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8 results on '"Awad, K. M."'

1. Reactions of phosphate and zinc fertilizers in Iraqi calcareous soils

Author

Awad, K. M.

Subjects
631.4, Soil Science & pedology
Abstract

The objectives of this research were: (i) to investigate the phosphorus and zinc status of Iraqi calcareous soils, (ii) to describe the characteristics of both phosphate and zinc fertilizer reactions in such soils, and (iii) to test the nature of phosphate-zinc interactions in soils and on plant growth. Six soil samples were studied: three alluvial calcareous soils from the Lower Mesopotamian Plain and three desert calcareous soils from the southern desert region. Chemical and physical examination showed that the alluvial soils were generally more fertile than the desert soils. However, poor structure and high salinity of the alluvial soils limit their agricultural potential. Reaction of fertilizer P with soils involved initial rapid adsorption of P, followed by a gradual change in solution composition toward equilibration with octocalcium phosphate (OCP). Hydroxyapatite was unlikely to be involved because of its very slow rate of formation. Dicalcium phosphate dihydrate (DCPD) could be produced initially in all soils, but it was less persistent in the alluvial soils than in the desert soils, suggesting that persistence of DCPD was greater in a soil low in salts and/or carbonate. It was further shown that an increase in calcium ion concentration enhanced DCPD hydrolysis as evidenced by the formation of OCP. Formation of amorphous zinc silicate (Zn2SiO4) may play a major role in controlling Zn solubility in such soils. ZnCO3, Zn(OH)2 and Zn3(PO4)2.4H2O are too soluble to account for the zinc concentration. The solubility of Zn was somewhat higher in the desert soils than in the alluvial soils. P/Zn interactions in soils and plants were observed, but the reaction in the soil external to the plant is not adequate to explain crop effects. P-induced Zn deficiency in maize caused by imbalance in P/Zn ratio is basically a consequence of the differential translocation rates of P and Zn from the root to the top.

Published
1982

3. EFFECT OF CONCENTRATED SUPER PHOSPHATE FERTILIZER APPLICATION METHODS ON ITS REACTION AND ITS AVAILABILITY ON CALCAREOUS SOILS.

Author

Awad, K. M. and Ashoor, N. I.

Subjects
*PHOSPHATES, *FERTILIZERS, *SOILS, *PHOSPHATE fertilizers, *IRRIGATION water
Abstract

Studies were conducted to determine the effect of concentrated super phosphate fertilization placement on its reaction and phosphorous availability using two calcareous soils from south Iraq. The phosphate fertilizer was added at four rates (0 , 50 , 100 & 200 kg P2O5 . ha-1) either mixed with soil, broad casting on the soil surface , subsurface application or dissolving with irrigation water . Results indicated that the mixed method plays a significant role in increasing phosphate immobilization and retarding the formation of the more soluble phosphate compounds. The method of fertilizer dissolving in water formed the less soluble compounds as compared with the broadcasting & mixed application. However, the broadcasting method had the superiority over the others methods in keeping the phosphate availability for along period in the both soil. [ABSTRACT FROM AUTHOR]

Published
2006

4. Immobilization of Diammonium Phosphate and Monocalcium Phosphate in Calcareous Soils

Author

Amer, Fathi, Shams, M. S., Awad, K. M., and Khalil, M. A.

Abstract

Immobilization of monocalcium phosphate (MCP) and diammonium phosphate (DAP) was investigated in an alluvial soil (4.1% CaCO3) and in a desert soil (39% CaCO3). Laboratory experiments were performed to study P solubility in the fertilized soils as affected by wetting and drying cycles and by moisture tension. In addition, the relationship between NH3volatilization and P solubility was evaluated for DAP, and the agronomic effectiveness of the two fertilizers was tested in a greenhouse experiment. At 4,900 ppm P both fertilizers saturated the alluvial soil during the first 10 cycles with respect to dicalcium phosphate dihydrate (DCPD). The MCP‐treated desert soil was DCPD‐saturated for the first cycle then suffered a sharp decline in soluble P, but maintained DCPD saturation with the addition of organic matter. DAP, on the other hand, failed to saturate the desert soil with DCPD and a negative relationship was obtained between NH3volatilization and P solubility. In soil columns soluble P increased with depth for DAP while for MCP it was dependent on the moisture tension, the lower the tension the higher the solubility. Greenhouse results were in agreement with the laboratory findings. DAP and MCP were equally effective in the alluvial soil but MCP was superior in the highly calcareous desert soil, especially when combined with organic matter application.

Published
1980
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5. Negative selection of thymocytes: A novel polymerase chain reaction-based molecular analysis detects requirements for macromolecular synthesis

Author

Luciano D'Adamio, Clayton, L. K., Awad, K. M., and Reinherz, E. L.

Subjects
Immunology, Immunology and Allergy
Abstract

Self-tolerance is mainly established through clonal deletion of autoreactive T cells during thymic differentiation. The mechanisms by which deletion is achieved are poorly understood. Here we use a specific polymerase chain reaction-based system to characterize DNA fragmentation and show that after in vivo treatment of neonatal mice with staphylococcus enterotoxin B, selective apoptosis of V beta 8+ thymocytes occurs. This process precedes detectable deletion of V beta 8+ cells as determined by phenotypic analysis. Moreover, in vivo administration of cycloheximide and, to a lesser extent, actinomycin D, inhibits apoptosis of staphylococcus enterotoxin B specific thymocytes. Thus, macromolecular synthesis is a requirement for negative selection.

6. Respiratory muscle power (RMP) in normal subjects, asthmatics, trained police officers and healthy obese adults in Sudan.

Author

Musa, O. A., Elbadri, O. A., Ibrahim, S. E., Magzoub, A. A., Awad, K. M., Abdalla, F. G., and Hussein, B. A.

