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Biomedical subjects

R Castro

Publications and source records attributed to R Castro.

At least 127 records · Page 7Linked to original sources
PubMed1987

Undrugged rotational response in nigro-striatal system-lesioned rats is related to the previous early response to apomorphine when repeatedly administered.

Development and time-course characteristics of undrugged rotational response weeks or months after repeated apomorphine administration in 6-hydroxydopamine-lesioned rats were explored. In one series of experiments, all groups received several drug doses two-three weeks post-lesion and remained undrugged at different intervals from the last drug injection. Weeks or months later, they were injected with saline in the same environment where they previously had received apomorphine. In this way we studied acquisition, time-course and extinction of the rotational response after saline. Furthermore, we related this undrugged response which does not fully develop until two weeks after treatment, and which previously had not been related to a specific parameter of the rotational response to the drug, to a critical point of the time-course response to the drug, i.e., the early rotational response in the first minute after injection. This early response is a learning phenomenon based on the environmental cues where drug has been repeatedly administered. Finally, we state the concept of pharmacological conditioning using this animal model of Parkinson's disease, in agreement with our own results and the previous results of Silverman and Ho (1981).

Animals↗
PubMed1987

Tyrosine administration to pregnant rats induces persistent behavioral modifications in the male offspring.

Pregnant rats were given, by stomach intubation, 1-tyrosine (20 or 500 mg/kg), beginning on day 11 post-coitus. Tyrosine or saline solution administrations were continued on a once-daily basis until day 20 of gestation. When male offspring were seventy days old, the spontaneous locomotor activity, open field test, swim test and motor ability test were performed. The offspring treated with large tyrosine doses showed a marked increase in both spontaneous locomotor activity and open field locomotion as adults. However, activity in the swim test decreased. The number of defecation boluses produced in the open field test and the motor ability in the rotating rod test diminished. The behavior of the rats treated with small doses of tyrosine was similar, in all tests performed, to that of rats treated with saline solution. These findings strongly suggest that a large increase in diet tyrosine during pregnancy modifies the behavior of male offspring.

Animals↗
PubMed1987

Methodology of premature chromosome condensation and its potential for relapse prediction in acute leukemia of children and adolescents.

Premature chromosome condensation has been examined as a method for measuring the proliferative potential of bone marrow cells derived from children with acute leukemia with the intention of finding a predictor of relapse. A proliferative potential index (PPI) has been determined for patients with active disease at diagnosis and relapse, as well as at onset of remission and at extramedullary relapse. A modification of the technique established by Hittelman is described, which can be easily performed by the leukemia cytogeneticist. A PPI of 35% or greater is usually obtained for patients at diagnosis or in relapse. At the onset of remission, the PPI declines to values significantly below 35% and during extramedullary relapse the value of the PPI is near normal (12%). The method for the determination of the PPI is given in detail.

Acute Disease↗
PubMed1987

Premature chromosome condensation as a predictive indicator of relapse in children and adolescents with acute leukemia: initial observations.

Premature chromosome condensation has been used to determine a proliferative potential index (PPI) in a study of children in leukemia remission at varying times during the disease. Values 35% and greater were considered predictive of relapse. Such values preceded relapse with a mean of 5 months in acute lymphoblastic leukemia (ALL) patients who had previously relapsed and in myeloid leukemia patients. ALL patients followed from diagnosis and children off therapy had fluctuating and false predictive PPI values preceding long courses of continued remission. This study suggests that the PPI as a predictive indicator for relapse may be useful for patients with ALL who have previously relapsed and for patients with myeloid leukemias. Future exploration to further evaluate this mechanism of prediction is to be attempted by investigating the ability to obtain similar and more detailed information through the use of peripheral blood rather than bone marrow samples.

Acute Disease↗
PubMed1986

Different roles of intrahypothalamic and nigrostriatal dopaminergic systems in thermoregulatory responses of the rat.

Classically, two neurotransmitters in the brain have been implicated in thermoregulation: 5-hydroxytryptamine and norepinephrine. A dopamine action is less well-known and usually has been studied by means of pharmacological rather than physiological procedures. In the present work using a physiological approach to the problem, the role of different central dopaminergic systems in the thermoregulatory response of rats exposed to cold (4 degrees C) or warm (45 degrees C) environments has been studied. Rostral incertohypothalamic neurons in the medial preoptic area synthesized and released more dopamine in response to a warm but not to a cold environment. On the other hand DA and DOPAC levels in nigrostriatal systems were decreased by cold but not warm environments. The dopaminergic neurons projecting to nucleus accumbens or hypothalamus do not appear to be related to the thermoregulatory response in the rat.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1986

Further studies on the ELISA-spot technique. Its application to particulate antigens and a potential improvement in sensitivity.

