Biomedical subjects
Publications and source records attributed to M Nicolae.
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The present study focused on energy and protein metabolism in pregnant and lactating mares, including the suckling and weaned growing horses, in order to determine feed availability, as also the energy and protein requirements. The authors found that the feeding diets, consisting of alfalfa hay, oats and compounds, had different availability values in terms of energy and protein, according to animal physiological conditions and age. Thus, the pregnant mares utilized the metabolizable energy (ME) and digestible crude protein (DCP) intake in average proportions of 64.5 +/- 3.2%, 54.6 +/- 3.0%, respectively, while in the lactating mares the values were 60.1 +/- 2.8%, respectively, 50.1 +/- 4.0%. However the amount of energy and protein required for maintenance was similar in these two animal physiological conditions: 531 kJ, ME/kg0.75, 529 KJ, ME/kg0.75 and 3 g DCP/kg0.75, respectively. The suckling colts had a daily average gain between 1405 and 891 g and the young horses after weaning up to 2 years of age between 773 and 447 g. The net efficiency of ME and of DCP for growth in the suckling colts was of 40.6 +/- 2.1% and 46.1 +/- 3.2%, respectively and in young horses after weaning had similar values of 40.3 +/- 4.0%, respectively 44.4 +/- 2.2%, but the maintenance requirement of energy and protein differed from 506 kJ, ME/kg0.75 and 4.51 g DCP/kg0.75 respectively to 587 kJ, ME/kg0.75 and 3.51 g DCP/kg0.75, respectively.
C57BL/6 mice with EL4 leukemia cells in ascitic form were intraperitoneally treated with ricin A chain-multivalent antibody immunotoxins. The immunotoxins containing rabbit IgG anti-Thy 1.2 antibodies complemented by protein A of Staphylococcus aureus were able to interact specifically with the target cells and to induce an antitumor effect as revealed by an increase in survival time of the mice. No apparent secondary effects consecutive to a cytotoxic action on the normal Thy 1.2 antigen bearing cells were observed with the immunotoxin doses used.
Two immunotoxins, the ricin A chain-multivalent hybrid antibody (750 kDa) and the complex A chain-staphylococcal protein A-rabbit IgG antibody (370 kDa), were prepared. A simple method was elaborated to test the immunotoxins' efficiency in selectively killing target cells in tumor-bearing mice. The target cell (murine EL4 leukemia) was coated with a xenogenic molecule by a method conserving its ability to proliferate and kill the inoculated animals. When the challenged animals were treated with these immunotoxins, which were specific for the antigenic molecule coating the tumor cells, survival time was lengthened compared with that of untreated animals, corresponding to a proportion of over 90% cells killed. This demonstrates the efficiency of the immunotoxins and the validity of the method elaborated.
The interaction between the Fc receptor for IgA (FcR alpha) and human secretory IgA (sIgA) was studied in a heterologous system by using rabbit alveolar macrophages or splenic lymphocytes. The capacity of FcR alpha-bearing cells to interact with the ligand via the Fc region was demonstrated. The proportion of FcR alpha-bearing lymphocytes and macrophages was found to be 11 and 17%, respectively. The cell-bound radiolabelled ligand showed a release half-time of 70 min for lymphocytes and 45 min for macrophages. The equilibrium constant (K) and the maximum number of ligand molecules bound per cell (n) in mean values was 5.2 +/- 0.05 X 10(8) M-1 and 3.3 +/- 0.15 X 10(5) molecules per cell, respectively. Increased percentages of FcR alpha-bearing cells and of ligand density per cell were obtained after stimulation by lung inflammation. A significant increase of the K value was recorded with macrophages from rabbits with lung acute inflammation (mean value 7.3 +/- 0.21 + 10(8) M-1) while the increase with lymphocytes was not significant. The calculation method of K and n is discussed.
