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Biomedical subjects

P Parra

Publications and source records attributed to P Parra.

At least 19 recordsLinked to original sources
PubMed2000

Quantitation of nifedipine in human plasma by on-line solid-phase extraction and high-performance liquid chromatography.

An analytical methodology for nifedipine quantitation in plasma by on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contain C2 and the analytes nifedipine and nitrendipine (internal standard) are separated on a C18 column with a mobile phase consisting of acetonitrile-13 mM phosphate buffer pH 7 (65:35, v/v) followed by UV detection at 338 nm. Validation of the method demonstrated good recoveries (>90%), sensitivity (limit of quantification, 2 ng/ml), based on a 500 microl sample volume, accuracy and precision (<5.5% in concentrations greater than the limit of quantitation). This methodology has been used for bioequivalence studies.

Calcium Channel Blockers↗
PubMed2000

Quality of the information contained in the minimum basic data set: results from an evaluation in eight hospitals.

To assess the quality of the information included in the minimum basic data set (MBDS) of the eight public hospitals of the Murcia region in order to ascertain what should be improved to be valid and reliable. An external encoder performed a recoding of a random sample of hospital discharges, using the patients hospital records and comparing afterwards the information obtained with the one reflected in the MBDS databases. Quality was assessed using 12 criteria. The reviewed discharges sample consisted at least of 96 cases per hospital (Type I error = 0.05, Type II = 0.10, for the most unfavorable case). A total of 796 cases were reviewed. The MBDS disagreement percentages with the patient record data were higher for the clinical data, with 41.6% for the main diagnosis and 33.5% for the main surgical procedure, being in both cases higher in those hospitals that had used to codify just the discharge record with regard to those that did so with the complete patient record. The variation rate in the diagnosis-related group (DRG) assignment was of 29.6%, and there was a decrease in the case-mix index of 1.07397 when reviewing with the patient record to 1.05555 in the MBDS. Within the administrative data, the highest disagreement rate was for the physician that signs the discharge (60.5%) and the patient's address (31.6%). In many of these assessed aspects there are significant differences between hospitals. A reliability problem was identified in the collected data, which mainly affects the clinical variables. It is therefore advisable to carefully assess the use of this information (both the MBDS directly as well as its grouping through the use of patient classification systems), and the indicators derived from it as its quality is not guaranteed. Systematic assessment and quality control of the MBDS production is advised.

Databases, Factual↗
PubMed2000

The retrograde inhibition of IPSCs in rat cerebellar purkinje cells is highly sensitive to intracellular Ca2+.

The Ca2+-dependent retrograde inhibition of inhibitory postsynaptic currents (depolarization-induced-suppression of inhibition; DSI) was investigated using fura-2 Ca2+ measurements and whole-cell patch-clamp recordings in rat cerebellar Purkinje cells. DSI was studied in cells loaded with different concentrations of the Ca2+ chelators BAPTA and EGTA. A concentration of 40 mM BAPTA was required to significantly interfere with DSI, whereas 10 mM BAPTA was almost ineffective. 40 mM EGTA reduced DSI, but was less effective than 40 mM BAPTA. Ratiometric Ca2+ measurements indicated that the extent of DSI depended critically on the changes in intracellular calcium ([Ca2+]i). The relationship between DSI and peak Delta[Ca2+]i could be approximated by a hyperbolic function, with apparent half-saturation concentrations of 200 and 40 nM for dendritic and somatic [Ca2+]i, respectively. It is suggested that DSI is due to somatodendritic exocytosis of a retrograde messenger, and that this exocytosis is highly sensitive to [Ca2+]i.

Animals↗
PubMed1999

Piroxicam quantitation in human plasma by high-performance liquid chromatography with on- and off-line solid-phase extraction.

