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Biomedical subjects

M A Pacheco

Publications and source records attributed to M A Pacheco.

22 records · Page 2Linked to original sources
PubMed1988

Phospholipase A2 injection in mice induces immunity against the lethal effects of Crotalus durissus terrificus venom.

Phospholipase A2, purified from crotoxin obtained from C. d. terrificus venom, alone or incorporated in Freund's complete adjuvant (FCA) or in Al(OH)3 was used as an antigen to immunize mice against the lethal effects of C. d. terrificus venom. The animals were intracutaneously (i.c.) or subcutaneously (s.c.) injected with 60 micrograms of phospholipase A2, divided into three equal doses and injected every 7 days. Samples of blood were collected just before each injection and the sera used to determine the antibodies against whole venom by the ELISA method. The animals were s.c. challenged with 8 LD50 or with 16 LD50 28 or 95 days after immunization. The animals that received two s.c. doses of antigen followed by a third i.c. dose were partially resistant to 8 LD50 (58% protection). This resistance increased when the first two injections consisted of phospholipase A2, the third of whole venom, all i.c., all in Al(OH)3 (67% of protection). The maximal protection (90%) was attained when the animals were i.c. injected with phospholipase A2 in Al(OH)3 in all three immunizing doses. Antibodies against whole venom were detected 15 days after immunization, reaching a plateau on the twenty-eighth day and remaining unchanged at least until the ninety-fifth day after immunization.

Aluminum Hydroxide↗
PubMed1986

Quantification of the initial phases of rapid brain enlargement in the chick embryo.

Rapid brain enlargement requires a hydraulic mechanism in the chick embryo. Such a mechanism involves a closed, fluid-filled system that generates positive pressure. For the chick embryo this study determined when rapid brain enlargement begins, assessed the relative contributions of cavity expansion and tissue growth to overall brain enlargement, and evaluated mathematical models of overall brain enlargement and expansion and growth of the component parts. Three to five embryos were collected at each Hamburger and Hamilton state (11, 12, 14, 16, and 18) and processed for paraffin serial sectioning. Brain growth was determined over a 24-hr period (stages 11-18) by calculating volumes from area measurements of sections of brains from individual embryos by using a computerized image-analysis system. Statistical analysis indicated that a linear model adequately described cavity expansion, and a linear model was rejected for the description of tissue growth and total brain enlargement. At the onset of brain enlargement, the cavity expands faster than the tissue grows; but after 12 hr the reverse is true. Initially (i.e., at stage 11), the cavity accounts for 60% of the total brain volume and tissue for 40%. At stages 12-16, cavity and tissue contribute 50% each. Finally at stage 18, cavity accounts for 55% and tissue for 45%. In order to better distinguish changes in cavity expansion and tissue growth over the 24-hr period studied, this period was divided into four intervals (I-IV). The rates of both cavity expansion and tissue growth increase between intervals I and II, decrease between intervals II and III, and increase between intervals III and IV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

[Determination of colonic transit time in healthy subjects in Mexico City. Prospective study].

UNLABELLED: Colonic transit time (CTT) is determined by multiple factors; currently, normal values for the Mexican population are not available. In order to get an estimate one must look at the values reported in the international literature, but cultural, ethnical, nutritional and economic differences may lead to different values. OBJECTIVE: To determine the normal values of colonic transit time in healthy people in Mexico City by the use of radiopaque markers. PATIENTS AND METHODS: Prospective, longitudinal and observational study, which included healthy patients ranging from 18 to 60 years old; excluding pregnant women. The whole group of patients was given before breakfast a gelatin capsule which had 20 radiopaque markers inside -the markers were each 2mm long, and were made by the researcher-. After that, they were taken a simple abdominal X-ray film every 24 hours until they totally eliminated the markers. Their eating and defecation habits were evaluated and also the total amount of liquid they consumed. Inferential statistics were used; data was validated with both parametric and non-parametric tests, considering a significance of p < 0.05. RESULTS: A hundred patients were included in the sample in which 48% were female and 52% male, they were divided in three groups: group A (31%)from 18 to 25 years, group B (37%)from 26 to 40 and group C (32%)from 41 to 60 years; there were no important differences in their water consumption, which was in average of 1.87 lts. in 24 hours; also, there were no considerable differences regarding to their meat, vegetables and fruits' consumption, which was in average of 4.4 times a week; the whole group eliminated the markers according to X-rays which was in 54% after 72 hrs, 45% after 48 hrs and 1% after 24 hrs. We can observe an increase of the CTT related to age: in group C 94% eliminated the markers after 72 hrs and there was no significant difference (statistically) with regards to the other groups. A tendency of an increase of CTT with regards to age was observed: in group A, 80% eliminated the markers after 48 hrs, in group B 49% eliminated them after 48 hrs and 51% after 72 hrs and, in group C, 94% eliminated them after 72 hrs without any statistically significant differences among the study groups. CONCLUSION: The CTT in healthy patients is in a 100% of the cases studied lower or equal to 72 hrs with a tendency to increase in relation to age.

Adolescent↗