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Biomedical subjects

L Spero

Publications and source records attributed to L Spero.

At least 37 records · Page 2Linked to original sources
PubMed1979

Purification and characterization of different types of exfoliative toxin from Staphylococcus aureus.

Exfoliative toxin was isolated from strain DI of Staphylococcus aureus using carboxymethyl cellulose and hydroxylapatite chromatography. This purified toxin was compared with that produced by strain TA. The specific biological activity of the two toxins was the same, but they were serologically distinct. These strains have different loci (plasmid or chromosomal) for toxin production; differences were seen in molecular weight and amino acid composition. N-terminal amino acid sequences from the two strains showed significant homology using a single unit alignment shift.

Amino Acid Sequence↗
PubMed1979

Cross-reactions between tryptic polypeptides of staphylococcal enterotoxins B and C.

The strong cross-reactions demonstrated for staphylococcal enterotoxins B (SEB) and C1 (SEC1) by measurement of antigen-binding capacity were reflected in well defined polypeptides obtained by limited tryptic digestion from SEB and SEC1. Two antigenic determinants on each enterotoxin were capable of reacting with heterologous antibody, one on the first 57 amino acids and one on the last 150 residues of the polypeptide backbone. The larger, carboxyl terminal polypeptides bound efficiently to homologous antiserum but about two orders of magnitude less efficiently to heterologous antibody. The amino terminal peptides showed only weak homologous binding but nearly comparable heterologous binding. It is proposed that the determinant on the amino terminal polypeptides is largely responsible for the strong reciprocal binding of the intact enterotoxins and that their low antigen-binding capacity is due to a random or a structurally distorted conformation in solution.

Animals↗
PubMed1978

The L-dopa on-off effect in Parkinson disease: treatment by transient drug withdrawal and dopamine receptor resensitization.

It has been suggested that patients with Parkinson disease partially compensate for neuron loss by developing denervation supersensitivity, and, if so, that prolonged levodopa (L-dopa) therapy might lead to desensitization. As a preliminary test of this hypothesis, and in order to study whether it was possible to "resensitize" a patient who had already presumably been desensitized by previous L-dopa therapy, a patient who had become unpredictably responsive to L-dopa was investigated. The patient had been taking L-dopa for eight years and had exhibited severe dyskinesia-akinesia oscillation ("on-off" phenomenon) before the study. There was no consistent response to his hourly doses of Prolopa (L-dopa and benserazide in a 4:1 ratio). He was first lowered, over 33 days, to 20% of his original Prolopa dose. The dosage was then increased until a consistent response was observed. The three main results achieved were, first, overall reduction by 64% of the daily requirement for L-dopa; second, conversion from a previously unpredictable to a predictable response to each dose of L-dopa; and, third, change in his movement fluctuations to a pattern more typical of "end-of-dose" akinesia than the "on-off" phenomenon. The results support the idea of dopamine receptor resensitization upon reduction of the L-dopa dosage.

Humans↗
PubMed1978

Atropine blockade of cholinergic drugs on rabbit stomach muscle.

The competition between atropine and a full agonist, carbachol, was tested on dibenamine-pretreated smooth muscle of rabbit stomach. Even after extensive irreversible blockade by dibenamine, atropine blockade of the response to carbachol was still competitive and the atropine affinity constant was unchanged. This differed from the noncompetitive action of atropine in blocking the contractile effects of partial agonists such as pilocarpine or heptyl trimethylammonium. The results thus indicate that it is not possible to convert a full agonist into a partial agonist merely by reducing the number of available cholinergic receptors. The present study compares the competitive effect of atropine on the actions of the full agonist carbachol, under conditions of irreversible blockade, with the competitive effect of atropine on partial agonists such as pilocarpine or heptyl trimethylammonium.

Animals↗
PubMed1978

A study of carbachol-atropine interaction on intestinal smooth muscle vesicles, using a fluorescent probe.

Plasma membrane vesicles were prepared from guinea pig ileum longitudinal muscle. The vesicles were characterized by electron microscopy and analysis of lipid and protein content. They were shown to be free of gross contamination from actomyosin, sarcoplasmic reticulum, and mitochondria. 8-Anilino-1-naphthalene sulphonic acid (ANS) binding characteristics were similar to those found in other membranes. Both carbachol and atropine increased the fluorescence of ANS bound to this membrane, the maximum increase for atropine being greater than that for carbachol. Since neither drug effected the apparent affinity constant for the ANS-membrane interaction. It may be assumed that the increased fluorescence was due to an increase in the number of ANS binding sites. The carbachol-dependent increase in ANS fluorescence was blocked noncompetitively by atropine but not by tubocurarine or diphenhydramine. These latter two antagonists also increased ANS fluorescence but at much higher concentrations than either carbachol or atropine. Neither atropine nor carbachol increased ANS fluorescence on either erythrocyte ghosts or liposomes (prepared from a lipid extract of the muscle membrane).

Anilino Naphthalenesulfonates↗
PubMed1978

The effects of acetylcholine and atropine on the 22Na+ permeability of intestinal smooth muscle vesicles.

