30% of the fibers, often followed by inactivation. Bradykinin (1 to 100 microMs) produced a long-lasting response in almost 50% of the units. Warming the receptive field recruited 20% of the explored units, whereas 17% were activated by low temperature. CONCLUSIONS: Two main functional types of sensory fibers innervating the iris and the ciliary body were distinguished: (1) mechanoreceptors, corresponding to afferent units sensitive only to mechanical stimuli were generally silent at rest, had relatively higher force thresholds, and discharged phasically in response to long-lasting mechanical stimulation; (2) polymodal nociceptors, which were activated by mechanical as well as by chemical and/or thermal stimuli, usually displayed spontaneous activity, had lower force thresholds, and fired tonically upon sustained mechanical stimulation.

Acetates↗
PubMed1994

The prevalence of cocaine abuse during pregnancy in Barcelona.

The aim of our study was to determine the prevalence of cocaine abuse, by means of positive urine toxicology screens or targeted questionnaire, among women in labor at our hospital. The prospective study included 1773 women who delivered consecutively in our institution. All of them underwent a standardized questionnaire including drug use and demographic data. Urine samples were obtained during labor. Urine toxicology screens for cocaine and its metabolites, opiates, and ethanol were performed by enzyme multiplied immunoassay technique. Information was coded in order to maintain anonymity. Among the 1773 women in labor we screened, the mean age was 27.8 years and the overall prevalence of a positive questionnaire for cocaine was 0.3% and a positive urine toxicology was 0.8%. Results by drug and by demographic items are analysed. There was a substantial denial of cocaine use among the toxicologically positive patients, since only 43% of them referred its use at any time during pregnancy, in conclusion, the use of illicit drugs is common among pregnant women in our institution, but cocaine does not seem to be as prevalent as it is in the USA, while in the labor room most women with a positive test do not refer the use of the drug. Urine toxicology screening increases the rate of detection of substance abuse in this population of women. These studies are necessary to target educational programs among pregnant women.

Adult↗
PubMed1992

Active and problem-based learning: two years' experience in physiology at the Medical School of the University of Barcelona.

Traditional educational methods are used in most medical schools. The introduction of new methods including active and problem-solving learning in traditional medical schools is difficult. The aims of this experiment were: (1) to introduce a self-learning system with a problem-solving approach in physiology; (2) to promote active student participation; (3) to introduce early clinical exposure; (4) to evaluate the response of the students to this experiment; and (5) to evaluate the feasibility and usefulness of a self-learning and problem-solving approach in only one discipline. Our experience has shown that it is possible to change the learning system in a traditional medical school, with good acceptance by the students and with a high level of satisfaction on the part of the teachers.

Curriculum↗
PubMed1991

The chick chorioallantoic membrane promotes survival of co-transplanted rat carotid bodies and nodose ganglia.

Carotid bodies and nodose ganglia, removed from adult rats, were co-implanted onto the chorioallantois of 6- to 12-day chick embryos. Implants were rapidly vascularized and incorporated into the chorioallantoic membrane, where they survived and grew for up to 12 days. The morphological characteristics of grafted tissues were largely preserved. Regenerating axons from nodose neurons invaded the carotid body and contacted some glomus cells through morphologically immature synapses. Thus, the chick chorioallantoic membrane may be a useful substrate to study carotid chemoreceptor-sensory neuron interactions.

Allantois↗
PubMed1991

Effects of dihydropyridines and inorganic calcium blockers on aggregation and on intracellular free calcium in platelets.