Subjects
MUSCLE strength, RESPIRATION, PHYSICAL training & conditioning
Abstract

Respiratory muscle power (RMP) is the main drive for respiration in health and disease. Negative correlation was found between age- and RMP for both sexes. Height, obesity and physical training have been shown to increase RMP. The use of RMP in asthma as a tool of investigation and as a predictor of training has not been investigated. Asthma diagnosis when mild or intermittent is a clinical challenge in between attacks, and the common pulmonary function tests (PFTs) are not very sensitive. An extensive study has been performed on the RMP in normal individuals, in asthmatics as a new diagnostic tool, in trained police officers, and in obesity. Methods: A total of 653 subjects from Gezira and Khartoum states, Sudan were included. Two hundred and sixty normal adult volunteers both sexes, aged 16-60 years have performed RMP measurement (Maximum Expiratory and Inspiratory Pressures, MEP and MIP) by mouth pressure meter and pulmonary function (FVC, FEV1 & PEFR) by microplus spirometer. RMP and PFTs in 30 young adults aged 16-23 years were compared with 30 old subjects aged 65-85 years. Respiratory muscle thickness at the end of quiet and maximum inspiration were measured using ultrasound device .Fifty asthmatic and 50 matching controls have performed reversibility test and spontaneous variability by RMP and PFTs. Fifty nine trained policemen and 28 policewomen were compared with 61 matching control. Diaphragmatic thickness and RMP was performed in 10 chronic asthmatics, matched with 10 controls. Obesity and RMP was studied in 52 obese individuals and 43 matching controls. Results: Both RMP and PFTs in males were significantly higher than in females (mean MIP (cmH2O) and FEV1 (L) were 111±21 and 3.7±0.5 in males compared to 75.8±16.3 and 2.8±0.3 in females. Both RMP and PFTs values decreased with age in both sexes (mean MIP and FVC (L) in young subjects were 114.3±28.4 and 4.1±0.5 compared to 78±19 and 2.9±0.5 in old subjects. The sensitivity of MEP and MIP was better than FEV1 and PEFR in asthma diagnosis by reversibility test (49% & 71% for MEP & MIP, and 40% & 31% for FEV1 and PEFR) and in variability test (53% & 61% for MEP & MIP and 40% & 46% for FEV1 and PEFR). MEP and MIP significantly increased in obese subjects (p=0.01 and 0.00 respectively) and insignificant difference (p=0.73) was found in lung function between obese subjects and controls (Mean FVC (L), MEP and MIP (cmH2O) were 3.58 ±0.9,109±29.8 and 78±17.2 respectively in obese subjects compared to 3.63±0.7, 94.6±27.7 and 67.8±18.7 respectively in non-obese controls). The diaphragm muscles thickness was significantly increased in chronic asthmatics compared to healthy controls (diaphragm thickness in quiet inspiration was 4 mm in asthmatics and 3.1 mm in controls). RMP and PFTs were found significantly higher in trainee polices officers compared to controls (mean MIP and FVC in policemen were 106.9±28.2 and 3.96±0.5 compared to 88.1±31 and 3.58±0.8 in controls). In conclusions: RMP differences between males and females and in younger and old adults can explain the differences in their lung function values. RMP reversibility and variability is a new potential diagnostic tool for asthma. Obese and trained subjects have Higher RMP which could explain their lung function values. [ABSTRACT FROM AUTHOR]

Published
2013

8. Thymic and peripheral apoptosis of antigen-specific T cells might cooperate in establishing self tolerance.

Author

D'Adamio L, Awad KM, and Reinherz EL

Subjects
Animals, Base Sequence, CD4-Positive T-Lymphocytes cytology, CD8 Antigens analysis, Cell Differentiation, Clone Cells, Enterotoxins immunology, Gene Rearrangement, beta-Chain T-Cell Antigen Receptor, Lymphocyte Activation, Mice, Mice, Inbred Strains, Molecular Sequence Data, Oligodeoxyribonucleotides chemistry, T-Lymphocytes cytology, Thymus Gland cytology, Apoptosis, Immune Tolerance, Receptors, Antigen, T-Cell, alpha-beta metabolism, T-Lymphocytes immunology
Abstract

Aside from CD4+CD8+ double-positive (DP) thymocytes, the subpopulations of T lineage cells affected by negative selection are unknown. To address whether this process occurs in more mature cell types, we have compared the responses of purified single-positive (SP) murine thymocytes and peripheral T cells to the superantigen staphylococcal enterotoxin B (SEB) utilizing as antigen-presenting cells (APC) a fibroblast cell line expressing transfected I-Ek class II molecules. Whereas approximately 70% of SEB-reactive SP thymocytes, either CD4+ or CD8+, undergo programmed cell death (apoptosis) and, therefore, negative selection, CD4+ and CD8+ antigen-specific peripheral T cells are predominantly activated and proliferate to APC+SEB. Thus, mature thymocytes and peripheral T cells, with identical patterns and levels of expression of CD4, CD8 and T cell receptor (TCR), are programmed to elicit different responses following TCR stimulation. Unexpectedly, however activation of peripheral T cells was preceded by deletion of a large fraction of V beta 8+ T lymphocytes (SEB specific). This surprising phenomenon was also observed in in vivo studies: in fact, administration of SEB to adult mice resulted in depletion of the majority of antigen-specific T cells from the peripheral lymphoid tissues analyzed (lymph nodes and spleen). This depletion is the consequence of deletion as indicated by program cell death of V beta 8+ T cells and is followed by proliferation of the remaining SEB-reactive T cells. Clonal elimination of peripheral T cells may represent a mechanism by which tolerance to self antigens never expressed in and/or exported to the thymus is achieved.

Published
1993
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