Showing papers by "National University of La Plata published in 1977"
TL;DR: The delta6 desaturation of unsaturated acyl-CoA is the first reaction involved in the normal biosynthesis of all polyunsaturated fatty acids families in animal microsomes and is sensitive to hormones concentration.
Abstract: Polyunsaturated fatty acids are synthesized in animals by a sequence of desaturation and elongation reactions which, as we know now, follow special rules. The starting substrates are CoA thioesters of palmitoleic, oleic, linoleic and α linolenic acids. The acyl-CoA synthesis is faster than elongation or desaturation reactions (Marcel and Suzue, 1972). The enzymes involved in the elongation are found either in the endoplasmic reticulum or in mitochondria but the specificity of each group is different. The microsomal system prefers Δ6 unsaturated acyl-CoA and hexanoyl CoA whereas the mitochondrial prefers medium chain acyl-CoA (Podack et al, 1974; Hinsch and Seubert, 1975).
146 citations
TL;DR: In this paper, the unit cell parameters of AlVO4 have been determined from powder diagrams and the infrared spectra of the system has been recorded and discussed using a series of solid solutions in the system.
Abstract: The unit cell parameters of AlVO4 have been determined from powder diagrams. The compound pertains to the triclinic system and is isostructural wi7h FeVO4. The infrared spectra of AlVO4 and FeVO4 and of a series of solid solutions in the system AlVO4/FeVO4 has also been recorded and discussed.
54 citations
TL;DR: In this article, the authors studied the metabolic activity of endogenous substrates by microsomes and found that they are involved in drug metabolism and drug metabolism reviews: Vol. 6, No. 2, pp 155-212.
Abstract: (1977). Metabolism of Endogenous Substrates by Microsomes. Drug Metabolism Reviews: Vol. 6, No. 2, pp. 155-212.
49 citations
TL;DR: The relaxing effect of the beta agonist seems to be related to the activation of the protein kinase system since perfusions with dibutyryl 3',5'-cAMP had a greater effect on the relaxation of the hearts.
Abstract: The relaxing effect of two positive inotropic interventions was studied in the isolated rat heart beating at constant rate and perfused at constant coronary flow. Experiments were performed under i...
43 citations
TL;DR: In this article, the electric field gradient in hafnium pyrovanadate has been measured at Hf sites at different temperatures with the time-differential perturbed angular correlation method.
Abstract: The electric field gradient EFG in hafnium pyrovanadate has been measured at Hf sites at different temperatures with the time-differential perturbed angular correlation method. The results obtained show the existence of a phase transition around 110°C.
29 citations
TL;DR: In this article, the powder diagramm of CeP2O7 has been reinvestigated and the presence of a superlattice was definitively proved, also the infrared spectrum of the compound has been recorded and interpreted.
Abstract: Das Pulverdiagramm von CeP2O7 wurde erneut untersucht und ausgewertet, das Vorhandensein einer Uberstruktur-Zelle konnte jetzt eindeutig bestatigt werden. Auch das IR-Spektrum der Verbindung wurde aufgenommen und gedeutet. Die Untersuchung des thermischen Verhaltens der Substanz zeigte, das bei Temperaturen uber 700°C eine langsame Zersetzung beginnt, welche durch O2- und P4O10-Abgabe und intermediarer Bildung von CeP3O9, zu reinem CePO4 fuhrt.
Crystallographic Data, IR Spectrum, and Thermal Behaviour of Cerium(IV) Diphosphate
The powder diagramm of CeP2O7 has been reinvestigated and the presence of a superlattice was definitively proved. Also the infrared spectrum of the compound has been recorded and interpreted. The investigation of the thermal behaviour of the substance shows that at temperatures higher than 700°C a slow decomposition begins which, under evolution of O2 and P4O10 and the intermediate formation of CeP3O9, finally gives pure CePO4.
27 citations
01 Jan 1977
TL;DR: In vitro studies of fatty acid synthesis in which liver supernatant of 105,000 xg and microsomal preparations were incubated with the hormone showed that thyroxine inhibits de novo synthesis of palmitate and stimulates the desaturation reactions.
