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Biomedical subjects

J Guevara

Publications and source records attributed to J Guevara.

At least 19 recordsLinked to original sources
PubMed2006

Morphometric analysis of brain lesions in rat fetuses prenatally exposed to low-level lead acetate: correlation with lipid peroxidation.

The effect of prenatal lead acetate exposure was studied microscopically together with the concentration of lead and lipid fluorescent products (LFP) in the brain of rat fetuses. Wistar rats were intoxicated with a lead solution containing either 160 or 320 ppm of lead acetate solution during 21 days through drinking water. The control group (ten rats) received deionized water for the same period. The rats were killed on gestation day 21 and fetuses were obtained; the placenta, umbilical cord and parietal cortex (Cx), striatum (St), thalamus (Th) and cerebellum (Ce) were collected for measuring tissue lead concentration, LFP as an index of lipid peroxidation and histopathologic examination. Lead contents were increased in placenta, umbilical cord, St, Th and Cx in both lead-exposed groups. Lead exposure increased (LFP) in placenta and umbilical cord, St, Th and Ce as compared to the control group. Histopathological examination showed severe vascular congestion in placenta, the Cx, St, Th and Ce with hyperchromatic and shrunken cells. Interstitial oedema was found in all regions studied of both lead exposed groups. The morphometric evaluation of the studied brain regions showed an absolute decrease in total cell number and increased number of damaged cells and interstitial oedema. Our results show that morphological changes in rat brain are correlated with increased lipid peroxidation, and the lead levels of the umbilical cord, however it is not clear whether oxidative stress is the cause or the consequence of these neurotoxic effects of lead.

Animals↗
PubMed2005

Cellular distribution of insulin-like growth factor-II/mannose-6-phosphate receptor in normal human brain and its alteration in Alzheimer's disease pathology.

The insulin-like growth factor-II/mannose-6-phosphate (IGF-II/M6P) receptor is a multifunctional membrane glycoprotein, which binds different classes of ligands including IGF-II and M6P-bearing lysosomal enzymes. Besides participating in the process of endocytosis this receptor functions in the trafficking of lysosomal enzymes from the trans-Glogi network (TGN) or the cell surface to lysosomes. In Alzheimer's disease (AD) brain, marked overexpression of certain lysosomal enzymes in vulnerable neuronal populations and their association to beta-amyloid (Abeta) containing neuritic plaques has been correlated to altered metabolic functions. In the present study, we measured the levels of IGF-II/M6P receptor and characterized its distribution profile in selected regions of AD and age-matched normal postmortem brains. Western blot analysis revealed no significant alteration in the levels of IGF-II/M6P receptor either in the hippocampus, frontal cortex or cerebellum between AD and age-matched control brains. However, a significant gene dose effect of apolipoprotein E (APOE) epsilon4 allele on IGF-II/M6P receptor levels was evident in the hippocampus of the AD brain. At the cellular level, immunoreactive IGF-II/M6P receptors were localized in the neurons of the frontal cortex, hippocampus and cerebellum of control brains. In AD brains, the labeling of the neurons was less intense in the frontal cortex and hippocampus than in the age-matched control brains. Additionally, IGF-II/M6P receptor immunoreactivity was observed in association with a subpopulation of Abeta-containing neuritic plaques as well as tau-positive neurofibrillary tangles both in the frontal cortex and the hippocampus. Reactive glial cells localized adjacent to the plaques also occasionally exhibited IGF-II/M6P receptor immunoreactivity. These results, when analyzed in context of the established role of the IGF-II/M6P receptor in the regulation of the intracellular trafficking of lysosomal enzymes, suggest that alterations in IGF-II/M6P receptor levels/distribution are possibly associated with altered functioning of the lysosomal enzymes and/or loss of neurons observed in AD brains, especially in patients carrying APOE epsilon4 alleles.

Aged↗
PubMed2005

HUVECs from newborns with a strong family history of myocardial infarction overexpress adhesion molecules and react abnormally to stimulating agents.