[Ca2+]i increase is necessary in physiological platelet activity, particularly aggregation and release. The increase of [Ca2+]i observed during platelet activation depends in part on Ca2+ influx from the extracellular medium. The participation of voltage-operated Ca2+ channels as a pathway for Ca2+ entry is controversial. In the present study we have attempted to reinvestigate this problem by measuring aggregation and [Ca2+]i changes in platelets activated by ADP or thrombin and incubated with organic or inorganic blockers of calcium channels. The main findings of the present paper can be summarized as follows: (i) Ni2+, Co2+ and Mn2+, well known inorganic blockers of Ca2+ channels, inhibited platelet aggregation induced by ADP or thrombin in a dose-dependent manner, Ni2+ being the most effective agent. (ii) Thrombin induced a rise in free [Ca2+]i in platelets incubated both in 1 mmol/l Ca(2+)-containing medium and in nominally Ca(2+)-free medium; the rise of free [Ca2+]i was in the first case up to 370 +/- 31 nmol/l and in the second case up to 242 +/- 26 nmol/l, indicating that this observed difference was due to Ca2+ entry from the extracellular medium. Co2+ and Ni2+ abolished that difference by inhibiting Ca2+ influx. (iii) Nisoldipine, nitrendipine and nimodipine (10-50 nmol/l) inhibited in a dose-dependent manner platelet aggregation induced by either ADP or thrombin in platelets incubated in normal-Ca2+ normal-K+ medium, also, aggregation was inhibited to a similar extent in platelets incubated in normal-Ca2+ high-K+ medium. (iv) Nisoldipine--the most effective dihydropyridine to inhibit platelet aggregation--also inhibited Ca2+ influx in platelets incubated in normal-Ca2+ medium, either in normal-K+ or high-K+ media. Our data support the existence of voltage-operated, dihydropyridine-sensitive calcium channels (L-type) and a physiological role for them in platelet function.

Adenosine Diphosphate↗
PubMed1989

Influence of sodium conductances on platelet activation.

The effects of extracellular Na+ and tetrodotoxin on resting membrane potential, cytosolic free Ca2+ levels and aggregation of human platelets have been studied. Neither the decrease in extracellular Na+-concentration (from 140 mmol/l to 0 mmol/l) nor the addition of tetrodotoxin (10(-7) to 10(-5) mol/l) modified the platelet membrane potential. Zero extracellular Na+ concentration or the presence of tetrodotoxin in the medium inhibited platelet aggregation; however, K+-depolarized platelets showed an unchanged aggregation induced by ADP or thrombin in media with zero or low extracellular Na+ concentrations or in the presence of tetrodotoxin. Moreover, zero extracellular Na+ concentration or tetrodotoxin inhibited calcium mobilization in platelets during activation induced by thrombin. Hence, voltage-dependent activation linked to Na+ influx appears to be necessary for ADP- and thrombin-induced platelet aggregation under control conditions. Mechanisms for the role of Na+ conductances in platelet function are discussed.

Adenosine Diphosphate↗
PubMed1989

Intraocular pressure effects of water loading and venous compression tests in normal and denervated pigmented rabbits.

We have compared IOP elevations induced by water-loading and by increased cephalic venous pressure in normal and denervated pigmented rabbits. Denervations were performed by sympathetic ganglionectomy and/or blockade of the sensory and autonomic innervation of the eye through retrobulbar anesthesia; retrobulbar anesthesia induced significant decreases of the basal IOP in control but not in ganglionectomized eyes. The water-loading test induced a peak pressure elevation approximately 30 min after water administration that could be counteracted by retrobulbar anesthesia. Ganglionectomized rabbits exhibited steeper IOP rises and greater IOP increases following water-loading than the control eyes; retrobulbar anesthesia in ganglionectomized eyes delayed the IOP response to water-loading. Compressions of the neck lasting 30 min elicited significant IOP elevations that were more pronounced in ganglionectomized eyes. In these eyes, retrobulbar anesthesia further increased the IOP rise elicited by neck compression. An IOP decrease below control values was observed at the end of the venous compression. The results indicate that an intact efferent innervation of the eye contributes to buffer IOP elevations induced by water-loading or cephalic venous stasis, presumably through the vascular effects of the ocular autonomic nerves.

