Biomedical subjects

G Castillo

Publications and source records attributed to G Castillo.

At least 19 recordsLinked to original sources

PubMed2003

Endometrial blood flow mapping using transvaginal power Doppler sonography in women with postmenopausal bleeding and thickened endometrium.

OBJECTIVE: To evaluate the role of transvaginal power Doppler sonography to discriminate between benign and malignant endometrial conditions in women presenting with postmenopausal bleeding and thickened endometrium at baseline sonography. METHODS: Ninety-one postmenopausal women (median age, 58 years; range, 47-83 years) presenting with uterine bleeding and a thickened endometrium (> or = 5-mm double-layer endometrial thickness) on transvaginal sonography were included in this prospective study. Endometrial blood flow distribution was assessed in all patients by power Doppler immediately after B-mode transvaginal sonography. Three different vascular patterns were defined: Pattern A: multiple-vessel pattern, Pattern B: single-vessel pattern and Pattern C: scattered-vessel pattern. Histological diagnoses were obtained in all cases. No patient taking tamoxifen citrate or receiving hormone replacement therapy was included. RESULTS: Histological diagnoses were as follows: endometrial cancer: 33 (36%), endometrial polyp: 37 (41%), endometrial hyperplasia: 14 (15%), endometrial cystic atrophy: 7 (8%). Blood flow was found in 97%, 92%, 79% and 85% of cases of carcinoma, polyp, hyperplasia and endometrial cystic atrophy, respectively. A total of 81.3% of vascularized endometrial cancers showed Pattern A, 97.1% of vascularized polyps exhibited Pattern B and 72.7% of vascularized hyperplasias showed Pattern C. Sensitivity and specificity for endometrial cancer were 78.8% and 100%. For endometrial polyp these respective values were 89.2% and 87% and for hyperplasia they were 57.1% and 88.3%. CONCLUSIONS: Transvaginal power Doppler blood flow mapping is useful to differentiate benign from malignant endometrial pathology in women presenting with postmenopausal bleeding and thickened endometrium at baseline sonography.

Aged↗

PubMed2002

Overview of results from the WaterTox intercalibration and environmental testing phase II program: Part 1, statistical analysis of blind sample testing.

There is an urgent need to evaluate the presence of toxicants in waters used for human consumption and to develop strategies to reduce and prevent their contamination. The International Development Research Centre undertook an intercalibration project to develop and validate a battery of bioassays for toxicity testing of water samples. The project was carried out in two phases by research institutions from eight countries that formed the WaterTox network. Results for the first phase were reported in the special September 2000 issue of Environmental Toxicology. Phase II involved toxicity screening tests of environmental and blind samples (chemical solutions of unknown composition to participating laboratories) using the following battery: Daphnia magna, Hydra attenuata, seed root inhibition with Lactuca sativa, and Selenastrum capricornutum. This battery was also used to assess potential toxicity in concentrated (10x) water samples. Results are presented for a set of six blind samples sent to the participating laboratories over a 1-year period. Analyses were performed for each bioassay to evaluate variations among laboratories of responses to negative controls, violations of test quality control criteria, false positive responses induced by sample concentration, and variability within and between labs of responses to toxic samples. Analyses of the data from all bioassays and labs provided comparisons of false positive rates (based on blind negative samples), test sensitivities to a metal or organic toxicant, and interlaboratory test variability. Results indicate that the battery was reliable in detecting toxicity when present. However, some false positives were identified with a concentrated soft-water sample and with the Lactuca and Hydra (sublethal end-point) tests. Probabilities of detecting false positives for individual and combined toxic responses of the four bioassays are presented. Overall, interlaboratory comparisons indicate a good reliability of the battery.

Animals↗

PubMed2002

Overview of results from the WaterTox intercalibration and environmental testing phase II program: part 2, ecotoxicological evaluation of drinking water supplies.