A technique is described which has enabled us to measure change in 22Na+ efflux from smooth muscle plasma membrane vesicles. The resting 22Na+ efflux from these sealed vesicles showed a concentration-dependent increase in response to acetylcholine and other muscarinic agonists, in similar concentrations to those which increased 42K+ efflux in whole muscle. The kinetics of this efflux were complex and could not be described by less than three exponential processes. The response to agonists has, therefore, been characterized by measurement of the half-life of 22Na+ efflux (t1/2). The acetylcholine effect was inhibited by atropine, but unlike the situation in the whole muscle, this inhibition was noncompetitive. Tubocuraine (a nicotinic antagonist) had no effect on this acetyl-choline response. Atropine has no effect by itself on the resting 22Na+ efflux, neither did tetrodotoxin or ouabain. 22Na+ efflux from erythrocyte ghosts and liposomes, prepared from lipid extracts of the smooth muscle plasma membrane, was not modified by acetylcholine or atropine.

Acetylcholine↗
PubMed1978

On the cross-reactivity of staphylococcal enterotoxins A, B, and C.

Strong cross-reactions were demonstrated for staphylococcal enterotoxins B (SEB) and C1 (SEC1) by antigen-binding capacity and by competitive binding ability. Both SEB and SEC1 combined completely with the heterologous antibody although requiring four times as much antiserum as the homologous enterotoxin and both displaced about one-third of the other enterotoxin from a heterologous antigen-antibody system. It is proposed that one of the three major antigenic determinants of these enterotoxins possesses a significant similarity but probably not an identity of structure. SEB and SEC1 did not combine with antiserum to enterotoxin A nor inhibit the reaction of SEA with anti-SEA. SEA had no intrinsic binding capacity for anti-SEB or anti SEC1 nor did it inhibit the binding of either enterotoxin to its own antibody. Affinity chromatography was employed to demonstrate that a small apparent binding of SEA to anti-SEB was due to antibody to SEA in the anti-SEB serum and that an almost complete displacement of SEC1 binding to anti-SEC1 was caused by contaminating SEC (about 0.01%) in preparations of enterotoxin A.

Antigen-Antibody Reactions↗
PubMed1976

Effect of single and double peptide bond scission by trypsin on the structure and activity of staphylococcal enterotoxin C.

Two peptide bonds of staphylococcal enterotoxin C, were hydrolyzed concurrently at quite different rates during limited digestion with trypsin. A Lys-Val at about position 92 in the disulfide loop was the first bond cleaved, followed by a Lys-Asx at about position 57 on the NH2-terminal side of the loop. Preparations of singly cleaved material (enterotoxin C1-T1) contained about 93% of the cleaved protein and 7% unreacted enterotoxin. Preparations of the doubly cleaved material (enterotoxin C1-T2) consisted of 98% enterotoxin C1-T2 and 2% enterotoxin C1-T1. In the absence of denaturant, enterotoxin C1-T2 behaved as a single particle. It gave a single peak on Sephadex G-75 with a sedimentation coefficient of 2.85 S and a molecular weight of 29,100 by sedimentation equilibrium. Circular dichroic spectra indicated only minor conformational differences between enterotoxins C1-T2 and C1. However conformational stability was significantly affected with the unfolding of enterotoxin C1-T2 in 4 M guanidine hydrochloride proceeding at about twice the rate of native enterotoxin. Enterotoxin C1-T2 was separated into 6,500 and 22,000 molecular weight polypeptides by gel filtration on Sepharose 6B in 6 M guanidine hydrochloride. Complementation (as measured by CD spectra, serologic activity and mitogenicity) of the two polypeptides was readily achieved from solution in 6 M guanidine hydrochloride by dialysis against phosphate buffer. The 22,000 molecular weight polypeptide was further separated into two peptides (Mr = 4,000 and 19,000 after alkylation of the reduced disulfide bridge. Summation of the amino acid composition of the constituent peptides of enterotoxin C1-T2 agreed well with the composition of enterotoxin C1. A comparison of the 6,500 and 4,000 molecular weight polypeptides from enterotoxin C1-T2 with structurally equivalent segments of enterotoxin B suggested structural homology between the two antigenic variants. Enterotoxins C1, C1-T1, and C1-T2 gave reactions of complete identity in Ouchterlony immunodiffusion and were indistinguishable in the quantitative precipitin reaction. Enterotoxins C1-T1 and C1-T2 were highly mitogenic but were slightly less potent than the native enterotoxin. Enterotoxin C1-T2 had equivalent emetic activity to enterotoxin C1 in rhesus monkeys. It is suggested that the exceptional lability to limited enzymic hydrolysis exemplified by enterotoxin C1 is associated with beta turn structures at protein surfaces.

Amino Acids↗
PubMed1976

Effects of a series of alcohols on the binding of a fluorescent dye to erythrocyte membranes.

