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P Alvarez

Publications and source records attributed to P Alvarez.

At least 55 records · Page 3Linked to original sources
PubMed1994

Memory consolidation and the medial temporal lobe: a simple network model.

Some forms of memory have been shown to depend on a system of medial temporal lobe structures that includes the hippocampus and the adjacent cortical areas (entorhinal, perirhinal, and parahippocampal cortex). The role of this system is only temporary, however, as indicated by the fact that, after damage to the medial temporal lobe, recent memories are impaired but very remote memories are intact. Here we review the evidence that the medial temporal lobe memory system is involved in a process of consolidation: memories are initially dependent on this system but gradually become established in other areas of the brain. We then review some of the ideas that have been proposed about the phenomenon of consolidation and suggest a synthesis of these views. Finally, we describe a simple neural network model that captures some key features of consolidation.

Animals↗
PubMed1994

The animal model of human amnesia: long-term memory impaired and short-term memory intact.

Normal monkeys and monkeys with lesions of the hippocampal formation and adjacent cortex (the H+ lesion) were trained on the delayed nonmatching to sample (DNMS) task with a delay of 0.5 s between the sample and the choice. The animals with H+ lesions learned the task normally at this short delay and also exhibited the same pattern of response latencies as normal monkeys. This finding contrasts with previous observations that initial learning of the DNMS task with delays of 8-10 s is impaired after H+ lesions. The absence of an impairment at a delay of 0.5 s indicates that the H+ lesion does not affect short-term memory. In contrast, when monkeys with H+ lesions were tested at longer delays (> 30 s), an impairment was observed. This selective impairment occurred when the delays were presented sequentially (from 0.5 s to 10 min) and also when delays were presented in a mixed order (1 s, 1 min, and 10 min). The data indicate that the H+ lesion produces a selective impairment in long-term memory, in the absence of a detectable deficit in short-term memory or perception. Accordingly, the findings confirm the long-standing idea, based primarily on studies of humans, that short-term memory is independent of medial temporal lobe function. The findings thereby establish an important parallel between memory impairment in monkeys and humans and provide additional support for the validity of the animal model of human amnesia in the monkey.

Amnesia↗
PubMed1993

["Sacroiliitis" as the initial manifestation of hepatocarcinoma].

The hepatocellular carcinomas rarely develop in absence of a previous hepatopathy and their first clinical manifestations are not related, in general, to the metastasis located at the bones of the pelvic girdle. We present a multifocal hepatocarcinoma in a 17-year-old woman without known risk factors, whose initial manifestation was a clinical radiological picture suggesting left sacroiliitis. We stress this rare manifestation preceding the diagnosis of neoplasia two years later.

Adolescent↗
PubMed1989

Detection and characterization of antigens from Taenia solium cysticercus in cerebrospinal fluid.

Dot-ELISA and standard-ELISA were used to detect T. solium cysticercus antigens in cerebrospinal fluid for the diagnosis of neurocysticercosis. The results indicate that both assays are sensitive, specific and economically adequate for the diagnosis of this disease. Using SDS-PAGE, electroblotting and dot-ELISA we have found that the antigen is a protein with a molecular weight of 66,000 daltons.

Adult↗
PubMed1988

Critical control points for foods prepared in households whose members had either alleged typhoid fever or diarrhea.

