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Biomedical subjects

C C Yang

Publications and source records attributed to C C Yang.

At least 289 records · Page 16Linked to original sources
PubMed1984

Cardiotoxic effects of Naja nigricollis venom phospholipase A2 are not due to phospholipid hydrolytic products.

N. nigricollis phospholipase A2 (200 micrograms) has marked cardiotoxic actions on the perfused rat heart including the induction of arrhythmias, increases in ventricular thresholds, conduction and resting tension, and decreases in contractile tension. In contrast, perfusion with lysophosphatidyl choline and oleic acid, in concentrations comparable to those estimated to be formed during N. nigricollis treatment, has little effect on cardiac function. The less toxic N. n. atra phospholipase A2 also has little effect on cardiac function even though it causes approximately the same low percentage of phospholipid hydrolysis as produced by N. nigricollis phospholipase A2. Perfusion with albumin did not alter the phospholipase A2 induced changes in cardiac function. Lysophosphatidyl choline in concentrations higher than expected to be formed during N. nigricollis phospholipase A2 treatment, increased conduction time to a greater extent than ventricular threshold whereas the reverse was true for phospholipase A2. We conclude that the cardiotoxic effects of N. nigricollis phospholipase A2 are not due to the accumulation of phospholipid hydrolytic products, and on the basis of prior studies with chemically modified phospholipase A2 enzymes we suggest that N. nigricollis phospholipase A2 has a direct, non-enzymatic, cardiotoxic action.

Analysis of Variance↗
PubMed1984

Structure of pseudobactin 7SR1, a siderophore from a plant-deleterious Pseudomonas.

When grown in iron-limiting culture medium, sugar beet deleterious Pseudomonas 7SR1 produced extra-cellularly the yellow-green, fluorescent siderophore pseudobactin 7SR1. Pseudobactin 7SR1 had a molecular formula of C46H63N13O23 and a molecular mass of 1166 g/mol. Pseudobactin 7SR1 contained a cyclic octapeptide with the amino acid sequence L-Ala-Gly-Ser-Ser-threo-beta-OH-Asp-Thr-Ser-N delta-OH-Orn. Since pseudobactin 7SR1 was not affected by nonspecific enzymes, it might contain D-amino acids. A yellow-green, fluorescent quinoline derivative is postulated to be attached via an ester bond to the serine residue following the glycine. A malamide group was attached to carbon 3 of the quinoline derivative. The three bidentate iron(III)-chelating groups consisted of an alpha-hydroxy acid group derived from beta-hydroxyaspartic acid, an omicron-dihydroxy aromatic group derived from the yellow-green, fluorescent chromophore, and a hydroxamate group derived from N delta-acetyl-N delta-hydroxyornithine. The chemical structure of pseudobactin 7SR1 is remarkably similar to that of pseudobactin, the siderophore of plant growth promoting Pseudomonas B10.

Amino Acid Sequence↗
PubMed1984

Effect of carboxylate group modification on enzymatic and cardiotoxic properties of snake venom phospholipases A2.

By treating Naja nigricollis and Naja naja atra phospholipase A2 with carbodiimide and semicarbazide, we obtained derivatives having varied numbers of modified carboxylate groups. When tested on artificial and natural substrates, derivatives of both enzymes with a modified carboxylate group at the active site (Asp-49) retained little enzymatic activity (1/41 to 10%). However, the derivatives of N. nigricollis also lost most of their lethal potency (5% of native), while those of N. n. atra retained considerable lethality (29%). Carboxyl modification with protection of Asp-49 in N. n. atra enzyme resulted in a derivative with lethal potency equal to or greater than the native enzyme and enzymatic activity which was low on all substrates (12-17% of native). Similar protection of Asp-49 at the active site in N. nigricollis enzyme produced a derivative with decreased enzymatic activity on artificial substrate (22% of native) and decreased lethality (17-33% of native), but with full enzymatic activity on natural substrates. When tested on electrical and mechanical properties of the isolated perfused heart and the isolated ventricle muscle wall, the derivatives of both enzymes retained considerably more of the cardiotoxic activity than would have been expected based on their residual enzymatic activity. The one exception occurred with the least modified N. nigricollis derivative which had an unaltered Asp-49, this enzyme retained both cardiotoxic activity and full enzymatic activity on natural substrates. The extent of phospholipid hydrolysis following treatment was measured in the isolated heart preparation and in hearts removed from mice following i.v. injection of the phospholipases. Very low levels of phospholipid hydrolysis were observed and no correlation could be made between the extent of hydrolysis and the pharmacological potencies of these enzymes. Modification of the enzymatic active site, whether of Asp-49 in this study of His-48 in prior studies, leads to a large decrease in both enzymatic activity and lethal potency. Asp and Glu residues outside of the enzymatic site contribute significantly to the lethal potency of the N. nigricollis enzyme and to the enzymatic activity of the N. n. atra enzyme. Based on these and previous data we conclude that changes in isoelectric points are not responsible for altered lethal potencies following chemical modification and that some pharmacological effects of snake venom phospholipases A2 are due to a non-enzymatic action, suggesting two distinct but perhaps overlapping active sites.

