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Biomedical subjects

A Meneses

Publications and source records attributed to A Meneses.

At least 55 records · Page 3Linked to original sources
PubMed1997

Effects of nimodipine on learning in normotensive and spontaneously hypertensive rats.

It is well known that the calcium channel blocker, nimodipine, has beneficial effects on learning in either aged or hypertensive animals and humans. However, no attempts have been made to investigate if nimodipine can reverse the synergistic deleterious effects of aging and hypertension in the same subject. Therefore, this study investigated the effects of stable infusions of nimodipine in the autoshaping learning task using middle-aged normotensive (WKY) and hypertensive (SHR) rats. WKY and SHR of 12 months of age were implanted with osmotic minipumps releasing either vehicle or nimodipine (0.4 mg/kg/day). After 3 weeks of treatment, the animals received autoshaping training sessions during 4 consecutive days. The WKY animals treated with nimodipine exhibited the highest levels of learning during the last session, the rank order being WKY-nimodipine > SHR-nimodipine > WKY-vehicle > SHR-vehicle. These results confirm that nimodipine can reverse the impairing effects of either aging or hypertension on learning; the presence of both conditions, however, might produce more severe dysfunctional changes that cannot be totally reversed by nimodipine.

Aging↗
PubMed1997

A pharmacological analysis of serotonergic receptors: effects of their activation of blockade in learning.

1. The authors have tested several 5-HT selective agonists and antagonists (5-HT1A/1B, 5-HT2A/2B/2C, 5-HT3 or 5-HT4), an uptake inhibitor and 5-HT depletors in the autoshaping learning task. 2. The present work deals with the receptors whose stimulation increases or decreases learning. 3. Impaired consolidation of learning was observed after the presynaptic activation of 5-HT1B, 5-HT3 or 5-HT4 or the blockade of postsynaptic 5-HT2C/2B receptors. 4. In contrast, an improvement occurred after the presynaptic activation of 5-HT1A, 5-HT2C, and the blockade of presynaptic 5-HT2A, 5-HT2C and 5-HT3 receptors. 5. The blockade of postsynaptic 5-HT1A, 5-HT1B, 5-HT3 or 5-HT4 receptors and 5-HT inhibition of synthesis and its depletion did no alter learning by themselves. 6. The present data suggest that multiple pre- and postsynaptic serotonergic receptors are involved in the consolidation of learning. 7. Stimulation of most 5-HT receptors increases learning, however, some of 5-HT subtypes seem to limit the data storage. 8. Furthermore, the role of 5-HT receptors in learning seem to require an interaction with glutamatergic, GABAergic and cholinergic neurotransmission systems.

Animals↗
PubMed1997

[Epidermoid carcinoma originating from a mature cystic ovarian teratoma. Report of two cases and review of the literature].

The incidence of developing malignancy in a mature cystic teratoma of the ovary is 1-2%. Most of the reported cases occur in postmenopausal women. This paper reports two cases of squamous cell carcinoma arising in a mature cystic teratoma of the ovary of which one occurred in a young woman. In the other case we could support the fact that the carcinomatous component has its origin in the columnar epithelium and epidermis of the teratomatous tissues.

Adnexa Uteri↗
PubMed1996

Resumption of ovarian activity in zebu cows (Bos indicus) in the humid tropics: influence of body condition and levels of certain blood components related to nutrition.

This study investigated the relationship between resumption of ovarian activity and body condition in a herd of 20 zebu cows in the humid tropics. Blood chemistry profiles to monitor nutritional status were also evaluated. Plasma progesterone was used to determine ovarian activity. During the study, which lasted 18 weeks post partum, 7 of the animals resumed ovarian activity while 13 remained in the anoestrous stage. The beginning of the first luteal phase was registered on day 87 +/- 19 (range 60 to 106). The animals which resumed cyclicity were in significantly better body condition and had significantly higher mean body weight than anoestrous cows. In the group which resumed ovarian activity, calcium levels decreased significantly from 3 weeks before until the first rise of progesterone in the first normal cycle. The study was divided into 2 periods corresponding to weeks 0 to 8 (I) and 9 to 18 (II) based on the finding that until week 8 all animals were reproductively inactive. During period I there were no significant differences between the groups in blood concentrations of albumin, glucose, urea, cholesterol, calcium and phosphorus. During period II albumin was significantly higher and urea significantly lower in the cows resuming ovarian activity. The results suggest that cows able to maintain their body condition from calving through the early post-partum period will have shorter intervals to first post-partum oestrus than cows which have lost body weight. The lower urea and higher albumin levels in the cyclic animals probably reflected a better feed efficiency--the demands of lactation were compensated by an altered nitrogen metabolism.