Atherosclerosis is a complex disease involved in major fatal events such as myocardial infarction and stroke. It is the result of interactions between metabolic, dietetic and environmental risk factors acting on a genetic background that could result in endothelial susceptibility. Our aim was to determine the patterns of expression of adhesion molecules and whether phosphatidylserine is translocated to the cell surface of human umbilical vein endothelial cells (HUVECs) isolated from healthy newborns born to parents with a strong family history of myocardial infarction under TNF-alpha or oxLDL stimulated conditions. Compared to control HUVECs, experimental cords showed: (a) a four-fold increase in VCAM-1 expression under basal conditions, which showed no change after stimulation with the pro-atherogenic factors; (b) a two-fold increase in basal P-selectin expression that reached a 10-fold increase with any of the pro-atherogenic factors; (c) a basal ICAM-1 expression similar to P-selectin that was not modified by the pro-atherogenic molecules; (d) a similar PECAM-1 expression. Unexpectedly, phospathidylserine expression in experimental cord HUVECs was significantly increased (211 817 versus 3354 TFU) but was not associated to apoptotic death as the percentage of dead cells induced by TNF-alpha treatment was very low (0.55 versus 9.87% in control HUVECs). The latter result was corroborated by TUNEL staining. T cell adherence to HUVECs was highly up-regulated in the genetically predisposed samples. The analysis of nonpooled HUVECs, from newborns to family predisposed myocardial-infarction individuals, might represent a useful strategy to identify phenotypical and functional alterations, and hopefully, to take early preventive actions.

Case-Control Studies↗
PubMed2004

Coexistence of reactive plasticity and neurodegeneration in Alzheimer diseased brains.

Alzheimer's disease (AD) is a pathological process characterized by neuron degeneration and, as recently suggested, brain plasticity. In this work, we compared the reactive plasticity in AD brains associated to O-glycosydically linked glycans, recognized by lectins from Amaranthus leucocarpus (ALL) and Macrobrachium rosenbergii (MRL), and the tau neuritic degeneration. The neuritic degenerative process was evaluated by the quantification of aggregated neuritic structures. Lesions were determined using antibodies against hyperphosphorylated-tau (AD2), amyloid-beta, and synaptophysin. In these conditions, we classified and quantified three pathological structures associated to the neuritic degenerative process: 1) Amyloid-beta deposits (AbetaDs), 2) Classic neuritic plaques (NPs), and 3) Dystrophic neurites clusters (DNCs) lacking amyloid-beta deposits. Reactive plasticity structures were constituted by meganeuritic clusters (MCs) and peri-neuronal sprouting in neurons of the CA4 region of the hippocampus, immunoreactive to synaptophysin (exclusively in AD brains) and GAP-43. Besides, MCs were associated to sialylated O-glycosydically linked glycans as determined by positive labeling with ALL and MRL. Considering that these lectins are specific for the synaptic sprouting process in AD, our results suggest the co-occurrence of of several areas of reactive plasticity and neuron degeneration in AD.

Aged↗
PubMed2002

Population-based surveillance and a case-control study of risk factors for endemic lymphocutaneous sporotrichosis in Peru.

Population-based surveillance and a case-control study were conducted in Abancay, Peru, to estimate the burden of disease and to determine risk factors for sporadic lymphocutaneous sporotrichosis (LS). Laboratory records from local hospitals were reviewed for the years of 1997 and 1998, and prospective surveillance was conducted for the period of September 1998 through September 1999. A case-control study was conducted with 2 matched control subjects per case patient. The mean annual incidence was 98 cases per 100,000 persons. Children had an incidence 3 times higher than that for adults and were more likely to have LS lesions on the face and neck. Identified risk factors included owning a cat, playing in crop fields, having a dirt floor in the house, working mainly outdoors, and having a ceiling made of raw wood or conditions associated with a lower socioeconomic status. Decreased environmental exposure, such wearing protective clothing during construction activities for adults or limiting contact with cats and soil for children, and improvements in living spaces may decrease the incidence of LS.

Adolescent↗
PubMed2001

Toluidine blue-O staining of prion protein deposits.

