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Biomedical subjects

M A Castillo

Publications and source records attributed to M A Castillo.

15 recordsLinked to original sources
PubMed2001

Initial evaluation of quantitative performance of chromatographic methods using replicates at multiple concentrations.

The introduction of a novel analytical method must be supported by consistent information about its quantitative potentialities; this is critical for whoever considers its utilization for an specific application. Unfortunately, literature abounds in papers proposing excellent chromatographic methods of analysis that have been subjected to comparatively poor quantitative evaluation. The methodology proposed in the present work makes use of some of the performance characteristics whose measurement is recommended in validation protocols; pertinent to this stage of method development are the detection and quantitation limits, the linear range and the repeatability. All this information can be calculated from the results of a calibration with several replicates at each analyte level. Replicates enable the calculation of reproducibility at several analyte levels and the estimation of the linear range; more important, replicates are necessary to detect changes in peak area standard deviation with analyte amount. Regression of calibration data by means of unweighted least-squares (ULSR) can only be performed in those cases in which homoscedasticity has been previously verified; heteroscedastic calibration data demand regression by means of weighted least-squares (WLSR), since ULSR results in gross overestimation of prediction limits at low analyte concentration. The proposal is used for the preliminary quantitative evaluation of a method for the determination of nine biogenic amines by means of pre-column derivatization with dabsyl chloride and separation of derivatives by RPLC. Limits of detection are calculated by a regression approach and by the classical signal-to-noise ratio method (S/N approach). No significant difference was detected for the amines limits of detection estimated by WLSR and by the S/N approach; ULSR estimated limits of detection are between 7 and 78 times larger than those obtained by the other two methods, as a consequence of the heteroscedasticity of calibration data.

Calibration↗
PubMed1999

Insecticidal, anti-juvenile hormone, and fungicidal activities of organic extracts from different Penicillium species and their isolated active components.

Organic extracts from mycelium and culture broth of 21 Penicillium isolates have been tested for insecticidal, insect anti-juvenile hormone (anti-JH), and antifungal activities. Culture broth extracts were the most active, mainly against insects; nearly 25% of them have shown high entomotoxicity (100% mortality at 100 microg/cm(2)). A strong in vivo anti-JH activity against Oncopeltus fasciatus Dallas was detected in the culture broth extracts from P. brevicompactum P79 and P88 isolates. The two new natural products isolated from P79, N-(2-methyl-3-oxodec-8-enoyl)-2-pyrroline (1) and 2-hept-5-enyl-3-methyl-4-oxo-6,7,8,8a-tetrahydro-4H-pyrrolo[2,1-b]-1, 3-oxazine (2), possessed anti-JH and insecticidal activity, respectively, against O. fasciatus. Synthesized natural compound 1 has shown an ED(50) of 0.7 microg/nymph when assayed on newly molted fourth-instar nymphs of O. fasciatus. Promising biological activities have also been detected in the synthetic precursors.

Animals↗
PubMed1993

Chronic insulin treatment in rats: evidence against a role for insulin as a pressor agent.

1. The present study was undertaken to test whether insulin acts as a pressor agent and causes hypertension in rats. 2. Insulin at doses of 10 or 100 units day-1 kg-1 was administered daily by subcutaneous injection to normal rats for 6 weeks. As it has been suggested that sodium retention plays a major role in the putative hypertensive activity of this hormone, insulin was also administered to saline- (1% NaCl) drinking rats according to the same protocol. Water- and saline-drinking rats served as controls. 3. After 6 weeks of insulin treatment, the mean arterial blood pressure did not increase in any of the insulin-treated or the insulin-salt-treated groups. However, in both insulin-salt-treated groups, absolute and relative ventricular and renal hypertrophy with increased ventricular water content as well as increased urine output with reduced osmolality were observed. 4. All insulin-treated groups showed increased plasma levels of glucose, insulin and antidiuretic hormone when compared with their respective controls. 5. These results demonstrate that chronic insulin treatment did not increase blood pressure in rats, even when drinking water was supplemented with NaCl, and suggest that a polyuria-polydipsia syndrome was present in both insulin-salt-treated groups. Moreover, increased plasma levels of antidiuretic hormone were observed in all insulin-treated groups.

Animals↗
PubMed1992

Methimazole treatment reduces cardiac hypertrophy and mortality without a concomitant reduction in blood pressure in established Goldblatt two-kidney one clip hypertension.