Abstract: Many studies have revealed that thyroid hormones markedly affect lipid metabolism in man and in several species of animals. Concerning fatty acid biosynthesis it was demonstrated that the administration of thyroxine stimulates the incorporation of l–14c acetate into fatty acids in rats and mice (Dayton et al, 1960) (Gompertz and Greenbaum, 1966) (Marchi and Mayer, 1959). According to Gompertz and Greenbaum (1966) these observations appear to be associated with an increase of stearyl-CoA desaturase activity. Moreover Myant and Iliffe (1963) found that rats treated with thyroxine showed an inhibition of acetate incorporation, but not of malonate incorporation, into fatty acids by mitochondria free, subcellular liver preparations. Other authors have shown that the thyrotoxic state was accompanied by an increased incorporation of acetyl-CoA to fatty acid and a rise in the activity of fatty acid synthetase in rat livers (Diamant et al, 1972) (Roncari and Murthy, 1975). However, in vitro studies of fatty acid synthesis in which liver supernatant of 105,000 xg and microsomal preparations were incubated with the hormone showed that thyroxine inhibits de novo synthesis of palmitate and stimulates the desaturation reactions (Faas et al, 1972).
23 citations
TL;DR: By a mathematical approach, the endogenous pool size of α-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, and the capacity of the cell to convertα-linoleic acid to eICosa-4,9,12,15,15-tetraenoic acids, were calculated.
Abstract: Minimal Deviation Hepatoma 7288 C cells were cultured in confluent layer with labeled stearic, oleic, linoleic andα-linolenic acids. The kinetics of incorporation and conversion to higher homologs was studied. The maximum amounts incorporated in nmoles per mg of cellular protein for stearic, oleic, linoleic andα-linolenic acids were 39, 115.6, 90 and 230 respectively.α-linolenic acid was converted to octadeca-6,9,12,15-tetraenoic acid (18:4), eicosa-11,14,17-trienoic acid (20:3), eicosa-8,11,14,17 and 5,11,14,17-tetraenoic acids (20:4) and eicosa-5,8,11,14,17-pentaenoic acid (20:5), and also to myristic, palmitic, palmitoleic, stearic and oleic acids. By a mathematical approach, the endogenous pool size ofα-linolenic acid available for conversion to eicosa-5,8,11,14,17-pentaenoic acid, and the capacity of the cell to convertα-linolenic acid to eicosa-5,8,11,14,17-pentaenoic acid, were calculated. Both values decreased when the cells were preincubated with unlabeledα-linolenic acid.
19 citations
07 Dec 1977
TL;DR: The earliest Cenozoic record of amphibians and reptiles in South America consists of remains of turtles and crocodiles from the Lower Paleocene as mentioned in this paper. But they do not constitute a representative sample of the herpetofauna then inhabiting that continent, for the deposits of that age that have hitherto yielded fossils correspond to a peculiar facies.
Abstract: Originis and evolution of the Cenozoic amphibians and reptiles of South America?. The earliest Cenozoic record of amphibians and reptiles in South America consists of remains of turtles and crocodiles from the Lower Paleocene. But they do not, however, constitute a representative sample of the herpetofauna then inhabiting that continent, for the deposits of that age that have hitherto yielded fossils correspond to a peculiar facies. Fortunately a rich and diversified assemblage of Late Paleocene age gives a more complete picture of the groups living at that time. Within this assemblage it is possible to recognize elements of different historical background that joined the South American fauna heterochronously.
18 citations
TL;DR: The Δ6 desaturase recognizes the number of double bonds of the substrate since α-linolenate is desaturated faster than linoleate and this one faster than oleate, however, it is not known yet the effect of the chain length of the acid on the activity of the enzyme.
Abstract: Oleic, linoleic and α-linolenic acids are desaturated by the same microsomal enzyme called Δ6 desaturase since it introduces the double bond between carbons 6–7 (Brenner and Peluffo, 1966; Brenner, 1971; Inkpen et al, 1969; Brenner, 1974). This enzyme is different from the Δ5 desaturase that converts eicosa-8, 11-dienoic, eicosa-9, 11, 14-trienoic and eicosa-8, 11, 14, 17-tetraenoic acids to eicosa-5, 8, 11-trienoic, eicosa-5, 8, 11, 14-tetraenoic and eicosa-5, 8, 11, 14, 17-pentaenoic acids respectively. (Ninno et al, 1974; Alaniz et al, 1975; Gaspar et al, 1975). It is also different from the Δ9 desaturase (Brenner, 1971). The Δ6 desaturase recognizes the number of double bonds of the substrate since α-linolenate is desaturated faster than linoleate and this one faster than oleate (Brenner and Peluffo, 1966). However, it is not known yet the effect of the chain length of the acid on the activity of the enzyme.
