Showing papers by "National University of La Plata published in 1971"
128 citations
TL;DR: The serum glucose and immunoreactive insulin levels were determined in mice during a 24-hr period and showed a clear circadian rhythm, having their highest and lowest values located in the resting (light) and activity (darkness) period, respectively.
Abstract: The serum glucose and immunoreactive insulin levels were determined in mice during a 24-hr period. Both parameters showed a clear circadian rhythm, having their highest and lowest values located in the resting (light) and activity (darkness) period, respectively. However, they were not hourly coincident, since the glucose peak preceded the insulin peak by 4 hr. This fact is explained on the basis of hormone interaction during the day. The present results show the importance of chronobiology in endocrine studies. {Endocrinology 88:1529,1971) A LTHOUGH glucose has been pointed out as J\. the most physiological stimulus for insulin release, several other substances have been described as having such effect upon this process. Agents capable of inducing the secretion of insulin are certain aminoacids (1), short chain fatty acids (2), tolbutamide (3), glucagon (4), cyclic AMP (5). On the other hand, several hormones are able to modify the pancreatic beta cell behavior; e.g., catecholamines block the glucose-induced insulin secretion (6), whereas this secretion is enhanced in the presence of hormones like growth hormone (7) and corticoids (8). Hence, both the serum insulin levels and the pancreatic response in the whole animal must be considered a multiple-dependent process rather than a simple stimulus-secretory response interaction. On the basis of this assumption, the beta cell effect of any substance administered to an experimental animal would be conditioned by the action of the animal's intrinsic regulators at that moment. Since our main field of interest is related to the regulatory mechanisms of insulin secretion, we assumed that it should be important to study the spontaneous fluctuations of both the serum glucose and immunoreactive insulin (IRI) levels during the 24-hr period. Materials and Methods Female mice of the C3H-S strain, 10 weeks old, from the Instituto de Embriologia, Biologia e Histologia, Facultad de Ciencias Medicas, UniReceived December 4, 1970. This paper was partially supported with funds from the Consejo Nacional de Investigaciones Cientificas y Te"cnicas de la Republica Argentina (Grant 3477a/69), Comisidn de Investigaciones Cientificas de la Universidad Nacional de La Plata and Comisidn de Investigaciones Cientificas de la Provincia de Buenos Aires. versidad Nacional de La Plata, were used. They were caged in a room at a temperature of 25 ± 1 C with water and food ad lib. and illumination (fluorescent light 40W) from 0600 (6 AM) to 1800 (6 PM) alternating with 12 hr darkness. Since the animals engage in exercise and food intake only during the darkness period, this is called the "activity period," the other one being the "resting period" (9). This nomenclature provides an appropriate way to compare animal and human experiments. Lots of 40 animals each were bled through a retro-orbital plexus with a heparinized capillary tube at 0000, 0400, 0800, 1200, 1600 and 2000 hr on different days. The blood collected at every time point was divided into several pools in order to obtain a suitable volume for the glucose and IRI determinations. The serum obtained after centrifugation was kept frozen at — 20 C until the determinations were performed. Glucose concentration and IRI levels were determined by the Otoluidine (10) and the charcoal-dextran immunoassay method (11), respectively.
45 citations
TL;DR: Circadian variations in DNA synthesis after tritiated thymidine and autoradiography, mitotic activity with the Colcemid method, and cell size, represented inversely by the number of cells per microscopic field are reported for the hepatocyte population of the young immature growing liver of the male mouse.
Abstract: Circadian variations in DNA synthesis after tritiated thymidine and autoradiography, mitotic activity with the Colcemid method, and cell size, represented inversely by the number of cells per microscopic field, are reported for the hepatocyte population of the young immature growing liver of the male mouse. The peak of DNA synthesis is at 04:00 hours and that of mitotic activity at 12:00 hours. The 8-hour interval between the two peaks is considered, in agreement with other authors, a good estimation of the lag period between DNA synthesis and the initiation of mitotic activity. The minimum cell number per microscopic field, which is considered to correspond to the maximum cell size, coincides with the starting of the circadian mitotic wave. The significance of this coincidence and the relationships of the circadian curves of the parameters controlled with the feeding pattern and food consummatory curve of standardized mice, are discussed.