Animals↗
PubMed1996

Systemic injection of p-chloroamphetamine eliminates the effect of the 5-HT3 compounds on learning.

There is evidence that 5-HT3 antagonists enhance learning and memory; however, their mechanisms of action are unknown. The aim of the present work was to investigate further the role of 5-HT3 receptors involved in learning, using the specific 5-HT3 agonist 1-(m-chlorophenyl)-biguanide (mCPBG) and the 5-HT3 antagonists ondansetron and tropisetron. p-Chloroamphetamine (PCA) pretreatment was used to determine whether pre- or postsynaptic 5-HT3 receptors are involved in learning. The posttraining intraperitoneal (IP) injection of each drug was analyzed on a lever-press response on autoshaping, which is an associative learning task. The results showed that mCPBG impaired retention of the conditioned response (CR), whereas tropisetron and ondansetron improved it. In other animals, PCA alone did not affect CR but was able to block the effects of the 5-HT3 ligands. The present data suggest that the actions of 5-HT3 compounds could be due to their interaction with presynaptic 5-HT3 receptors.

Animals↗
PubMed1996

Tinnitus and Post-Traumatic Vertigo - A Review.

Fifteen neuro-otological patients have been investigated for post-traumatic vertigo, hearing loss and tinnitus. Clinical examination and laboratory tests included audiometry and equilibriometry in all patients. Statistically significant findings are reported for tinnitus, vertigo, hearing loss. Correlations for vertigo with the type of head trauma, nystagmus frequency Slow Phase Velocity (SPV) and associated complaints of hearing loss and tinnitus were analyzed. The most frequent symptom reported was vertigo (73.3%); lift sensation (46.6%); tilting and falling (26.6%); and tinnitus (40%).

Journal Article↗
PubMed1996

Effects of aging and hypertension on learning, memory, and activity in rats.

A comparison between behavioral alterations induced by hypertension and aging was made in spontaneously hypertensive (SHR) and Wistar-Kyoto rats (WKY) of different ages (3-24 months old), trained to perform autoshaping learning and activity tasks. Food-deprived rats received autoshaping training sessions during 6 days; the animals were retrained 1 month later. Two weeks after autoshaping training, the animals were evaluated in the spontaneous activity task during 2 consecutive days. The results show an age-related decrease in learning, memory, and spontaneous activity. Independently of the age group compared, WKY, though showing lower activity, learned and retrieved more than SHR. Accordingly, the reductions in learning and memory were correlated with both aging and hypertension. The combined influence of these two factors had synergistic detrimental effects on cognitive functions.

Aging↗
PubMed1995

Plasmacytoid myoepithelioma of the laryngeal region: a case report.

The first case of plasmacytoid myoepithelioma of the laryngeal region is presented. The tumor showed immunoreactivity for the S-100 protein, low molecular weight cytokeratin, and vimentin. Staining was negative with muscular actin and glial fibrillar acid protein. By electron microscopy the tumor cells showed abundant microfibrillar material, elongated densities resembling smooth muscle dense bodies, pinocytic vesicles, and replicated basal lamina. The myoepithelial nature of plasmacytoid tumors of the salivary gland has been questioned.

Female↗
PubMed1995

Effect of fluoxetine on learning and memory involves multiple 5-HT systems.

