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R Rosas

Publications and source records attributed to R Rosas.

18 recordsLinked to original sources
PubMed2006

Attention-deficit hyperactivity disorder involves differential cortical processing in a visual spatial attention paradigm.

OBJECTIVE: Inattention is undoubtedly one of the main characteristics of Attention-deficit hyperactivity disorder (ADHD). Nevertheless, a growing corpus of evidence shows that not all attentional processes are affected in this condition. This study aimed to explore the distribution of attentional resources in children with ADHD via a spatially shifted double-oddball visual task. METHODS: We recorded event-related potentials (ERPs) for all visual stimuli. Subjects were instructed to allocate attention in a specific area of visual space while ignoring all stimuli presented outside. Ten male children (age: 9-14; mean = 11.6 +/- 2.1) who met DSM-IV criteria for the ADHD combined subtype participated in the study, along with ten age- and sex-matched healthy controls (9-14; mean = 11.2 +/- 2.3). RESULTS: ADHD subjects showed late differential cortical responses to initially suppressed irrelevant stimuli. The amplitude of early N1-P1 components were mainly modulated by stimulus location and showed no significant differences between groups, but a late P300-like positivity was clearly evoked in the ADHD group by peripheral stimuli. CONCLUSIONS: These results suggest that ADHD may not compromise the early attentional spatial filter but rather entails a different distribution of attentional resources at later stages of cortical processing. Perhaps these differences may be attributable to individual differences in attentional mechanisms. SIGNIFICANCE: ADHD may not affect initial focusing of visual attention but rather the allocation of processing resources in later stages.

Adolescent↗
PubMed1996

[Persistence of the cognitive effects of early stimulation assessed with an animal model].

Human and animal studies have clearly demonstrated the advantageous effects of sensorially enriched rearing environments. Nevertheless, little work has been done concerning the long-lasting persistence of all these behavioral modifications. To undertake this question, a very early enrichment animal model was used. From days 10 to 24 after birth, 28 male albino rats were exposed to a multisensory stimulated environment, while other 28 littermates constituted the control group. At 3 and 6 months old two cognitive abilities were analyzed; the spatial working memory (short term memory) and the latent learning capacity (long term memory). The results evidenced an improved working memory in both 3 and 6 months old rats exposed to the early enriched environment. Moreover, the adult early stimulated group performed as well as younger subjects both on error scores and speed to solve this test. Only in the adult group of rats a superior latent learning capacity of stimulated subjects was evidenced. To conclude, the early enriched environment induced: a) persistent cognitive benefits in the adult rat and b) a more relevant influence on the subsequent behavior of older rather than younger subjects.

Age Factors↗
PubMed1991

Role of sulfhydryl groups in the stimulatory effect of captopril on vascular prostacyclin synthesis.

The effect of captopril on vascular prostacyclin production was studied, evaluating which of its components--sulfhydryl (SH) group or proline--is responsible for this effect. Rat aortas were incubated with captopril (10-100 microM), 2-mercaptoethanol or proline (10 microM), and captopril plus the SH-binding reagents N-ethylmaleimide or ethacrynic acid (50 microM). Prostacyclin was measured by radioimmunoassay of 6-keto-prostaglandin F1 alpha. Captopril stimulated prostacyclin production. This effect was associated with an enhanced conversion of arachidonate to prostacyclin and was not related to bradykinin. Since 2-mercaptoethanol increased vascular prostacyclin per se and proline did not, the stimulatory effect of captopril appears to be dependent upon the SH group; in addition, both SH blockers, N-ethylmaleimide and ethacrynic acid, antagonized this effect. This study shows that captopril stimulates vascular prostacyclin synthesis directly and that the SH group plays a key role in this action. This stimulation of prostacyclin synthesis may contribute to the antihypertensive action of captopril.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Atrial natriuretic factors (ANF) and antidiuretic agents.

The effects of lysine-vasopressin (VP) and pepsanurin (PU) on the diuretic-saluretic action of ANF were investigated. Anaesthetized female rats under constant intravenous perfusion with isotonic glucose solution (0.6 ml/h/100 g body weight) were used. Blood pressure was recorded continuously and in the urine collected every 20 min, volume, NA and K excretion were measured. In each rat two intravenous boluses of either 2.5 ug synthetic rat atriopeptin II or an equivalent amount of a semipurified rat atrial extract were assayed. Thirty min before the ANF second bolus, an i.v. injection of lysine-vasopressin was given. Doses of 0.1, 1, 5, 10 and 50 mU were used. PU in the dose of 0.5 ml, obtained from 20 ml of human plasma was administered intraperitoneally, 40-60 min before the second bolus of ANF. The smaller doses of VP did not inhibit the urinary response to ANF, and the higher one (50 mU) produced a significant facilitation of ANF effect. Contrariwise, PU produced a considerable inhibition on water, NA and K excretion promoted by ANF.