Because of rapid population growth, industrial development, and intensified agricultural production increasing amounts of chemicals are being released into the environment, polluting receiving water bodies around the world. Given the potential health risk associated with the presence of toxicants in water sources used for drinking yet the scarcity of available data, there is a need to evaluate these waters and develop strategies to reduce and prevent their contamination. The present study examined the applicability of a battery of simple, inexpensive bioassays in environmental management and the relevance of the test results in establishing the toxicological quality of water sources and drinking water within the framework of the eight-country WaterTox Network, sponsored by the International Development Research Centre, Ottawa, Canada. Seventy-six samples were collected from surface and groundwater sources and seven samples from drinking water treatment plants. Each sample was tested with a core battery of bioassays (Daphnia magna, Hydra attenuata, and Lactuca sativa root inhibition tests) and a limited set of physical and chemical parameters. In addition, three labs included the Selenastrum capricornutum test. When no toxic effects were found with the battery, samples were concentrated 10x using a solid-phase extraction (SPE) procedure. Nonconcentrated natural water samples produced a toxic response in 24% of cases with all three core bioassays. When all bioassays are considered, the percentage of raw samples showing toxicity with at least one bioassay increased to 60%. Of seven treated drinkingwater samples, four showed toxicity with at least one bioassay, raising the possibility that treatment processes in these instances were unable to remove toxic contaminants. The Daphnia magna and Hydra attenuata tests indicated a high level of sensitivity overall. Although only three of the eight countries used S. capricornutum, it proved to be an efficient and reliable bioassay for toxicity assessment.

Animals↗

PubMed2002

Operational factors and nutrient effects on activated sludge treatment of Pinus radiata kraft mill wastewater.

The biodegradability of Pinus radiata bleached kraft mill wastewater by an activated sludge treatment during a period of 280 days was evaluated. The effect of varying hydraulic retention time (HRT) in the range of 48 to 4.5 h and nitrogen (N) and phosphorus (P) addition on removal of biological oxygen demand (BOD5), chemical oxygen demand (COD), suspended solids (TSS and VSS), total phenolic compounds, tannin and lignin and reduction of toxicity was investigated. Removal of BOD5 was higher than 90% when HRT varied from 16 to 6 h, but decreased when HRT was less than 6 h. Similar performance was observed for COD removal, which was about 60% when HRT was varied from 16 to 6 h. Removal of total phenolic compounds and tannin and lignin was seriously affected by HRT. N and P addition to maintaining a ratio of 100:5:0.3 provided optimal BOD5, COD and suspended solids removal when HRT varied from 16 to 7 h, and no toxicity (using Daphnia) was detected in the treated effluent. When HRT was less than 6 h, the system showed destabilisation and pH, COD, BOD5 and suspended solids removal decreased.

Bioreactors↗

PubMed2002

Influence of hydrolysis, purification, and calibration method on furosine determination using Ion-pair reversed-phase high-performance liquid chromatography.

The influence of HCI concentration (6M, 8M, and 10M) and the ratio of sample protein to acid (1 or 5 mg of protein per mL of acid) on furosine formation during sample hydrolysis is studied. The conditions that maximize furosine formation are 10M HCI in the ratio of 1 mg of protein to 1 mL of acid. Purification of the hydrolysate by solid-phase extraction is also considered by examining the effect of hydrolysate volume and volume of 3M HCI used to elute the furosine. Furosine quantitation is carried out using the standard additions and external standard methods. The results indicate that there is no interference by the sample matrix and that external calibration is adequate.

Calibration↗

PubMed2001

Thrombocytopenia in HIV-infected drug users in the HAART era.

The present case-control study compared 26 HIV+ drug users having persistent thrombocytopenia (TCP<150 000/mm(3)) with 54 available age, gender and HIV CDC classification matched controls with normal platelet counts. Participants were followed longitudinally over a 2-year period (1998-2000), and hematological alterations evaluated in relationship to antiretroviral treatment, drug use and nutritional (selenium) status. Demographic information and medical history, including antiretroviral treatment were obtained. Blood was drawn for complete cell blood count, T lymphocytes and viral load. Sixty-nine percent of the individuals with persistent TCP and 49% of the controls were receiving antiretrovirals. At baseline, no significant differences in CD4 existed between the two groups. Over time, CD4 cell count declined in the cases (P = 0.05) and a significantly higher proportion of the cases (38%) developed AIDS (CD4<200 cell/mm(3)), as compared to the controls (18%, P = 0.004). A high risk for development of thrombocytopenia was observed with specific drug use (heroin 2.96 times, P = 0.0007), selenium levels below 145 microg/l (6 times, P = 0.008), and abnormal liver enzyme (SGOT) levels (2 times, P = 0.002). Together, these results indicate a number of factors that may be sensitive predictors of thrombocytopenia, which, despite antiretroviral treatment, appears to be related to more rapid disease progression in drug users.

