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Biomedical subjects

L M Simon

Publications and source records attributed to L M Simon.

At least 19 recordsLinked to original sources
PubMed2004

Effects of polyethylene glycol on stability of alpha-chymotrypsin in aqueous ethanol solvent.

The effects of polyethylene glycol (PEG) of different molecular weights (400, 2000, 6000, 12,000, 20,000, and 35,000) on the conformational stability and catalytic activity of alpha-chymotrypsin in 60% ethanol were studied. The inactivation caused by the organic solvent was not influenced by PEG 400. However, the PEGs with higher molecular weights up to 35,000 increased the stability of the enzyme, but this alpha-chymotrypsin stabilizing effect was molecular weight-independent. With increase of the molecular weight of PEG, a more stable tertiary structure of the enzyme was observed.

Chymotrypsin↗
PubMed2003

Effects of Ca2+ on catalytic activity and conformation of trypsin and alpha-chymotrypsin in aqueous ethanol.

The effects of calcium ions on the conformation and catalytic activity of trypsin and alpha-chymotrypsin were studied in aqueous ethanol. The activity of alpha-chymotrypsin was practically lost within 10 min in the presence of 60% ethanol while trypsin preserved about 40% of its original activity even in 85% ethanol at pH 3. The catalytic activity of alpha-chymotrypsin did not decrease in the presence of 1.2M CaCl2 and 0.6M CaCl2 with trypsin in ethanolic solvent. In the latter case an activation of enzyme was observed. The stabilizing effects of calcium ions were accompanied by an increase in the helical content in both enzymes, as followed by circular dichroism measurements.

Calcium↗
PubMed2002

Effects of polyhydroxy compounds on the structure and activity of alpha-chymotrypsin.

The effects of glycerol, polyethylene glycol, fructose, glucose, sorbitol, and saccharose on the conformation and catalytic activity of alpha-chymotrypsin were studied in 0.1 M sodium phosphate buffer and buffered aqueous 60% ethanol (pH 8.0). The enzyme activity was practically completely lost within 10 min in 60% ethanol, but in the presence of stabilizers the activity was retained. With the exception of polyethylene glycol, the stabilizing effect decreased with increase of the incubation time. The preservation of the catalytic activity was accompanied by changes in the secondary and tertiary structures of alpha-chymotrypsin.

Animals↗
PubMed2001

Structure and activity of alpha-chymotrypsin and trypsin in aqueous organic media.

The effects of different concentrations (20-95%) of organic solvents (ethanol, 1,4-dioxane and acetonitrile) were studied on alpha-chymotrypsin and trypsin from bovine pancreas. The changes in secondary structure were followed by CD measurements, and the apparent Michaelis constants (KMapp) and the stabilities of the enzymes were determined. Significant alterations in the CD spectra were found for both enzymes at the different organic solvent concentrations. The apparent KM values of trypsin and alpha-chymotrypsin decreased as the low solvent concentrations were elevated, but then increased in the presence of higher organic solvent concentrations. The stabilities of the enzymes changed on increase of the organic solvent concentration; trypsin exhibited a higher stability than that of alpha-chymotrypsin in all organic solvents. These results show that at an organic solvent content of 95% the manifestation of an enzyme activity similar to that measured in water can be attributed to the similar compositions of the secondary structural elements.

Acetonitriles↗
PubMed2000

An examination of the assumptions of specialization, mental disorder, and dangerousness in sex offenders.

Sex offenders have been singled out for differential treatment by the legal and mental health systems. This article attempts to inform law reform efforts and criminal justice mental health policy by examining the assumptions underlying differential legal and mental health treatment of sex offenders. These assumptions include the theories that sex offenders are mentally disordered and in need of treatment, specialists in sex crimes, and more dangerous than other criminal offenders. Empirical findings demonstrate that sex offenders are not specialists in sex crimes and are not mentally disordered. Examination of past research suggests that sex offenders are not at more risk than other criminal offenders to commit future sex crimes. Implications of research findings for selective prosecution of sex crime cases, mental health policy, sex offender legislation, and predictions of future dangerousness are discussed. Proposals for future research needs and law reform are presented.

Adult↗
PubMed1999

Effects of synthetic pyrethroids and methidation on activities of some digestive enzymes in carp (Cyprinus carpio L.).

The effects of pyrethroid pesticides (deltamethrin, permethrin and cypermethrin) and an organophosphate ester (methidation) on the activities of carp trypsin, alpha-chymotrypsin, carboxypeptidase A and lipase were studied. The enzymes were isolated from the gastrointestinal tract and the effects of the pesticides were investigated during incubation for 5 min. The activity of trypsin was influenced only slightly by the presence of deltamethrin and methidation, whereas permethrin and cypermethrin caused significant inhibition. The pyrethroid pesticides at lower concentrations resulted in a slight activation of alpha-chymotrypsin. Methidation inhibited the alpha-chymotrypsin activity by about 20%. These pesticides modified the lipase activity to a lesser extent; the highest inhibition was measured with cypermethrin. The carboxypeptidase A activity was inhibited by both pyrethroid pesticides and methidation. The results suggest that these pesticides might interact with the active conformation of the studied hydrolytic enzymes, resulting in changes in their activities.