Animals↗
PubMed1978

Effects of prostaglandin E2 and prostaglandin F2alpha upon urinary kallikrein excretion in rats.

1. In normally hydrated rats prostaglandin F2alpha (PGF2alpha) in doses of 5 microgram/100 g body weight given subcutaneously every 2 h (three times) induced a significant increase in urinary kallikrein activity, and in sodium, potassium and water excretion for 8 h after the first injection. In moderately hyperhydrated rats loaded 2.5% of body wt. with 0.5% NaCl solution, PGF2alpha produced similar changes in kallikrein activity and electrolyte excretion. 2. In normally hydrated rats prostaglandin E2 (PGE2) in the same conditions and doses as in 1 had no effect on kallikrein activity, showing a tendency to decrease potassium and water excretion. 3. PGE2 in doses of 5, 12.5 and 25 microgram/100 g body wt. in overhydrated rats given 2.5% and 0.5% NaCl and 5% of tap water/100 g body wt. 1 h later, significantly increased kallikrein activity in the urine collected for 120 min after the injections. A significant decrease in potassium and water excretion was observed with the highest dose. 4. PGF2alpha, had no effect on kallikrein activity in overhydrated rats, but an increase in sodium and a decrease in potassium excretion was seen at the highest dose. 5. The different actions of PGE2 and PGF2alpha may be part of a regulatory mechanism associated with the kallikrein-kinin system which contributes maintainance of extracellular fluid homeostasis.

Animals↗
PubMed1977

Renal kallikrein system, volemia, and renal hypertension.

Plasma, blood, and urine volumes, renal kallikrein, and arterial pressure were measured in control and renal hypertensive rats in order to study the role of the renal kallikrein system in regulating arterial pressure and its relation with the alterations in water handling observed in hypertension. A decrease in kallikrein content of the kidney (157 +/- 17 versus 236 +/- 16 ng bradykinin equivalents per gram of tissue in control rats) was associated with an increase in plasma volume (38.0 "/- 1.6 versus 32.0 +/- 0.9 ml/kg body weight in control rats) and an increase in urine volume (45.5 +/- 4.9 versus 20.3 +/- 1.6 ml/kg body weight per 24 hours in control rats). No linear correlation was found between these factors and the arterial pressure of hypertensive animals. These findings support the hypothesis that changes in renal kallikrein are more directly related to water and electrolyte metabolism than to the arterial pressure regulation. Our results also suggest an interaction between the kallikrein-kinin and the renin-angiotensin-aldosterone systems. The possible relations of both enzymatic systems to the regulation of arterial pressure and of water-electrolyte handling are summarized schematically.

Animals↗
PubMed1976

Renal urinary kallikrein in normotensive and hypertensive rats during enhanced excretion of water and electrolytes.

1. Urinary kallikrein excreted by normal rats is significantly increased (P less than 0-001) 2 h after: (a) water loading, (b) water loading plus frusemide, 0-27 mmol (10 mg) per rat, (c) salt loading. In water-loaded rats, 5 i.u. of renin strikingly reduced kallikrein excretion (P less than 0-01) but considerably increased sodium excretion (P less than 0-001). 2. Renal kallikrein, measured by its kininogenase activity within 2 h of water loading, was significantly increased (P less than 0-05); after water loading and frusemide it was 40% decreased (P less than 0-001) and after salt loading it was reduced by approximately 50% (P less than 0-02). Renin did not change renal kallikrein. 3. Severely hypertensive (one-kidney) rats (blood pressure greater than 150 mmHg) showed no increase of urinary kallikrein after water loading, although there was a marked natriuresis, in moderately hypertensive rats (blood pressure less than 150 mmHg) urinary kallikrein was only one-third of that observed in control normotensive rats, after an equal degree of water loading.

Animals↗
PubMed1975

The renin-angiotensin system in rats made hypertensive by ligation of the kidney poles (38584).