39 citations
TL;DR: In this article, the authors established the following result: if X is a nonsingular, compact, connected, analytic space (resp. a complete algebraic variety over C) of dimension m and Y is an arbitrary closed subvariety of X, U = X E, then the standard exact sequences 1)..---+ HI(U, C ), HP(X, C)-* He(Y, C), C)--~Hy + '(U,C)-+...
Abstract: Our principal application of the techniques developed in this note appears in w 7 where we establish the following result. Let X be a nonsingular, compact, connected, analytic space (resp. a complete algebraic variety over C) of dimension m and let Y be an arbitrary closed subvariety of X, U = X E Then the standard exact sequences 1) ..---+ HI(U, C ) , HP(X, C)-* He(Y,, C)--~Hy + '(U, C)-+ . . . 2) . . . < H e m p ( g , C ) ~ ~ H 2 m p ( x , C ) , ~ H 2 m p ( x , C )
35 citations
TL;DR: New carbon-14 dates presented here, on the nutshell and a trash heap, confirm this to be the oldest viable seed known.
Abstract: THE longevity of a viable seed of Canna considered to be about 550 years old1–3 has been questioned by Godwin4. The specimen, enclosed in a Juglans australis nutshell forming part of a rattle necklace was collected from tomb 92 in Santa Rosa de Tastil, Argentina. New carbon-14 dates presented here, on the nutshell and a trash heap, confirm this to be the oldest viable seed known.
33 citations
TL;DR: The mass spectral decomposition modes of hydantoin and derivatives containing alkyl and phenyl substituents have been investigated using isotopic labeling techniques as discussed by the authors, and the loss of carbon monoxide from the molecular ions of these compounds was shown to preferentially involve the C-4 carbonyl group.
Abstract: The mass spectral decomposition modes of hydantoin and derivatives containing alkyl and phenyl substituents have been investigated using isotopic labeling techniques. The loss of carbon monoxide from the molecular ions of these compounds was shown to preferentially involve the C-4 carbonyl group. Other fragmentation processes characteristic of the hydantoin ring system and the effect on this of alkyl and phenyl substitution are described.
30 citations
TL;DR: The infrared spectra of LnVO4 (LnCe, Pr, Nd, Sm, Eu and Gd) compounds are recorded between 4000 and 300 cm−1 and interpreted using the site symmetry rules as discussed by the authors.
Abstract: Die Infrarotspektren der Verbindungen LnVO4 (LnCe, Pr, Nd, Sm, Eu und Gd) wurden im Bereich zwischen 4000 und 300 cm−1 untersucht und mittels der “Site-Symmetrie-Regeln” diskutiert.
The infrared spectra of LnVO4 (LnCe, Pr, Nd, Sm, Eu and Gd) compounds are recorded between 4000–300 cm−1 and interpreted using the “site symmetry” rules.
26 citations
TL;DR: Electro microscopic data suggest increased synthesis and release of growth hormone in STH cells stimulated by hepatectomy and may also suggest increase in the number of large lysosomes of the autophagic vacuole type.
Abstract: An electron microscopic analysis was performed on the pars distalis of the hypophysis of hepatectomized mice. Intact and sham operated mice served as controls. The STH cells presented striking changes that were most intense and widespread in those animals sacrificed at midnight of the second day after hepatectomy. These changes can be summarized as follows: 1) Hypertrophy of the Golgi complex with increased number of immature granules within the Golgi zone. This change appeared also in otherwise unmodified STH cells. 2) Strong dilatation of the endoplasmic reticulum whose cisternae contained much electron dense material. 3) Granules with partially diminished electron density, some of them in spatial relation with the plasma membrane and others swelling and bursting within the cytoplasm. All transitions between unchanged 350–400 mμ granules and extremely altered ones, were seen. 4) Release sites, characterized by dense zones in the plasmalemma, close to aggregates of electron lucent microvesicles, and almost empty granule membranes. 5) Increase in the density of the mitochondria which appeared grouped near the Golgi zone. 6) Increase in the number of large lysosomes of the autophagic vacuole type. 7) Irregular nuclear outlines. These data suggest increased synthesis and release of growth hormone in STH cells stimulated by hepatectomy.
24 citations
TL;DR: In this paper, the electrochemical behavior of passivated iron electrodes in molten alkali nitrites has been investigated in the range of temperature from 230 to 310°C, and the first potentiostatic steady E/i curve is characterized by four different regions.
