Showing papers by "National University of La Plata published in 1983"
TL;DR: The results suggest that neurally mediated proteolytic cleavage of the circulating inactive mitogenic precursor pro-γ-MSH at the adrenal gland is the major mechanism of control of compensatory growth.
Abstract: Regulation of the rapid compensatory growth seen in the remaining adrenal gland of rats following unilateral adrenalectomy is poorly understood. The role of adrenocorticotropic hormone (ACTH) is obscure as immunoneutralization of circulating ACTH does not affect the observed compensatory growth or hyperplasia. This finding, together with the fact that mechanical manipulation of one adrenal without extirpation is followed by growth only in the contralateral gland, has led to the concept of neural regulation of compensatory adrenal growth via a loop from one adrenal through the hypothalamus and back to the contralateral gland which is independent of ACTH secretion. We recently showed that peptides from the N terminal of ACTH precursor proopiocortin (POC), not containing the gamma-melanocyte-stimulating hormone (gamma-MSH) sequence, can stimulate adrenal mitogenesis and proposed that normal long-term adrenal growth and proliferation involves post-secretional proteolytic cleavage of pro-gamma-MSH [or N-POC(1-74)] to generate the mitogenic factor N-POC(1-48/49) and a C-terminal fragment N-POC(50-74), or rat gamma 3-MSH. We have now investigated this hypothesis further in rats by selectively quenching different regions of circulating POC peptides with specific antisera and observing the effect on the increases in weight, RNA and DNA normally seen in the remaining gland following unilateral adrenalectomy. Our results, reported here, suggest that neurally mediated proteolytic cleavage of the circulating inactive mitogenic precursor pro-gamma-MSH at the adrenal gland is the major mechanism of control of compensatory growth.
135 citations
TL;DR: In this paper, a nonlinear oscillator externally driven by an impulsive periodic force is investigated, and an exact analytical expression is obtained for the stoboscopic or Poincar\'e map for all values of parameters.
Abstract: A nonlinear oscillator externally driven by an impulsive periodic force is investigated. An exact analytical expression is obtained for the stoboscopic or Poincar\'e map for all values of parameters. The model displays period-doubling sequences and chaotic behavior. The convergence rate of these cascades is in very good agreement with Feingenbaum theory.
90 citations
Journal Article•
TL;DR: The extinction of these huge mammals, together with the extinction of many other relatively giant and striking mammals, mark the end of the Deseadan Age, it is interpreted as the effect of decisive climatic-environmental changes, the same that affected similarly the mammal communities all over the world.
Abstract: NEW AND ELOQUENT CRANIAL REMAINS OF THE DESEADAN (EARLY OLIGOCENE) Proborhyaena gigantea AMEGHINO, 1897 (MARSUPIALIA, BORHYANIDAE, PROBORHYAENINAE). AN EXAMPLE OF COEVOLUTION. - The most complete remains of tbe Deseadan (Early Oligocene) giant marsupial Proborhyaena gigantea Ameghino, 1897 (Borhyaenidae, Proborhyaeninae ) are described. These remains, together with different remains since long known, allow to recognize for the first time most of the unique carnivore dental adaptations that characterize this peculiar marsupial: (1) short rostrum; (2) C1 hipertrofied, "saber-tooth" like, but ovoidal in section, not blade-like, (3) c1, unusually enlarged; (4) cheek-teeth series complete: P1,2/P1_2 inserted obliquely, almost transversely; P3/P3 enlarged; M1_3 with reduced protocone and extended shearing metacrist. Suggestively this peculiar carnivorous marsupial coexisted with very large-sized herbivorous (Edentata and "ungulates" s.l.), and all became extinct simultaneously. The differentiation and extinction of those gigantic predator and herbivores appear to be a conspicuous South American example of coevolution. The extinction of these huge mammals, together with the extinction of many other relatively giant and striking mammals, mark the end of the Deseadan Age, it is interpreted as the effect of decisive climatic-environmental changes, the same that affected similarly the mammal communities all over the world.
