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Biomedical subjects

P Alvarez

Publications and source records attributed to P Alvarez.

At least 19 recordsLinked to original sources
PubMed1995

Retrograde amnesia and memory consolidation: a neurobiological perspective.

The fact that information acquired before the onset of amnesia can be lost (retrograde amnesia) has fascinated psychologists, biologists, and clinicians for over 100 years. Studies of retrograde amnesia have led to the concept of memory consolidation, whereby medial temporal lobe structures direct the gradual establishment of memory representations in neocortex. Recent theoretical accounts have inspired a simple neural network model that produces behavior consistent with experimental data and makes these ideas about memory consolidation more concrete. Recent physiological and anatomical findings provide important information about how memory consolidation might actually occur.

Amnesia, Retrograde↗
PubMed1995

Zinc supplementation and growth of infants born small for gestational age.

To analyze the effect of zinc supplementation on postnatal growth of infants born small for gestational age, we selected 68 infants at birth and followed them monthly for 6 months. They were randomly assigned to a supplemented group (group S, n = 35) receiving 3 mg of Zn (acetate) per day, or to a placebo (group P, n = 33), in a double-blind study. Weight increments in group S were significantly higher than those in group P at 2 months (p < 0.003); z scores showed catch-up growth only in group S. Length increments were also greater in group S than in group P, ending at 6 months were 64.9 +/- 1.8 versus 63.4 +/- 3.5 cm (mean +/- SD; p < 0.01); changes in z scores for 6 months were -1.28 to -0.66 in group S and -1.43 to -1.47 in group P (p < 0.001). Weight-for-length improved similarly in both groups (z score, -2.2 to +0.2). The increase in weight-for-age was higher in group S girls (p < 0.034), ending at 6 months with -0.13 +/- 0.59, versus -0.52 +/- 0.62 in group S boys, -1.15 +/- 0.49 in group P girls, and -1.05 +/- 0.80 in group P boys (+/- SD). More infants in group P received cow milk-based formula before 4 months because of inadequate weight increments. An additive effect on weight increase was observed between Zn supplementation (p < 0.02), exclusive breast-feeding after 4 months of age (p < 0.001), and gender (p < 0.02). Plasma and hair Zn values showed a downward trend, less marked in group S than in group P. We conclude that Chilean infants born small for gestational age have better weight and linear growth during the first 6 months of life if they receive Zn supplementation.

Acetates↗
PubMed1995

Factors affecting variation of udder traits of dairy ewes.

Udder depth, width, and circumference; cistern height; teat position, angle, length, and width; and milk yield at 120 d were studied in 113 Churra sheep from three flocks. Means were 9.30, 12.18, and 46.55 cm, respectively, for udder depth, width, and circumference; 1.48 cm for cistern height; 3.64 (scored from 1 to 5) for teat position; 50.39 degrees for teat angle; 3.83 and 1.93 cm, respectively, for teat length and width; and 132.39 L for milk yield. Analysis of variance showed significant effects for lactation month, flock, parity number, and milk yield. The traits related to udder size (depth, width, and circumference) were significantly influenced by lactation month, flock, and milk yield and showed low repeatability (.17 to .18). The traits related to cistern morphology (cistern height, teat position, and angle) were significantly influenced by flock and parity number. These traits, together with teat length and width, had high repeatabilities (.45 to .77). Cistern height, teat position and angle, and size of teats are related to aptitude of the udder for mechanical milking. This association, as with cattle, would justify focusing genetic improvement on these traits.

Animals↗
PubMed1995

Damage limited to the hippocampal region produces long-lasting memory impairment in monkeys.

Research in humans and monkeys has demonstrated a system of anatomically related structures in the medial temporal lobe that is important for memory function. This system is comprised of the hippocampal region (i.e., the dentate gyrus, hippocampus proper and subicular complex) and the entorhinal, perirhinal, and parahippocampal cortices. While the hippocampal region has long been thought to be important in memory, there are few systematic studies in primates of the effects on memory of damage limited to the hippocampal region. We have used magnetic resonance imaging techniques, together with a stereotaxic approach, to produce bilateral lesions limited to the hippocampal region (the H lesion). Damage to the adjacent perirhinal, entorhinal, and parahippocampal cortex was minimal. Monkeys with the H lesion exhibited significant and long-lasting impairment on the delayed non-matching to sample task. At the same time, on this and other amnesia-sensitive tasks, monkeys with the H lesion performed better overall than monkeys with lesions of the hippocampal region that also included damage to the adjacent entorhinal and parahippocampal cortices (the H+ lesion). These findings show that, first, the hippocampal region itself is essential for normal memory function; and second, the adjacent entorhinal and parahippocampal cortices, either alone or in combination, are also an essential component of the medial temporal lobe memory system.

Animals↗
PubMed1994

A new system for the release of heterologous proteins from yeast based on mutant strains deficient in cell integrity.

A system has been developed for the release of heterologous proteins from Saccharomyces cerevisiae, based on the use of thermosensitive osmotic-remedial mutants, deficient in cell integrity, that lyse at the non-permissive temperature, thus releasing the bulk of intracellular proteins and leaving behind cell ghosts and debris. The strains developed combine the lyt2 mutation (which is allelic to gene SLT2/MPK1 coding for a MAP kinase homolog), with the disruption of genes PEP4 and PRB1 known to produce a protease-deficient background. Cells transformed with the appropriate bacterial gene, released about 70% of the heterologous protein chloramphenicol acetyl transferase (CAT) in bioreactor cultivation upon switching growth temperature to 37 degrees C, or by osmotic shock of the cells preincubated at 37 degrees C in the presence of 1 M sorbitol. It is suggested that our release system could be advantageous for obtaining large-scale protein preparations for downstream processing without any mechanical breakage of the cells, enzymatic treatment or chemical extraction.

Chloramphenicol O-Acetyltransferase↗
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↗
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

[Adoerse effects by the administration of salicylates].

Two cases that illustrate one of the side-effects of salicylates are presented. Both cases manifested as non thrombocytopenic purpura. Indications and contraindications for the use of salicylates are described. Emphasis is made not to use them as analgesics or antipyretics in cases with congential or acquired defects in the coagulation mechanism. Other side-effects of salicylates are described.

Blood Coagulation Disorders↗
PubMedDate not supplied

[Manifestations of paralytic ileus in infants hospitalized for acute diarrheal syndrome].

In order to assess and characterize adynamic ileus (AI) complicating acute diarrhoea (AD) in infants, 802 consecutive admissions were studied. Diagnosis was suspected in 23 patients with abdominal distension and confirmed by radiological study in 16 whose age range was 14 ds to 6 mo. Of these late patients, 9/16 were malnourished. Age was less than, but nutritional status similar to that of all patients admitted with ADD. Vomiting (14/16), silent or almost silent abdomen (10/16), protracted course of diarrhoea (9/16) and increased gastric content (6/16) were the most common clinical findings in addition to abdominal distension and X Ray films suggestive of AI (inclusion criteria). Lack of constipation was a relevant finding. Treatment included temporal discontinuance of oral feedings, intravenous fluids administration, nasogastric and rectal tube and antibiotics. Lethality rate was 4/16. Duration of AI was an average of 2 days in survivors and 4 days in the remainder infants. It is concluded that AI is an infrequent complication of AD (0.19% of cases), which should be suspected in infants less that 6 mo old with diarrhoea and abdominal distension.

Acute Disease↗