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Biomedical subjects

N F Adham

Publications and source records attributed to N F Adham.

31 records · Page 2Linked to original sources
PubMed1978

Alpha2-macroglobulin deficiency in a patient with Ehlers-Danlos syndrome.

A new genetic defect, alpha2-macroglobulin deficiency, was found in a patient with Ehlers-Danlos syndrome (EDS). Other members of the family of five exhibiting this abnormality were the mother and one sister. All members, including the patient, had normal serum albumin and alpha1-antitrypsin levels. The deficiency, reported here for the first time, appears to be inherited by an autosomal co-dominant mode. Statistical evaluation of the dihybrid crosses for independent assortment between EDS and hypo-alpha2-macroglobulinemia showed a probability of 0.7 to 0.75. However, a possible link between EDS and hypo-alpha2-macroglobulinemia is suggested since the observed ratios of four siblings are exactly as expected, assuming that double gene defects are linked in the mother's genotype.

Adolescent↗
PubMed1977

Binding of zinc to alpha-2-macroglobulin and its role in enzyme binding activity.

Physicochemical studies performed on alpha-2-macroglobulin were correlated with the biological activities of this protein. Equilibrium dialysis of the binding of 65Zn by alpha-2-macroglobulin at pH 7.9 showed heterogeneous binding which could be attributed to two classes of binding sites. The site of greatest affinity for zinc had an apparent stoichiometry (n1 in gatoms/mol of alpha-2-macroglobulin monomer) of 12 and an apparent association constant (K1) of 3.06.10(7). The second binding site had an n2 of 60 and K2 of 1.32.10(5). The trypsin binding activity of alpha-2-macroglobulin did not depend on the presence of zinc in this protein since all but traces of this metal could be removed by EDTA without loss of trypsin binding activity. Saturation of site 1 with zinc did not affect the trypsin binding activity of alpha-2-macroglobulin, but binding of the metal by site 2 progressively decreased the trypsin binding activity by causing an irreversable association of the alpha-2-macroglobulin molecules. Removal of excess zinc from alpha-2-macroglobulin did not restore its trypsin binding activity. Our results also indicate that the high zinc content of alpha-2-macroglobulin (320--770 microgram/g protein) reported in the literature is an artifact and that native alpha-2-macroglobulin contains approximately 150--180 microgram Zn/g protein.

Dialysis↗
PubMed1976

A simple, highly sensitive colorimetric method for the determination of zinc in serum.

A simple, reliable, highly sensitive method for the determination of zinc in biological fluids is described. Interfering trace metals are removed as insoluble iodides or hydroxides prior to complex formation of zinc with dithizone in a Tris-buffered trichloroacetate centrifugate. Absorbance of the chelate is read at 555 nm. The sensitivity of the new method is comparable to that of atomic absorption spectrophotometry, and the results of zinc determinations of 23 sera by the two procedures agree to within acceptable limits of experimental error.

Absorption↗
PubMedDate not supplied

A possible zymogen self-destruct mechanism preventing pancreatic autodigestion.

Incubation at 37 degrees C of human cationic trypsinogen purified by PAGE electrophoresis, results in development of proteolytic activity (enzyme Y) capable of rapidly degrading cationic and anionic trypsinogens to inert products. Enzyme Y appears to be a serine protease with a molecular weight of about 20,000 daltons and is different from any of the known pancreatic enzymes. The active enzyme may be derived from trypsinogen itself or a hitherto unrecognized precursor contaminating the trypsinogen fraction used in this work. Appearance of enzyme Y activity seems to be associated with the presence of traces of free trypsin. Enzyme Y possesses insignificant or no activity when tested with a variety of synthetic trypsin, chymotrypsin and other protease substrates. It is not inactivated by the specific trypsin and chymotrypsin inhibitors TLCK and TPCK, but its activity is reduced gradually by increasing concentrations of pancreatic secretory trypsin inhibitor. Ca2+ concentrations greater than 3 mM strongly inhibit enzyme Y, and diisopropylfluorophosphate completely inactivates it. The enzyme is stable when incubated at pH 1.9 and 37 degrees C for 30 min and its activity is not abolished by treatment with Hg2+. When added to pancreatic juice with low inhibitor content it causes rapid inactivation of zymogens without significant release of active enzymes or reduction of pancreatic trypsin inhibitor. Its physiological role may be perceived as a second line of defense against premature intrapancreatic activation of zymogens. Enzyme Y activity may be generated when trypsin inhibitor, the first line of defense, is sufficiently depleted by complex formation with inappropriately released trypsin to permit dissociation of a small amount of trypsin from this complex. This in turn may lead to activation of enzyme Y and inactivation of the zymogens of pancreatic proteases.

Autolysis↗