36 citations
TL;DR: The composition of lipids and fatty acids of male and female gonads of D. delodontus at different sexual stages were studied and the main differences were found in the percentages of triacylglycerols, cholesterol esters and phospholipids.
Abstract: 1. 1. The composition of lipids and fatty acids of male and female gonads of D. delodontus at different sexual stages were studied. 2. 2. The main differences were found in the percentages of triacylglycerols, cholesterol esters and phospholipids. 3. 3. Female gonads with few immature gametes contained more triacylglycerolds and less phospholipids than male gonads in similar conditions. 4. 4. Spermatogenesis increased the sterol esters of male gonads. Oogenesis increased triacylglycerols and sterol esters of female gonads. Non-fertilized eggs contained a high percentage of triacylglycerols and a low percentage of sterol esters. 5. 5. The fatty acid composition of gonads was low in saturated fatty acids. The unsaturation was scattered in 16 : 1, 18 : 1, 20 : 1, NMI 22 : 2 and polyunsaturated acids of ω6 and ω3 families. Only 20 : 1 exceeds the 10% of total fatty acids. Similarly to other Diplodon species, the ratio of ω3 : ω6 acids was low and typical of fresh water molluscs. 6. 6. Oogenesis increased the proportion of palmitoleate, α-linolenate and oleate: stearate ratio. The change of the fatty acid composition was mainly produced in the triacylglycerols. The changes were not due to unsaturated fatty acid biosynthesis in the gonads. However, oocytes were able to elongate palmitic and stearic acids.
36 citations
TL;DR: In this article, a model of heat and mass transfer with simultaneous chemical reaction is proposed for analyzing the influence of operating variables on the reducing sugar content at the surface of blanched potatoes.
Abstract: A model of heat and mass transfer with simultaneous chemical reaction is proposed for analyzing the influence of operating variables on the reducing sugar content at the surface of blanched potatoes. This content is partially responsible for the color of the finished product. The involved parameters (potato thermal conductivity, heat transfer coefficient of the system and kinetic constants for overall reaction of reducing sugar generation) were evaluated in separate experiments. The apparent diffusion coefficient of reducing sugars in potatoes was the only parameter obtained from blanching experiments. Temperature and concentration profiles and effect of blanching temperature on surface reducing sugar content are analyzed using the developed model. The possible underestimation of the diffusion coefficient when simultaneous starch hydrolysis is not taken into account is also considered.
31 citations
TL;DR: In this paper, the internal oxidation of dilute (a few ppm) Ag-math{In}$ alloys at different annealing conditions was investigated by time-differential perturbed angular correlation technique.
Abstract: The internal oxidation of $\mathrm{Ag}\mathrm{In}$ alloys has been investigated by time-differential perturbed angular correlation technique on $^{111}\mathrm{In}$ probes. We studied the oxidation kinetics of dilute (a few ppm) $\mathrm{Ag}\mathrm{In}$ alloys at 300\ifmmode^\circ\else\textdegree\fi{}C under different annealing conditions and 1 at.% indium alloys at 300\ifmmode^\circ\else\textdegree\fi{}C and 550\ifmmode^\circ\else\textdegree\fi{}C. In some cases, the time dependence of the oxidation-front advance was ruled by a power law with an exponent different from 0.5. We determined the hyperfine parameters of ${\mathrm{In}}_{2}$${\mathrm{O}}_{3}$ and studied the influence of the oxidation temperature on the indium sesquioxide precipitation in the silver matrix. A consistent description of the oxides formed at different temperatures is given.
27 citations
TL;DR: In this article, the first-forbidden charge exchange resonances are discussed in the framework of a schematic model and the screening of the weak coupling constants induced by both the giant resonances and the Δ-isobar is evaluated.
24 citations
TL;DR: A participatory role of SR in the ischaemic impairment of left ventricular systolic and diastolic performance is discussed.
