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Biomedical subjects

M Valenzuela

Publications and source records attributed to M Valenzuela.

At least 19 recordsLinked to original sources
PubMed2002

Relationship between plasma homocysteine levels and brain atrophy in healthy elderly individuals.

The authors examined the association of total plasma homocysteine (Hcy) levels with measures of atrophy and white matter disease on MRI scans in 36 healthy elderly individuals. Hcy had a significant positive relationship with lateral ventricle-brain ratios in the anterior (r = 0.49) and middle (r = 0.43) ventricular regions as measures of central atrophy, but not with cortical atrophy or white matter hyperintensities. In a logistic regression analysis, elevated Hcy was a significant determinant of increased anterior ventricle-brain ratio (> or =0.34) after controlling for age, folate, B12, creatinine, and white matter disease (OR = 2.3; CI, 1.03-5.09).

Aged↗
PubMed2001

A rat mammary tumor model induced by the organophosphorous pesticides parathion and malathion, possibly through acetylcholinesterase inhibition.

Environmental chemicals may be involved in the etiology of breast cancers. Many studies have addressed the association between cancer in humans and agricultural pesticide exposure. Organophosphorous pesticides have been used extensively to control mosquito plagues. Parathion and malathion are organophosphorous pesticides extensively used to control a wide range of sucking and chewing pests of field crops, fruits, and vegetables. They have many structural similarities with naturally occurring compounds, and their primary target of action in insects is the nervous system; they inhibit the release of the enzyme acetylcholinesterase at the synaptic junction. Eserine, parathion, and malathion are cholinesterase inhibitors responsible for the hydrolysis of body choline esters, including acetylcholine at cholinergic synapses. Atropine, a parasympatholytic alkaloid, is used as an antidote to acetylcholinesterase inhibitors. The aim of this study was to examine whether pesticides were able to induce malignant transformation of the rat mammary gland and to determine whether alterations induced by these substances increase the cholinergic activation influencing such transformation. These results showed that eserine, parathion, and malathion increased cell proliferation of terminal end buds of the 44-day-old mammary gland of rats, followed by formation of 8.6, 14.3, and 24.3% of mammary carcinomas, respectively, after about 28 months. At the same time, acetylcholinesterase activity decreased in the serum of these animals from 9.78 +/- 0.78 U/mL in the control animals to 3.05 +/- 0.06 U/mL; 2.57 +/- 0.15 U/mL; and 3.88 +/- 0.44 U/mL in the eserine-, parathion-, and malathion-treated groups, respectively. However, atropine alone induced a significant (p < 0.05) decrease in the acetylcholinesterase activity from the control value of 9.78 +/- 0.78 to 4.38 +/- 0.10 for atropine alone, to 1.32 +/- 0.06 for atropine in combination with eserine, and 2.39 +/- 0.29 for atropine with malathion, and there was no mammary tumor formation. These results indicate that organophosphorous pesticides induce changes in the epithelium of mammary gland influencing the process of carcinogenesis, and such alterations occur at the level of nervous system by increasing the cholinergic stimulation.

Acetylcholinesterase↗
PubMed2001

Differences in morphological age-related dental changes depending on postmortem interval.

Morphological methods for age estimation from teeth have been developed and applied to samples without taking the postmortem interval into consideration. We studied differences in morphological age-related changes between fresh extracted teeth and teeth from human skeletal remains in order to develop appropriate dental age estimation methods according to the time after death. Forty-three permanent teeth from dental patients were compared to 37 teeth obtained from human skeletal remains with a postmortem interval from 21 to 37 years. Morphological age-related changes were investigated by measuring variables on intact and half-sectioned teeth. A new computer assisted image analysis procedure to avoid subjectivity was developed to measure variables in sectioned specimens. Dental color, translucency length, attrition, cementum apposition, and secondary dentin showed higher values in teeth from human skeletal remains than in fresh extracted teeth. Variables obtained by morphometric analysis of computer-generated images (tooth length, tooth width, root length, and root area) showed higher values in fresh extracted teeth than in teeth from skeletal remains. The postmortem interval affects age-related morphological changes, and therefore different methods should be used for teeth of unknown postmortem interval.

Adult↗
PubMed1999

Plasticity of 5-hydroxytryptamine(1B) receptors during postnatal development in the rat visual cortex.

