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Biomedical subjects

C Little

Publications and source records attributed to C Little.

At least 109 records · Page 6Linked to original sources
PubMed1981

Purification of rat uterine peroxidase.

Using a combination of gel filtration, affinity chromatography on immobilized concanavalin A and hydrophobic adsorption chromatography, a peroxidase has been isolated from the uteri of oeastrogen-primed rats. The enzyme was purified some 306-fold with respect to the uterine extract and to greater than 95% homogeneity. The final product had an apparent molecular weight of 48 000, an absorption maximum at 412 nm (A412/A280 = 0.47) and a specific activity very similar to those of several other pure haemoprotein peroxidases.

Animals↗
PubMed1981

Effect of some divalent metal cations on phospholipase C from Bacillus cereus.

Incubation of phospholipase C from Bacillus cereus with certain divalent metal cations caused enzyme inactivation with Cu(II) being particularly effective. The inactivation arose from the reversible exchange of Zn(II) in the enzyme with the metal cations. Both zinc atoms in the enzyme exchanged rapidly with Cu(II) whereas only one exchanged spontaneously with Co(II). With lecithin substrates, CoZn-phospholipase C had a specific activity of 3.6-11.3% of that of ZnZn-phospholipase C, whereas the CoCo-enzyme was less than 1% active relative to the native enzyme. The CoZn-enzyme had the same Km value for dihexanoyllecithin as had the native enzyme, but the Vm value was markedly lower. ZnZn-, CoZn- and CoCo-phospholipase C all had very low activities towards sphingomyelin micelles, although for the CoCo-enzyme, the sphingomyelinase activity was 4-7-fold greater than for the native enzyme.

Bacillus cereus↗
PubMed1980

Prognostic significance of serum lactate dehydrogenase in malignant lymphoma.

The pretreatment serum lactate dehydrogenase level (LDH) was the single most important prognostic variable in 30 patients with diffuse histiocytic lymphoma treated between January 1973 and January 1977 with a poly-drug chemotherapy program called the cyclophosphamide L2 protocol at the Memorial Sloan-Kettering Cancer Center. A highly significant difference was found between the survival patterns of patients with LDH levels of 500 U or less and those with LDH levels greater than 500 U. (Two-year survival rates were 67% and 13%, respectively.) A similar trend was observed for 25 patients with diffuse, poorly differentiated lymphocytic lymphoma treated with the same protocol, although this difference was not statistically significant. (Corresponding two-year survival rates were 74% and 33%, respectively.) The association of LDH level with survival was evident even after adjustment for other factors of potential prognostic significance. Pretreatment serum LDH determinations may provide a useful means of stratifying patient populations when comparing treatment programs for advanced stage non-Hodgkin's lymphoma.

Antineoplastic Agents↗
PubMed1980

Lysis of erythrocytes from stored human blood by phospholipase C (Bacillus cereus).

The ability of phospholipase C (Bacillus cereus) to lyse erythrocytes from human blood that had been stored under Transfusion Service conditions for up to 16 weeks has been examined. When incubated at 20 degrees C with enzyme (0.03 mg/ml, 55 units/ml) for up to 1 h fresh erythrocytes were not lysed. After about 4 weeks of storage a population of very readily lysed erythrocytes appeared. The morphological changes in erythrocytes from blood stored up to 16 weeks were examined by scanning electron microscopy. The proportion of very readily lysed erythrocytes correlated well with the proportion of spheroechinocytes I. This morphological form was shown to be preferentially removed by phospholipase C and before lysis a transient appearance of smooth spheres occurred. The decrease in blood ATP concentrations on storage was measured and found to correlate with the disappearance of discoid erythrocyte forms, but not directly with the increased susceptibility of the erythrocytes to lysis by the enzyme. However, erythrocytes of up to at least 15 weeks of age could be made less susceptible to lysis by pre-incubation in a medium designed to cause intracellular regeneration of ATP. During the lysis of spheroechinocytes I by electrophoretically pure recrystallized phospholipase C a rapid degradation of phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine + phosphatidylinositol) occurred together with a slower degradation of sphingomyelin.

Adenosine Triphosphate↗
PubMed1980

Ageing of blood in hereditary spherocytosis.

Blood from 5 patients suffering from hereditary spherocytosis (HS) was stored in acid-citrate-dextrose anticoagulant at 4 degrees C for up to 6 weeks. The erythrocyte morphology and susceptibility to lysis by phospholipase C (Bacillus cereus) were examined at 2-weekly intervals and compared with erythrocytes from 6 different donations of stored normal blood. the hereditary spherocytes went through essentially the same series of morphological changes as did normal erythrocytes. Fresh hereditary spherocytes were very resistant to lysis by phospholipase C, but, like normal erythrocytes, became progressively more susceptible to lysis upon storage. In terms of erythrocyte morphological changes and development of susceptibility to lysis by the enzyme, blood from HS patients aged less rapidly than did normal blood. Splenectomy appeared to have no marked effect on the storage properties of blood from these patients as indicated by erythrocyte morphology and susceptibility to lysis by phospholipase C.