A comparative study of two analytical methodologies for piroxicam quantitation in plasma by off-line and on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contained C8 for both extraction methods. The analytes piroxicam and tenoxican (internal standard) were separated on a C18 column with a mobile phase consisting of acetonitrile:20 mM phosphate buffer pH 3.1 (50:50, v/v) followed by UV detection at 360 nm. The validation of the methods demonstrated good recoveries (over 90%), sensitivity (limits of quantification of 0.05 microgram/ml with on-line SPE and 0.1 microgram/ml with off-line SPE, based on a 100 microliters and 200 microliters sample volume, respectively), accuracy and precision (better than 9.5%). Both methodologies have been used for bioequivalence studies.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1998

Chick cerebellar Purkinje cells express omega-conotoxin GVIA-sensitive rather than funnel-web spider toxin-sensitive calcium channels.

Voltage-gated calcium channels form a complex family of distinct molecular entities which participate in multiple neuronal functions. In cerebellar Purkinje cells these channels contribute to the characteristic electrophysiological pattern of complex spikes, first described in birds and later in mammals. A specific calcium channel, the P-type channel, has been shown to mediate the majority of the voltage-gated calcium flux in mammalian Purkinje cells. P-type channels play an essential role in synaptic transmission of mammalian cerebellum. It is unclear whether the P-type calcium channel is present in birds. Studies in chick synaptosomal preparations show that the pharmacological profile of calcium channels is complex and suggest a minimal expression of the P-type channel in avian central nervous system. In the present work, we studied voltage-gated calcium channels in dissociated chick cerebellar Purkinje cells to examine the presence of different calcium channel types. Purkinje cells were used because, in mammals, they express predominantly P-type channels and because the morphology of these cells is thought to be phylogenetically conserved. We found that omega-conotoxin GVIA (omega-CgTx GVIA), a specific antagonist of N-type calcium channel, rather than the synthetic funnel-web spider toxin (sFTX), a P-type channel antagonist, blocks the majority of the barium current flowing through calcium channels in chick Purkinje neurons.

Animals↗
PubMed1998

How many subtypes of inhibitory cells in the hippocampus?

Hippocampal inhibitory cells are diverse. It is supposed that they fall into functionally distinct subsets defined by a similar morphology and physiology. Switching between functions could be accomplished by activating receptors for modulating transmitters expressed selectively by different subsets of interneurons. We tested this hypothesis by comparing morphology, physiology, and neurotransmitter receptor expression for CA1 hippocampal interneurons. We distinguished 16 distinct morphological phenotypes and 3 different modes of discharge. Subsets of inhibitory cells were excited or inhibited by agonists at receptors for noradrenaline, muscarine, serotonin, and mGluRs. Most cells responded to 2 or 3 agonists, and 25 different response combinations were detected. Subsets defined by morphology, physiology, and receptor expression did not coincide, suggesting that hippocampal interneurons cannot easily be segregated into a few well-defined groups.

2-Amino-5-phosphonovalerate↗
PubMed1996

Ethnicity, social status, and families' experiences of caring for a mentally ill family member.

There is growing attention to the role of families nas caregivers of family members with serious mental illness. This paper presents presents data from a multicultural sample of 90 family caregivers from diverse ethnic backgrounds. The paper examines families' experiences with mental health services; their support networks and family burdens; and their conceptions of mental illness. The paper both provides one of the first comparative studies of family caregivers from different ethnic groups and suggests an agenda for future research in this area.

Black or African American↗
PubMed1993

Direct enantiomeric separation of cis-(+/-)diltiazem in plasma by high-performance liquid chromatography with ovomucoid column.

A method is proposed for the direct enantiomeric separation of cis-(+/-)diltiazem in plasma. The method is based on a commercial Ultron ES-OVM column with a mobile phase of different mixtures of ethanol-phosphate buffer. The degree of extraction of the enantiomers was more than 86%. The detection limit of the method used was 5 ng of racemic mixture on column (coefficient of variation = 13%), corresponding to 3.2 ng for cis-(+/-)diltiazem and 1.8 ng for cis-(+/-)diltiazem.

Chromatography, High Pressure Liquid↗
PubMed1992

Si dios quiere: Hispanic families' experiences of caring for a seriously mentally ill family member.