The distribution of 5-hydroxytryptamine1A and 5-hydroxytryptamine1B receptors in the visual cortex was studied by quantitative autoradiography during postnatal development. Overall, receptor densities increased throughout development, but exhibited regional rearrangements, particularly in the case of 5-hydroxytryptamine1B receptors. Neonatal treatment with 5,7-dihydroxytryptamine, which causes selective degeneration of serotoninergic neurons, had no effect on the density of 5-hydroxytryptamine1A receptors in the visual cortex. However, a transient increase in 5-hydroxytryptamine1B at postnatal days 10-12 was observed after this treatment, suggesting a regulation of postsynaptic receptors. Neonatal enucleation resulted in a marked increase in 5-hydroxytryptamine1B binding sites in all layers of the visual cortex by P16, whereas it had no effect upon 5-hydroxytryptamine1A binding sites. These results show that both receptor subtypes do not exhibit striking transient features in the visual cortex during postnatal development, but rather undergo discrete reorganizations. 5-Hydroxytryptamine1B receptors show changes in density after either neonatal degeneration of serotoninergic neurons or enucleation, indicating that the serotoninergic system involving this receptor subtype can exhibit some postnatal plasticity in the visual cortex.

5,7-Dihydroxytryptamine↗
PubMed1998

How patients adapt diabetes self-care recommendations in everyday life.

BACKGROUND: Our study explored behavioral factors affecting what patients with type 2 diabetes do for self-care and why they do it. The findings were used to develop clinical recommendations to improve intervention strategies. METHODS: Interviewers, using open-ended questions, explored patients' own perceptions and assessments of self-care behaviors. The fifty-one subjects were self-identified Mexican Americans who had type 2 diabetes for at least 6 months, and had no major impairment as a result of this diabetes. Texts of patient interviews were analyzed by building and refining matrixes to display and compare central themes regarding treatment strategies and their contexts. RESULTS: All patients were trying to control their diabetes, but none of them followed recommendations completely. Instead, they adapted self-care behaviors to the exigencies of everyday life. Key factors influencing patients' treatment choices were: (1) the belief in the power of modern medicine; (2) the desire to act and feel "normal"; (3) the desire to avoid physical symptoms; and (4) limited economic resources. CONCLUSIONS: As patients apply treatment recommendations in the context of their everyday lives, they continually must make many small decisions affecting self-care behavior. The specific contexts of patients' lives, including their economic, educational, and cultural circumstances, determine how the generalized principles of type 2 diabetes management are implemented. Clinical strategies must be responsive to these circumstances in order to enable patients to make appropriate decisions when adapting their self-care behaviors to their own situations.

Adult↗
PubMed1997

Maternal sensitivity in a developing society: the context of urban poverty and infant chronic undernutrition.

This study focuses on young children's chronic undernutrition and its association with maternal sensitivity, sociodemographic variables, children's play, and problem-solving measures. Data were obtained with home observations and laboratory procedures on 85 mothers and infants (M age = 18 months) in a low-income urban population in Santiago, Chile. Maternal sensitivity was correlated with maternal education, maternal weight, and marital satisfaction. Observed in a variety of maternal roles, maternal sensitivity was also significantly associated with children's nutritional status, attachment security, and mastery behavior. These findings demonstrate the relevance of the maternal sensitivity construct outside industrialized societies and underline the need for intervention strategies to extend beyond nutritional supplementation to address deficits of maternal care associated with specific caregiver's roles.

Adult↗
PubMed1997

Bilingual telephone-assisted computerized speech-recognition assessment: is a voice-activated computer program a culturally and linguistically appropriate tool for screening depression in English and Spanish?

The purpose of this study was to evaluate an automated voice-interactive program for screening depression in English and Spanish. The Center for Epidemiological Studies-Depression Scale (CES-D) was administered in two interview formats: a speech recognition program presented by cellular telephone, and a face-to-face method. In a single-session counterbalanced design, 32 English speakers and 23 Spanish speakers completed randomly ordered administrations of the two CES-D methods, the Beck Depression Inventory (BDI), and the Short Acculturation Scale (SAS). There was strong evidence that the two CES-D methods were psychometrically equivalent, reliable, and valid in both languages. The two methods were highly rated by both language groups. The Spanish speakers did not display a preference for either method, but the English speakers preferred the face-to-face method. The results also suggested that verbal response latency time was positively correlated with depression scores. Last, the Spanish-speakers' acculturation levels were not correlated with depression scores. Differences in age, education, and income between the language groups were confounded by unequal sample sizes. The findings generally supported the viability of the automated CES-D as a culturally and linguistically appropriate tool for screening depression in English and Spanish. Furthermore, the analyses of respondent voice characteristics show promise as a method for screening depression in both languages.