Abstract: Effects of myocardial ischaemia on sarcoplasmic reticulum (SR) of dog hearts were investigated. Regional ischaemia was produced by occlusion of the left circumflex artery, and a microsomal fraction enriched in vesicles of SR was isolated from subendocardium (Endo) and subepicardium (Epi) of control and ischaemic areas of the heart. No significant changes occurred in ischaemic Epi. A loss of in vitro activities (ie calcium transport and ATPase) was found for SR from ischaemic Endo which paralleled the changes in the histology of the tissue. At 5 min of coronary occlusion, Ca2+ binding and Ca2+-ATPase activities of SR from ischaemic Endo were normal. A decrease in the activities of SR was first evident at 15 min after the occlusion, decreased further at about 30 min and remained at that level at 60 min of ischaemia. The maximal rate of Ca2+ uptake did not parallel the Ca2+-binding and Ca2+-ATPase activities. The degree of cAMP-dependent phosphorylation by endogenous and exogenous protein kinase was not different between SR from control and ischaemic areas. A participatory role of SR in the ischaemic impairment of left ventricular systolic and diastolic performance is discussed.
23 citations
TL;DR: Small, oligotrophic, herbaceous plants were observed on many species of trees and bushes growing in the arboretum of the Faculty of Agronomy and in parks of the city and would be susceptible to attack in the future.
23 citations
TL;DR: In this paper, a perturbation theory for determinants of differential operators regularized through the ζ-function technique is presented, and the application of this approach to the study of chiral changes in the fermionic pathintegral variables is discussed.
Abstract: A perturbation theory for determinants of differential operators regularized through the ζ-function technique is presented. The application of this approach to the study of chiral changes in the fermionic path-integral variables is discussed.
21 citations
TL;DR: In this paper, the first quantitative results on internal oxidation of impurities in a noble-metal host, using the time-differential perturbed angular correlation technique, were reported, and they were in good agreement with a parabolic dependence of the depth of the internal oxidation front on the elapsed oxidation time.
Abstract: The first quantitative results on internal oxidation of impurities in a noble-metal host, using the time-differential perturbed angular-correlation technique, are reported here. The system studied was indium-silver, with a few ppm of indium. The existence of a well-defined oxidation front is found for this highly dilute alloy. The kinetics of oxidation were determined for oxidating temperatures of 400 and 500\ifmmode^\circ\else\textdegree\fi{}C. Our results are in good agreement with a parabolic dependence of the depth of the internal oxidation front on the elapsed oxidation time. No unique indium-oxygen configurations were found in the range 280-900\ifmmode^\circ\else\textdegree\fi{}C.
TL;DR: The Kustaanheimo-Stiefel transformation was applied to the nonrelativistic hydrogen atom in this article, which provides one of the rare examples of a free particle moving on a four-dimensional homogeneous space.
Abstract: The Kustaanheimo-Stiefel transformation as applied to the nonrelativistic hydrogen atom provides one of the rare examples of a free particle moving on a four-dimensional homogeneous space.
TL;DR: Trifluormethylsulfenylbromid was obtained by a new preparative method as discussed by the authors, and its IR and Raman spectra were fully characterized and an assignment was proposed for the observed bands.
Abstract: Trifluoromethylsulfenyl bromide was obtained by a new preparative method. Its IR (vapour and pure solid) and Raman (liquid) spectra are fully characterized and an assignment is proposed for the observed bands. A normal coordinate analysis was made by means of a stewise-coupling method. Thermodynamic properties in the temperatur range between 200—1000 K are tabulated.
Darstellung, IR- und Raman-Spektren, Kraftfeld- und thermodynamische Konstanten des Trifluormethylsulfenylbromids, CF3SBr
Trifluormethylsulfenylbromid wurde nach einer neuen Praparations-methode erhalten. Die IR- (Gas u. fest) und Raman-(flussig) Spektren wurden aufgenommen und eine Zuordnung der Banden vorgenommen. Eine Normalkoordinatenanalyse erfolgte mit Hilfe eines Kopplungsstufenverfahrens. Die thermodynamischen Eigenschaften im Temperaturbereich von 200 bis 1000 K werden angegeben.