Hazard analysis of food preparation practices were conducted in four households and eleven others were visited to survey both food preparation practices and environmental conditions. Households selected had members who were suffering from either diarrhea of unknown etiology or alleged typhoid fever. Hazard analyses and sanitary surveys included gathering data on time-temperature exposures of foods, collecting samples of food and drinking water, sampling sewage or drains, and obtaining stool specimens from persons with diarrhea and from family controls. Food samples were tested for aerobic mesophilic colony counts and common foodborne pathogens; specimens were tested for Salmonella, Shigella, Campylobacter and Yersinia. Campylobacter was isolated from two persons purported to have diarrhea, but neither Salmonella, Shigella nor Yersinia were recovered from alleged cases or controls. Salmonella agona was recovered from a latrine. Most foods were cooked to internal temperatures to or near to boiling. Those not promptly eaten were held at ambient room or outside temperatures until a subsequent meal, until a family member returned home, or until lunch time when taken to the fields. During these intervals, microorganisms multiplied and mesophilic aerobic organisms increased often reaching 10(8)/g or greater before consumption. None of these foods were reheated before eating. Bacillus cereus was isolated from 4 of 10 samples; one sample of 'moro' (beans and rice) exceeded 10(6)/g, two other samples exceeded 10(3)/g. Staphylococcus aureus was isolated from 7 of 14 samples, one exceeded 10(5)/g. Fecal coliforms were isolated from 8 of 14 food samples, five exceeded 10(5)/g. Neither Salmonella nor Shigella were isolated from any food, the community water supplies or from vessels of water within houses. Fecal coliform counts of water were less than 3/ml, except one sample from a clay vessel (9/ml). Risks associated with cooked foods which were not promptly eaten appeared to be greater than that associated with water.

Adolescent↗
PubMed1987

Detection of Cysticercus cellulosae antigens in cerebrospinal fluid by dot enzyme-linked immunosorbent assay (Dot-ELISA) and standard ELISA.

The dot enzyme-linked immunoassay and standard enzyme-linked immunoassay were used to detect Cysticercus cellulosae antigens in cerebrospinal fluid of patients suffering with neurocysticercosis. Using the dot enzyme-linked immunoassay, 10 of 17 patients (59%) were positive at a reciprocal titer of 128 (range 128-1,024). In the standard assay, 13 of 17 (77%) were positive (range 128-512). Specificity was 100% in both assays using 48 cerebrospinal fluids from patients with various central nervous system infections. The quantification of antigens in cerebrospinal fluid using standard assay and photometric readings showed a range of 17 to 138 ng/ml. The results indicate that both assays are sensitive, specific, and economical for the diagnosis of neurocysticercosis.

Adult↗
PubMed1980

[Cerebral tuberculoma: an atypical case (author's transl)].

A case is reported of a 72 year-old female patient with multiple cerebral tuberculomas and a clinical course of 11 months that was characterized by personality changes, disorientation and progressive mental obtundation. The patient had a fatal outcome in spite of ventricular drainage and antituberculous therapy. Postmortem examination disclosed small tuberculomas in the cerebellum and brain stem, as well as residual tuberculous lesions in the upper lobe of the right lung. The clinical interest of this case lies in the old age of the patient, the rarity of the disease in western countries, and the location of tuberculomas in the brain stem with associated tuberculous meningitis. The higher incidence of cerebral tuberculomas in eastern and african countries is commented upon, and its anatomical, clinical, diagnostic and therapeutic features are reviewed. Finally, the two existing pathological forms and their respective clinical and therapeutic peculiarities are analyzed.

Aged↗
PubMedDate not supplied

Reproductive effects of hexachlorobenzene in female rats.

Hexachlorobenzene (HCB) is a polyhalogenated aromatic hydrocarbon widely distributed in the environment. In animal testing, HCB has been shown to be a reproductive toxin. Previous investigations of the effects of HCB on ovarian function have yielded equivocal results. Thus, the effects of chronic administration of HCB (1 g kg(-1) body wt.) on the ovary and pituitary hormone levels, hepatic and uterine oestradiol receptors, ovarian histopathological changes and oestrus cycle characteristics were investigated in spontaneously cycling rats. Our data demonstrate that HCB treatment, under the conditions of the present study, reduced circulating levels of oestradiol and prolactin without differences in serum concentrations of progesterone. Follicle-stimulating hormone serum levels were elevated. Hexachlorobenzene treatment resulted in irregularity of cycles, characterized mainly as prolonged periods of oestrus with a reduced number of ova recovered. In addition, HCB administration resulted in significantly decreased uterine nuclear oestrogen receptor levels. Histopathological examination revealed degenerative changes of the ovarian follicles and germinal epithelium and increased numbers of atresic follicles.

Animals↗
PubMedDate not supplied

NGF in experimental models of Parkinson disease.