Action Potentials↗
PubMed1984

Colicin V-treated Escherichia coli does not generate membrane potential.

Colicin V-treated Escherichia coli was inhibited in its capacity to carry out active transport of proline and was unable to generate a membrane potential. Colicin V also prevented membrane potential formation by isolated cytoplasmic membrane vesicles. We conclude that a primary effect of this colicin involves the cytoplasmic membrane as a target.

Biological Transport, Active↗
PubMed1983

Dissociation of pharmacological and enzymatic activities of snake venom phospholipases A2 by modification of carboxylate groups.

The carboxylate groups in an acidic and in a basic phospholipase A2 (PLA2) enzyme, purified, respectively, from Naja naja atra and Naja nigricollis snake venoms, were modified with carbodiimide and semicarbazide. The derivatives modified at pH 3.5 and pH 5.5 had less than 1% (N. nigricollis) or 2% (N. n. atra) residual enzymatic activity, whereas 12-16% enzymatic activity remained following modification at pH 5.5 in the presence of Ca2+. In marked contrast, these derivatives retained variable, but significantly greater, levels of lethal potency, hemolytic and anticoagulant activities, and abilities to block indirectly and directly induced contractions of the diaphragm. By this modification of aspartic and glutamic acid residues we have, for the first time, obtained derivatives of PLA2 which selectively retain greater pharmacological activity relative to enzymatic activity. Previously, we had found that modification of lysine and arginine residues produced derivatives which retain enzymatic activity but show a loss of pharmacological properties. These findings suggest that some pharmacological effects of snake venom PLA2 enzymes are due to a non-enzymatic action, suggesting two distinct but perhaps overlapping active sites.

Animals↗
PubMed1983

Effect of methylation of histidine-48 on some enzymatic and pharmacological activities of snake venom phospholipases A2.

The effects on some pharmacological and enzymatic properties were determined following methylation of histidine at the enzymatic active site of the basic relatively toxic Naja nigricollis and the acidic relatively non-toxic Naja naja atra phospholipases A2. Following methylation a very low residual enzymatic activity (0.4-1% of control) was accompanied by a parallel loss in intraventricular lethality, anticoagulant potency, direct hemolytic action and ability to block directly and indirectly evoked contractions of the mouse phrenic nerve-diaphragm preparation. Since methylation does not impair the enzyme's ability to bind monomeric or micellar substrates or Ca2+, the results suggest that the pharmacologically active region of the molecule is different from the micellular substrate binding site but strongly influenced by the invariant histidine-48 located at the enzymatic active site.

Animals↗
PubMed1983

Rectal malacoplakia in a patient with Hodgkin's disease. Report of a case and review of the literature.

A 37-year-old man was found to have classic malacoplakia of the rectum after three courses of chemotherapy for stage IV Hodgkin's disease. Sigmoidoscopy with excisional biopsy was performed because of rectal bleeding. The biopsy specimen of the rectal lesion showed focal extensive granulomatous changes with large macrophages containing round, dense Michaelis-Gutmann bodies. Electromicroscopy demonstrated calcifying spheres with laminated concertric structures (Michaelis-Gutmann bodies) and coliform bacillus in the cytoplasm of macrophages (Von Hansemann bodies). Review of the literature revealed that association of malacoplakia with Hodgkin's disease has never been documented, although it has been reported to be associated with conditions such as malignancy, organ transplantation, collagen disease, and leukemia. The possible role of immune disturbance as an underlying cause of malacoplakia is discussed.

Adult↗
PubMed1983

Ethoxyformylation and guanidination of snake venom phospholipases A2: effects on enzymatic activity, lethality and some pharmacological properties.

Lysine residues in the basic and relatively toxic N. nigricollis phospholipase A2 and in the acidic and relatively nontoxic N. n. atra phospholipase A2 were modified by acylation with ethoxyformic anhydride (in the presence or absence of the substrate dihexanoyl lecithin) or guanidination with O-methylisourea. Ethoxyformylation gave rise to some protein fractions in which enzymatic activity was preserved to a greater degree than intraventricular lethality. Guanidination had little effect on the isoelectric point or catalytic activity of either enzyme or on the lethal potency of the N. n. atra enzyme. However, the intraventricular lethality of the N. nigricollis enzyme was decreased much more than was its intravenous lethality, direct hemolytic potency, anticoagulant activity or cardiotoxic action on rat atrium. These results are compared to those previously obtained when the lysines in these two enzymes were carbamylated with potassium cyanate, a procedure which markedly decreased the isoelectric point of the enzymes. It is concluded that charge alone does not account for differences in toxicity. The data also indicate that there are at least two distinct active sites in both enzymes, one being primarily responsible for enzymatic activity and the other(s) associated with lethal and pharmacological effects of the protein. Modification of lysines affects the latter site(s), while having little or no effect on enzymatic activity.