TL;DR: In this paper, the quadrupole hyperfine interactions in HfF 4 and Hf 4 ·3H 2 O determined by time differential-perturbed angular correlations technique are reported.
TL;DR: In this paper, a 1-kW prototype with closed-loop overcurrent protection in an inverse-phase-control version is presented, where the absence of turn-off circuits and bulky radio frequency interference (RFI) filtering circuitry are the main advantages of the method.
Abstract: V-shaped metal-oxide-semiconductor (VMOS) dimmers in direct and inverse phase control schemes are analyzed and compared with conventional thyristorized ones. The absence of turn-off circuits and bulky radio frequency interference (RFI) filtering circuitry are the main advantages of the method. A 1-kW prototype with closed-loop overcurrent protection in an inverse-phase-control version is presented.
Journal Article•
TL;DR: In this paper, the faunal remains of the archaeological site Cortaderas (San Cayetano county, Buenos Aires province) were analyzed and the following species were recorded: Canis (Pseudalopex) gymnocercus, Canis culpaeus, Lyncodon patagonicus, Lama glama guanicoe, Blastoceros bezoarticus, Chaetophractus villosus, Zaedyas pichiy, Tolypeutes sp. and Ctenomys sp.
Abstract: CHOROLOCICAL CHANCES OF SOME MAMMALS IN THE "AREA INTERSERRANA" OF THE BUENOS AIRES PROVINCE DURING THE HOLCENE. - The faunal remains of the archaeological site Cortaderas (San Cayetano county, Buenos Aires province) are analysed. The following species have been recorded: Canis (Pseudalopex) gymnocercus, Canis (Pseudalopex) culpaeus, Lyncodon patagonicus, Lama glama guanicoe, Blastoceros bezoarticus, Chaetophractus villosus, Zaedyas pichiy, Tolypeutes sp. and Ctenomys sp. These remains were found in sediments assigned to the upper part of the Holocene, which corresponds to the most recent climatic variations related to processes derived from eolian, fluvial and paedogenetic action. The chorologic changes affected patagonic, relatively euritermic, or central species. The most probable hypothesis is that the aridity process is the product of the reduction of the average rainfall. In this site, as in most of the Interserrana area (both sinchronic and diachronic), guanaco remains are predorninant. This enables us to postulate the hypothesis that this species was the main animal protein source during the Holocene before the Spanish Conquest.
TL;DR: Evidence is provided that the negative effect ofprotein malnutrition appears to be promoted at least in part, by the effect of protein depletion on the supply of polyenoic acids for normal development and metabolic adaptations.
Abstract: The effect of protein deficiency on the activity of A6 desaturase in the mother during lactation was determined in the liver microsomal fraction and the fatty acid composition of milk lipids from the analyzed stomach contents. The activity of A6 desaturase was profoundly affected by protein deprivation during pregnancy and only reached the values of controls at about 10 days after parturition. This fact did not affect the fatty acid pattern of milk lipids and no significant differences in the contents of arachidonic acid were detected between the two groups. Nevertheless, protein de ficiency apparently affected milk production. The effects of protein deprivation on the supply of polyenoic acids of cross-fostering rats at birth from protein-deficient to protein- sufficient diets and vice versa, and rats maintained during pregnancy and lactation on a low protein or control diet were examined. The fatty acid pattern of liver phospholipids of the four groups under study was determined and used as a biochemical parameter for evaluating polyenoic acid status. Protein deficiency markedly affected the fatty acid pattern of liver phospholipids. A significant decrease of both arachidonic and docosa- hexaenoic acids was observed. This fatty acid pattern was reversed when protein-de ficient animals were placed on the control diet at birth. On the other hand, the fatty acid composition of controls was negatively affected by cross-fostering to a deficient diet. The findings from the present experiment provide evidence that the negative effect of protein malnutrition appears to be promoted at least in part, by the effect of protein depletion on the supply of polyenoic acids for normal development and metabolic adaptations. J. Nutr. US: 314-319, 1983.