Prion diseases or transmissible spongiform encephalopathies are a group of fatal neurodegenerative diseases caused by an abnormal form of prion protein (PrP(sc)). In this study, we developed a sensitive histochemical detection of PrP(sc) deposits in a Gertsmann-Sträussler-Scheinker disease (GSS) patient using toluidine blue-O staining, a specific reagent to stain mucins and mucopolysaccharides. Detection of prion deposits correlated with immunohistochemistry using anti-prion antibodies. Control assays were performed using amyloid-beta (Abeta) plaques from Alzheimer's disease (AD) brains. Our results demonstrated that toluidine blue-O staining allowed to recognize 69.1+/-2.6% of the total plaques recognized by the anti-prion antibody. Furthermore, in the 15 studied brain regions from the GSS patient, toluidine blue-O revealed the same recognition pattern as anti-prion labeling. Toluidine blue-O stained specifically the prion deposits but not the Abeta plaques in AD brains. The specificity of the technique was confirmed in a Creutzfeldt-Jakob disease brain. This method opens several possibilities for postmortem diagnoses. Our results also suggest the relevance of specific post-translational modifications of PrP(sc), identified by toluidine blue-O, that might participate in the transformation of PrP(c) to PrP(sc).

Aged↗
PubMed2001

Regional and temporal progression of reactive astrocytosis in the brain of the myelin mutant taiep rat.

Reactive astrocytosis in taiep rats was shown by glial fibrillary acidic protein (GFAP) immunoreactivity measured by means of enzyme-linked immunosorbent assay and indirect immunofluorescence. Increased GFAP immunoreactivity was first observed in the brainstem of 15-day-old taiep rats and was widespread throughout all brain regions at 6 months of age. Characteristically, astrocytes were hypertrophic and displayed strong GFAP fluorescence. The pattern of these reactive cells may correlate with the process of dysmyelination in the taiep rat.

Animals↗
PubMed2001

Sialylation is modulated through maturation in hemocytes from Macrobrachium rosenbergii.

In this work we identified in adult and juvenile freshwater prawn, Macrobrachium rosenbergii, three major type of circulating hemocytes: fusiform; rounded; and large ovoid hemocytes. Rounded and large hemocytes represent the first defense line, since this type of cells exerts phagocytic activity as well as lectin synthesis. Considering that glycosylation plays important roles in cell communication and as a target for pathogenic microorganisms, in this report was also described the main glycosidic modifications that occur in the large and rounded hemocytes from the freshwater prawn during maturation as determined with lectins. Neu5Acalpha2,6Gal, was identified homogeneously distributed in the membrane in 90% of hemocytes from juvenile organisms. Maturation of the freshwater prawn induced a decrease or complete loss of Neu5Acalpha2,6Gal residues that were replaced with Neu5Acalpha2,3 molecules in practically all hemocytes from adult organisms. This change was paralleled by a diminution in 9-O-acetyl-neuraminic acid (Neu5,9Ac(2)) expression. T and Tn antigens (Galbetal,3 GalNAcalpha1-0-Ser/Thr or GalNAcalpha1-0-Ser/Thr, respectively), as well as N-glycosidically linked glycans, seem to be highly conserved throughout maturation. Our results show that sialylation of freshwater prawn hemocytes is modulated throughout the maturation process.

Animals↗
PubMed2001

O-Glycosylation in sprouting neurons in Alzheimer disease, indicating reactive plasticity.