Adult↗

PubMed2001

Laparoscopic cholecystectomy: fundus-down approach.

BACKGROUND AND PURPOSE: Laparoscopic cholecystectomy (LC) is the primary treatment of gallstone disease. Although refinements have made it safer, bile duct injury remains more common than with the open approach. The major difference in these techniques is that open cholecystectomy approaches the gallbladder from the fundus downward, whereas conventional laparoscopic cholecystectomy proceeds in the reverse direction. A handful of fundus-down techniques appear in the literature. The use of special instruments or port sites is common. We present a technique that is safe and utilizes instruments familiar to the surgeon performing conventional LC. PATIENTS AND METHODS: Fifty consecutive LCs were included in the study. The variables monitored were age, comorbidities, postoperative diagnosis, pathologic diagnosis, length of operation, hospital length of stay, and complications. RESULTS: The average operating time for chronic cholecystitis was 1 hour, and the average time for acute cholecystitis was less than 2 hours. Except for one early case of bleeding, in which the procedure was completed using the familiar conventional method, no complications and no unusual technical difficulties were encountered. There were no differences between conventional and fundus-down LC with regard to time and complications. CONCLUSIONS: This technique is safe and has several benefits: (1) standard trocar sites that offer the surgeon flexibility in the approach; (2) the ability to resect as much cystic duct as desired; and (3) utilization of standard instruments familiar to the surgeon, thus avoiding costly special instruments. The approach may offer the benefit of reducing the rate of common bile duct injury to that of open cholecystectomy.

Bile Ducts↗

PubMed2001

Liquid chromatographic determination of the total available free and intrachain lysine in various foods.

A method for the quantitative determination of the total available lysine in various foods is developed. The method is based on the reaction of the amino groups on the lysine molecule with fluorodinitrobenzene and is capable of furnishing simultaneous determination of the available intrachain lysine (known as N-epsilon-[2,4-dinitrophenyl]-L-lysine) or the available free and/or N-terminal lysine (known as N,N'-di-[2,4-dinitrophenyl]-L-lysine). Optimum conditions for separation and quantitation are studied. The results show the proposed method to be both accurate and precise and suitable for food samples containing hydrolyzed proteins.

Chromatography, High Pressure Liquid↗

PubMed2001

Water quality improvement of treated wastewater by intermittent soil percolation.

Our research aimed to evaluate intermittent soil infiltration of treated sewage for reuse in the north of Chile. Aerated lagoon effluent was infiltrated in columns packed with native soils (sandy-lime, lime-gravel and limey-sand). Columns were operated for more than a year under different cycles of filling and drying, depths and load pressures depending on soil characteristics. The efficiency of the system was determined through influent-effluent microbiological indicators level (faecal coliforms, E. coli, Salmonella spp, MS2 phage, and protozoan cysts), physicochemical characterisation (TOC, COD, BOD, nitrogen), and hydraulic flow measurement. Results showed: (a) high reduction of enteric bacteria (5-7 log10), some inactivation of phage (2-4 log10) and complete removal of intestinal cyst; (b) stable removal of organic matter (80-90% reduction of TOC, COD, BOD); and (c) partial ammonia reduction through adsorption and nitrification with denitrification mainly occurring in sandy soil. Preliminary data from pilot plant working in the field showed better results that those obtained in the laboratory especially removal of microbiological indicators. Microbiological quality of effluent met Class A regulations for agricultural reuse (WHO, 1989) and the system looks like an attractive alternative to cope with water shortage in the region.

Ammonia↗

PubMed2000

Development and application of a synthetic peptide-based osteocalcin assay for the measurement of bone formation in mouse serum.