TL;DR: In this article, the retention volumes of eighteen hydrocarbons representative of different families and of acetone, diisopropyl ether and three chloromethanes were measured at four temperatures within the range 12-22°C on columns containing five different percentages of propylene glycol (PG) as the stationary phase.
TL;DR: Since SIN-1 has a greater relaxant effect than NTG in spite of the fact that Sin-1 induces less of an increase in cGMP levels, the causal nexus between GMP level elevation and relaxation effect after sydnonimines should be challenged.
Abstract: In vitro experiments on precontracted canine coronary arteries were performed to study the direct relaxant effects of molsidomine (MOLS) and its active metabolite, SIN-1, and to determine if there is a relationship between effect and cGMP level elevations. The effects of MOLS and SIN-1 were compared with those of a classic vasodilator, nitroglycerin (NTG). At equimolar doses (10(-6)M) SIN-1 exerted greater relaxant effect than NTG (80 +/- 2% and 60 +/- 5%, respectively) in spite of the fact that it produced less of an increase in cyclic guanosine monophosphate (cGMP) levels. cGMP levels fell rapidly after they peaked, but relaxation was maintained. cGMP elevation preceded the induction of relaxation by NTG but not that induced by SIN-1. Relaxation occurred faster after NTG than after SIN-1. Since SIN-1 has a greater relaxant effect than NTG in spite of the fact that SIN-1 induces less of an increase in cGMP levels and the fact that the peak elevation does not precede the onset of relaxation, the causal nexus between GMP level elevation and relaxation effect after sydnonimines should be challenged.
01 Jan 1983
TL;DR: The total synthesis of (±)-ribaline is reported in this paper, which represents the first formal total synthesis for (+-)-ribalinidine, in combination with earlier findings.
TL;DR: They are the only species of Curimatidae known with more than 85 scales in the lateral line, and the validity of Gasterotomus Eig.
Abstract: Semitapiscis squamoralevis sp. nov. (Osteichthyes: Curimatidae) with Considerations on the Genus. A morphological description is given of Semitapiscis squamoralevis sp. nov. recorded from the fluvial system of the Parana River and River Plate in the Argentine Republic. The maximum and minimum numerical and meristic values belonging to the holotype and 25 paratypes are tabulated. The differences and similarities with the other species of the genera Semitapiscis and Potamo‐rrhina pristigaster are considered. They are the only species of Curimatidae known with more than 85 scales in the lateral line. A key for their identification is given. The validity of Gasterotomus Eig., 1910 and Suprasinelepichthys Fernandez Yepez, 1948 is discussed.
Journal Article•
TL;DR: One hypothesis explaining the presence of species inherited from patagonic and central dominions in the archaeological site Canada de Rocha (north astern of Buenos Aires Province) is proposed in this paper.
Abstract: DISTRIBUTION OF SOME MAMMALS SPECIES IN NORTHEASTERN BUENOS AIRES PROVINCE DURING THE HOLOCENE. - One hypothesis explaining the presence of species inherited from patagonic and central Dominion in the archaeological site Canada de Rocha (north astern of Buenos Aires Province) is proposed. Environmental conditions more arid than present-day ones allowed the dispersion of species which do not live today in the area i.e. Lama glama guanicoe, Dolichotis patagonum and Canis (Pseudalopex) griseus. On the other hand, characteristic species from Subtropical Dominion (Blastocerus tlichotomus, Myocastor coypus and Hydrochoerus hydrochaeris) were absent or they were rare in Canada de Rocha. However, these species were well registered in other archaeological sites of the area (La Maza I, Rio Lujan, Canada Honda, Islas Las Lechiguanas, Campana), where the guanaco was not found or it was rare. A climatic oscillation may have modified the Faunistic distribution. According to the Canada de Rocha evidences, this site was occupied during an arid or semiarid climatic moment. Therefore, Canada de Rocha may be diachronous in regard to the other sites, which must have been inhabited during humid climatic moments, similar to the present. The fauna obtained from Canada de Rocha corresponds to "native" fauna; there were neither exotic fauna nor pleistocenic megamammals. Thus, the sediments which contain the faunistic and cultural elements are referred to the late Holocene. As there were no cultural elements indicating a Spanish contact, it can be inferred that Canada de Rocha was inhabited before the XVIth century.