Reactive plasticity, including axonal and dendritic sprouting and reactive synaptogenesis, has been proposed to contribute to the pathogenesis of several neurological disorders. This work was aimed at identifying the possible role of protein glycosylation in the brain from patients with Alzheimer disease (AD), using lectin histochemistry, as determinants of reactive plasticity. Results indicate an increase in the production of cryptic O-glycosidically linked proteins (NeuAcalpha2,6 Galbeta1,3GalNAcalpha1,0 Ser/Thr or sialyl-T-antigen) in neuritic sprouting in AD brains as determined by positive labeling with Amaranthus leucocarpus (ALL, T-antigen-specific) and Macrobrachium rosenbergii (MRL, specific for NeuAc5,9Ac2) lectins. Immunohistochemistry indicated that lectin staining was specific for the synaptic sprouting process (meganeurites) in AD. These results were confirmed using anti-synaptophysin and anti-GAP 43 antibodies, which recognized meganeurites and dystrophic neurites around amyloid-beta deposits. In normal control brains, labeling with the aforementioned lectins was restricted to microvessels. Control experiments with neuraminidase-treated brain samples revealed positivity to the lectin from Arachis hypogaea (PNA), which is specific for galactose. Our results suggest specific O-glycosylation patterns of proteins closely related to neuronal plasticity in AD.

Aged↗
PubMed2001

Utilization and cost of health care services for children with attention-deficit/hyperactivity disorder.

BACKGROUND: Despite an increasing prevalence of diagnosed attention-deficit/hyperactivity disorder (ADHD) among children, the impact of ADHD on utilization and costs of health care services is largely unknown. OBJECTIVE: To examine differences in health care utilization and costs between children with and without ADHD. DESIGN: Retrospective matched cohort study conducted from January 1 to December 31, 1997. Setting. Health maintenance organization in western Washington State. PARTICIPANTS: Children aged 3 through 17 years who were continuously enrolled in the health maintenance organization and used services during 1997 were eligible. Children were identified with ADHD if they had a diagnosis of ADHD or a prescription for a stimulant medication using automated patient files. Children without ADHD were randomly selected as controls and matched 4:1 to children with ADHD on age and sex. OUTCOME MEASURE: Utilization and costs of specific categories of health care services. Results. A total of 2992 children (5.2%) were identified with ADHD. Children with ADHD incurred significantly greater per capita total costs ($1465 vs $690) than children without ADHD. Children with ADHD had 9.9 times more outpatient mental health visits (1.35/year vs 0.14/year), 3.4 times more pharmacy fills (11.25/year vs 3.30/year), and 1.6 times more primary care visits (3.84/year vs 2.36/year) than children without ADHD. The adjusted incremental costs were estimated to be $375 (95% confidence interval: $336-$416) for children with ADHD alone and $812 (95% confidence interval: $671-$973) for children with ADHD plus coexisting mental health disorders. CONCLUSIONS: Children with ADHD use significantly more health care resources and incur significantly higher costs than children without ADHD. Coexisting mental health disorders substantially increase the cost of treating ADHD. Resource allocation decisions should consider the contributions of primary care, outpatient mental health, and pharmacy costs to the overall costs of care for children with ADHD.

Adolescent↗
PubMed2001

Isolation, quantitation, and characterization of a stable complex formed by Lp[a] binding to triglyceride-rich lipoproteins.

Lipoprotein [a] (Lp[a]) is a cholesterol-rich lipoprotein resembling LDL to which a large polymorphic glycoprotein, apolipoprotein [a] (apo[a]), is covalently coupled. Lp[a] usually exists as a free-standing particle in normolipidemic subjects; however, it can associate noncovalently with triglyceride-rich lipoproteins in hypertriglyceridemic (HTG) subjects. In this study, 10-78% of the Lp[a] present in five HTG subjects was found in the triglyceride-rich lipoprotein (TRL) fraction. The Lp[a]-TRL complex was resistant to dissociation by ultracentrifugation (UCF) alone, but was quantitatively dissociated by UCF in the presence of 100 mM proline. Of this dissociated Lp[a], 70-88% was in the form of a lipoprotein resembling conventional Lp[a]. Incubation of Lp[a]-depleted TRL with native Lp[a] resulted in a reconstituted Lp[a]-TRL complex that closely resembled the native isolates in all examined properties. Complex formation was inhibited by several compounds in the order proline > tranexamate > epsilon-aminocaproate >> arginine > lysine. Neither plasminogen nor LDL inhibited binding of Lp[a] to TRL. We observed the preferential binding of Lp[a] containing higher apparent molecular weight apo[a] polymorphs to TRL both in native and reconstituted Lp[a]-TRL complexes. A disproportionate amount of Lp[a] was bound to the larger TRL particles. Although most apo[a] bound to TRL was in the form of conventional Lp[a] particles, lipid-free recombinant apo[a] was observed to bind TRL. These results provide unequivocal evidence of the existence of an Lp[a]-TRL complex under pathophysiologic conditions. The metabolic fate of the Lp[a]-TRL complex, which is more abundant in hypertriglyceridemia, may be different from that of conventional Lp[a], and may contribute uniquely to the progression or severity of cardiovascular disease.

