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Biomedical subjects

H Saavedra

Publications and source records attributed to H Saavedra.

30 records · Page 2Linked to original sources
PubMed1989

[Genetic factors as determinants of drug response].

Pharmacogenetics deals with the influence of genetic factors upon the response to drugs. Therapeutic and side effects are affected by pharmacokinetic and pharmacodynamic changes. Classic examples are presented, in particular those concerning mechanisms of oxidation, acetylation and hydrolysis. The impact of this discipline on therapeutics is discussed.

Drug Therapy↗
PubMed1989

[The use of opiates in hospital practice].

We analyzed the type and dosage of opiates used for pain in a large general hospital from April to September 1985. Information was obtained from the computerized data base in 234 patients with a mean age of 49 years. Most patients came from the surgical service. The route of administration was intramuscular in 64% and not specified in 10% of patients. The most common drug was meperidine, the dose being 65 +/- 26 mg intramuscular and 39 +/- 26 intravenously. Methadone and morphine were used with less frequency. Good analgesic effect was recorded in 42 of 71 (59%) of patients, but the effect was not written down in the majority of subjects (70%). Other analgesics were associated in 73% of cases, most commonly a pyrazolone derivative. Nausea or vomiting was observed in only 12 patients; there were no instances of respiratory depression. We conclude that the dose of opiate used was frequently low and the associated drugs were not the best to obtain increased analgesic effect. Better recording of clinical effect of analgesics is needed in medical practice.

Analgesia↗
PubMed1988

Output pathway for turning behavior from the neostriatum and substantia nigra in cats.

The goal of the present work was to study the output pathway of the information for turning behavior originating in the striatum and coursing through the substantia nigra pars reticulata (SNR). In 45 adult cats distributed in 3 groups, Ni-Cr electrodes were implanted in the caudate nucleus and substantia nigra pars reticulata and depending on the animal group in the superior colliculus (SC), nucleus ventralis lateralis/nucleus ventralis medialis (VL/VM) complex or nucleus tegmenti pedunculopontinus (TPP) of one cerebral hemisphere. The threshold current required to evoke turning behavior was determined in each animal for each implantation site. An electrolytic lesion of the superior colliculus, the VL/VM complex or the nucleus tegmenti pedunculopontinus was carried out in each group of cats. The effects of the lesions on behavior and on the electrical threshold currents were determined and compared with the prelesion values. Finally the extent of the lesions and electrode positions were analyzed. The results show that the substantia nigra pars reticulata is the structure with the lowest thresholds for turning and that the superior colliculus appears to be more relevant for carrying the information for turning than either the VL/VM complex or the nucleus tegmenti pedunculopontinus.

Animals↗
PubMed1988

Extracellular unit responses in the pulvinar-lateral posterior complex of the cat through electrical stimulation of substantia nigra reticulata and lateralis.

Extracellular single-unit responses of neurons in the ipsilateral pulvinar-lateral posterior complex were recorded in 10 encéphale isolé cats with stimulating electrodes implanted in the substantia nigra pars reticulata and pars lateralis. Fifteen percent of 101 pulvinar-lateral posterior complex thalamic neurons increased their spike discharges when the substantia nigra was stimulated and none decreased its activity. The excitatory effect of this stimulation is discussed in relation to the eventual excitatory or inhibitory character of the efferent projection from the substantia nigra pars reticulata and lateralis to the pulvinar-lateral posterior complex.

Animals↗
PubMed1987

Study of the morphological, electrophysiological and behavioral effects of unilateral kainic acid injection into the cat's substantia nigra.

Morphological, electrophysiological and behavioral studies were carried out in cats after unilateral kainic acid injection in the substantia nigra. A forced contralateral head turning and compulsive circling was observed after surgery. Fifteen days after, when asymmetry disappeared, apomorphine induced an ipsilateral head and body turning, that was blocked by haloperidol. The percentage of turning, after electrical stimulation in the superior colliculus or pulvinar-lateralis posterior complex, was affected by substantia nigra lesion. This work demonstrates that the nigro-pulvinar-lateral posterior and the nigrotectal projection modulate the capability of electrical stimulation of the target structures to elicit turning, and after unilateral substantia nigra lesion, two opposite directions of asymmetry appear, which are time-dependent and modulated by different neurotransmitters.