The effects of methimazole, an antithyroid drug, on blood pressure and other parameters were evaluated in the established phase of Goldblatt two-kidney one clip (G2K-1C) hypertension. Methimazole was administered via drinking water for five weeks, starting five weeks after hypertension had been induced. After this period of treatment, similarly high blood pressures were observed in methimazole-treated and non-treated G2K-1 C rats, despite the fact that a hypothyroid state had been achieved in methimazole-treated rats. Methimazole-treated G2K-1 C rats showed reductions in heart rate, ventricular weight, ventricular/body weight ratio and mortality in comparison with rats not treated with methimazole. These results clearly demonstrate that hypothyroidism induced by methimazole: a) does not reverse G2K-1 C hypertension, but b) improves the rate of survival and c) reduces relative cardiac hypertrophy, possibly by the reduction in cardiac work observed in Goldblatt hypothyroid rats.

Animals↗
PubMed1992

Effects of methimazole on low-renal-mass hypertension: changes in blood pressure and pressor responsiveness to vasoconstrictors.

The administration of the antithyroid drug methimazole to rats via drinking water prevented the development of hypertension that usually accompanies subtotal nephrectomy and saline drinking (1% NaCl). In methimazole-treated rats, elevated blood pressure induced 5 weeks previously returned to normotensive levels. Pressor responsiveness to angiotensin, vasopressin and norepinephrine in unanesthetized rats was studied after prevention of hypertension in control, low-renal-mass hypertensive (LRM) and low-renal-mass methimazole-treated (LRM-M) rats, and in the reversion study in LRM and LRM-M rats. In LRM rats, responsiveness to vasoconstrictors was increased, whereas responsiveness to vasoconstriction was clearly reduced in LRM-M rats after prevention and reversion studies. These results suggest that (a) thyroid hormones are required in the early and established phases of LRM hypertension, and (b) the decreased pressor responsiveness to vasoconstrictors may play a role in the prevention and reversion of this type of hypertension following methimazole administration. However, the changes in pressor responsiveness may also be secondary to the reduction in blood pressure.

Administration, Oral↗
PubMed1991

Urinary excretion of digoxin-like immunoreactive factor and arginine-vasopressin in rats after several osmotic loads.

Urinary digoxin-like immunoreactive factor (DLIF), arginine-vasopressin (AVP) and other urinary parameters were investigated under normal conditions and after the i.p. injection of the following solutions: distilled water, isotonic and hypertonic NaCl, NaHCO3, KCl and urea, at a rate of 3 ml/100 g body weight. The measurement of digoxin-like immunoreactivity by two different radioimmunoassays showed that DLIF was stimulated by all volume loads regardless of the presence or absence of osmolar compounds. This dissociation between DLIF and urinary sodium excretion suggests that DLIF may not constitute the natriuretic hormone. Moreover, a dissociation between DLIF and AVP excretion also were found, which speaks against the hypothesis of a common mechanism of stimulation for both substances.

Animals↗
PubMed1990

[Developement and quality control of a radioimmunoassay for measurement of endogenous digoxin].

It has been suggested that sodium renal excretion is regulated, at least partially, by a factor with natriuretic properties called digoxin-like factor (DLF). As this substance crossreacts with digoxin antibodies, it was measured with a radioimmunoassay used to determine exogenous digoxin. Methodological conditions and quality control to determine DLF in plasma and urine have been established. Good correlation coefficients in specificity as well as dilution studies were obtained. Within--and between--assay coefficients of variations indicate good reproducibility. Moreover, changes in plasma DLF levels were detected in patients with cirrhosis or with renal failure, diseases which thrive on alterations in salt and water metabolism. In conclusion, this radioimmunoassay method for measuring DLF may be useful to investigate the role of this factor in several physiological and pathological conditions.

Adolescent↗
PubMed1989

Effects of selective and non-selective beta 1-blockade on renin secretion in the isolated rat kidney.

The participation of beta 1-adrenoceptor on renin secretion was studied in perfused rat kidney. Administration of propranolol, inhibited the renin release mediated by isoproterenol. Likewise, metoprolol and practolol, showed a similar potency to propranolol in inhibiting isoproterenol-induced renin secretion. These results suggest that the for isoproterenol-induced renin release in rats is a beta 1-type adrenoceptor.

Adrenergic beta-Antagonists↗
PubMed1988

Decrease in tumor-cell attachment and in a 140-kDa fibronectin receptor correlate with greater expression of multiple 34-kDa surface proteins and cytoplasmic 54-kDa components.