Animals↗
PubMed1998

Carboxypeptidase A-catalyzed dipeptide synthesis in organic media.

The carboxypeptidase A-catalyzed syntheses of dipeptides from L-amino acids (Phe, Tyr, Trp, Leu and Ile) were studied in various water-miscible (acetone, acetonitrile, ethanol, methanol and 1,4-dioxane) organic solvents. The highest yield (43%) was achieved in acetonitrile with L-Phe as substrate, after a 24-h incubation. The optimal conditions of Phe-Phe synthesis in acetonitrile were determined. For maximal conversion 1.2 mM L-Phe, 1.4 mg ml-1 enzyme and about 10% water are needed in buffered aqueous acetonitrile (pH 5.5) at 30 degrees C.

Acetonitriles↗
PubMed1994

Coenzyme production using immobilized enzymes. III. Immobilization of glucose-6-phosphate dehydrogenase from bakers' yeast.

Glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate: NADP+ 1-oxidoreductase, EC 1.1.1.49) from Bakers' yeast was immobilized with the highest activity on polyacrylamide beads possessing carboxylic functional groups activated by a water-soluble carbodiimide. The optimal pH values for the catalytic activity of the soluble and the immobilized glucose-6-phosphate dehydrogenase were practically identical, lying between pH 9.0 and 9.2. The optimal temperature for both the soluble and the immobilized enzyme was about 50 degrees C. The apparent Km values of the immobilized enzyme were slightly higher than those of the soluble enzyme. The immobilization improved the stability of the enzyme in the pH range 6.0-9.0 at 45 degrees C. The operational stability of the immobilized glucose-6-phosphate dehydrogenase proved favorable in a column experiment during 37 days of operation.

CME-Carbodiimide↗
PubMed1990

Effects of polyethylene terephthalate on yeast alcohol dehydrogenase.

Yeast alcohol dehydrogenase (alcohol: NAD+ oxidoreductase, EC 1.1.1.1) was adsorbed onto polyethylene terephthalate, a synthetic polymer. The effects of the polymer on the properties of the enzyme were studied. The specific activity of the bound enzyme on protein basis was only 1.2 per cent of the specific activity of the soluble enzyme. The optimum pH for the catalytic activity was strongly shifted toward acidic direction. The apparent temperature optimum of the bound enzyme was identical with that of the soluble form. The apparent Michaelis constants of the bound enzyme were higher for both ethanol and NAD+. The conformational stability of the enzyme against heat treatment and urea was decreased as a consequence of adsorption.

Adsorption↗
PubMed1988

Endotoxin and pulmonary cell injury.

The physiopathologic similarity between adult respiratory distress syndrome (ARDS) secondary to sepsis and endotoxin-induced pulmonary abnormalities has provided extensive descriptive information confirming bacterial endotoxin as a factor initiating the heterogeneous pulmonary changes in ARDS. The present studies have used an established in vitro model for pulmonary cell injury to examine bacterial endotoxin 1, as a direct cytotoxic agent on the two major alveolar cell types, pulmonary endothelium and epithelium; 2, as a stimulant of neutrophil-mediated pulmonary cell injury, and 3, to examine effector mechanisms of cell-mediated damage by studying the potential effectiveness of antioxidants and antiproteolytic agents in the inhibition of this process. Endotoxin direct toxicity and stimulation of neutrophil-mediated pulmonary cell injury was observed in both pulmonary cell populations in systems free of activated serum complement. Endothelial cells were observed to be more susceptible to both the direct effect of endotoxin and to neutrophil-mediated injury when compared with epithelial cell derived monolayers. The addition of an antiprotease (soybean trypsin inhibitor [STI]) was superior to antioxidants (catalase, superoxide dismutase) in reducing the neutrophil-mediated endothelial toxicity (stimulated 51CR per cent release) observed. A 92 per cent degree of protection was observed with the highest dose of STI (5 milligrams per milliliter) used. Proteases released by activated neutrophils on endotoxin stimulation appear to be the predominant toxic species responsible for endothelial injury in this system.

Antioxidants↗
PubMed1988

Determination of glycolytic intermediates in a flow injection system using immobilized enzymes.

