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J Parra

Publications and source records attributed to J Parra.

At least 19 recordsLinked to original sources
PubMed2000

Mechanism of mifepristone-induced spasmolytic effect on isolated rat uterus.

Mifepristone, a synthetic 19-norsteroid, relaxed the KCl-induced tonic contraction in isolated rat uterus in a concentration-dependent way and CaCl2 (0.1 to 10 mM) counteracted it. This effect was similar to other steroids although the mechanisms involved are unclear. Before adding the contracturant, tissue was incubated with actinomycin D (10 microM), cycloheximide (300 microM), TPCK (3 and 10 microM), Rp-cAMPS (30 microM), DDA (100 microM) and H-7 (1 microM). None of these modified the relaxing effect of mifepristone. Incubation with drugs that interfere with cGMP such as a nucleotide analogue DDG (100 microM), a soluble guanylyl cyclase inhibitor ODQ (1 microM) and an inhibitor of protein kinase G 8pCPTcGMPS (1 microM) significantly modified the effect of mifepristone, increasing its IC50.

Animals↗
PubMed2000

A short training programme for the rapid improvement of both aerobic and anaerobic metabolism.

The aim of this study was to evaluate the changes in aerobic and anaerobic metabolism produced by a newly devised short training programme. Five young male volunteers trained daily for 2 weeks on a cycle ergometer. Sessions consisted of 15-s all-out repetitions with 45-s rest periods, plus 30-s all-out repetitions with 12-min rest periods. The number of repetitions was gradually increased up to a maximum of seven. Biopsy samples of the vastus lateralis muscle were taken before and after training. Performance changes were evaluated by two tests, a 30-s all-out test and a maximal progressive test. Significant increases in phosphocreatine (31%) and glycogen (32%) were found at the end of training. In addition, a significant increase was observed in the muscle activity of creatine kinase (44%), phosphofructokinase (106%), lactate dehydrogenase (45%), 3-hydroxy-acyl-CoA dehydrogenase (60%) and citrate synthase (38%). After training, performance of the 30-s all-out test did not increase significantly, while in the maximal progressive test, the maximum oxygen consumption increased from mean (SD) 57.3 (2.6) ml x min(-1) x kg(-1) to 63.8 (3.0) ml min(-1) x kg(-1), and the maximum load from 300 (11) W to 330 (21) W; all changes were significant. In conclusion, this new protocol, which utilises short durations, high loads and long recovery periods, seems to be an effective programme for improving the enzymatic activities of the energetic pathways in a short period of time.

Adult↗
PubMed2000

The distribution of rest periods affects performance and adaptations of energy metabolism induced by high-intensity training in human muscle.

The effect of the distribution of rest periods on the efficacy of interval sprint training is analysed. Ten male subjects, divided at random into two groups, performed distinct incremental sprint training protocols, in which the muscle load was the same (14 sessions), but the distribution of rest periods was varied. The 'short programme' group (SP) trained every day for 2 weeks, while the 'long programme' group (LP) trained over a 6-week period with a 2-day rest period following each training session. The volunteers performed a 30-s supramaximal cycling test on a cycle ergometer before and after training. Muscle biopsies were obtained from the vastus lateralis before and after each test to examine metabolites and enzyme activities. Both training programmes led to a marked increase (all significant, P < 0.05) in enzymatic activities related to glycolysis (phosphofructokinase - SP 107%, LP 68% and aldolase - SP 46%, LP 28%) and aerobic metabolism (citrate synthase - SP 38%, LP 28.4% and 3-hydroxyacyl-CoA dehydrogenase - SP 60%, LP 38.7%). However, the activity of creatine kinase (44%), pyruvate kinase (35%) and lactate dehydrogenase (45%) rose significantly (P < 0.05) only in SP. At the end of the training programme, SP had suffered a significant decrease in anaerobic ATP consumption per gram muscle (P < 0.05) and glycogen degradation (P < 0.05) during the post-training test, and failed to improve performance. In contrast, LP showed a marked improvement in performance (P < 0.05) although without a significant increase in anaerobic ATP consumption, glycolysis or glycogenolysis rate. These results indicate that high-intensity cycling training in 14 sessions improves enzyme activities of anaerobic and aerobic metabolism. These changes are affected by the distribution of rest periods, hence shorter rest periods produce larger increase in pyruvate kinase, creatine kinase and lactate dehydrogenase. However, performance did not improve in a short training programme that did not include days for recovery, which suggests that muscle fibres suffer fatigue or injury.