Diverse evidence suggests that 5-HT uptake blockers enhance learning and memory. However, there is no information about the mechanisms of action involved in such effects. The aim of the present work was to investigate the nature of the receptors involved in the effects of fluoxetine on learning. Therefore, a dose-response curve of posttraining injection (intraperitoneal) of fluoxetine was carried out in an associative learning task (auto-shaping). Fluoxetine or the vehicle was injected 10 min after 5-HT antagonists: (+/-)-pindolol, (+/-)-propanolol, NAN-190, ketanserin, ritanserin, mesulergine, MDL 72222, or SDZ 205-557. Presynaptic activity was eliminated by means of chloroamphetamine pretreatment. Scopolamine (an anticholinergic) and dizocilpine (a noncompetitive NMDA receptor antagonist) were also used. Results showed that fluoxetine enhanced learning of the conditioned response (CR) in a dose-dependent fashion. All 5-HT antagonists had no effects by themselves but inhibited the effects of fluoxetine at different degrees. Decrement of CR produced by scopolamine was reversed by fluoxetine. Dizocilpine did not affect CR but prevented the effects of fluoxetine. The present findings suggest that the actions of fluoxetine on learning are due to an interaction with multiple receptors of postsynaptic nature.

Animals↗
PubMed1995

Changes in endothelium-dependent vascular responses associated with spontaneous hypertension and age in rats.

The aim of this study was to investigate if the endothelium-dependent relaxation and the inhibitory effect of endothelium against vasoconstrictor stimuli are reduced by aging and hypertension in rat aorta. Both relaxation and isometric contraction of intact and denuded aortic rings from spontaneously hypertensive rats (SHR) of 7-9, 12-18, 28-36 and more than 70 weeks old and from age-matched Wistar-Kyoto rats (WKY) were measured in parallel. An age-related decrease of endothelium-dependent relaxation to acetylcholine was found, which was greater in arteries from SHR (p < 0.05). Indomethacin normalized the endothelium-dependent relaxations in aortic rings from either old or hypertensive rats. Relaxations elicited by nitroglycerin were slightly enhanced with age in both WKY and SHR (p < 0.05). Moreover, endothelium removal increased responsiveness to indanidine and to 5-hydroxytryptamine (5-HT). Endothelium-dependent inhibition on the contraction decreased with aging (to a greater extent in SHR). These results indicate that aging and hypertension are associated with a decrease in the endothelium-dependent responses. Endothelium-dependent relaxations of aortae from old normotensive and hypertensive rats were impaired by the production of a cyclooxygenase-derived contractile factor. However, the higher response to nitroglycerin suggests a lesser production of endogenous nitric oxide by endothelial cells.

Aging↗
PubMed1994

Mechanism of action of 8-OH-DPAT on learning and memory.

It has been previously demonstrated that pretraining injection of 8-hydroxy-2-(di-n-propilamino)tetralin (8-OH-DPAT, a 5-HT1A agonist) impairs conditioned response (CR) in an autoshaping learning task. Therefore, in the present work we intended to determine whether such an effect could be prevented by pretraining, and whether pre- or postsynaptic 5-HT receptors are involved. Groups of rats received or did not receive food magazine training. On the next day, all groups in both conditions, pre- or posttraining, were treated with 8-OH-DPAT (0, 0.062, or 0.250 mg/kg). Posttraining groups were tested on a second session of autoshaping 24 h later. In a second experiment, naive rats received para-chlorophenylalanine (PCPA) (300 mg/kg x 3 days) before pre- or posttraining injection of 8-OH-DPAT. Results showed that in those groups trained to food magazine and treated 24 h later with 8-OH-DPAT, CR was not affected or enhanced. PCPA injection had no effect by itself, but blocked or attenuated the effect of a post- or pretraining injection of 8-OH-DPAT. The present data suggest that a) the pretraining effect of 8-OH-DPAT eliciting a decrease in CR can be eliminated by a food magazine training session; and b) presynaptic 5-HT1A receptors are involved in the effect of 8-OH-DPAT on the acquisition and consolidation of learning.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Modification of 8-OH-DPAT effects on learning by manipulation of the assay conditions.