Aminocaproic Acid↗
PubMed1998

Altered glycosylation pattern of proteins in Alzheimer disease.

Post-translational modifications due to glycosylation of proteins in human brains from patients with Alzheimer disease (AD) were analyzed using lectin histochemistry. Results indicate a significant increase in the production of O-glycosylated (containing Galbeta1,3GalNAc alpha1,0 Ser/Thr or GalNAc alpha1,0 Ser/Thr) proteins in neuritic plaques and neurofibrillary tangles which are the major histopathological hallmarks of AD brains. These alterations were determined by positive labelling with lectins obtained from Amaranthus leucocarpus (ALL) and Macrobrachium rosenbergii (MRL) respectively. Immunohistochemistry indicated that the lectin-staining labelled specifically both neurofibrillary tangles and neuritic plaques. In contrast, lectins labelling was restricted to microvessels in normal control brains. These results provide evidence that modifications of the specific glycosylation patterns are closely related with the presence of the hallmark lesions of this disease, suggesting that an abnormal enzymatic processing of proteins may be an early event in the neuronal degeneration which characterises AD.

Aged↗
PubMed1996

Interaction of apolipoprotein[a] with apolipoproteinB-100 Cys3734 region in lipoprotein[a] is confirmed immunochemically.

Monospecific polyclonal antibodies (MPAbs) to apoB-100 regions Cys3734 and Cys4190 were isolated by affinity chromatography using the synthetic polypeptides, Q3730VPSSKLDFREIQIYKK3746 and G4182IYTREELSTMFIREVG4198, respectively, coupled to a hydrophilic resin. Molecular modeling and fluroescence labeling studies have suggested that Cys67 located in kringle type 9 (LPaK9, located between residues 3991 and 4068 of the apo[a] sequence inferred by cDNA) of the apo[a] molecule is disulfide linked to Cys3734 of apoB-100 in human lipoprotein[a] (Lp[a]). This possibility has been further explored with MPAbs. Four species of MPAbs directed to a Cys3734 region of apoB-100 (3730-3746) were isolated from goat anti-human LDL serum by a combination of synthetic peptide (Q3730VPSSKLDFREIQIYKK3746) affinity chromatography and preparative electrophoresis (electrochromatography). MPAbs to the Cys4190 region of apoB-100, a second or alternative disulfide link-site between apo[a] and apoB-100, were also isolated using a synthetic peptide (G4182IYTREELSTMFIREVG4198) affinity resin. Results of immunoassays showed that binding of these four MPAbs to Lp[a] was significantly lower than to LDL. In contrast, MPAbs to the apoB-100 region 4182-4198 which contains Cys4190, a second or alternative disulfide link-site between apo[a] and apoB-100, displayed a less significant difference in binding to Lp[a] and LDL. These results provide additional evidence that the residues 3730-3746 of apoB-100 interact significantly with apo-a- in Lp-a-, and that Cys3734 is a likely site for the disulfide bond connecting apo[a] and apoB-100.

Amino Acid Sequence↗
PubMed1995

Evidence that apoB-100 of low-density lipoproteins is a novel Src-related protein kinase.

