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Biomedical subjects

E Daniel

Publications and source records attributed to E Daniel.

At least 91 records · Page 5Linked to original sources
PubMed1979

Haemoglobin from the tadpole shrimp, Lepidurus apus lubbocki Characterization of the molecule and determination of the number of polypeptide chains.

Haemoglobin from the tadpole shrimp, Lepidurus apus lubbocki, was found to have a sedimentation coefficient (s020,w) of 19.3 +/- 0.2 S and a molecular weight, as determined by sedimentation equilibrium, of 798000 +/- 20000. The amino acid composition showed the lack of cysteine and cystine residues. A haem content of 3.55 +/- 0.03% was determined, corresponding to a minimal mol.wt. of 17400 +/- 200. The pH-independence in the range pH 5-11 of the sedimentation coefficient indicates a relatively high stability of the native molecule. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis gave one band with mobility corresponding to a mol.wt. of 34000 +/- 1500. The molecular weight of the polypeptide chain was determined to be 32800 +/- 800 by sedimentation equilibrium in 6 M-guanidinium chloride and 0.1 M-2-mercaptoethanol. The findings indicate that Lepidurus haemoglobin is composed of 24 identical polypeptide chains, carrying two haem groups each.

Amino Acids↗
PubMed1979

Irritable bowel syndrome: a test of the colonic hyperalgesia hypothesis.

This study tested the hypothesis that, patients with irritable bowel syndrome (IBS), there is a primary hyperalgesia of the colon. Previous work, which examined these patients and normals, has not included subjects who provide a control for relevant psychological characteristics. We compared ratings of pain, following varying degrees of distension of the sigmoid colon, in normals, patients with IBS, and patients who were psychologically disturbed but without bowel symptoms. Psychological characteristics were assessed by a psychiatric interview and psychometric inventories; response to distension was tested by placing a tube in the rectosigmoid colon and successively inflating a nd deflating a balloon at its tip at 10 cm3 increments up to 50 cm3. Ratings of pain were recorded at each volume. The results indicated that the two patient groups were psychologically similar and both were more disturbed than normals. A linear relation was found between reports of pain and volume of distension in all three groups. There were no significant differences between the proportions of subjects experiencing pain in each group or the average of the ratings. There were no significant associations between the pain ratings and measures of anxiety, depression, neuroticism, and extraversion. The data do not support the hypothesis that colonic hyperalgesia is an important contributory factor in the etiology of the irritable bowel syndrome.

Adolescent↗
PubMed1978

A spectral study of human ceruloplasmin.

The absorption, luminescence and CD spectra of human ceruloplasmin were studied. The absorption spectrum in the infrared, and the CD spectrum in the ultraviolet, both indicate the presence of beta conformation in the native structure of the protein. From the magnitude of the measured ellipticity, it is estimated that 0.46 of the amino acid residues are in the beta conformation, the remaining 0.54 being in unordered form. A comparison of the fluorescence and phosphorescence properties of native and apoceruloplasmin shows that the presence of copper causes the quenching of tryptophanyl luminescence, probably through energy transfer to the copper chromophores. By the combined resolution of the absorption and CD spectra, it was concluded that the copper chromophores are involved in six electronic transitions in the region 300--900 nm. Our results provide evidence for an interaction between the copper chromophores responsible for the 330 nm absorption in ceruloplasmin.

Apoproteins↗
PubMed1977

The mode of binding of potential transition-state analogs to acetylcholinesterase.

