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Biomedical subjects

G Santillan

Publications and source records attributed to G Santillan.

9 recordsLinked to original sources
PubMed2002

Modulation of cytosolic calcium levels in osteoblast-like osteosarcoma cells by olpadronate and its amino-derivative IG-9402.

The molecular mechanisms as well as the structure/activity relationships involved in the antiresorptive actions of bisphosphonates on bone cells are still not clear. Replacement of the R1-hydroxyl by an NH2 group in olpadronate (OPD) abolishes its antiresorptive activity. We show here that in the rat osteosarcoma-derived osteoblast-like ROS 17/2.8 cell line, OPD and IG-9402 (NH2-OPD; [3-(N,N-dimethylamine)-1-aminopropylidene bisphosphonate]), similar to 1,25(OH)2-vitamin D3, rapidly modulate cytosolic calcium levels ([Ca2+]i). As for the steroid hormone, the osteosarcoma cell Ca2+i response to OPD was rapid (30 sec) and sustained (>5 min), exhibiting a biphasic profile. The response to IG-9402 was also fast but smaller than that of OPD and 1,25(OH)2D3, and rapidly declined to levels near basal. The effect of these bisphosphonates on [Ca2+]i was dose-dependent, being maximal at 10(-8) M and was not observed in non-bone cellular systems, e.g., skeletal muscle and breast cells. Pretreatment of the ROS 17/2.8 cells with the Ca2+ channel blockers nifedipine and verapamil markedly reduced (>70%) the influx phase of the response to OPD and almost completely inhibited that of IG-9402, indicating the participation of voltage-dependent Ca2+ channels in the action of both compounds. Moreover, preincubation with the phospholipase C inhibitors U73122 and neomycin or depletion of inner stores with thapsigargin completely blocked the response to either olpadronate or its amino-derivative. Both OPD and IG-9402 significantly increased osteocalcin release into the culture medium of osteosarcoma cells. The results support the involvement of the Ca2+ signaling pathway as part of the mechanism by which bisphosphonates induce bone cellular responses.

Animals↗
PubMed2000

Canine echinococcosis: an alternative for surveillance epidemiology.

The essential activities for programmes of cystic echinococcosis control are the census of all dogs from the program and identification of parasitised animals. Currently, in South America evaluations and epidemiological surveillance are based on the administration of arecoline hydrobromide. This method has the disadvantage of increasing environmental pollution and risk for operators and owners of treated dogs. A genus-specific ELISA capture method has been employed for recently issued faeces and the confirmation of positive examination was performed by dog autopsies. Our work presents an alternative method based on collection of dry field-dispersed faeces, followed by serological diagnosis by Copro-ELISA and confirmation by Copro-Western blot. If Copro-ELISA were used to define positive samples of dry faeces, the Copro-Western blot assay would provide 70% sensitivity and 100% specificity. Global efficiency of the system using dry faeces would reach 76%, allowing epidemiological surveillance to be oriented to analysis of surface units instead of dog as measurement unit.

Animals↗
PubMed1998

Detection of human Toxoplasma-specific immunoglobulins A, M, and G with a recombinant Toxoplasma gondii rop2 protein.

The Toxoplasma gondii rhoptry protein Rop2 was expressed in Escherichia coli as a fusion protein containing 44 kDa of the 55-kDa mature Rop2, supplied with six histidyl residues at the N-terminal end (Rop2196-561). Humoral response during Toxoplasma infection of humans was analyzed by immunoglobulin G (IgG), IgA, and IgM enzyme-linked immunosorbent assay with Rop2196-561 as the antigen substrate. The analyzed sera were divided according to T. gondii-specific serological tests (IgG, IgA, or IgM indirect immunofluorescence and IgA or IgM immunosorbent agglutination assay) as group A (IgG+ IgA- IgM-; n = 35), group B (IgG+ IgA+ IgM+; n = 21), group C (IgG+ IgA+ IgM-; n = 5), and group D (IgG+ IgA- IgM+; n = 16). Twenty-six T. gondii-seronegative sera from individuals with other infections were also included (group E). Anti-Rop2 IgG antibodies were detected in 82.8% of group A sera and in 97.6% of the sera with acute-phase marker immunoglobulins (groups B, C, and D). The percentage of IgA antibody reactivity against Rop2196-561 was 17.1% in group A, 50% in group D, and 80.8% in groups B and C. The percentage of IgM antibody reactivity was 0% in groups A and C and 62% in groups B and D. Sera from group E failed to show IgA, IgM, or IgG antibody reactivity. Since T. gondii Rop2 elicits a strong humoral response from an early stage of infection, it is suggested that recombinant Rop2196-561 would be suitable for use in diagnostic systems, in combination with other T. gondii antigens, to detect specific IgG, IgA, and IgM antibodies.

Animals↗
PubMed1997

Effects of calcitriol and its analogues, calcipotriol (MC 903) and 20-epi-1alpha,25-dihydroxyvitamin D3 (MC 1288), on calcium influx and DNA synthesis in cultured muscle cells.