16 citations
TL;DR: The existence in toad cardiac muscle of a mechanism that tends to return contractility to control levels after a change in Pco is defined, and this mechanism, present even after inhibition of catecholamine action, completely counteracts the primary negative inotropic effect of high Pco, and the positive inotropic action of hypocapnia.
Abstract: SUMMARY Experiments were performed on strips dissected from toad ventricles driven at a constant frequency of 12 beats/min. After equilibration, the Pco2 of the medium was altered from 25 to 95 mm Hg or from 95 to 25 mm Hg. Developed tension (DT) and maximal rate of tension development (dT/dW,) were recorded during a 30-minute period after the change in Pco 2. In the first experimental series at 30°C, increasing Pco, resulted in a decrease in DT and dT/dtmas, followed by a recovery of contractility that reached levels higher than controls. In the second and third series, performed after the addition to the bath of practolol (1 x 10"" M) or after reserpinization, high Pco, depressed contractility but the recovery did not surpass control values after 30 minutes of hypercapnia. In this series, when high PcO; was replaced by low Pco, there was an increase in DT and dT/dtmax followed by a decrease that reached control levels within a 30-minute period. In the fourth series, at 22°C the significant decreases in DT and dT/dtmax observed after increasing Pco, were followed by a recovery that surpassed control values. These results define the existence in toad cardiac muscle of a mechanism that tends to return contractility to control levels after a change in Pco,. Within 30 minutes this mechanism, present even after inhibition of catecholamine action, completely counteracts the primary negative inotropic effect of high Pco, and the positive inotropic action of hypocapnia.
TL;DR: An indirect method for the rapid estimation of individual carotenoids of P. tricornutum is proposed and its eventual application to other Chrysophyta species and to sea water is discussed.
Abstract: The equations of Parsons and Strickland (1963) have been applied to calculate the concentration of total carotenoids in Phaeodactylum tricornutum, and the same pigments have simultaneously been determined on the individual fractions after TLC (thinlayer chromatography) separation. Comparison of both sets of data shows that for diverse carotenoids: chlorophyll a ratios, the direct spectrophotometric values range from 80 to 130% of the chromatographic values; wide variations in the proportions of different carotenoids account for such difference. On the basis of correlations between the proportion of each carotenoid and the absorbance ratio 480:663 nm, an indirect method for the rapid estimation of individual carotenoids of P. tricornutum is proposed. Its eventual application to other Chrysophyta species and to sea water is discussed.
TL;DR: In this paper, a Radiokohlenstoffdatierung an eingelagertem organischen material bestatigt das angenommene Alter and legt gleichzeitig ein Interstadial fest (Interstadial Aguamiro, 12 500 Jahre B.P.).
Abstract: Der Gebirgszug Raura im zentralen Peru (ungefahr 10° 25′ sudl. Breite und 76° 45′ westl. Lange) ist ein wichtiger Gletscherkernpunkt an der Kontinentalwasserscheide. An seiner NO-Seite, wo der Maranon bzw. Amazonas entspringt, lassen sich im Gebiet von Lauricocha eine Reihe alter Gletschervorstose nachweisen, die der letzten pleistozanen Vereisung der Anden zugeordnet werden (A.Cardich, 1958, 1963, 1964). Eine Radiokohlenstoffdatierung an eingelagertem organischen Material bestatigt das angenommene Alter und legt gleichzeitig ein Interstadial fest (Interstadial Aguamiro, 12 500 Jahre B.P.). Die Gletschervorstose vor diesem Zeitpunkt waren bedeutender, sowohl in ihrer Ausdehnung und der Eismachtigkeit (bis 300 m) als auch in ihrer Dauer. Die spateren Vorstose waren kleinraumiger und kurzlebiger, wie aus dem geringeren Volumen der glazialen Ablagerungen hervorgeht. Ein Vergleich mit anderen untersuchten Gebieten unterstutzt bei Berucksichtigung der14C-Datierung grostenteils die fruher aufgestellte Systematik.