Animals↗
PubMed1988

Platelet membrane potential as a modulator of aggregating mechanisms.

The membrane potential of platelets suspended in physiological medium and membrane potential changes induced by high potassium concentrations, ouabain and cooling have been measured using a cyanine fluorescent dye (3,3'-dipropylthiodicarbocyanine) [corrected]. The membrane potential of platelets suspended in physiological medium was -63.8 mV. High potassium concentrations, ouabain and cooling induced depolarization of platelet membrane. Depolarization using the above procedures enhanced platelet aggregation induced by ADP, adrenaline and collagen. These results suggest that the membrane potential could modulate platelet activity.

Adult↗
PubMed1988

Acute effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on catecholamines in heart, adrenal gland, retina and caudate nucleus of the cat.

The short-term (24 h) effects of 10 mg/kg of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) on cat catecholamine levels of heart, adrenal gland, retina, and caudate nucleus were studied. Significant differences in catecholamines, including adrenomedullar adrenaline, heart noradrenaline, and retinal dopamine, were observed. No differences were found in caudate nucleus dopamine. In this organ, the levels of dopamine metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were significantly lower after MPTP treatment. Biochemical changes caused by MPTP with respect to its effects on the peripheral catecholaminergic organs are discussed.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1985

Structural and functional changes of cat carotid body following superfusion with Ca2+ and/or Ba2+.

The effect of saline solutions containing zero or 2.16 mM of Ca2+ and/or Ba2+ on the cat carotid body superfused in vitro was investigated morphologically and electrophysiologically. The ultrastructure of preparations exposed for 30 min to zero [Ca2+-2.16 mM Ba2+]0 revealed profound reactive alterations among all constituents of the lobule with a loss of granular vesicles from glomus cells. Solutions containing barium ions provoked an initial dramatic increase in nerve discharge which practically disappeared in about 40 min. The zero [Ca2+-2.16 mM Ba2+]0 medium reversed a dopamine-induced inhibitory effect, but did not qualitatively alter the responses to acetylcholine or NaCN during or after the initial increase in activity.

Acetylcholine↗
PubMed1985

Effects of ocular blood flow changes on the efferent activity of cat ciliary nerves.

The efferent activity of the short ciliary nerves was studied in 23 anesthetized cats. Spontaneous activity was recorded in all preparations, and 33% showed a rhythmic discharge. Ipsilateral common carotid occlusion (ICCO) at constant intraocular and arterial pressures changed the discharge frequency in 14 of 33 filaments. Of these, 13 filaments showed a decrease in their firing frequency whereas in only one the discharge increased. Contralateral common carotid occlusion (CCCO), at constant intraocular pressure, changed the firing frequency in 8 of 20 filaments: 5 of them showed a decrease in their discharge frequency, whereas in 3 of them the discharge increased. This occurred when systemic arterial pressure was allowed to increase. These results suggest the presence of an efferent pathway involved in the nervous modulation or control of intraocular blood flow, aqueous humor dynamics, and/or intraocular pressure.

Animals↗
PubMedDate not supplied

Does the concept of a standard drink apply to viticultural societies?

The use of standard drink units (SDUs) in the measurement of individual alcohol consumption has become widely popular in recent years. However, the ethanol content of drinks varies from country to country and is usually arrived at without scientific backing. The present study was designed to establish an SDU for a predominantly wine-drinking country (Spain). Two field studies were simultaneously conducted to gather data about home and public alcohol consumption in eight regions of the country with a total of 10751 subjects. The average alcohol content of a drink was very similar for wine and beer, whereas in the case of spirits it was almost double. Relevant differences were found across regions, drinking settings and city sizes. A Spanish SDU was set at 10 g of ethanol for wine and beer, with a measure of spirits accounting for two SDUs. The use of SDUs should be encouraged in primary health care settings. However, dispersion of data suggests that, when SDU is used as a screening tool, additional information should always be obtained in borderline cases.

Alcohol Drinking↗