16 citations
TL;DR: In this paper, the dependence of electrical resistance R on thickness d and annealing temperature TT has been studied on thin cobalt films formed by deposition of the vapour at 77 °K, and the intrinsic resistivity ρ0, that films would have if there were no size effects has also been obtained through the Fuchs-Sondheimer theory.
15 citations
TL;DR: Se sugiere that el factor estimulante del plasma de ratones hepatectomizados en hormona de crecimiento se estimula al igual que la hormona oferta pura, la síntesis de ADN de los hepatocitos y células litorales del hígado del ratón adulto intacto.
Abstract: El plasma de ratones hepatectomizados, recogido a la medianoche del segundo dia de la regeneracion, estimula, al igual que la hormona de crecimiento pura, la sintesis de ADN de los hepatocitos y celulas litorales del higado del raton adulto intacto. Este efecto no se observa con el plasma de ratones intactos sacrificados a medianoche ni con solucion fisiologica. Se sugiere que el factor estimulante del plasma de ratones hepatectomizados en hormona de crecimiento.
TL;DR: In this article, the authors investigated the film growth process occurring on platinum anodes when molten potassium thiocyanate is electrolysed at 190°C and investigated the kinetics of the process by the application of different relaxation techniques.
TL;DR: In this paper, the infrared spectra of perfluoromethyl perfluoroacetate (PFoacetate) and perfluoric carbonate (PC carbonate) in the gaseous (4000-400 cm−1) and solid phases (2000-600 cm −1) were presented and interpreted.
TL;DR: The kinetics of polycrystalline iron electrodes have been investigated under different experimental conditions, employing solutions of hydrogen chloride in dimethylsulphoxide in the presence of KClO4 as supporting electrolyte.
TL;DR: In this article, the anodic E/I curve shows a limiting current which is directly proportional to the nitrite-ion concentration, and is studied under convective diffusion control.
TL;DR: It was found that both, the protein content and the aminoacid incorporation values, depend on the time of the circadian period at which the experiment was performed, and the highest values for protein were found during the activity period while the corresponding incorporation ones were located within the resting period.
Abstract: The protein content of mouse diaphragm at different times of the year, as well as the C14‐leucine incorporation into that protein were studied. Lowry's method was employed for the protein estimation. The aminoacid incorporation was determined one hour after the in vivo administration of C14‐labelled leucine in the previously extracted diaphragmatic protein, with the aid of a liquid scintillation spectrometer. It was found that both, the protein content and the aminoacid incorporation values, depend on the time of the circadian period at which the experiment was performed. The highest values for protein were found during the activity period while the corresponding incorporation ones were located within the resting period. Furthermore, a seasonal variation of the circadian protein rhythm was found. These results stress again the importance of circadian variations in experimental biology.
TL;DR: In this article, the photochemical O 3 decomposition at 2537 A has been investigated in a static system at 5° and 25°C, where the O 3 pressure was varied between 10 and 100 torr, the O 2 pressure between 0.1 and 300 torr.
TL;DR: In this article, the electrochemical behavior of pure iron anodes in molten KHSO4 at 250°C was studied and a transition time related to the onset of full passivity was determined.
TL;DR: In this paper, the liquid phase formation of mesityl oxide from diacetone alcohol was studied, which involves a system of three parallel reactions, and differential reactor data were used to obtain kinetic equations of the Langmuir-Hinshelwood type by means of nonlinear regressions.
TL;DR: In this paper, the passivation of polycrystalline iron electrodes in solutions of HCl in DMSO has been studied and steady current/potential curves were determined and potential-sweep voltammetry has been applied.
TL;DR: The early increase of serum potassium by epinephrine was reduced and delayed by the beta blocking agent; the hypokalemic effect was clearly prevented by the three doses of propranolol used, suggesting a possible relation between the mechanism producing Hypokalemia and the beta adrenoceptors blocked by proPRanolol.
01 Jan 1971
TL;DR: In the kinetic study of heterogeneous reactions, which comprises, among others, electrode reactions, it is necessary to take into account the rates of the reacting species in reaching the reaction interface as mentioned in this paper.