Among Hispanics, the family is viewed as the primary care giver for seriously mentally ill family members. This paper reports on a study of minority families' conceptions of serious mental illness, of their interaction with mental health resources, and on the burdens experienced by families in caring for a seriously mentally ill family member. The focus of this paper is on Hispanic families in New Jersey, with some comparative data from other ethnic group families. Families' conceptions of serious mental illness are explored and analyzed to demonstrate the importance of concepts of nervios and fallo mental in shaping families' responses to their ill family member. Social support systems for families are also explored with particular attention to the role of religious institutions and religious healing as a major source of solace.

Acute Disease↗
PubMed1991

High-performance liquid chromatographic separation of caffeine, theophylline, theobromine and paraxanthine in rat brain and serum.

Caffeine and its metabolites theophylline, theobromine and paraxanthine have been determined in rat brain and serum samples by high-performance liquid chromatography with ultraviolet detection. The recovery, 85-103%, allowed quantification by external standard methods. The variability was found to be less than 3 and 7% for intra-day and inter-day assays, respectively. The detection limit, 1.57 ng of methylxanthines on column, allowed the determination of 62.5 ng/g or ml in biological material. Rats treated with 30 mg/kg caffeine (subcutaneously) were sacrificed at different times (1, 6, 12 and 24 h). Higher concentrations of methylxanthines (specially paraxanthine) were observed in the striatum than in the rest of the brain, and it was also observed that the clearance of methylxanthines was faster in serum than in brain structures.

Animals↗
PubMed1990

Paraxanthine displaces the binding of [3H]SCH 23390 from rat striatal membranes.

We present evidence showing that paraxanthine (1,7-dimethylxanthine), the main metabolite of caffeine in man, displaces the binding of [3H]SCH 23390, a radioligand which selectively labels dopamine D-1 receptors when used at low concentrations, from striatal membranes of the rat. The displacement was competitive and indicated the existence of two affinity states (Hill coefficient = 0.49; K(high) = 0.15 microM; K(low) = 95.9 microM, %R(high) = 32.4). When the stable GTP analog Gpp(NH)p was included, the displacement curve indicated the presence of only the low-affinity state (Hill coefficient = 1.16; Ki = 72.1 microM). However, paraxanthine did not displace the specific binding of [3H]spiperone. After injection of 30 mg/kg s.c. of caffeine, a maximum of 10 microM of paraxanthine was found in striatal homogenates, which could be sufficient to occupy dopamine D-1 receptors. Our results suggest that a dopaminergic action of paraxanthine could be involved in the behavioural stimulation produced by caffeine.

Animals↗
PubMed1990

Ultrastructural characteristics of anterior gut innervation of Gallus gallus.

The enteric nervous system of the bird's anterior gut is very well developed. Myelin fibres are seen accompanying the nervous trunks up to the mucous layer. Glial cells duplicate the number of neurons in the myenteric plexuses. Their number decreases at the submucous plexuses, but it is always higher than the neurons. Isolated neurons are widely spread in the circular muscle coat accompanying the nervous trunks which can be inter and intrafascicularly located. Direct synaptic contacts with the soma neuronal membranes are very often seen. We have never observed synaptic specializations. The most prominent varicosities either in the peripheric nervous trunk axons or directly laying on the soma membranes are those containing peptidergic or mixed vesicles of cholinergic and peptidergic types. The neurons show big nuclei of different size and shape. Neighbouring smooth muscle cells show abundant caveolae near the nervous elements. Although we have not observed close contacts with glands, thin axon bundles spread near the glandular cells of the mucous layer.

Animals↗
PubMed1988

Intrinsic and extrinsic innervation of the amphibians esophagic myenteric plexuses.

The innervation of Rana ridibunda esophagus myenteric plexuses has been studied by the following methods: demonstration of cholinesterase activity; FIF method for catecholamines; immunohistochemistry for VIP, SP and SOM, and conventional electron microscopy. The cholinergic innervation is important in the esophagus wall where, in addition to the well known extrinsic component, there is a rich intrinsic plexus with cells and fibres widely distributed. The esophagus, together with the intestine, are the Rana gut portions where the adrenergic component is more broadly expressed. The adrenergic innervation seems to be almost entirely of extrinsic origin. We have shown that, for the tested peptides, there is an intrinsic innervation represented by VIP, SP and SOM like plexuses. We do not discard nonetheless an extrinsic component. The ultrastructure reveals the morphological characteristics of the enteric neurons as well as the fine inter-relationships between the nervous elements and the functional components of the esophagic wall.