Erythrocyte Aging↗
PubMed1980

The effects of diet on high density lipoprotein cholesterol.

Twenty-nine patients with normal blood lipids were placed on diets. Thirteen, mainly attending hospital for varicose veins, were prescribed low-energy diets: HDL-cholesterol was raised after one month and significantly after three months (P less than 0.02); total cholesterol was lowered (P less than 0.05). Sixteen patients, mainly with irritable bowel symptoms, were prescribed high-fibre diet: HDL-C was raised after one month (P less than 0.05), but not significantly so after three months; total cholesterol was unchanged.

Adult↗
PubMed1980

A simple purification scheme yielding crystalline phospholipase C from Bacillus cereus.

A very simple and rather unusual purification scheme for phospholipase C from Bacillus cereus has been worked out. Air is bubbled vigorously through the bacterial culture and the foam collected. Liquified foam is centrifuged, dialyzed and heated at 74 degrees C for 5 min. After centrifugation, affinity chromatography is carried out on lipoprotein-Sepharose. The enzyme is then thermally denatured by exposure to 85 degrees C for 5 min and the precipitated material well washed and then renatured from solution in 4 M guanidinium chloride. The final enzyme preparations are electrophoretically homogeneous and easy to crystallize. The recovery of activity exceeds 80%.

Bacillus cereus↗
PubMed1979

Unfolding and refolding of phospholipase C from Bacillus cereus in solutions of guanidinium chloride.

1. Protein-fluorescence studies indicated that phospholipase C from Bacillus cereus is denatured in solutions of guanidinium chloride. The denaturation was not thermodynamically reversible and followed biphasic kinetics. 2. Guanidinium chloride solutions released the structural Zn2+ from the enzyme and rendered all histidine residues chemically reactive. In the presence of free Zn1+ the enzyme was much more resistant to denaturation. Also, the addition for free Zn2+ to the denatured enzyme induced refolding. 3. The Zn2+-free apoenzyme was much more sensitive to guanidinium chloride than was the native enzyme and the denaturation appeared to be thermodynamically reversible. 4. Guanidinium chloride denaturation was associated with a reversible inactivation of the enzyme. Heat-inactivated, coagulated enzyme was substantially re-activated on dissolution in guanidinium chloride solutions followed by dialysis against a Zn2+-containing buffer.

Apoenzymes↗
PubMed1979

The peroxidase activity of rat uterus.

The peroxidase activity in the uterine extract of rats previously given a low dose of oestradiol has been examined. From sexually mature rats, two peroxidases of apparent molecular weights of 92 000 (peroxidase I) and 40 000 (peroxidase II) and of different mobilities in polyacrylamide disc gel electrophoresis were found. The two peroxidases were separated and characterized in terms of their substrate specificities, kinetics, pH optima for activity, inhibitors and stabilities. Both enzymes appeared to be classic haemoprotein peroxidases of very similar properties. Peroxidase II was further purified.

Animals↗
PubMed1978

Conformational studies on phospholipase C from Bacillus cereus. The effect of urea on the enzyme.

1. When heated in 8 M-urea, phospholipase C(EC 3.1.4.3) from Bacillus cereus undergoes conformational transitions depending on the temperatures used. These transitions were studied by examining protein fluorescence, iodide quenching of protein fluorescence, u.v. difference spectroscopy, chemical availability of histidine residues in the enzyme, circular dichroism and catalytic activity. 2. Unless simultaneously exposed to elevated temperatures the enzyme appears to be unaffected by 8 M-urea. Removal of the two zinc atoms from the enzyme renders phospholipase C very sensitive to denaturation by 8 M-urea as indicated by fluorescence emission spectra and circular dichroism. 3. Both the native and the zinc-free enzymes are markedly more resistant to irreversible thermal inactivation in the presence of 8 M-urea than in its absence. 4. The response of the enzyme to 8 M-urea and the role of zinc in stabilizing the enzyme are discussed.

Amino Acids↗
PubMed1977

The histidine residues of phospholipase C from Bacillus cereus.

The inactivation of phospholipase C from Bacillus cereus at pH6 by diethyl pyrocarbonate parallelled the N-ethoxyformylation of a single histidine residue in the enzyme. The inactivation arose from a decrease in the maximum velocity of the enzymic reaction with no effect on the Km value. The inactivation did not apparently alter the ability of the enzyme to bind to a substrate-based affinity gel. The native enzyme contained only one reactive histidine residue. Removal of the two zinc atoms from the enzyme increased the number of reactive histidine residues to five, whereas in the totally denatured enzyme nearly eight such residues were available for reaction with diethyl pyrocarbonate. The enzyme thus appears to contain one histidine residue that is essential for catalytic activity and four that may be involved in co-ordinating the zinc atoms in the structure.

Bacillus cereus↗