The mouse is frequently used as an animal model to study skeletal mechanisms relevant to humans. Biochemical markers of bone formation and resorption provide one of the key parameters for assessing skeletal metabolism. One biochemical marker that has proven to be useful in the studies of mouse skeletal metabolism is osteocalcin. Assay for osteocalcin is available in the mouse. The present study describes development of an osteocalcin radioimmunoassay (RIA) using a synthetic peptide. Intact osteocalcin purified from mouse bone extracts shows parallel displacement with synthetic peptide. Sensitivity of the RIA was 19 ng/ml. The average (n = 9) intra- and interassay coefficient of variation for two controls was less than 10%; the averaged recoveries were 106%. The osteocalcin concentration measured by peptide RIA shows a high correlation (r = 0.88, n = 117, P < 0.0001) with an intact osteocalcin assay. In addition, when the intact assay and peptide assays were applied to evaluate skeletal perturbation, similar results were obtained. Accordingly, osteocalcin levels measured by both intact and peptide-based RIA in 8-week C57BL/6J (n = 8) mice treated with PTH 1-34 were twofold higher compared with the vehicle-treated control group. Further studies of the application of the peptide-based RIA for osteocalcin revealed that osteocalcin levels in 4-week postovariectomized (OVX) C57BL/6N mice (n = 10) were 80% higher than the sham-operated (n = 10) mice receiving vehicle. OVX mice receiving weekly injections of estradiol (400 microg/kg body weight) were 38% lower compared with the OVX group treated with vehicle. In conclusion, the peptide-based RIA has analytical and a discriminative power similar to that of the intact osteocalcin assay but has the advantage that the resources for this assay are much easier to accrue.

Animals↗

PubMed2000

Development and application of a serum C-telopeptide and osteocalcin assay to measure bone turnover in an ovariectomized rat model.

Biochemical markers applicable to the ovariectomized rat model can provide important tools for studying the bone remodeling process in this animal model of postmenopausal osteoporosis. We describe the development and application of two biochemical markers, a C-telopeptide (of type-I collagen) enzyme-linked immunosorbent assay (ELISA) for measuring bone resorption and an osteocalcin radioimmunoassay (RIA) for measuring bone formation in rat serum. The C-telopeptide ELISA is based on an affinity purified polyclonal antibody generated against human sequence DFSFLPQPPQEKAHDGGR. The antibody epitope involves amino acid sequence, which is similar in rat and human carboxyl terminal peptide of type-I (alpha 1) collagen. Sensitivity of the ELISA was 0.3 ng/ml. The averaged intra- and interassay variation was CV <7%. Averaged dilution and spiked recoveries were 91% and 105%, respectively. The second marker developed is a synthetic peptide-based osteocalcin RIA, which does not require isolation and purification of intact osteocalcin from rat bone. Osteocalcin antiserum used in the RIA was generated in rabbits against a synthetic peptide comprising amino acids 33-49 of the rat osteocalcin sequence. The sensitivity of the RIA was 0.15 ng/ml of peptide. The averaged intra (n = 10) and interassay variations for two controls were CV <9% and 12%, respectively. The averaged dilution and spiked recoveries were 99.6%. In vivo validation of the C-telopeptide ELISA and osteocalcin RIA was performed in an ovariectomized (OVX) rat model. In 12-week-old OVX Sprague Dawley rats, the C-telopeptide and osteocalcin concentrations were approximately 65% and 40%, respectively, higher than the sham group. Estradiol repletion significantly lowered the C-telopeptide and osteocalcin concentration to the levels of the sham group. In addition, changes in serum C-telopeptide concentration correlated negatively with trabecular BMD measured by pQCT (r = -0.51, P < 0.001). In conclusion, the C-telopeptide ELISA and osteocalcin RIA exhibited required sensitivity, accuracy, and adequate discriminatory power to be used for measuring bone resorption and bone formation in the ovariectomized rat model.

Amino Acid Sequence↗

PubMed2000

Development and evaluation of C-telopeptide enzyme-linked immunoassay for measurement of bone resorption in mouse serum.

The mouse is increasingly being used as an animal model for the study of skeletal phenotypes in humans, mainly because of the ease of genetic manipulation. Biochemical markers of bone metabolism provide a valuable parameter for the assessment of skeletal metabolism. In the mouse model, assays for bone formation have been available for a long time; however, little is known about bone resorption markers. The present study describes the development of a serum C-telopeptide enzyme-linked immunoassay (ELISA), which measures degradation products of type I collagen that are generated by osteoclastic bone resorption. The C-telopeptide ELISA uses affinity-purified antibodies generated against human sequence DFSFLPQPPQEKAHDGGR. The epitope involves an amino acid sequence, which is identical in the mouse and human C-terminal peptide of type I collagen (alpha1 chain). Sensitivity of the ELISA used was <0.1 ng/mL. The average intra- (n = 10) and interassay (n = 8) coefficient of variation for two controls was <12%. The average dilution and spike recovery rates were 98% and 97%, respectively. Application of the ELISA to measure C-telopeptide in 3-4-week postovariectomized (ovx) C57BL/6J (B6) mice (n = 9 or 10) showed a 45% higher C-telopeptide concentration than the sham-operated mice. Treatment of ovx mice with estradiol (400 microg/kg body weight) or alendronate (1.0 mg/kg body weight) resulted in a 20%-50% decrease in C-telopeptide levels compared to the vehicle-treated ovx group. In addition, B6 mice fed a calcium-deficient diet (0.01% calcium) showed a 50% higher C-telopeptide concentration compared to the B6 mice receiving a normal diet (0.6% calcium). In conclusion, the C-telopeptide ELISA exhibited acceptable analytical performance and sufficient discriminatory power to show expected directional changes in the rate of bone resorption following ovariectomy, ovx plus estradiol or alendronate treatment, and administration of a calcium-deficient diet. Therefore, the ELISA developed in this study could be used for measuring bone resorption in the mouse model.

