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C Quintana

Publications and source records attributed to C Quintana.

At least 55 records · Page 3Linked to original sources
PubMed1984

Effects of increased biliary resistance on bile secretion in the rat.

The effects of increased biliary resistance on bile secretion and biliary permeability properties were studied in rats. High biliary resistance produced significant reductions in bile flow and the secretion rate of cholesterol, but did not modify bile salt and phospholipid secretory rates. Decreased bile flow appeared to be secondary to a marked reduction in bile salt-independent fractions of bile flow, and bile salt-dependent flow was simultaneously increased. 14C-erythritol and 3H-inulin clearance studies suggest that decreased net canalicular secretion of water rather than increased water reabsorption at the biliary ducts is the mechanism involved in decreased bile flow. In addition, a marked increase in canalicular permeability to inulin was evident when rats were secreting against increased biliary resistance as well as during recovery.

Animals↗
PubMed1982

Observation and simulation of unstained DNA images in bright field TEM.

Images of unstained, unshadowed DNA prepared by the Kleinschmidt method have been obtained in bright field TEM with a usable contrast. Operating conditions include a strong defocus and a highly coherent illuminating beam. Observations suggest that a specific interaction exists between the nucleic acid and the carrier protein: cytochrome C. Computer simulations of beam-specimen interaction and of image formation were performed. The calculated dependence of contrast on defocus agrees qualitatively with the experimental results. We conclude that experiments with unstained biological specimens are feasible and are necessary (in spite of difficulties) to corroborate results obtained with stained material.

Chemical Phenomena↗
PubMed1982

[Effect of cobalt and vitamin B 12 on growth and survival of rumen ciliates in vitro as a function of bacterial population].

The effect of inorganic cobalt or organic cobalt in the form of vitamin B12 was studied on the growth of rumen ciliates in the presence of normal bacterial population and in the presence of reduced bacterial population. It was stated that concentration from 0.1 to 1 cobalt microgram/ml and 0.12 to 0.24 vitamin B12 microgram/ml stimulated growth of rumen ciliates. At rates 10 to 20 times weaker, cobalt in the form of vitamin B12 was more active than cobalt in inorganic form. With reduced bacterial population (10(3) B/ml) protozoa died within a few days but their survival was prolonged by adding cobalt, this effect being more pronounced with vitamin B12 than with inorganic cobalt. The growth of ciliates treated with antibiotics was stimulated by addition of bacteria, and this effect was more pronounced when the bacteria had been preincubated with cobalt. Incorporation of cobalt into rumen ciliates was studied using electron microprobe analysis. Cobalt was present in all the ciliate but essentially accumulated as granules in the endoplasm inside or outside the vacuoles. With reduced bacterial population, cobalt was also incorporated into the ciliates whatever the Co concentration. Indeed, ciliates seemed to need bacteria in order to use the organic cobalt for growth.

Animals↗
PubMed1981

The effect of complete biliary obstruction on bile secretion. Studies on the mechanisms of postcholestatic choleresis in the rat.

It has been previously shown that rats subjected to obstructive cholestasis demonstrate in the postcholestatic period, after release of common duct obstruction, a marked increase in canalicular bile flow relative to bile acid excretion. To characterize this phenomenon further, we investigated whether changes in canalicular permeability and in the activity of (Na+-K+)-ATPase in isolated liver surface membranes are associated with postcholestatic choleresis. With this purpose, the clearances of 14C-erythritol and 3H-insulin were simultaneously measured in rats subjected to a 3-day obstructive cholestasis and in controls, during spontaneous choleresis as well as during the intravenous infusion of sodium taurocholate at both submaximal and saturating rates. In additional groups of bile duct-ligated rats and controls, liver surface membrane fractions were isolated, and the activity of appropriate marker enzymes and (Na+-K+)-ATPase was determined. In both groups 14C-erythritol clearance closely approximated total bile flow, suggesting that bile flow was of canalicular origin. However, cholestatic rats showed a sixfold increase in 3H-inulin clearance compared to controls. These results suggest that canalicular permeability to inulin is markedly increased in cholestatic rats. On the other hand, (Na+-K+)-ATPase activity was significantly higher in cholestatic rats than in controls in both homogenate (1.27 +/- 0.07 and 0.89 +/- 0.07 U/mg of protein, respectively, p less than 0.001) and liver surface membranes (22.6 +/- 1.2 and 17.5 +/- 1.2 U/mg of protein, respectively, p less than 0.001). Thus enhanced choleretic response to bile acids in the postcholestatic period is associated with an increased permeability of canalicular structure to inulin and with a significant increase in both homogenate and surface membrane (Na+-K+)-ATPase activity. In addition, this study points out some important differences between bile secretory function of rats subjected to obstructive cholestasis and that described in models of bile secretory failure induced by drugs or monohydroxy-bile acids.