Some glycolytic enzymes (lactate dehydrogenase, pyruvate kinase, enolase and phosphoglyceromutase) were immobilized on a polyacrylamide-type bead polymer containing carboxylic functional groups activated by water-soluble carbodiimide. The immobilized enzymes were used for the determination of pyruvic acid, phosphoenolpyruvic acid, 2-phosphoglyceric acid and 3-phosphoglyceric acid in a flow injection system. The immobilized lactate dehydrogenase column was repeatedly employed for the determination of pyruvic acid in clinical samples. The results of the flow injection method accorded well in accuracy, sensitivity and reproducibility with those of soluble enzyme analysis.

Enzyme Stability↗
PubMed1986

Immobilization of lactate dehydrogenase on polyacrylamide beads.

Pig muscle lactate dehydrogenase (L-lactate:NAD oxidoreductase, EC 1.1.1.27) was covalently immobilized on polyacrylamide beads containing carboxylic functional groups activated by water-soluble carbodiimide. The effects of immobilization on the catalytic properties and stability of the lactate dehydrogenase were studied. There was no shift in the pH optimum of the immobilized enzyme compared to that of the soluble one. The apparent optimum temperature of the soluble enzyme was 65 degrees C, while that of the immobilized enzyme was between 50 and 65 degrees C. The apparent Km values of the immobilized enzyme with pyruvate and NADH substrates were higher than those of the soluble enzyme. As a result of immobilization, enhanced stabilities were found against heat treatment, changes in pH, and urea denaturation.

Acrylic Resins↗
PubMed1985

Comparative studies on soluble and immobilized rabbit muscle pyruvate kinase.

Rabbit muscle pyruvate kinase was immobilized by covalent attachment to a polyacrylamide support (Akrilex C) containing carboxylic functional groups. As a result of immobilization, the pH optimum for catalytic activity shifted into a more alkaline direction. The apparent Km value with phosphoenolpyruvate increased, and that with ADP slightly decreased. With respect to the stability against urea and thermal inactivation, the immobilized pyruvate kinase seemed to be the more stable at lower urea concentrations and between 45 and 55 degrees C. At 1.5 and 2.5M urea and at higher temperature, there were no marked differences between the soluble and the immobilized enzyme.

Animals↗
PubMed1985

Lung cell oxidant injury: decrease in oxidant mediated cytotoxicity by N-acetylcysteine.

Lung cell damage mediate by polymorphonuclear leukocyte (PMN) reactive oxygen metabolites has been suggested as a pathophysiologic mechanism in a variety of acute and chronic pulmonary disease states, while oxidant injury may be a non-specific cytotoxic mechanism. Reducing agents therefore represent one therapeutic direction for decreasing lung cell injury in several clinical circumstances. N-Acetylcysteine (NAC) is a known antioxidant which can be distributed in soluble form to multiple intrapulmonary sites. We have therefore examined a possible role for NAC against oxidant injury in a controlled in vitro model for oxygen metabolite cytotoxicity. Our data suggest that extracellular NAC is able to protect lung cells against PMN mediated oxidant injury. Pre-exposure of lung cells to NAC results in decreased susceptibility to oxidant damage by increasing intracellular antioxidant defense systems. An increase in extracellular and/or intracellular resistance to toxic oxygen metabolites by NAC may be one approach to the prevention of in vivo lung oxidant injury.

Acetylcysteine↗
PubMed1984

Studies on the properties of glucose-6-phosphatase from carp liver microsomes (Cyprinus carpio L.).

The effects of temperature and pH on the phosphohydrolase activity of carp hepatic glucose-6-phosphatase (EC 3.1.3.9) have been investigated. The enzyme activity was maximum at about 308 K and in the pH range 5-6.5. The apparent Michaelis constant (KM) and Vmax of the reaction with glucose-6-phosphate were found to be 14.8 mM and 2.27 nmol/min/mg protein. The enzyme activity was partly inhibited by EDTA, while in the presence of sufficient PCMB virtually total inhibition was observed.

Animals↗
PubMed1983

Transepithelial transport in cell culture: bioenergetics of Na-, D-glucose-coupled transport.

The renal cell line LLC-PK1 cotransports Na and D-glucose from the apical to the basolateral side of the cell monolayer, and the short-circuit current (Isc) measures the net amount of Na transported. Under conditions of maximal cotransport, the addition of phlorizin or removal of Na reversibly decreased oxygen consumption by one-half. In the absence of glycolytic substrates, alpha-methyl-D-glucoside stimulated Isc and oxygen consumption, although the Isc came to a steady state 50% less than when glycolytic substrates were present. The addition of other aerobic substrates did not increase Isc; however, when non-cotransported glycolytic substrates were introduced the Isc returned to a maximum with an associated fall in oxygen consumption and increased lactate production. Thus, in the absence of glycolytic substrates aerobic ATP formation may be rate-limiting for Na, D-glucose cotransport. For this epithelium glycolysis makes an important contribution to the provision of energy for transport. Oxygen consumption does not correlate well with Isc and is not a good measure of the energy used in transport.

Animals↗