Animals↗
PubMed1987

Evidence for a nigro-pulvinar-lateralis posterior complex projection in the cat using horseradish peroxidase neuronal retrograde technique.

The possible existence of a direct projection from the substantia nigra to the pulvinar-lateral posterior complex (Pul-LP) was investigated in the cat by using the horseradish peroxidase technique. In particular horseradish peroxidase was injected in the Pul-LP of 8 animals, either unilaterally or bilaterally. Tissue sections obtained from the cat's brain 24-48 hrs. after injection were prepared according to Mesulam's method as slightly modified by the authors. Retrogradelly labelled neurons were observed in substantia nigra pars lateralis and reliculata ipsilaterally to the injected pulvinar-lateral posterior complex. A small number of labelled cells were also found in the contralateral substantia nigra. These findings demonstrate the existence of a close connection between two system which are involved in turning behavior: the nigrostriatal and the pulvinar-lateral posterior complex-superior colliculus.

Animals↗
PubMed1986

Electrophysiological projections of pulvinar-lateralis posterior complex (P-LP) upon superior colliculus units in the cat.

The effect of Pulvinar-Lateral Posterior (P-LP) electrical stimulation on superior colliculus unitary responses and eye movements is analyzed in 17 encéphale isolé cats. Twelve of them were curarized. Out of a total of 190 recorded units, 117 were localized in the superior colliculus and 73 units in the Mesencephalic Reticular Formation (MRF) below the superior colliculus. Thirty eight per cent (n = 45) of the collicular units modified their discharge frequency when the ipsilateral P-LP was electrically stimulated. The current intensity thresholds of transynaptic activation had a range between 0.5 and 2.0 mA. Most of the orthodromic responses were produced by ipsilateral P-LP stimulation and were localized in the intermediate and deep layers of the superior colliculus. Three types of responses were obtained: short latency responses between 2 and 10 ms (57%); intermediate latency responses between 15 and 40 ms (29%), and long latency responses between 50 and 200 ms (14%). Thirty one per cent (n = 18) of the units recorded in the MRF responded to P-LP stimulation with 10 ms pulse-trains duration. In the MRF 3 types of responses were observed: 1) a decrease or blockade in the resting discharge during 20 to 100 ms after stimulation (20%); simple responses with a latency between 25 and 150 ms (40%), and complex responses with an early response and a latency between 15-40 ms, and a late response with a latency between 150 and 200 ms (40%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Effects of cortical ablations on the turning response evoked by stimulation of the pulvinar-lateralis posterior nucleus complex in the cat.

The role played by the cerebral cortex on turning responses elicited by electrical stimulation of P-LP was studied in 9 chronic cats. In three animals the sensorimotor cortex was bilaterally ablated and the threshold values for inducing a turning response were determined. None of the cats showed abnormal threshold values. In six cats the cerebral cortical area known to have reciprocal anatomical connections with P-LP was unilaterally removed. Seven days after surgery, 50% of the electrodes gave no responses; 25% evoked responses with high thresholds and 25% with normal thresholds. One month after surgery the percentages were: 14, 18 and 68 respectively. Histological findings show important fiber and neuronal degeneration in P-LP. It is postulated that this area of the cerebral cortex plays, a facilitatory role on the P-LP ability to induce turning response and that the recovery of this ability can be explained by the development of P-LP denervation supersensitivity.

Animals↗
PubMedDate not supplied

Comparison of the analgesic and anti-inflammatory effects of diclofenac potassium versus piroxicam versus placebo in ankle sprain patients.

In a double-blind between-patient study the efficacy of diclofenac potassium, a non-steroidal anti-inflammatory drug, was assessed in 93 patients with mild to severe sprained ankles; patients with more severe sports injuries were excluded. Patients were randomly allocated to receive 50 mg diclofenac potassium three times daily, 20 mg/day piroxicam or placebo for 7 days. Diclofenac potassium was more effective than piroxicam or placebo in reducing pain at rest and on walking, but did not significantly reduce the degree of swelling when measured volumetrically by water displacement. No serious side-effects were reported. It is concluded that diclofenac potassium is useful in the treatment of moderately inflammatory processes with the advantage that it had a rapid onset of action with good overall tolerability.

Adolescent↗