Acculturation↗
PubMed1996

Colitis cystica profunda: imaging diagnosis and conservative treatment: report of two cases.

UNLABELLED: Rectally localized colitis cystica profunda can simulate mucosecretory carcinoma. PURPOSE AND METHODS: Because endoscopic examination and barium enema do not clarify the diagnosis, other diagnostic imaging methods such as transrectal ultrasonography, computerized tomography, or magnetic resonance imaging are needed. RESULTS: Transrectal ultrasonography identifies multiple cysts in the rectal submucosa, with areas of echorefringent fibrosis between cysts, and confirms the absence of lymph node involvement or invasion of the muscular layer. Findings with computerized tomography and magnetic resonance imaging have not previously been described for colitis cystica profunda. With computerized tomography, the lesion appears as a noninfiltrating entity in the submucosa, with loss of perirectal layers of fatty tissue and thickening of the levator ani muscle. With nuclear magnetic imaging, nodulations produce intense signals that increase in T2, illustrating the mucoprotein content of the cysts. The presence in surgical biopsy material of large, whole cysts confirms the diagnosis. CONCLUSION: Reeducation of bowel habits aimed at avoiding straining and a high-fiber diet together with bulk laxatives can lead to complete remission of lesions in 6 to 18 months.

Adult↗
PubMed1996

Parietal cell hyperactivity is not due to Helicobacter pylori infection in patients with duodenal ulcer.

OBJECTIVE: To determine the relationship between Helicobacter pylori infection and parietal cell mass and functional status in 10 patients with duodenal ulcer and 22 patients with functional dyspepsia. METHODS: We measured pentagastrin-stimulated acid secretion, determined the activity status of parietal cells on the basis of ultrastructural morphological features, and measured parietal cell mass and canalicular area with computerized densitometric morphometry. The number of antral G cells per square millimeter of mucosa was estimated inmunohistochemically, and basal serum gastrinemia was determined. RESULTS: In patients with duodenal ulcer, acid secretion, the percentage of activated parietal cells, and canalicular area were increased, but there was no difference between patients and dyspeptic controls in parietal cell mass. Helicobacter pylori infection did not modify these parameters, although it was associated with basal hypergastrinemia. CONCLUSION: In patients with duodenal ulcer, parietal cells display functional hyperactivity, which causes hypersecretion of acid; this effect is apparently unrelated to Helicobacter pylori infection.

Case-Control Studies↗
PubMed1995

[The analysis of the gastric mucosa by computerized densitometry].

An analytical method of histologic imaging of the gastric mucosa by computerized densitometry based on the extraction of components of an image on the basis of its luminous density is described. A group of 10 healthy controls, a group of 10 subjects with gastric ulcer and 10 with duodenal ulcer were included in the study. The method was particularly useful in the identification of atrophic and hypertrophic processes. A decrease was found in the density of parietal and chief cells in atrophic gastritis of the gastric body. In atrophic gastritis of the gastric antrum a decrease was observed in global cell density of the antrum. Patients with gastric ulcer did not present variations versus the control group. In those with duodenal ulcers an increase was observed in the density of surface cell of the gastric body with no variation in the density of parietal and principal cells. This finding challenges the classical concept on the increase in parietal cell mass accompanying duodenal ulcers.

Adolescent↗
PubMed1990

Attachment in chronically underweight young children.

This study, conducted in Chile with a low-income population, was designed to assess quality of mother-infant attachment in 17-21-month-old children of different nutritional status. 43 nutritionally healthy and 42 chronically underweight children were seen with their mothers in the Ainsworth Strange Situation. Children were classified in the conventional B (secure) and A and C (anxious) attachment patterns. In addition, an A/C pattern of anxious attachment was found to be frequent among children who consistently fail to gain adequate weight-for-age. Results showed a greater proportion (93%) of anxious attachments in the underweight group as compared to the group of children without a history of nutritional deficits (50%). Children classified as A/C presented the most serious weight deficits within the underweight group, indicating an association between severity of the nutritional deficits and insecure/disorganized attachments. Various hypotheses concerning the association between chronic nutritional deficits and insecure/disorganized attachments in infancy are discussed.

Chile↗