Applications of the ELISA-spot technique to particulate antigens (sheep erythrocytes and E. coli) are reported; sheep erythrocytes were used to ensure a rigorous comparison of the spot assay and the haemolytic plaque assay. The spot technique was also applied to soluble antigens (dextran and trinitrophenyl-lipopolysaccharide) to assess the putative occurrence of non-haemolytic antibodies. In most instances, the spot assay disclosed higher numbers of antibody-secreting cells than the plaque assay. An examination of the kinetics of spot formation demonstrated that spot development was most rapid during the first and second hours of enzyme activity and slowed thereafter, although the numbers of spots at 16 h were higher than those at 2 h. To shorten the assay time a redox reaction (which yields an insoluble formazan) was coupled to the enzymatic reaction. In duplicate assays, this improved technique gave larger numbers of spots in a shorter time, than the conventional assay.

Animals↗
PubMed1986

Rotative agitation RIA. A high sensitivity technique for hepatitis B surface antigen (HBsAg) determinations.

With the objective of finding a simpler and more sensitive method than conventional radioimmunoassay testing to detect HBsAg, we have modified the sample volume and first incubation procedure of the Ausria IIA method. There was an up to 9-fold increase in sensitivity without loss of specificity, in different assays, when the first incubation was carried out with a serum sample of 1 ml that was rotatively agitated for 22 h at room temperature. Additionally, 71 samples from which conventional testing had isolated hepatitis B core antibodies were tested with the modified rotative agitation technique and 9 of these specimens (12.67%) were positive for HBsAg. Routine employment of the rotative agitation radioimmunoassay technique to screen HBsAg by blood banks, to detect potential infectious donations that escape conventional testing, could be an effective as well as low-cost procedure to prevent post-transfusion hepatitis B.

Blood Banks↗
PubMed1986

[Role of the presynaptic receptors in the control of dopamine synthesis in the striate complex and nucleus accumbens].

The role of presynaptic receptors on dopamine synthesis, at both nigrostriatal and mesolimbic systems, has been studied after dopamine uptake drastically increases the dopamine and DOPAC levels at n. accumbens but not at striatum. The present data suggest that presynaptic receptors are a decisive factor regulating dopamine synthesis at nigrostriatal system. However, the end-product inhibition could be the most important autoregulatory mechanism at the mesolimbic system.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1985

Increased or decreased locomotor response in rats following repeated administration of apomorphine depends on dosage interval.

Administration of drugs that reduce the influence of dopamine at its receptor site can lead to postsynaptic supersensitivity, whereas treatment with dopamine (DA) agonists can cause postsynaptic subsensitivity. Both unaltered and enhanced postsynaptic responses to DA have been shown after pretreatment with DA agonists. In the present manuscript pretreatment with apomorphine, a dopaminergic agonist, is shown to induce either increased or reduced locomotor activity. When a drug-free period between successive injections was allowed, apomorphine induced an enhanced locomotor response, whereas a reduced response occurred when each dose was injected before the previous apomorphine dose had been completely metabolized. Pretreatment with both high (1 and 3 mg/kg) and low (0.05 mg/kg) apomorphine doses enhanced the response. Apomorphine treatment that caused enhanced locomotor responses did not modify the stereotypy response to the drug. Similar enhanced or reduced response were found in rats with partial lesions of the nigrostriatal system. These altered responses to DA agonists may have important clinical consequences. The present data also suggest the existence of a different DA systems for locomotor and stereotypy actions of dopaminergic agonists.

Animals↗
PubMed1985

Polychemotherapeutic treatment for ovarian carcinoma (our experience).

Since September 1980 to June 1983 we have treated 32 patients with ovarian cancer. Most patients were submitted to time polychemotherapy cyclophosphamide, adriamycin and cis-platinum. The maximum of survival time was 24 months; six patients died; the period of survival of the remaining 24 patients is between 2 and months.

Adult↗