01 Jan 1983
TL;DR: In this article, photoelectric UBVRI data for stars in the young open cluster Tr 14 in the Great Carina Nebula (NGC 3372) are presented, which gives an age of about 5×106 yr.
Abstract: New photoelectric UBVRI data for stars in the young open cluster Tr 14 in the Great Carina Nebula (NGC 3372) are presented. The two-color diagram separates clearly the member from the nonmember stars. Thus, the membership of about 39 stars is suggested. Those located in the compact core of the cluster, have smaller reddening dispersion than those around it. No star appears above the Main Sequence at the faint end of the color-magnitude diagram. A distance modulus ofV0−Mv=12.20±0.2 is obtained, which gives an age of about 5×106 yr. From only the photometry it is concluded to be slightly older than the nearby cluster Tr16.
TL;DR: It is concluded that despite their apparent stability, a substantial number of DCTs were altered by both biological (like sex) and environmental factors imposed at different stages of postnatal development.
Abstract: The influences of protein-calorie malnutrition (PCM), and sex during lactation and post-lactation on the frequencies of 25 discontinuous cranial traits (DCT), were investigated in Holtzman rats. Significant differences were observed in about 20% of the traits. Those traits were: the interfrontal fusion, the posterior incurvation of the palatine border, the double maxillary foramen, the double posterior palatine foramen, and the double frontal foramen. Total PCM was the nutritional factor which showed the greatest influence on the variability of the DCTs. It was followed, in decreasing order, by the PCM imposed during post-lactation and lactation. Sex had more influence than early PCM but less than late PCM. It is concluded that despite their apparent stability, a substantial number of DCTs were altered by both biological (like sex) and environmental factors (like nutritional deficiencies) imposed at different stages of postnatal development.
TL;DR: The thermal dependence of the hyperfine quadrupolar interaction of181Ta at Zr sites in K2ZrF6 has been studied by TDPAC between RT and 511 °C as mentioned in this paper.
Abstract: The thermal dependence of the hyperfine quadrupolar interaction of181Ta at Zr sites in K2ZrF6 has been studied by TDPAC between RT and 511 °C. Four phases of ever increasing symmetry have been found in the range RT-437 °C. The possible existence of a healing mechanism with an activation energy of 0.187±0.040 eV is discussed for the lattice recovery in the range 270 °C–335 °C. The results at temperatures above 437 °C can be understood assuming a thermal decomposition of the compound.
TL;DR: In this article, time-differential perturbed angular correlation (TDPAC) measurements in NH4Hf2F9 were performed between 15 and 580 K. The compound was found to be stable in the whole temperature range and no phase transitions were observed.
Abstract: Time-differential perturbed angular correlation (TDPAC) measurements in NH4Hf2F9 were performed between 15 and 580 K. The compound was found to be stable in the whole temperature range and no phase transitions were observed. Experimental results could be explained assuming two equally populated quadrupole interactions which suggest a neat inequivalence between the two sites occupied by the hafnium atoms in the molecule.
TL;DR: In this paper, the equivalence between a finite many-body problem (Huckel model) for a nonrelativistic and nonspin molecular system of N electrons and N one-dimensional Ising models was shown.
TL;DR: In this paper, the infrared spectra of potassium azidopentacyanocobaltate(III) dihydrate (PACDH) were obtained from the polycrystalline substance, both normal and deuterated, and from the monocrystal using a polarization analyzer.
Abstract: Infrared spectra of potassium azidopentacyanocobaltate(III) dihydrate (PACDH) were obtained from the polycrystalline substance, both normal and deuterated, and from the monocrystal using in this case a polarization analyzer Raman spectra of the normal powder were also obtained The observed bands were assigned either to the internal vibrational modes of the azidopentacyanocobaltate(III) ion (AC) or to the internal and librational modes of the hydration water