The fast actions of the secosteroid hormone 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3; calcitriol] and the synthetic analogues calcipotriol (MC 903) and 20-epi-1alpha,25(OH)2D3 (MC 1288) on cell calcium influx were compared in rat duodenum enterocytes as well as in cells from chick embryo skeletal muscle (myoblasts) and heart (myocytes), at various concentrations (10(-12) to 10(-8) M) and treatment intervals (1-10 min). In enterocytes, at a concentration of 10(-11) M, MC 1288 was significantly more active than 1,25(OH)2D3 in rapidly stimulating 45Ca2+ uptake by enterocytes (80 vs 38% above controls, respectively), whereas MC 903 was devoid of activity. However, calcipotriol increased Ca2+ influx in myocytes and myoblasts to a greater extent than the natural hormone, whereas MC 1288 was more active only in myoblasts. Analogously to 1,25(OH)2D3, the fast MC 903- and MC 1288-induced stimulation of 45Ca2+ uptake in enterocytes and muscle cells could be blocked by both verapamil and nifedipine. In addition, MC 903 and MC 1288 were more effective than 1,25(OH)2D3 in stimulating DNA synthesis in proliferating myoblasts and in inhibiting DNA synthesis in differentiating myoblasts. The results suggest, therefore, that modifications in the side-chain of the 1,25(OH)2D3 molecule increase its ability to modulate muscle cell Ca2+ metabolism and growth. These findings are potentially relevant for the development of analogues for the treatment of vitamin D-dependent myopathies.

Animals↗
PubMed1984

Red cell velocity and autoregulation in the cerebral cortex of the cat.

This report deals with a comparison of total and regional cerebral blood flow with red cell velocity in the microcirculation of the ecto- and suprasylvian areas of the cerebral cortex of the cat and their response to changes in systemic blood pressure. Total and regional blood flows were measured during a steady-state with radioactive microspheres; a newly devised method, based on transillumination was employed for direct visualization of the microcirculation in the cerebral cortex. Craniotomy failed to influence either autoregulation or red cell velocity under the skull opening or of the total cerebral flow. Autoregulation of total and regional cerebral flow was present. In contrast marked pressure-dependent variations in microcirculatory red cell velocity occurred. A fall in systemic pressure was accompanied by a decrease in red cell velocity; return of pressure resulted in increased red cell velocity and in some instances, in an overshoot. Considerable inhomogeneity of red cell velocity in different microcirculatory vessels was encountered. In some cases a fall in systemic pressure led to complete disappearance of red cells.

Animals↗
PubMed1984

Microbubble dynamics visualized in the intact capillary circulation.

The potential for the use of contrast echocardiography to study myocardial perfusion has generated efforts to develop standardized echo contrast agents. The two methods used in this laboratory to generate microbubbles in solutions serving as contrast agents included the widely used hand-agitation method and the newer ultrasonic microcavitation (sonication) method. The latter has been demonstrated to generate smaller and more uniform microbubbles in an in vitro system. The present study was designed to observe, by direct microscopic examination of a cat mesentery preparation, the behavior and fate of the microbubbles in an in vivo system. The in vivo mesentery observations confirm the critical role of microbubble size in its unhindered passage through the capillary vasculature. The smaller and more uniform sonicated microbubbles passed rapidly through the microcirculation along with the red blood cells, whereas the larger microbubbles were observed to coalesce and interrupt the flow of blood and subsequently collapse or shrink.

Animals↗
PubMed1983

The effect of 5-hydroxytryptamine and arterial blood withdrawal on cerebral microcirculation in the cat, arterial permeability in the rabbit.

Studies dealing with the effect of 5-HT on cerebral cortical microcirculation of cats and on permeability of femoral arteries to RISA of rabbits are presented. The effect of 5-HT on cerebral cortical microcirculation was compared to that of arterial blood withdrawal and blood reinfusion. The effect of topical administration of 5-HT was also studied. Cortical microcirculation was observed by transillumination using a microtransilluminator. Motion pictures were taken at a speed of 400 frames/sec. and a magnification of 3000X. Permeability was investigated using arterial RISA uptake in vessels perfused in vitro, with continuous recording of perfusion pressure. Microcirculatory studies revealed that arterial blood withdrawal and injection of 5-HT diminished red cell velocity, although to a different degree. With blood withdrawal and reinjection, good correlation existed between blood pressure and red cell velocity. In contrast, no correlation between blood pressure and red cell velocity was found after intracarotid injection of 5-HT. Reactive hyperemia was noted during reinfusion of blood. Both arterial blood withdrawal and 5-HT injection resulted in disappearance of red cells in individual vessels (unperfused channels). Good correlation of blood pressure with capillary red cell velocity during arterial blood withdrawal suggests absence of autoregulation in this portion of the microcirculation. Topical administration of 5-HT caused general vasoconstriction. Permeability to 5-HT to RISA followed a parabolic curve. With slight arterial vasoconstriction, permeability declined, while it rose with severe vasoconstriction.

Animals↗
PubMed1980

Toxicity, pharmacokinetics, and cholesterol-inhibitory effect of 7-ketocholesterol.

The possible toxic effect of intravenous 7-ketocholesterol (7-KC), a steroid which has been shown to inhibit cholesterol flux in the arterial wall, was investigated in rabbits. The histology, hematology and blood chemistry were compared in 4 control animals, 3 animals receiving high doses (5.50 +/- 0.33 mg/kg/day) and 4 animals injected with lower doses 1.85 +/- 0.28 mg/kg/day) of the oxygenated sterol. Each animal received a total of 16 injections at the rate of 2 injections per day. Pharmacokinetic studies on the disappearance rate of [4-(14)C]7-KC were also carried out. Pathologic changes in the organs of animals injected with 7-KC were few. In one animal exposed to the higher concentration of 7-KC, some granulomatous angiitis in the lung was noticed. Changes in the liver were not significantly different from those observed in the control animals. Inhibition of arterial flux of cholesterol (inhibition of 55%) was noticed with high and low doses of the oxidized sterol. The disappearance curves of [14C]cholesterol in blood and plasma were characteristic of a 2-compartment model. The rate constant determining tissue uptake of 7-KC was higher than tissue efflux and there was no appreciable reflux into red cells. The results indicate that it is possible to reduce cholesterol flux in the arterial wall of rabbits without causing major toxic changes and that both red cells and tissue act as a reservoir for the oxygenated sterol.

Animals↗