Animals↗
PubMed1988

Dense cored vesicles in presynaptic profiles of the rabbit dorsal lateral geniculate nucleus.

We are carrying out a study about the synaptic relations between identified synaptic profiles in the dorsal lateral geniculate nucleus (dLGN) of the rabbit. Here, the types of synaptic vesicle containing profiles of the dLGN are described. There are presynaptic large profiles containing round vesicles and pale mitochondria (RLP terminals) and small profiles that contain round vesicles and dark mitochondria (RSD terminals) which respectively arise from the retina and the visual cortex. Another type of presynaptic profile contains elliptical vesicles (F-boutons) which can be subdivided according to their cytoplasmic content. These F-boutons arise from dLGN interneurons. We have found different sized vesicles that have a dense core within RLP, and F terminals and a possible RSD terminal. The significance of the coexistance of pale and dense cored vesicles in the presynaptic profiles of the rabbit dLGN is discussed.

Animals↗
PubMed1987

The autonomic innervation of Rana ridibunda intestine.

1. The innervation of Rana ridibunda intestine has been studied by the following methods: (a) demonstration of cholinesterase activity; (b) FIF method for catecholamines; (c) immunohistochemistry for VIP, SP and SOM, and (d) conventional electron microscopy. 2. The intrinsic intestinal innervation is represented by cholinergic-, VIPergic-, SP- and SOM-like plexuses. The intestinal adrenergic component is of extrinsic origin. 3. The intestinal peptidergic innervation is the most developed, the large intestine being the portion where the studied peptidergic plexuses are more widely distributed. 4. Against a poorly developed cholinergic/adrenergic innervation, it seems that there is a predominant peptidergic innervation in the amphibians intestine wall. 5. Taking into account that amphibians sacral parasympathetic as well as sympathetic innervation development are limited, it could be considered that in vertebrates the intestinal peptidergic innervation is phylogenetically earlier and hence better developed.

Adrenergic Fibers↗
PubMed1986

The distribution of VIP-immunoreactive neurons in the visual cortex of adult rabbits and during postnatal development.

In the adult rabbit, the majority of the VIP-immunoreactive neurons are distributed in layer II-III of the visual cortex. Labeled cells are also seen in layers VI, IV, V and occasionally in layer I. During postnatal development, we can see labeled neurons on the 2nd day of life, and in layers II-III-IV-V-VI on the 4th day. On the 7th day, these neurons reach a distribution typical in the adult animal. From the 2nd to the 10th day the number of VIP-neurons increases, and from the 10th day to maturity, there is a 15-20% loss in the number of labeled cells.

Aging↗
PubMed1986

The enteric nervous system of Rana ridibunda stomach.

The innervation of Rana ridibunda stomach has been studied by the following methods: demonstration of cholinesterase activity; FIF method for catecholamines; immunohistochemistry for VIP; SP and SOM and conventional electron microscopy. The cholinergic innervation is important in the stomach wall where in addition to the intrinsic plexuses there is an extrinsic contribution coming with the vagus nerve. The density of the fibres decreases towards the pyloric sphincter. The adrenergic innervation seems to be almost entirely of extrinsic origin. Fine networks have been localized at the myenteric and submucosal plexuses. The fibres density increases at the pylorus. At the myenteric plexus, apart from the cholinergic neurons, we have found VIP and SOM like cells. The VIP like plexus is very well developed. A SOM like plexus is also present but with scarce fibres in comparison with the VIPergic one. The submucosal plexus is exclusively made by nervous fibres of the types described for the myenteric one. We have got positive immunoreactivity for SP only on the fibres. They are scarce in the stomach wall, only at the pyloric region their density increases. We describe the ultrastructural morphological characteristics of the enteric neurons as well as the fine inter-relationships between the nervous elements and the functional components of the stomach wall.

Animals↗