Antibodies of the IgG class, specifically interacted with H-2 antigens of murine leukemia EL4 cells, were used to bind the ricin toxin covalently linked to protein A of Staphylococcus aureus. The toxin thus complexed, introduced in the cytoplasm by endocytosis, was able to kill the leukemic cells inoculated in animals. The interaction of immunotoxin with the leukemic cells was performed in vitro using one, two or three treatments and the cytotoxic effect on the target cells was followed up in vivo. The time interval between immunotoxin treatments was indicated by the membrane turn-over study of EL4 cells coated with specific antibodies in their monomeric form, complexed by protein A or interacted with protein A--ricin toxin conjugate. A proportion of 99.8% cells killed was obtained after three treatments.
A multivalent hybrid antibody complex composed of two IgG molecules specific for ricin toxin and two specific for the H-2 antigens of murine leukemia EL4 cells, cross-linked by SpA, was used as vector of the toxin to the target cells. The high affinity of the hybrid antibody for the specific antigens achieved an efficient attachment to the EL4 cell membrane and binding of ricin toxin; this high-molecular-weight complex, introduced by endocytosis into the leukemic cell cytoplasm, was able to specifically deliver the toxin to the target cells. The effect of multivalent hybrid antibody-vectorized toxin was followed up in vivo. This method enabled determination of the proportion of killed cells (over 90% after a single treatment of leukemic cells or about 99% after double treatment). The presence of a low proportion of tumoral cells maintaining their proliferative capacity is discussed.
4 heifers (268 to 400 kg live weight) were fed with four rations containing corn silage and corn flour in ratios of 82:18 (I), 65:35 (II), 45:55 (III) and 25:75 (IV). Urea was added to achieve an N balance. The rations were aimed at a daily weight gain of 700-800 g. The digestibility of the rations, their metabolizable energy, heat production and retained energy were determined. The digestibility of the organic matter was, in the sequence of I-IV = 73.2, 74.3, 75.4 and 75.8%. In the same sequence the energy intake per animal and day in MJ was = 95.9, 92.8, 91.3 and 89,7; the digestibility of the energy was 71.5, 72.2, 73.8 and 74.8%. In urine 3.1, 2.5, 2.7 and 2.9% and in methane 7.6, 7.8, 7.6 and 7.2% of the energy intake were excreted. Metabolizable energy was 60.8, 62.0, 63.5 and 64.7%, heat production 48.7, 48,7, 48.2 and 49.8% of the energy intake. 12.2, 13.2, 14.4 and 14.9% of the energy intake were retained. 51.6, 48.8, 42.4 and 40.1% of the retained energy was protein energy. The energetic feed value of both ration components has been calculated and stated according to various mathematical methods.
The efficiency of utilisation of food energy by female growing minks, from weaning to adult age, was studied. The food given, pelleted according to an original technology, has the following chemical composition on a DM basis: 87.0% organic matter, 37.1% crude protein, 11.7% crude fat, 2.6% crude fiber, 35.6% nitrogen-free extractives and 13.0 per cent ash. Young minks had a feed intake, in relation to body weight, warying from 11.6 g to 58.6 g DM/d. Maximum feed intake related to kg0.75 was recorded at 700 g body weight (approximately 98 g DM/kg0.65). Digestibility of the given food expressed in DE, averaged 87.7 +/- 1.2%, while metabolizability, 82.3 +/- 1.1%. Total heat production related to the intaked gross energy, was 48.0 +/- 3.0%, and the retained energy, 34.3 +/- 4.0 per cent. The net efficiency of the metabolizable energy used for maintenance and production could not be accurately determined. However, taking to account the calculated values required for maintenance, of 649 kJ/kg0.75 in 300 to 600 g young minks, and of 607 kJ/kg0.75 in 600 to 1100 g young minks and also the maintenance efficiency, Km = 0.75, the coefficient for ME utilisation in protein and fat synthesis, of 0.50 and 0.75, respectively, it was able to determine the average ME efficiency used as net energy for maintenance and production: 70%. The highest values of nictemeral metabolism were recorded in the evening, and the lowest ones, at noon; the difference between the maximal and the minimal value did not exceed 6 per cent.
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