Protein-tyrosine kinases of signal transduction pathways occur and function intracellularly. In contrast, the low-density lipoprotein (LDL) particle circulates in plasma, where its function is to solubilize and transport lipid. Recently, several reports showed that LDL may have a role in signal transduction. We have identified a region in the apoB-100 primary structure which shows similarity to Src-homology-1 (SH1) domains, the kinase region of protein-tyrosine kinases. Results obtained in protein kinase assays of highly purified LDL showed that only the apoB-100 was phosphorylated, suggesting that apoB-100 has the capacity to undergo autophosphorylation like known protein-tyrosine kinases. Phosphorylation was not observed for any other apolipoprotein in LDL or for any component of high-density lipoprotein and lipoprotein [a]. Our results suggest that apoB-100 may be a novel and functional member of the src protein kinase family.

Amino Acid Sequence↗
PubMed1994

Identification and quantification of apolipoproteins in addition to apo[a] and apo B-100 in human lipoprotein[a].

The protein moiety of Lp[a] is widely believed to consist of one molecule of apo B-100 and one molecule of apo[a] per particle, linked by at least one disulfide bond. In this study we have re-examined the composition of Lp[a] to determine if other less abundant apolipoproteins might be present. Analysis of Lp[a] by sodium dodecyl sulfate-polyacrylamide electrophoresis under reducing conditions showed bands corresponding to < 200 kD but > 50 kD, 40 kD, 26 kD, 23 kD and 9 kD when stained with silver. Western immunoblot analysis of three preparations of Lp[a] revealed the presence of apoE and apoD. Enzyme-linked immunoassays were used to quantify apoA-I, apoA-II, apoC-I, apoC-II, apoC-III, apoE and apo B-100 in Lp[a] and autologous LDL isolated from three healthy males. There is a significant amount of apoA-I in the Lp[a], although the levels varied widely among the different samples. ApoE concentrations were consistent in the three Lp[a] samples and were between 22 and 26% of relative apo B-100 concentrations. Relatively minor amounts of apoA-II and no apoCs were detectable in the three Lp[a] preparations. In contrast, the autologous LDL preparations contained relatively higher amounts of apoA-I, apoA-II, apoE, apoC-I, apoC-II and apoC-III. The identity of the multiple bands corresponding to < 200 kD and > 54 kD and 9 kD is not established.

Adult↗
PubMed1994

Long distance runners and body-builders exhibit elevated plasma levels of lipoprotein(a).

A one-point cross-sectional study of 20 sedentary individuals, 20 low-aerobic athletes (body-builders), and 20 high-aerobic athletes (long distance, endurance runners) was conducted in Mexico City, Mexico to determine the influence of these diverse life-styles on the plasma levels of Lp(a). Only non-obese male subjects, aged 23-33, who were nonsmokers, non-alcoholics, and had never used anabolic steroids were included in this study. Blood samples were drawn 24 h following the last period of physical activity, and after a 12-14-h fast-period and a 15-min sitting-rest. Plasma levels of Lp(a) and other parameters, including postheparin lipoprotein lipase (LPL) and hepatic lipase (HL) activities, triglycerides (TG), total cholesterol (TC), LDL cholesterol (LDL-C), and HDL cholesterol (HDL-C), as well as % body fat and muscle mass, and maximum aerobic capacity (VO2max) were measured to determine possible correlations with Lp(a) and to serve as convenient internal standards. Mean Lp(a) concentrations were significantly higher in the runners (52 +/- 19 mg/dl) than in the body-builders (40 +/- 6.4 mg/dl, P < 0.05) and the sedentary subjects (24 +/- 5 mg/dl, P < 0.001). Positive correlations between Lp(a) and Vo2max (P < 0.001), HDL-C (P < 0.005) and HDL2-C subfraction (P < 0.005), and a negative correlation with TG were determined. Agglomerative cluster methods suggested three close-distance clusters and a fourth cluster which is composed of four runners who exhibited low LDL-C/HDL-C and high LPL/HL ratios, high mean Lp(a), HDL2-C, and Vo2max levels, but low TG levels. These data show that some individuals who maintain a life-style of very high level physical exertion may have remarkably elevated plasma Lp(a) concentrations. The highly increased concentrations of Lp(a) in high exercise athletes may represent a normal metabolic response to repeated small tissue injuries resulting from frequent and prolonged large muscle movement.

Adult↗