1. The effects of a series of aliphatic alcohols (methanol to octanol) on membrane proteins of erythrocytes were studied by monitoring the flueorescence of a dye (1-anilino-8-naphthalenesulfonic acid (ANS)) that adsorbs to erythrocyte ghost membranes. Low concentrations of all the alcohols reduced the ANS fluorescence of the membrane-ANS suspensions; lent to those which protect against hypotonic hemolysis on intact erythrocytes; higher concentrations markedly increased the fluorescence. Ethanol and methanol decreased ANS fluorescence at all concentrations. 2. Lytic concentrations of saponin did not increase ANS fluorescence and did not modify the membrane action of the alcohols. 3. None of these effects were observed in liposomes prepared from lipid extracts of the erythrocyte membrane. 4. Since the apparent dissociation constant for the ANS-membrane interaction was unchanged in the presence of the alcohols, it was assumed that the fluorescence changes anesthetic concentration of the alcohols alter the conformation of membrane proteins, as indicated by the decreased number of ANS binding sites.

Alcohols↗
PubMed1975

Winter illness and vitamin C: the effect of relatively low doses.

After their random -llocation to one of three treatment aroups, 622 volunteers received either vitamin C or placebo in a maintenance dose of 500 mg once weekly and a therapeutic dose of 1500 mg daily on the 1st day and 1000 mg on the next 4 days of any illness. Two forms of vitamin C were employed: a sustained-release capsule containing ascorbic acid and a regular tabet containing a mixture of sodium and calcium ascorbate. In the 448 subjects who completed an average of 15 weeks in the study of total of 635 episodes of illness were recroded. Respiratory symptoms were recorded on at least 1 day in 92 per cent of these episodes. There were no consistent or significant differences in the sickness experience of the subjects receiving the sustained-release vitamin capsules compared to those receiving the vitamin tablets, but subjects in both vitamin groups experienced less severe illness than subjects in the placebo group, with approximately 25 per cent fewer days spent indoors because of the illness (P smaller than 0.05). These results are compatible with the belief that supplementary vitamin C can reduce the burden of winter illness, but the intake need not be as high as has sometimes been claimed.

Adolescent↗
PubMed1975

Immunogenicity of formaldehyde-inactivated enterotoxins A and C1 of Staphylococcus aureus.

Quantitative precipitation of antisera specific for native enterotoxin revealed that 70% and 60%, respectively, of the antigenic determinants of enterotoxins A and C1 of Staphylococcus aureus were inactivated by formaldehyde at pH 5.0 or 7.5 contained large polymers (excluded by Sepharose 2B) and induced strong humoral immune responses in rhesus monkeys. Enterotoxin A inactivated at pH 5.0 or 7.5 was composed mostly of small polymers (excluded by Sephadex G-100 but included by Sepharose 2B); it provoked a poor immune response in monkeys (about equivalent to the response obtained with weakly reactive toxin inactivated at alkaline pH). It was concluded that potent enterotoxoids were formed by extensive cross-linking of enterotoxin C1 into large polymers in acidic or neutral formaldehyde solution.

Animals↗
PubMed1975

Intrinsic and chemically produced microheterogeneity of Staphylococcus aureus enterotoxin type C.

Staphylococcus aureus enterotoxins C1 (SEC1) and C2 (SEC2) produced from 50-liter quantities of crude culture supernatants were purified chromatographically in a neutral or acid milieu. Microheterogenity of SEC1 was markedly increased by treatment of the purified toxin with alkali, and new more acidic charged species appeared. SEC2 was more heterogenous than any of the other S. aureus enterotoxins and was affected only slightly by treatment with alkali. Prolonged incubation of the organism during production of the SEC2 produced changes in charged species that may be related to a bacterial deamidase, since similar changes were not seen with alkaline treatment of the purified toxin. Although SEC1 and SEC2 showed complete identity immunologically, they are separate, distinct toxins, and alkali treatment of SEC1 did not produce SEC2.

Alkalies↗
PubMed1975

Mitogenicity of formalinized toxoids of staphylococcal enterotoxin B.

Staphylococcal enterotoxin B is a potent mitogen for mouse and human lymphocytes. Mitogenic activity was retained after detoxification of the enterotoxin by formaldehyde at pH 5.0, 7.5, OR 9.5. The most active toxoid (pH 7.5) was separated into a monomeric, a dimeric, and a polymeric fraction (1 x 10(5) to 3 x 10(5) molecular weight) by gel filtration, and although each fraction demonstrated mitogenic activity, the polymeric fraction was clearly the most efficacious. These data show that mitogenicity of staphylococcal enterotoxin B does not depend on toxicity. This suggests that the mitogenic and toxic activities are effected by different sites on the molecule.

Animals↗
PubMed1975

Production, purification, and chemical characterization of Staphylococcus aureus exfoliative toxin.

Methods for the production and isolation of exfoliative toxin are described. Fermentation conditions were established under which large quantities of the crude material can be produced. Column chromatography methods, including carboxymethyl cellulose and hydroxyapatite, were utilized to purify the toxic protein. The pure toxin had a molecular weight of 26,000 as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The pure toxin is a simple protein composed of 17 amino acids. Tests for carbohydrate and for alpha- and beta-hemolysin were negative. The mean effective dose of the purified toxin was 0.5 mug per newborn mouse.

Amino Acids↗