TL;DR: In this article, it is shown that using the available data for 0+ → 0+ superallowed transitions it is possible to extract a meaningful upper limit for the induced scalar coupling constant ƒs.
01 Dec 1977
TL;DR: In this article, the electron capture to positron emission ratios for allowed Gamow-Teller transitions from the decay of 22Na and 65Zn were measured and compared with theoretical results.
Abstract: The electron capture to positron emission ratios for allowed Gamow-Teller transitions from the decay of22Na and65Zn were measured. The values ɛ/gb+=0.1128±0.0057 andK/Β
+= 31.3±2.0 were obtained for22Na and65Zn, respectively. A detailed comparison with previous data is made. Theoretical ratios were calculated using the most recent Fermi and Coulomb functions. It was found an excellent agreement between our experimental data and the theoretical results evaluated without including contributions due to induced interactions.
TL;DR: In this paper, a study was made of electrodeposits of copper onto highly perfect electropolished (001) faces of copper single crystals of purities: Tough Pitch, OFHC (99.98%), and High Purity ( 99.99%), and the dependence of the structure in relation to the current density and to the deposit thickness was determined by X-ray diffraction.
TL;DR: Rat liver microsomes have the capacity to convert stearoyl CoA to oleylCoA by an enzymatic reaction requiring both oxygen and the integrity of the NADH-linked microsomal electron transport chain of which Δ9 desaturase is the terminal component.
Abstract: Rat liver microsomes have the capacity to convert stearoyl CoA to oleyl CoA by an enzymatic reaction requiring both oxygen and the integrity of the NADH-linked microsomal electron transport chain of which Δ9 desaturase is the terminal component (Wilson et al., 1967).
TL;DR: After water loading, rats bearing ocular grafts of the pars intermedia of the pituitary showed that the content of sodium increased in urine, whereas potassium excretion and diuresis did not vary significatively.
Abstract: After water loading, rats bearing ocular grafts of the pars intermedia of the pituitary showed that the content of sodium increased in urine, whereas potassium excretion and diuresis did not vary significatively. These results suggest that in the rat the pars intermedia is involved in the regulation of the electrolyte metabolism.
TL;DR: HTC cells (designated HTC for hepatoma tissue culture) were derived from the ascites form of a rat-carried Morris hepatoma 7288 C and it was demonstrated that culture HTC cells preserved the ability to desaturate stearic to oleic acid, α-linolenic acid to octdeca-6, 9,12,15-tetraenoic acid and eicosa-8, 11, 14-trienoic acid.
Abstract: HTC cells (designated HTC for hepatoma tissue culture) were derived from the ascites form of a rat-carried Morris hepatoma 7288 C (Thompson et al, 1966). Previous studies have revealed that cells of this kind are able to desaturate and elongate fatty acids. In this respect it was demonstrated that culture HTC cells preserved the ability to desaturate stearic to oleic acid (Δ9 desaturase), α-linolenic acid to octdeca-6, 9,12,15-tetraenoic acid (Δ6 desaturase), and eicosa-8,11,14-trienoic acid to arachidonic acid (Δ5 desaturase) (Alaniz et al, 1975). They are also able to convert α-linolenic acid to higher homologs with 5 and 6 double bonds by desaturation and elongation reactions. These results also proved the existence of Δ4 desaturase activity (Alaniz et al, 1975). However, it was shown that the cell cultured in Swim’s medium supplemented with serum possessed a very low capacity to convert labeled linoleic acid of the medium to arachidonic acid. Nevertheless, these tumor cells readily converted eicosa-8,11,14-trienoic acid to arachidonic acid (Alaniz et al, 1975; Gaspar et al, 1975). Therefore, the difficulty of these cells to synthesize arachidonic acid from linoleic acid may reside in a step previous to the Δ5 desaturation of eicosa-8, 11, 14-trienoic acid. This step could be a Δ6 desaturation of linoleic acid. The discrepancy between the biosynthesis of linoleic and α-linolenic acid series is difficult to explain considering that the same enzyme desaturates linoleic and ±-linolenic acids in Δ6 position (Brenner and Peluffo, 1966) (Brenner, 1971; Brenner, 1974) (Ninno et al, 1974).