Alendronate↗

PubMed1999

An adipogenic cofactor bound by the differentiation domain of PPARgamma.

Ligand activation of the nuclear receptor PPARgamma induces adipogenesis and increases insulin sensitivity, while activation of other PPAR isoforms (-alpha and -delta) induces little or no fat cell differentiation. Expression and activation of chimeras formed between PPARgamma and PPARdelta in fibroblasts has allowed us to localize a major domain of PPARgamma responsible for adipogenesis to the N-terminal 138 amino acids, a region with AF-1 transcriptional activity. Using this region of PPARgamma as bait, we have used a yeast two-hybrid screen to clone a novel protein, termed PGC-2, containing a partial SCAN domain. PGC-2 binds to and increases the transcriptional activity of PPARgamma but does not interact with other PPARs or most other nuclear receptors. Ectopic expression of PGC-2 in preadipocytes containing endogenous PPARgamma causes a dramatic increase in fat cell differentiation at both the morphological and molecular levels. These results suggest that interactions between PGC-2, a receptor isoform-selective cofactor and PPARgamma contribute to the adipogenic action of this receptor.

Adipocytes↗

PubMed1999

Madangolide and laingolide A, two novel macrolides from lyngbya bouillonii (Cyanobacteria)

Two new macrolide derivatives, madangolide (2) and laingolide A (3), have been isolated from the cyanobacterium Lyngbya bouillonii, collected in Papua New Guinea. Their structures (without stereochemistry) have been established by detailed high-field 1D and 2D NMR studies and, in the case of 3, by comparison with the spectroscopic data of laingolide (1), previously isolated from the same organism.

Journal Article↗

PubMed1999

Overexpression, purification and characterization of Mycobacterium bovis BCG alcohol dehydrogenase.

A previous study of the effect of zinc deprivation on Mycobacterium bovis BCG pointed out the potential importance of an alcohol dehydrogenase for maintaining the hydrophobic character of the cell envelope. In this report, the effect of the overexpression of the M. bovis BCG alcohol dehydrogenase (ADH) in Mycobacterium smegmatis and M. bovis BCG is described. The purification of the enzyme was performed to apparent homogeneity from overexpressing M. bovis BCG cells and its kinetic parameters were determined. The enzyme showed a strong preference for both aromatic and aliphatic aldehydes while the corresponding alcohols were processed 100-1000-fold less efficiently. The best kcat/Km values were found with benzaldehyde > 3-methoxybenzaldehyde > octanal > coniferaldehyde. A phylogenetic analysis clearly revealed that the M. bovis BCG ADH together with the ADHs from Bacillus subtilis and Helicobacter pylori formed a sister group of the class C medium-chain alcohol dehydrogenases, the plant cinnamyl alcohol dehydrogenases (CADs). Comparison of the kinetic properties of our ADH with some related class C enzymes indicated that the mycobacterial enzyme substrate profile resembled that of the CADs involved in plant defence rather than those implicated in lignification. A possible role for the M. bovis BCG ADH in the biosynthesis of the lipids composing the mycobacterial cell envelope is proposed.

Alcohol Dehydrogenase↗

PubMed1999

Transient transcriptional activation of the Vibrio cholerae El Tor virulence regulator toxT in response to culture conditions.