Adaptation, Physiological↗
PubMed2000

Magnetic source imaging in fixation-off sensitivity: relationship with alpha rhythm.

A patient in whom a variety of abnormal EEG findings can be elicited by elimination of central vision and fixation demonstrates fixation-off sensitivity. The underlying mechanisms of fixation-off sensitivity and its relationship with alpha rhythm remain unclear. To obtain a better understanding of this issue, we used a whole-head magnetoencephalograph to study an epileptic child with fixation-off sensitivity resulting in a 3-Hz, large-amplitude oscillation (300 microV) over the occipital regions on the EEG. Magnetic source localization revealed alpha activity around the calcarine fissure and surrounding parieto-occipital areas. Magnetic sources of abnormalities relating to fixation-off sensitivity, however, usually were located deeper in the brain, suggesting more extensively distributed sources, with involvement of the cingulate gyrus and the basomesial occipitotemporal region. Distributions of the sources of both types of activities show independent clusters but also an appreciable domain of overlap. Our findings indicate that abnormalities related to fixation-off sensitivity can emerge in thalamocortical networks, with larger and more anterior cortical distribution than those that generate alpha rhythm. Transition in the type of oscillation appears not only to depend on a change in cellular dynamics but also to be reflected in a different spatial distribution of the underlying neuronal networks.

Alpha Rhythm↗
PubMed2000

The "forgotten" cross-tolerance between phenobarbital and primidone: it can prevent acute primidone-related toxicity.

PURPOSE: We report on the effect that pretreating patients with phenobarbital has on averting adverse events when primidone is introduced. METHODS: Thirty patients with intractable partial epilepsy were pretreated with phenobarbital before starting primidone. Therapy with primidone was started at a dosage of 500 mg/day, and the phenobarbital was stopped. The primidone dose was then increased by 125 to 250 mg every 3 weeks until adverse events or a seizure-free state was reached. All previous antiepileptic medications were tapered down to yield a primidone monotherapy regimen. RESULTS: Twenty-six patients (87%) tolerated the introduction of primidone with minimal or no adverse events. Only one patient had to discontinue primidone during the initial 4 weeks because of severe dizziness. This was the only patient in whom primidone monotherapy could not be reached because of adverse events. Three other patients experienced dizziness severe enough to interfere with their activities. This symptom disappeared in two patients after the dose was lowered; in the other patient, primidone was stopped and phenobarbital was restarted for another 4 days. No symptoms recurred when primidone was reintroduced on the fifth day. CONCLUSIONS: Pretreatment with phenobarbital can minimize the occurrence of intolerable adverse events associated with the introduction of primidone.

Adolescent↗
PubMed2000

[Photogenic epilepsy].

INTRODUCTION: The commonest reflex seizures are those induced by visual stimuli, and amongst these, those provoked by intermittent luminous stimulus. DEVELOPMENT: A directed anamnesis and suitable intermittent light stimulation are important during electroencephalographic studies for the confirmation of the diagnosis of photosensitive epilepsy. The photogenic epilepsies, that is those in which all the epileptic seizures are provoked by visual stimuli, form a small group of epilepsies within the idiopathic generalized epilepsies with their onset during adolescence. These seizures have had great social impact, since media diffusion of the possibility of their appearance whilst watching television or playing video games. CONCLUSION: The correct diagnosis and preventive measures, together with the correct anti-epileptic treatment are in favour of a good prognosis in the great majority of patients.

Adolescent↗
PubMed1999

Contractile activity modifies Fru-2,6-P(2) metabolism in rabbit fast twitch skeletal muscle.