TL;DR: In this paper, the infrared spectra of the title compounds, as well as that of the structurally related mineral meta-autunite, [Ca(UO2)2(PO4)2·n H2O], are reported and discussed using the available crystallographic data.
Abstract: The infrared spectra of the title compounds, as well as that of the structurally related mineral meta-autunite, [Ca(UO2)2(PO4)2·n H2O], are reported and discussed using the available crystallographic data. The results can be considered as representative for the full group of the so-called “torbernite”-minerals.
TL;DR: It has been established that the enzyme system involved in stearyl-CoA desaturation reaction has three integral components of the microsomal membrane: the NADH-cytochrome b5 reductase, cyto Chrome b5 and the desaturase.
Abstract: It has been established that the enzyme system involved in stearyl-CoA desaturation reaction has three integral components of the microsomal membrane: the NADH-cytochrome b5 reductase, cytochrome b5 and the desaturase (Gaylor et al, 1970; Holloway et al, 1970; Holloway, 1971; Oshino et al, 1971, Shimakata et al, 1972). All these components have been separated and purified (Strittmatter et al, 1974; Enoch et al, 1976).
TL;DR: In this article, the potentiostatic current of Fe, Co and Ni in molten LiNO2, NaNO3 and KNO3 eutectic is studied in both the passive and transpassive regions.
TL;DR: In this article, the competition between pairing and multipole fields is studied within the framework of a two-level model, employing different theoretical approaches, and the importance of a self-consistent tretment is clearly revealed.
Abstract: The competition between pairing and multipole fields is studied within the framework of a two-level model, employing different theoretical approaches. The importance of a self-consistent tretment is clearly revealed. Special attention is payed to the microscopic mechanisms that take place when the system undergoes various phase transitions.
TL;DR: In this paper, the hyperfine interaction of 140Ce in nickel has been investigated by the time-differential perturbed-angular-correlation technique (TDPAC), which was produced by isotope separator implantation of the fission product140Xe, the β- decay chain of which finally populates excited states of140Ce.
Abstract: The hyperfine interaction of140Ce in nickel has been investigated by the time-differential perturbed-angular-correlation technique (TDPAC). The probe was produced by isotope separator implantation of the fission product140Xe, the β- decay chain of which finally populates excited states of140Ce. Different spin rotation spectra were observed before and after an 8 h annealing at 415°C. The analysis of the spectra led to the conclusion that the Ce ions were in the diamagnetic 4+ state. The dominant contributions to the hyperfine interaction are two different magnetic hyperfine fields: |H
hf
1|=385±7 kOe and |H
hf
2|=276±12 kOe.H
hf
1 disappears after annealing. The fraction of nuclei which observeH
hf
2 is increased by the annealing procedure from 16% to 75%. It is assumed thatH
hf
1 is the hyperfine field of CeNi in an unperturbed substitutional site andH
hf
2 is attributed to Ce ions which have trapped a single vacancy.
TL;DR: In this paper, the influence of peroxide groups on the bond properties of the other ligands and some characteristics of the metal-peroxide interactions are analyzed, and the infrared spectra of the title compounds are reported and discussed.
Abstract: The infrared spectra of the title compounds are reported and discussed. The influence of the peroxide groups on the bond properties of the other ligands and some characteristics of the metal—peroxide interactions are analyzed.
TL;DR: The infrared and electronic spectra of NH4[VO(O2)2NH3] are recorded and interpreted in this article, where the results are discussed and some comparisons with related species are made.
Abstract: The infrared and electronic spectra of NH4[VO(O2)2NH3] are recorded and interpreted. The results are discussed and some comparisons with related species are made.
TL;DR: Tumor cells are known to differ from normal cells in lipid metabolism, and laboratories have focused their interest to make some insight on the relationship between malignancy and alteration in cholesterol metabolism.
Abstract: Tumor cells are known to differ from normal cells in lipid metabolism. Many laboratories have focused their interest to make some insight on the relationship between malignancy and alteration in lipid metabolism, since lipids are recognized in their importance as components of membrane structures.
TL;DR: The equations of Fonds, Brinkmann and Los allow a more exact theoretical evaluation of pulse polarographic phenomena than it is possible with their counterparts in classical polarography.