A role for the 5-HT1A receptor in learning and memory has been suggested by diverse evidence. The present paper deals with the acute effect of 8-OH-DPAT (a 5-HT1A agonist) administered to rats before or after training in an autoshaped lever-press response (a model of associative learning). The results show that 8-OH-DPAT improved consolidation of the conditioned response (CR) when injected post-training, but impaired it with pretraining administration. Both effects were time-dependent. When the compound was administered pre- or post-training to free-feeding or prefeeding animals, they did not learn the CR. When it was administered to retrained food-deprived animals, the compound was also inactive. However, with retrained animals on a free-feeding schedule, pre- or post-training administration of 8-OH-DPAT enhanced retrieval in a dose-dependent fashion. Pretraining administration of 8-OH-DPAT impaired food intake and exploration, and therefore learning. The present results strongly suggest a role of 5-HT1A receptors in the consolidation and retrieval of learning. Such improvement is independent of food intake.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1993

Modification of the anxiolytic effects of 5-HT1A agonists by shock intensity.

Contradictory evidence exists concerning the anxiolytic effects of 5-HT1A agonists in the conflict test. In the present work, a modification of the Vogel conflict model was used to assess different doses of diazepam (0.1-5.6 mg/kg), ipsapirone (1.0-17.8 mg/kg), buspirone (1.7-17.8 mg/kg), and indorenate (0.56-17.8 mg/kg) in rats receiving two different electric shock intensities (0.16 and 0.32 mA). The results show that the three 5-HT1A agonists had a smaller anticonflict effect than diazepam. The anticonflict effect with each compound was of a greater magnitude at 0.16 mA intensity than at 0.32 mA. This study shows that, using different electric shock intensities, compounds produce a differential effect: the anticonflict effects were more pronounced with the lower electric shock intensity than with the higher intensity. The present results suggest that the use of different shock intensities can play distinct roles over the drug's effect in the conflict test.

5-Methoxytryptamine↗
PubMed1993

Oral findings in Mexican AIDS patients with cancer.

Oral findings of 42 Mexican AIDS patients with cancer were reviewed. Kaposi's sarcoma (KS) was the most frequent malignancy (81%) followed by non-Hodgkin's lymphoma (NHL) (12%). All cases of NHL were of high or intermediate grade and most of them were extranodal. Out of the 34 individuals with KS, 22 (65%) showed oral KS and in 21 of them the palate was involved. The clinical features of oral KS including site, appearance and size are described. Pseudomembranous candidosis (PC), hairy leukoplakia (HL) and exfoliative cheilitis (ECh) were also found in these patients. There was no association of these lesions with any type of cancer. A strong association of oral candidosis and history of this infection was found, RR = 7.0 (1.3-4.1). There was evidence of severe immunosuppression in most patients, with mean average CD4 counts of 116 mm3 (range 4-841/mm3). Oral KS, ECh, PC and HL were more common in patients with lower CD4 counts. Our findings illustrate the most frequent oral lesions associated with HIV-1 infection in patients with AIDS and cancer, and further support the importance of oral examination in HIV infected patients.

AIDS-Related Opportunistic Infections↗
PubMed1993

Radiotherapy compared to chemotherapy as initial treatment of angiocentric centrofacial lymphoma (polymorphic reticulosis).

Polymorphic reticulosis has recently been characterized as an angiocentric lymphoproliferative disorder of the peripheral T-lymphocytes. However, its treatment is still a matter of controversy. In order to study efficacy and toxicity of the primary treatment, we reviewed clinical features and therapeutic results in 29 patients seen at the Instituto Nacional de Cancerologia de Mexico. Nineteen patients received primary local irradiation and 10 patients primary combination chemotherapy. In the radiotherapy group, 14 (74%) patients achieved complete response, but only 4 (40%) did so in the primary chemotherapy group. Five patients in the latter group died of treatment-related complications. The 5-year actuarial survival rate was 70% in the irradiation group, while the 1-year survival rate was only 15% in the chemotherapy group. These data strongly suggest that, in polymorphic reticulosis, initial chemotherapy may be very toxic.

Adolescent↗