Modification of muscular contractile patterns by denervation and chronic low frequency stimulation induces structural, physiological, and biochemical alterations in fast twitch skeletal muscles. Fructose 2,6-bisphosphate is a potent activator of 6-phosphofructo-1-kinase, a key regulatory enzyme of glycolysis in animal tissues. The concentration of Fru-2,6-P(2) depends on the activity of the bifunctional enzyme, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2/FBPase-2), which catalyzes the synthesis and degradation of this metabolite. This enzyme has several isoforms, the relative abundance of which depends on the tissue metabolic properties. Skeletal muscle expresses two of these isoforms; it mainly contains the muscle isozyme (M-type) and a small amount of the liver isozyme (L-type), whose expression is under hormonal control. Moreover, contractile activity regulates expression of muscular proteins related with glucose metabolism. Fast twitch rabbit skeletal muscle denervation or chronic low frequency stimulation can provide information about the regulation of this enzyme. Our results show an increase in Fru-2,6-P(2) concentration after 2 days of denervation or stimulation. In denervated muscle, this increase is mediated by a rise in liver PFK-2/FBPase-2 isozyme, while in stimulated muscle it is mediated by a rise in muscle PFK-2/FBPase-2 isozyme. In conclusion, our results show that contractile activity could alter the expression of PFK-2/FBPase-2.

Animals↗
PubMed1999

Psychiatric and neurologic predictors of psychogenic pseudoseizure outcome.

OBJECTIVE: To investigate the patterns of occurrence of psychogenic pseudoseizures (PPS) of 45 consecutive patients during a 6-month period after diagnosis, and to determine whether psychiatric and neurologic variables identified previously in PPS patient series can predict their recurrence after diagnosis, and whether any of these variables are associated with a particular outcome pattern. METHOD: Postdiagnosis PPS recurrence was assessed twice: during the first month and during a period ranging from the second to the sixth month. Outcome was categorized as follows: class I, complete cessation of PPS; class II, PPS only during one of the two observation periods; and class III, persistent PPS during the two observation periods. The authors used a logistic regression model to identify predictors of PPS recurrence (versus no PPS) among four neurologic and nine psychiatric variables, and compared their frequency among the three outcome classes. RESULTS: Class I, n = 13 (29%); class II, n = 12 (27%); and class III, n = 20 (44%). The presence of an abnormal MR image predicted PPS recurrence during the second observation period with a 75% accuracy. The presence of all nine psychiatric variables predicted PPS recurrence during both the first and second observation periods with a 93% and an 89% accuracy respectively. Patients with a class III outcome had a markedly higher frequency of recurrent major depression, dissociative and personality disorders, and a history of chronic abuse. Patients with a class II outcome displayed a notably higher frequency of denial of stressors and psychosocial problems, refusal of treatment recommendations, and new somatic symptoms after disclosure of diagnosis. Conversely, one episode of major depression was the one common diagnosis in patients with a class I outcome. CONCLUSIONS: PPS outcome after disclosure of diagnosis can be predicted by the presence of certain psychiatric characteristics. More than one psychopathogenic mechanism appears to operate in PPS.

Adult↗
PubMed1999

Effect of chronic electrostimulation of rabbit skeletal muscle on calmodulin level and protein kinase activity.

(a) Chronic electrostimulation of fast-twitch skeletal muscles makes them resemble slow-twitch muscles. The involvement of second-messenger cascades in this muscle reprogramming is not well understood. The goal of this study was to examine protein kinase activities and calmodulin levels as a function of the duration of electrostimulation. (b) Fast-twitch rabbit muscle was subjected to continuous low-frequency electrostimulation for 2 weeks. The extensor digitorum longus was taken and examined for calmodulin concentration and cAMP-dependent (PKA). Ca(2+)-phospholipid-dependent (PKC) and Ca(2+)-calmodulin-dependent (CaM kinase or PKB) protein kinase activities. (c) Electrostimulation for 14 days led to a significant increase in total calmodulin level and PKB activity, both rising in the cytosolic fraction. Protein kinase C translocated to the membrane fraction, although total activity did not change. (d) These changes could be related with electrostimulation-induced changes in excitation-contraction coupling.