Phenylacetone, 4-phenyl-2-butanone, and 4-oxopentyltrimethylammonium chloride were tested as potential transition state analogs for eel acetylcholinesterase (acetylcholine hydrolase, EC 3.1.1.7). Phenylacetone is a competitive inhibitor of the enzyme but not a transition state analog, since its binding constant is similar to that for the substrate phenyl acetate. 4-Phenyl-2-butanone binds 6-18 times more tightly than the inhibitors 4-phenyl-2-butanol and N-benzylacetamide and the substrate benzyl acetate and also blocks inactivation of the enzyme with methanesulfonyl fluoride. However, its binding is independent of pH in the range 5-7.5, whereas both V and V/Km for benzyl acetate hydrolysis decrease with decreasing pH in this range. These data indicate a specific but weak interaction between the ketone carbonyl and the enzyme, but probably do not justify considering this compound a transition state analog. 4-oxopentyltrimethylammonium iodide has previously been shown to bind about 125 times more strongly than the substrate acetylcholamine. It also binds about 375 times more strongly than the alcohol 4-hydroxypentyltrimethylammonium iodide. Furthermore, the ketone protects the enzyme from inactivation by methansulfony fluoride, while the corresponding quaternary ammonium alcohol accelerates this inactivation reaction. This additional information confirms that the ketone is a transition state analog.

Acetone↗
PubMed1977

Tyrosyl fluorescence in hemocyanin from the scorpion Leirus quinquestriatus.

The fluorescence properties of hemocyanin from the scorpion Leirus quinquestriatus were studied. Emission and excitation spectra were determined for protein in both its oxygenated and deoxygenated forms. Oxygenation was found to bring about a large blue shift in the position of the fluorescence maximum, in addition to a marked quenching of the fluorescence intensity as noted before for another hemocyanin. An appreciable tyrosyl contribution to the fluorscence of oxyhemocyanin was inferred from the wavelength dependence of its emission and excitation spectra. No tyrosyl fluorescence could be observed in either apo- or deoxyhemocyanin. It was concluded that the inability to observe tyrosyl emmision in deoxyhemocyanin is due to the dominating emission to tryptophan. The implication of the findings to the often noted failure to detect tyrosyl emission in proteins containing both tyrosine and tyrptophan is discussed.

Animals↗
PubMed1977

Chronic problems in rehabilitation of patients with Laennec's cirrhosis.

Hepatic encephalopathy and ascites are two major complications occuring in patients with Laennec's cirrhosis. Both may be intractable to treatment and may have poor prognoses. Many psychosocial problems are present, and counseling should be geared to optimizing maximum adaptation to the alterations that have resulted. Family and significant others are important support systems for the patient and should be included in as much of the nursing and medical care as possible. The nurse is responsible for a myriad of activities in providing care for cirrhotic patients who develop these chronic problems. Background knowledge regarding nursing theory, pharmacology, pathophysiology, psychology, sociology, and principles of teaching is imperative for effective intervention in these patient care situations.

Alcoholism↗
PubMed1975

Oxygen binding by hemocyanin from Levantina hierosolima. I. Exclusion of subunit interactions as a basis for cooperativity.

The effect of oxygen on the distribution of hemocyanin from Levantina hierosolima among the three sedimenting species 20, 60, and 100 S was determined under two sets of experimental conditions: (a) at pH 7.63 in the absence of Ca2+, where oxygen binding in noncooperative; (b) at pH 8.20 in the presence of 2 x 10-3 M Ca2+, where oxygen binding is cooperative. A comparison of the results in the two cases eliminates the possibility that equilibrium between species with different oxygen affinities is responsible for the cooperative behavior. Cooperative oxygen binding was demonstrated for the 20S subunits at pH 8.80 and 1 x 10-3 M Ca2+. Under these conditions, the concentration of calcium is sufficient to affect the oxygen affinity, but the concentration of calcium plus proton is not sufficient to bring about association. The findings exclude interactions among 20S subunits as a basis for cooperativity in hemocyanin.

Animals↗
PubMed1975

Oxygen binding by hemocyanin from Levantina hierosolima. II. Interpretation of cooperativity in terms of ligand-ligand linkage.

Oxygen binding by hemocyanin from Levantina hierosolima was studied at pH 7.30, in solutions containing calcium in the concentration range 0-1 M. The binding was found to be cooperative, the degree of cooperativity being calcium concentration dependent. The dependence on calcium concentration of the affinity toward oxygen for both deoxygenated and oxygenated hemocyanin was interpreted in terms of two oxygen-linked calcium ions, one promoting and the other opposing oxygen binding. The results show that cooperativity may be fully explained on the basis of a coupling of the free energy of binding between calcium and oxygen.

Animals↗