Abstract: In the kinetic study of heterogeneous reactions, which comprises, among others, electrode reactions, it is necessary to take into account the rates of the reacting species in reaching the reaction interface. In this sense, particularly for electrochemical reactions, much work has been done with the double purpose of establishing the phenomenological laws linked to the transport phenomena, and of elucidating the inner mechanism of this type of process.
TL;DR: Pudo demostrarse that los tres parámetros presentaron una clara variación circadiana, coincidiendo la aparición oficial de los valores máximos y mínimos para todos ellos durante el período of actividad (oscuridad) and reposo (luz) respectivamente.
Abstract: El contenido diafragmatico de proteina, glucogeno y DNA fue estudiado a intervalos de 4 h durante las 24 h. Los animales empleados fueron ratones hembras mantenidos en cuartos con periodos de luzoscuridad de 12 h cada uno. Pudo demostrarse que los tres parametros presentaron una clara variacion circadiana, coincidiendo la aparicion de los valores maximos y minimos para todos ellos durante el periodo de actividad (oscuridad) y reposo (luz) respectivamente.
TL;DR: The formazan did not give high contrast in the optical microscope, but localization with the EM was good, and lead staining was essential to secure good contrast.
Abstract: A new tetrazolium salt, yellow tetrazolium, has been used to localise succinatetetrazolium reductase with the electron microscope. As expected, the formazan did not give high contrast in the optical microscope, but localization with the EM was good. The size of the formazan granules was 60–100A; lead staining was essential to secure good contrast.
TL;DR: The formation constants of the systems cobalt(II)-acetate and cobalt-II-propionate have been measured at 25 and 50°C, ionic strength 1·0 and pH 5·0, using the ion-indicator polarographic method with slight modifications.
TL;DR: In animals bearing a fast growing as well as in those bearing a slow growing hepatoma, the STH cells presented changes indicating increased release and synthesis of its secretory product.
Abstract: An electron microscopic analysis was performed on the pars distalis of the hypophysis of mice bearing transplanted hepatomas. Normal mice served as controls. In animals bearing a fast growing as well as in those bearing a slow growing hepatoma, the STH cells presented changes indicating increased release and synthesis of its secretory product. These changes can be summarized as follows: 1) Increased number of granuledepleted STH cells which were very irregular in size and shape. 2) Very irregular and sometimes bizarre nuclei. 3) Plasma membranes irregular and convoluted. 4) Increased quantity of endoplasmic reticulum which appeared sometimes dilated and contained material of varying electron density. 5) Abundant, irregular and frequently ramified mitochondria. 6) Hypertrophic Golgi system with increased number of microvesicles. 7) Increased number of large lysosomes of different type. 8) Increased number of fat droplets.
01 Jan 1971
TL;DR: In this article, a biological fuel cell comprising a bioelectrode using a strain of Micrococcus cerificans metabolizing n-hexadecane and an oxygen electrode is described.
Abstract: A biological fuel cell comprising a bioelectrode using a strain of Micrococcus cerificans metabolizing n-hexadecane and an oxygen electrode is described. Experiments were made in the logarithmic phase of the growth curve. A correlation between the microorganism growth curve as determined by microbiological techniques and time dependence of the potential and current has been established. The potential reaches a nearly constant value during the log phase of the growth curve. The potential difference at zero current is 0.200 V. The electrochemical characteristics of the biological fuel cell were determined in the conventional way. The bioelectrode shows a slight polarization which is attributed to the electrochemical discharge of oxygen.
Journal Article•
TL;DR: La tecnica de tincion empleada en el diagnostico diferencial of las especies de Moniezia, supera en rapidez y seguridad a las utilizadas comunmente.
Abstract: RESUMEN: Por primera vez en la Republica Argentina se senala el hallazgo de Zygoribatula lata (AcarinaOribatulidae) como hospedador de Moniezia expansa (Cestoda Anoplocephalidae). Los ejemplares del citado oribatoideo revelaron la existencia de hasta dos cisticercoides en su cavidad celomatica. Moniezia erpansa resulto la especie mas abundante y por consiguiente la mas patogena. La tecnica de tincion empleada en el diagnostico diferencial de las especies de Moniezia, supera en rapidez y seguridad a las utilizadas comunmente. La miel demostro aceptable valor estabilizante como suspensor del arseniato de plomo. Analecta Veterinaria 3 (1,2,3): 21-28, 1971