Animals↗
PubMed1999

Are we overusing the diagnosis of psychogenic non-epileptic events?

In order to determine how often results of video/EEG (V-EEG) studies may change the clinical diagnosis of paroxysmal events, we prospectively studied 100 consecutive patients (75 females, 25 males) admitted for diagnosis of recurrent paroxysmal spells. The presumed diagnosis of the referring physician was obtained. Episodes were classified as epileptic seizures (ES), psychogenic non-epileptic events (PNEE), or physiologic non-epileptic events (PhysNEE). Eighty-seven patients had diagnostic events. A final diagnosis of ES was made in 21 patients, PNEE in 39, PNEE + ES in 20, and PhysNEE in seven. All PhysNEE were unsuspected. ES were misdiagnosed as PNEE more frequently than the reverse (57% vs. 12%, P < 0.001). Among the 64 patients with recorded events who had been suspected of having PNEE, 14 (21.9%) were misdiagnosed: two had PhysNEE and 12 (18.75%) had ES. Among the 23 patients with recorded events who were thought to have ES, 12 (39.1%) were misdiagnosed: seven had PNEE, five PhysNEE. V-EEG changed the clinical diagnosis in 29.8% of the patients with recorded events. Our data suggests that clinicians have become more aware of PNEE since the advent of V-EEG and have little problem recognizing them. However, they may be more prone to make a false-positive diagnosis of PNEE in ES with some atypical features. At this point, efforts should be channeled to better training in the proper recognition of ES that mimic PNEE.

Adolescent↗
PubMed1998

When should induction protocols be used in the diagnostic evaluation of patients with paroxysmal events?

PURPOSE: To determine the timing of spontaneous psychogenic nonepileptic events (PNEE) during video-EEG telemetry (VEEG), and the need to use induction protocols (IP). METHODS: We studied 100 consecutive patients (75 females, 25 males) admitted to our inpatient VEEG unit from July 1994 to June 1996 for differential diagnosis of paroxysmal events. We recorded the time to the first diagnostic spontaneous event, identified by the patient or a family member as typical. Episodes were classified as PNEE, physiologic nonepileptic events (PhysNEE), and epileptic seizures (ES). RESULTS: The mean duration of VEEG was 74+/-SD 54.1 h. In 82 patients, a diagnostic event occurred spontaneously. The first event was an ES in 22 patients, a PNEE in 53, and a PhysNEE in 7. The time to first diagnostic event was significantly shorter for PNEE than for ES [15.0+/-SD 16.3 h (range 5 min to 58 h) vs. 28.6+/-SD 34.0 h (range 1-110 h) F=15.621, p < 0.0001]. In the first 24 h, 77.4% of the patients with PNEE had an event. By 48 h, all but 2 (96.2%) had had diagnostic events. After the first 58 h of monitoring, all patients with PNEE experienced a spontaneous diagnostic event. CONCLUSION: Spontaneous events can be expected to occur within 48 h in most patients with PNEE. Therefore, if IP are to be used as a diagnostic tool, we suggest that they be withheld during the initial 48 h of VEEG monitoring.

Adolescent↗
PubMed1998

De novo psychogenic nonepileptic seizures after epilepsy surgery.

PURPOSE: The occurrence of de novo nonepileptic seizures (NES) after epilepsy surgery have been reported only twice in the literature (one article and one abstract). METHODS: We report three patients whose de novo NES were documented by video-EEG telemetry after epilepsy surgery. These patients were drawn from a sample of 166 consecutive patients who underwent epilepsy surgery at our center between 1989 and 1996. RESULTS: Two patients became seizure free after surgery, and one had significant improvement of her seizures. The interval between the date of surgery and the development of the symptoms was variable (8, 10, and 47 months, respectively). The clinical phenomena of NES differed from those of the epileptic seizures preceding surgery. Their diagnosis had not been suspected in two patients before the diagnostic video-EEG monitoring study. After the diagnosis of NES, spells stopped in two patients and recurred rarely in one. CONCLUSIONS: We conclude that de novo NES appears to occur rarely after epilepsy surgery. Given that the possibility of NES was suspected in only one patient, its incidence after surgery may be higher than so far reported. Physicians should therefore consider NES in the differential diagnosis of recurrent seizures after a seizure-free period after epilepsy surgery.