Vibrio cholerae El Tor require special in vitro culture conditions, consisting of an initial static growth period followed by shift to shaking (AKI conditions), for expression of cholera toxin (CT) and toxin coregulated pili (TCP). ToxT, a regulator whose initial transcription depends on the ToxR regulator, positively modulates expression of CT and TCP. To help understand control of CT and TCP in El Tor vibrios, we monitored ctxAB and ToxR-dependent toxT transcription by time course primer extension assays. AKI conditions stimulated CT synthesis with an absence of ctxAB transcription during static growth followed by induction upon shaking. ToxR-dependent toxT transcription was induced at the end of the static growth period but was transient, stopping shortly after shaking was initiated but, interestingly, also if the static phase was prolonged. Immunoblot assays showed that ToxR protein levels were not coincidentally transient, implying a protein on/off switch mechanism for ToxR. Despite the transient activation by ToxR, transcription of ctxAB was maintained during shaking. This finding suggested continued toxT expression, possibly through relay transcription from another promoter. The 12.6-kb distant upstream tcpA promoter responsible for expression of the TCP operon has been proposed to provide an alternate toxT message by readthrough transcription. Activation of the tcpA promoter is supported by increased expression of TcpA protein during the shaking phase of the culture. Readthrough transcription of toxT from tcpA would be compatible with reverse transcription-PCR evidence for a toxT mRNA at times when ToxR-dependent transcription was no longer detectable by primer extension.

Bacterial Outer Membrane Proteins↗

PubMed1998

Resistance to antibiotic and heavy metals of motile aeromonads from Chilean freshwater.

In this work the resistance of 172 motile Aeromonas isolates recovered from raw drinking water supplies (56), irrigation waters (60) and runoff waters receiving sewage (56), to some antibiotics and heavy metals was investigated by agar diffusion and agar dilution methods. A high proportion of isolates from all water sources showed resistance to carbenicillin, erythromycin, streptomycin, cephradine and cadmium, and susceptibility to chloramphenicol, kanamycin, gentamicin, tetracycline, nalidixic acid, trimethoprim-sulphametoxazole and chromium. No amikacin-resistant Aeromonas were recovered. No relationship was found between antimicrobial resistance and Aeromonas species, with the exception of cephradine, that exhibited a significantly higher activity against the A. sobria isolates than the other Aeromonas species (P < 0.05). Moderately polluted waters showed lower antibiotic multiresistance and metal susceptibility than unpolluted and highly polluted ones. Although significant differences (P < 0.05), between resistance frequencies to erythromycin, carbenicillin, streptomycin and cephradine were found among isolates from different sources, the antimicrobial resistance patterns of aeromonads could not be related to the level of faecal pollution. These results indicate that aeromonads resistant to antibiotics and heavy metals are easily recovered from water sources in Chile, posing a potential public health risk.

Aeromonas↗

PubMed1998

Cognitive brain activity in Alzheimer's disease: electrophysiological response during picture semantic categorization.

Semantic memory deterioration is a major component of the cognitive decline seen in patients with dementia of the Alzheimer's type (DAT); however, the exact nature of this deficit remains unclear. Some research data support a procedural deficit where there is an inability to access or retrieve the contents of semantic memory, while other data point to a degraded semantic store where the actual content of semantic memory is degraded. Additional information about semantic processing in DAT can be obtained through the use of an event-related potential (ERP) component known as N400. In the present study, ERPs were recorded from 10 young control participants, 10 elderly control participants, and 10 DAT patients in a picture-semantic matching task. Stimuli were presented sequentially as prime-target pairs, with one-half of the targets matching the primes via semantic relationships (e.g., piano-violin) and the other half mismatching the prime (e.g., helmet-violin). The task was to discriminate between semantically related and unrelated pairs of pictures. In the young and elderly control groups, ERPs generated a larger N400 for unrelated than related target pictures, with a maximum amplitude around 380 ms in the young group and around 480 ms in the elderly group. The amplitude of the N400 was significantly reduced in the DAT patients. However, a separate analysis of congruent and incongruent ERPs trials revealed significant differences only with the incongruent trials. The amplitude of incongruent recordings was larger for the elderly control group than for the DAT patients, while the amplitude for congruent recordings was similar in both groups. These findings are consistent with the neuropathological evidence that Alzheimer's disease is a neocortical disconnection syndrome in which there is a loss of structural and functional integrity of long corticocortical tracts. The semantic activation created by the context is not used efficiently in processing stimuli, which affects access to specific concepts and gradually leads to a breakdown in the structure and organization of semantic memory.

Adult↗