Animals↗
PubMed1980

Electron microprobe analysis of zinc incorporation into rumen protozoa.

With the aid of electron microprobe analysis on ciliate spreads, we detected zinc in ciliates and its accumulation in the endoplasm. A correlation was found between the amount of zinc accumulation and its concentration in the medium. By the same microprobe analysis of of ultrathin sections, we determined semiquantitatively the zinc accumulation in the intracytoplasmic granules and its presence in macronuclei and in intra- and extracellular bacteria.

Animals↗
PubMed1979

[Distribution of organic and inorganic carbon in tissues containing calcium carbonate by secondary ion emission microanalysis].

The differences of emissivity of secondary ions at masses 12 (C+ and C-), 24 (C2-) and 26 (C2H2- or CN-) of organic moitie and CO3Ca of semi thin sections of egg shell of quail allow the distinction between organic and inorganic carbon on images obtained with Secondary Ion Mass Spectroscopy. There differences of emissivity do not correspond only to the difference of concentration but to the difference of ionic yield. The emissivity at mass 26 (C2H2- or CN-) is higher than those obtained at mass 24 (C2-) in glycoproteinic material (rich in Nitrogen) and lower in the embedding material (Araldite, poor in Nitrogen). This result indicates that the ion present at mass 26 could by CN- rather than C2H2-.

Animals↗
PubMed1979

The effect of complete biliary obstruction on bile flow and bile acid excretion: postcholestatic choleresis in the rat.

Bile secretory function was studied in rats subjected to a 7-day obstructive cholestasis induced by complete common duct obstruction. Bile flow and bile acid excretion were examined during bile depletion, following the release of the biliary obstruction, and during the infusion of sodium taurocholate at submaximal and saturating rates. A highly significant increase, greater than 100%, in bile flow was evident in cholestatic rats at any bile acid excretory rate, when compared to control sham-operated rats. 14C-erythritol clearance measurements performed during bile depletion and during the infusion of taurocholate suggest that bile flow was mainly of canalicular origin in cholestatic rats. Estimated taurocholate transport maximum (mumol/min per rat) was not statistically different between cholestatic and control rats. However, significantly greater taurocholate plasma levels at Tm in cholestatic rats suggest a decreased efficiency of the bile acid transport process. In addition, the relationship between bile flow and bile acid excretion was found to be nonlinear at low bile acid excretory rates in cholestatic rats. Thus important changes in bile formation occurred in rats subjected to temporary obstructive cholestatis, which differ from those observed in other models of cholestasis that are associated to a reduction in bile flow and bile acid transport capacity.

Animals↗
PubMed1978

[The shell of the quail's egg: ultrastructural and crystallographic study (author's transl)].

The egg-shell of Japanese quail was studied by several techniques. Semithin sections (1 micron thick) of non-decalcified shell were observed by normal and polarized light microscopy. Thin sections of non-decalcified shell, examined by transmission electron microscopy, permitted us to observe the forms and dimensions of crystals of calcite within different layers of the shell: mammilary layer, layer of cones, palissade layer and surface crystal layer. There appears to be two distinct zones in the layer of cones as well as in the superficial crystal layer. Electron microdiffraction revealed the orientation of calcite crystals in the columns. Some crystal defects (twins?) were described and the possibility of their artefactual formation during ultramicrotomy is discussed. Localization of Ca, Mg, P and S were made by X-ray microanalysis of semithin sections. This technique shows that shell membranes, and chiefly the true cuticle, are also mineralized but, in these layers, minerals are not crystallized. Otherwise the distribution of Mg is not uniform throughout the shell thickness; it is less concentrated in the external zone of the layer of cones. These results together with observation of developing shells by scanning electron microscopy allowed us to propose a scheme for shell organization of the quail egg. This organization was related with decalcification which occurs during hatching.

Animals↗