Adult↗
PubMed1997

Enhanced catalytic activity of hexokinase by work-induced mitochondrial binding in fast-twitch muscle of rat.

Using a teased muscle fiber preparation, we determined the activity of mitochondrially bound hexokinase in rat fast-twitch muscle under control conditions and after low-frequency stimulation periods for up to 2 h. As compared to soluble hexokinase, mitochondrial binding led to stimulation of glucose 6-phosphate production. Low-frequency stimulation greatly enhanced glucose 6-phosphate formation which was 100% and 250% elevated after 1 and 2 h, respectively. These observations point to a mechanism which rapidly increases the catalytic activity of hexokinase through binding to the mitochondrial surface.

Adenosine Diphosphate↗
PubMed1997

[Cerebral hemorrhage after carotid endarterectomy in a young adult].

INTRODUCTION: Cerebral haemorrhage after carotid endarterectomy is a rare complication. It follows 0.5% to 20% of all endarterectomies, but should be borne in mind because of the morbidity and mortality seen in most cases. CLINICAL CASE: We describe the case of a 42 year old man in whom carotid endarterectomy had been done 7 days before to treat a stenosis of 80%. He complained of a sudden onset of weakness of the right half of his body and changes in his speech. Physical examination showed right inferior facial paresia, right hemiparesia and right extensor cutaneous plantar reflex. On admission to the Emergency Department, before treatment, blood pressure was 80/60. Carotid auscultation and palpation were normal. Cerebral TRC showed a left lenticular haematoma. The patient progressed satisfactorily. DISCUSSION/CONCLUSIONS: We review the literature on the subject as well as the factors which should be considered as possibly predisposing to bleeding after carotid endarterectomy, such as arterial hypertension and occlusion or severe stenosis of the contralateral carotid artery. The detection of patients with the risk of postendarterectomy bleeding by simple noninvasive investigations, such as the transcranial doppler and the acetazolamide test, and early diagnosis of a clinical picture compatible with a hyperperfusion syndrome may contribute to the relief and prevention of sequelae in these patients.

Carotid Stenosis↗
PubMed1996

[Isolated thrombocytopenia in pregnancy. Etiopathogenic study and therapeutic approach in 60 patients].

BACKGROUND: We analyze the etiopathogenesis and clinical and immunohematological characteristics of 60 pregnant women with isolated thrombocytopenia (TP) (platelet count < 150 x 10(9)/l); and the frequency of TP and hemorrhagic complications in their newborn. We suggest the therapeutic approach for each maternal TP type. PATIENTS AND METHODS: We performed: clinical history, platelet count (EDTA K3, sodium citrate, microscopic exam) and investigation of antiplatelet antibodies (immunofluorescence) in all pregnant women. A familial history and ultrastructure of platelets were studied when hereditary macrothrombocytopenia (HM) was suspected. A Levine's test of homogenicity of variances was applied to compare the mean platelet count in each diagnostic group. A linear regression between maternal and newborn platelet counts was performed. RESULTS: In 37 thrombocytopenic women (62%) no antiplatelet antibodies were found, and the clinical history was negative for previous TP or abnormal bleeding. Four patients (7%) were diagnosed as pseudothrombocytopenia EDTA-mediated, and eight (13%) of HM. Finally, an autoimmune etiology was suspected in 11 women (18%) and antiplatelet antibodies were detected in 9. Mean platelet counts of mother with immune TP did not show statistically significant differences with other diagnostic groups. Abnormal bleeding was not observed in any patient or newborn. There was no correlation between platelet counts of mothers and newborns. Platelet count obtained by skull bone punction led to unnecessary caesarians in four cases. CONCLUSIONS: The frequency of immune thrombocytopenia in pregnant women is low (18%). There is a high prevalence of benign TP (62%). The pseudothrombocytopenias and HM are frequent findings (20%), and special care is advisable in these cases to avoid unnecessary therapeutic procedures.

Female↗