Animals↗
PubMed1983

Phospholipid hydrolysis in serum lipoproteins by a basic phospholipase A2 from Naja nigricollis snake venom and an acidic phospholipase A2 from Naja naja atra snake venom.

Apparent Km and Vmax values for PC and PE hydrolysis were determined following exposure of HDL, LDL, and VLDL to a basic phospholipase A2 from N. nigricollis snake venom and an acidic phospholipase A2 from N. nigricollis snake venom and an acidic phospholipase A2 from N. n. atra snake venom. Both enzymes hydrolyzed the lipoprotein phospholipids approximately as fast as they hydrolyzed pure phospholipids in mixed micelles, however, the N. nigricollis enzyme, which has a much stronger anticoagulant effect than the N. n. atra enzyme, had lower apparent Vmax values. These values were highest for phospholipids in VLDL and lowest for HDL, however, the differences between the lipoproteins were relatively small with the N. nigricollis enzyme while the differences were much larger with the N. n. atra enzyme. Fractions of the two enzymes in which varying numbers of lysines were carbamylated showed much larger differences in relative rates of phospholipid hydrolysis in HDL, LDL and VLDL. Triton X-100 eliminates these differences in rates of hydrolysis. These results are discussed in terms of the differences in the organized structure of the lipoprotein classes and in the penetration ability of the phospholipases.

Animals↗
PubMed1983

Changes in lymphocyte response to phytohaemagglutinin and serum immunosuppressive activity after thermal injury.

The present study consisted of two parts. In part one, 14 cases were divided into an invasive infection group (4 cases) and a non-invasive infection group (10 cases). A total of 68 assays for lymphocyte responses to PHA stimulation were carried out. The invasive infection group showed a significantly suppressed lymphocyte response, which occurred during invasive infection but neither before nor after the infection. The extent of third-degree burns was statistically significant between these two groups (P less than 0.05), but no significance was found between the total body surface area burned. In part two, 18 burn patients were studied for serum immunosuppressive activity. Both invasive infection cases and non-invasive infection cases showed serum immunosuppression during the course of the study and no significant difference was found between these two groups (P greater than 0.05). It is concluded that the extent of third-degree burn and the complicated systemic infection contribute to the impairment of lymphocyte responses to PHA stimulation, while the post-burn serum immunosuppression is unrelated to the occurrence of systemic infection.

Adult↗
PubMed1983

Changes of serum amino acids in severely burned patients.

The serum amino acids profile in ten severe burn patients was basically similar with the findings in major burns reported in our proceeding article, supporting the conclusion that burn patients might have a particular amino acid pattern. The larger was the burn size, the more severe was the nitrogen loss. Following a severe burn, the patient was faced with the challenge of acute protein malnutrition. After severe burns, the ratio of serum Phe/Tyr rose to a higher level than in the major burns. Moreover, the elevation of serum Met/Cys ratio indicated a more serious metabolic disturbance. During the first two weeks postburn, acute decrease of serum BCAA by 20-30 per cent of the normal value was associated with a striking increase of mortality. This fact indicated the level of BCAA might be of prognostic value. In severe burns, other than huge amount of calories and protein supplied, enriched BCAA, and perhaps, carnitine might be beneficial.

Adolescent↗
PubMed1983

Serum and erythrocyte amino acid pattern: studies on major burn cases.

Venous serum amino acids were measured in 13 patients with major burns. Erythrocyte amino acids and plasma cortisol, blood sugar and urine catecholamine were measured in two representative subgroups respectively. After burn injury, serum proline, glycine, valine, isoleucine and arginine were significantly decreased; phenylalanine, cysteine, methionine, leucine, glutamate, alanine, aspartic acid and tyrosine were significantly increased. Histidine and lysine fluctuated. This serum amino acid profile is considered as a specific pattern for major burns. Serum phenylalanine was markedly elevated in the hypermetabolic burn patients, its fluctuation coincided with the burn course and was negatively correlated with serum albumin level (P less than 0.001). These findings suggest that the ratio of phenylalanine tyrosine is a useful clinical parameter for assessing the patient's nutritional condition. Twenty-three simultaneous determinations of both serum and erythrocyte amino acid concentrations show similar changes, suggesting that the serum amino acid profile might reflect the change of total free amino acid pool. After burn injury, plasma cortisol, blood sugar and urine catecholamine were elevated as well as urine urea nitrogen. However, although the first three returned to normal by the end of the second week post burn, urine urea nitrogen remained high. This indicates that there are other factors controlling nitrogen loss in patients with major burns, it is also postulated that, due to the abnormal amino acid pattern revealed after major burns, the constituents of commercially available amino acid solutions should be modified.

Adult↗