B16 melanoma cells attach to matrix-bound fibronectin but fail to adhere to albumin-coated surfaces supplemented with soluble fibronectin. Attachment to substratum is also decreased in the presence of an adhesion-disrupting antibody, or when cells are seeded on substrates poorly adhesive for these cells, such as collagen gels. We have now investigated some of the more general adhesion-related alterations that occur between flattened and poorly attached cells. Immune blots of octylglucoside extracts with the adhesion-disrupting IgG revealed a 140-kDa component in flattened cells, in contrast to the increased detection of a 54-kDa species in a comparable assay with rounded cells. Surface iodination also showed a decreased external exposure of a 140-kDa fibronectin binding species and an increased labelling in multiple 34-kDa protein species, in cells with decreased attachment to substratum. Analysis of 35S-methionine-labelled cell aggregates cultured on collagen gels also revealed a decrease in the 140-kDa region and a greater labelling of multiple 54-kDa components, compared to the same cells flattened on fibronectin. A change in 54- and 34-kDa species was also seen in matrix-associated components of rounded cells that failed to attach with soluble fibronectin. Since the 34-kDa species increase in poorly adherent cells is mainly detected by iodination, and the 54-kDa species increase in the same cells is partly associated with the corresponding detergent-insoluble matrices, we propose that these 2 novel proteins may relate to cell rounding, through a transmembrane modulation involving both surface membrane and cytoskeletal structures.

Animals↗
PubMed1988

[Teaching-inservice integration in primary care. Experience of the Facultad de Enfermería de la Universidad Autónoma de Nuevo León, Mexico].

This paper presents the reasons which justify the need to integrate teaching in-service and health care delivery in nursing, and the mechanisms to achieve efficiency in health programs. In 1976 the Autonomous University of Nuevo Leon (Universidad Autónoma de Nuevo León), as an educational and training center and as a means for scientific and humanistic endeavor to foster the development of the community it serves, began a joint experimental project with the health sector, by means of the Guadalupe Health Program and the Nursing Development Program, with the participation of the Schools of Medicine, Nursing and Dentistry. Special importance is attached to the objectives and organization of these nursing programs, the teaching in-service methodology, and the functions and responsibilities of teachers, students and support staff. The achievements of eleven years of work are reported.

Education, Nursing↗
PubMed1985

Serum mediated changes in cell attachment and cytoplasmic organization of B16 melanoma correlates with selective alterations in secreted proteins.

B16 melanoma cells exhibited decreased adhesion to substration and the presence of cytoplasmic granules, resembling lipid inclusions, when cultured in vitro in the presence of syngenic serum from C57/BL6 mice. This constrasted with the rapid cell attachment and absence of cytoplasmic granules in cultures seeded in medium supplemented with an identical concentration of fetal bovine serum. Electrophoretic comparison of intracellular proteins revealed similar patterns in detergent-soluble and matrix-associated proteins from cells grown with bovine or mouse serum. However, a similar analysis of the conditioned media showed clear differences in methionine-rich species which migrated in the 100 kd region in cells grown with bovine serum, and as 110 kd component in cells grown with mouse serum. Our data indicate that the poor attachment to substratum and changes in cytoplasmic organization of B16 melanoma cells, is primarily associated with specific changes in secreted proteins.

Animals↗
PubMed1984

Unequal forms of 140-110 kD glycoproteins in B16 melanoma cells with differing detachment properties and metastatic behavior: influence of bromodeoxyuridine.

Growth of B16 melanoma metastatic variants with 2.5 micrograms/ml of bromodeoxyuridine (BrdU) decreases cell detachment from the substratum, as measured by resistance to release by trypsin-EDTA treatment. Using an antiserum to intact melanoma cells and metabolic labelling of melanoma metastatic variants with 3H-glucosamine and subsequent electrophoretic analysis, we are now able to show that: (1) differential solubilization and immune precipitation permit the identification of hydrophilic glycoproteins of about 140 kD and 110 kD in melanoma cells with low colonizing ability; (2) the effects of BrdU on B16 melanoma appear to be exerted differentially on cells with differing metastatic behavior, since only poorly invasive melanoma cells show a stimulating effect of BrdU on the expression of the hydrophilic 140 kD glycoproteins; (3) cells with increased lung colonizing ability reveal hydrophobic 140 and 110 kD glycoprotein species with increased susceptibility to mild protease treatment, as compared with the corresponding components from poorly invasive cells. The possible relationship of the 140-110 kD glycoproteins to B16 melanoma biological behavior and cell-substratum interactions is suggested by the fact that such components undergo significant changes in cells with differing invasive behavior and detachment properties.

Animals↗