Biomedical subjects

O Hammouda

Publications and source records attributed to O Hammouda.

6 recordsLinked to original sources

PubMed1999

Response of the paddy field cyanobacterium Anabaena doliolum to carbofuran.

Assessment of the influence of carbofuran on the nontarget cyanobacterium Anabaena doliolum revealed that this sheathless heterocystous form of cyanobacteria was more sensitive to the insecticide carbofuran. Anabaena doliolum was initially able to utilize low concentrations of carbofuran, whereas higher concentrations and the subsequent formation of hydrolytic breakdown products were toxic. Growth inhibition reached more than 50% by treatment with 80 and 100 ppm of the insecticide. Nitrogenase activity of the cyanobacterium was reduced by 38% after 48 h by treatment with 100 ppm carbofuran with no observed change in heterocyst frequency. Toxicity of the insecticide was the highest at pH 4-6 (46-59%) and the lowest at pH 7-10 (12-27%) due to the persistence of carbofuran and the resulting alkaline-catalyzed hydrolysis associated with the water regime of the rice fields. Doubling the initial population level of the cyanobacterium reduced the toxicity of the insecticide.

Anabaena↗

PubMed1996

Effect of heat shock on DNA-dependent RNA polymerase from the cyanobacterium Synechococcus sp.

Purification of DNA-dependent RNA polymerase from exponentially growing cells of the cyanobacterium Synechococcus sp. is described in cultures grown at normal temperature (39 degrees C) and after heat shock (HS) (47 degrees C). Polyethyleneimine precipitation followed by chromatography and gel filtration steps results in a 39% yield. The enzyme has a component of molar mass of 43 kDa, designated sigma, in addition to the typical procaryotic beta' beta alpha 2 and gamma. The results suggest that Synechococcus RNA polymerase is similar to that of cyanobacterial and E. coli RNA polymerases. Electrophoresis of the HS preparation showed that the enzyme has a component of 18 kDa. This suggests the existence of a functional relationship between this protein and the HS response of Synechococcus RNA polymerase, probably in salvaging denatured RNA polymerase or helping to regain its native structure.

Cyanobacteria↗

PubMed1995

Alterations in protein synthesis in the cyanobacterium Synechococcus sp. strain PCC 6301 in response to Calendula micrantha extract with molluscicidal activity.

The response to the extract of the Egyptian wild herb Calendula micrantha, with molluscicidal activity, was examined in the unicellular cyanobacterium Synechococcus sp. strain PCC 6301. Growth and chlorophyll a of the cells were only slightly affected by low concentrations but drastically reduced by high concentrations. The rate of protein synthesis progressively decreased by increasing extract concentration. The cells preferentially induced the synthesis of a limited number of polypeptides in response to the treatment. Among the induced polypeptides were those with apparent molecular weights of 161K (161,000), 96.7K, 93.4K, 85K, 69.9K, 59K, 49K, 45K, 35K, 32.4K, 28K, 24K, 21.7K, 18K, and 16K based on their mobilities in gel electrophoresis. These initial studies suggest that the plant extract exerted certain stress which stimulated alteration in the pattern of protein synthesis in Synechococcus sp. Some of the induced polypeptides are similar to that known to occur in other stresses, especially heat-shock stress.

Bacterial Proteins↗

PubMed1995

Microalgae and wastewater treatment.

The performance of microalgae aquaculture wastewater treatment system predominated mainly by Scenedesmus and Chlorella was assessed. Treatment induced a progressive reduction in both COD and BOD to values below the discharge limits. Different patterns were obtained for removal of phosphorus, nitrogen, and ammonia; however, the algal culture efficiencies reached 100% in their removal by the end of the treatment period. The applied aquatic systems demonstrated percentage reduction of heavy metals in the range between 52.3 and 100% in the batch system and 64.2 and 100% in the continuous system. Wastewater supported algal growth by inducing the incorporation of a significantly higher content of the individual amino acids Asp, Thr, Ser, Glu, Gly, and Tyr, and a markedly higher level of Pro. However, His, Lys, and Arg were markedly reduced compared to their levels in synthetic-medium-grown algae.

Aquaculture↗

PubMed1981

Isolation and partial characterization of bovine gingival AB collagen.

Limited proteolysis with pepsin solubilized 25% of the insoluble gingival matrix as mainly soluble collagenous material. Fractional salt precipitation at neutral pH resulted in the separation of types III and I at 1.8 and 2.6 M NaCl, respectively. In addition, a collagenous fraction accounting for 2% of the solubilized collagen and precipitating at 4.5 M NaCl was shown to be identical with type V collagen. Isolation and partial characterization of the constituent-alpha-chains of the 4.5 M PPT by gel filtration, ion exchange and hydroxylapatite chromatography as well as disc electrophoresis showed that gingival type V collagen contains alpha A and alpha B chains in a ratio alpha B/alpha A of 1.73-1.8. Electron microscopic examination of ATP-precipitates showed that this collagen type gave only one kind of SLS aggregates with asymmetric band pattern characteristically different from that of type I collagen. The data provide evidence that gingival AB collagen is a heteropolymer in which the alpha A and alpha B chains are assembled in the same macromolecule in a 1:2 ratio.

Amino Acids↗

PubMed1980

Gingival matrix collagen in chronic periodontitis.

The isolation and characterization of cyanogen bromide peptides derived from the human gingival collagen of patients with chronic periodontitis revealed the presence of both Type I and Type III collagens in this tissue. The amount of TYPE III collagen, however, was found to be lower than that in normal gingival tissue. In addition, a non-collagenous protein fraction, accounting for approximately 20% of the insoluble matrix, was relatively rich in acidic, hydrophobic, and hydroxy-containing amino acids. Amino acid analysis, likewise, revealed qualitative and quantitative differences between the normal and diseased tissues.

Adult↗