We have now applied the enzyme immunoassay using anti-NGF monoclonal antibody (MAb) 27/21 and a blocking test validating the specificity of the immunoreactivity for NGF in serum samples to examine NGF levels in normal rat sera, hemiparkinsonian rat sera, normal monkey sera, and MPTP-treated monkey sera. The levels of NGF in treated animals showed reductions when compared with serum from normal animals. The NGF level alterations observed in lesioned animals and in human parkinsonian patients evidence a relationship between this neurotrophic factor and the neurodegenerative changes observed in Parkinson disease (PD).

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMedDate not supplied

Altered [3H]imipramine and 5-HT2 but not [3H]paroxetine binding sites in platelets from depressed patients.

BACKGROUND: Serotonergic system alterations were studied in 51 depressed patients classified according to DSM-III-R criteria for major depression with melancholia compared to 31 healthy controls. METHOD: [3H]Imipramine and [3H]paroxetine binding sites and the 5HT2 receptor were simultaneously determined in blood platelet membranes. RESULTS: A significantly lower maximum binding in [3H]imipramine binding was observed in depressed patients compared to controls (1134+/-74 vs. 1712+/-106 fmol/mg protein, P<0.0001) without changes in the equilibrium dissociation constant (1.10+0.05 vs. 1.25-/+0.09 nM). [3H]Paroxetine binding did not differ between the two groups (Bmax, 1441+/-55 vs. 1280+/-81 fmol/mg protein; Kd, 0.060+/-0.002 vs. 0.062+/-0.002 nM). The K(d) value of 5HT2 binding was lower in depressed patients than controls (0.95+/-0.04 vs. 1.15+/-0.09 nM, P<0.039) without changes in maximum binding (140+/-11 vs. 127+/-14 fmol/mg protein). CONCLUSIONS: Taken together, these results suggest that [3H]imipramine and 5HT2 receptors may be good biological markers for serotonergic dysfunction in depressive disorders.

Adult↗
PubMedDate not supplied

Improvement of leukocyte functions in young prematurely aging mice after a 5-week ingestion of a diet supplemented with biscuits enriched in antioxidants.

In our previous studies, diet supplementation with therapeutic thiolic antioxidants improved the function of peritoneal leukocytes from mice, especially in adult prematurely aging mice (PAM). In the present work, we have studied the effects of ingestion during 5 weeks of a diet supplemented with 20% (wt/wt) of biscuits enriched with antioxidants (vitamin C, vitamin E, beta-carotene, zinc, and selenium) on several immune functions of peritoneal leukocytes from young PAM. The results show that, in macrophages, chemotaxis and phagocytosis as well as the intracellular free radical levels, which are depressed in PAM in comparison with the control nonprematurely aging mice (NPAM), increase after supplementation, especially in the PAM. An increase also occurs in lymphocyte chemotaxis, proliferative response to the mitogen concanavalin A, and interleukin-2 release, as well as in natural killer cell activity. However, the release of tumor necrosis factor-alpha, which increases with aging, decreases after 5 weeks of supplementation. As a well preserved function of the immune system is an excellent marker of health and longevity, the improvement of leukocyte functions after ingestion of the present diet suggests that this antioxidant supplementation may be useful for the preservation of health and functional longevity in aging populations.

Aging↗
PubMedDate not supplied

Differential effects of damage within the hippocampal region on memory for a natural, nonspatial Odor-Odor Association.

Debate continues on whether the role of rodent hippocampus in memory is limited to the spatial domain. Recently, this controversy has been addressed with studies on the social transmission of food preference, an odor-odor association task with no spatial requirements. Multiple reports have concluded that damage to the hippocampal region impairs memory in this task, but there remain questions about the extent of damage essential to produce an impairment. Furthermore, a recent study () found no effect of hippocampal lesions on memory in this task. We tested animals with complete lesions of the hippocampus (H) lesions of the hippocampus plus subiculum (HS), and lesions of the adjacent, anatomically related cortices of the parahippocampal region (PHR). H lesions produced an impairment on spatial delayed alternation, but not on memory for the social transmission of food preference, whereas HS and PHR lesions produced severe and equivalent impairments on memory for the socially acquired food preference. We discuss possible explanations for the discrepancy with the results of and conclude that the hippocampus and subiculum together play a critical role in the formation of this form of nonspatial, relational memory.

Animals↗