The renin-angiotensin system was studied in experimental renal hypertension produced by ligation of the poles of the left kidney followed by contralateral nephrectomy. Plasma renin concentration of renin substrate was lower and that of angiotensin I converting enzyme was higher in hypertensive animals. The juxtaglomerular index decreased in the medial zone of the kidney, while heavily granulated areas appeared in the poles. Ligated kidneys of rats that remained normotensive showed juxtaglomerular indices intermediate between the control and the hypertensive rats. Differences in renal renin content between the groups correspond to those for the juxtaglomerular index, but were smaller. No differences between the experimental groups were observed in iso-renin content in the brain; however in all animals with ligated kidney poles, hypertensive or normotensive, there was a tendency for iso-renin in the adrenals, left ventricular myocardium, and especially aorta to be lower than in controls.

Adrenal Glands↗
PubMedDate not supplied

Acetylcholinesterase and insect growth inhibitory activities of Gutierrezia microcephala on fall armyworm Spodoptera frugiperda J.E. Smith.

From the aerial parts of Gutierrezia microcephala (Asteraceae), four oxyflavones were isolated, namely 5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone (1); 5,7,4'-trihydroxy-3,6,8-trimethoxyflavone (2); 5,7,2',4'-tetrahydroxy-3,6,8,5'-tetramethoxyflavone (3); 5,2'-dihydroxy-3,6,7,8,4',5'-hexamethoxyflavone (4), and an ent-clerodane, bacchabolivic acid (5). Compounds 1-5, the synthetic methyl ester (6), n-hexane and MeOH extracts were evaluated against the fall armyworm (Spodoptera frugiperda). Gedunin, a known insect growth regulator isolated from Cedrela spp. was used as a positive control. When tested for activity on neonate larvae into the no-choice artificial diet bioassay, flavone (1), clerodane (5), its methyl ester (6), MeOH and n-hexane extracts caused significant larval mortality with MC50 of 3.9, 10.7, 3.46, 7.95 and 7.5 ppm at 7 days, respectively, as well as growth reduction. They also increased the development time of surviving larvae and a significant delay in time to pupation and adult emergence. Acute toxicity against adults of S. frugiperda was also found, 5, 6, gedunin and n-hexane extract had the most potent activity with LD50 value of 6.59, 15.05, 10.78, and 12.79 ppm, respectively. In addition, MeOH, n-hexane extracts, 5, 6 and gedunin caused acetylcholinesterase inhibition with 93.7, 100, 90.2, 62.0 and 100% at 50.0 ppm, respectively; whereas 1-4 exhibited only moderate inhibitory activity. Compounds 1, 5 and 6 showed inhibitory activities comparable with gedunin. These compounds could be responsible of the insect growth inhibitory activity of this plant.

Acetylcholinesterase↗
PubMedDate not supplied

[Utility of the copper/zinc ratio in patients with lymphoma or acute or chronic leukemias].

OBJECTIVE: To determine the diagnostic value of serum levels of copper, zinc and the Cu/Zn ratio in patients with hematological malignancies compared to gender- and age-matched control subjects. METHODS: A total of 44 patients with recently diagnosed and non-treated hematological malignancies were included: 17 lymphoma (11 non-Hodgkin), 15 acute leukemia (10 myeloblastic), and 12 with chronic leukemia (8 granulocytic); 95 healthy subjects were included. Copper and zinc serum levels were measured with a Perkin Elmer (model 2380) atomic absorption spectrophotometer. RESULTS: Serum copper levels (microgram/dL) were significantly lower in healthy subjects (54.4 +/- 8.9, p < 0.05) compared to patients with lymphoma (93.7 +/- 37.5), acute leukemia (80.6 +/- 44.6) or chronic leukemia (95.7 +/- 28.9) while serum zinc levels (microgram/dL) were significantly higher in healthy control subjects (100.4 +/- 14, p < 0.05) compared to patients with lymphoma (77.2 +/- 22.6), acute leukemia (66 +/- 15.6), or chronic leukemia (74.8 +/- 14.7). The Cu/Zn ratio was significantly lower in healthy subjects (0.54 +/- 0.13, p < 0.05) than in patients with lymphoma (1.21 +/- 0.5), acute leukemia (1.22 +/- 0.7), or chronic leukemia (1.28 +/- 0.4). Twenty three patients died during a mean follow-up period of 13 months and their serum zinc levels were significantly lower (68 +/- 21) than in the living patients (76 +/- 15, p < 0.05). CONCLUSION: Cu/Zn ratio is significantly higher in patients with lymphoma or acute and chronic leukemias compared to gender- and age-matched control subjects.

Acute Disease↗