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At least 307 records · Page 17Linked to original sources
PubMed1991

Interaction of 4-aminopyridine with normal and chloramine-T-modified K channels of neuroblastoma cells.

The steady-state effects and rate of action of 4-aminopyridine (4-AP) on normal and chloramine-T (CL-T)-modified voltage-dependent potassium (K) currents were studied in neuroblastoma cells with the whole-cell voltage-clamp current recording technique. 4-AP apparently slows both the activation and inactivation of the normal current but does not modify the time course of the CL-T-modified current. These differential effects of 4-AP are interpreted as resulting from the existence of two types of K channels with different 4-AP sensitivities under normal conditions and similar 4-AP sensitivities after CL-T, which furthermore slows their inactivation [8, 9]. While the onset of 4-AP action on the normal current is delayed and can be described by the difference of two exponentials, the onset of 4-AP action on CL-T-modified current starts immediately after the external application of the drug and can be described by the sum of two exponentials. The 4-AP-induced block of the normal current exhibits use-dependent features and is relieved by long conditioning depolarizations. In contrast, the block of the CL-T-modified current is not use-dependent. At high 4-AP concentrations (1-10 mM), the steady-state block of the normal current reaches a saturating value of 95%, while the steady-state block of the CL-T-modified current and the "unblocked" normal current only reaches a saturating value of 35%. The results suggest that CL-T inhibits a channel or membrane constituent which contributes to the inactivation of channels and increases their apparent affinity for 4-AP when they are in closed or open states.(ABSTRACT TRUNCATED AT 250 WORDS)

4-Aminopyridine↗
PubMed1983

Identification of a locus modifying the electrophoretic mobility of malate dehydrogenase isozymes in incense-cedar (Calocedrus decurrens), and its implications for population studies.

Using megagametophyte (maternal haploid) and embryo (diploid) tissues of incense-cedar seeds, the expression of one of three malate dehydrogenase (MDH) loci was found to be influenced by a second, unlinked, modifier locus. Whereas alleles of the affected structural locus are codominant, the modifier alleles show dominance. The action of the modifier, limited to 1 of 28 structural loci examined, results in a shift of electrophoretic mobility detectable in conventional starch gels. Both the structural and the modifier MDH loci are polymorphic in all populations surveyed. Studies of genetic variation in natural populations made without rigorous genetic analysis may not detect such modification. By misinterpreting the genetic basis of enzyme phenotypes, such undetected modification can result in overestimates of genetic diversity in natural populations and can cause an apparent excess of homozygotes relative to expectations. These effects on allele and genotype frequency estimates are dependent on the levels of polymorphism at both the structural and the modifier loci. Using procedures common to many surveys of electrophoretic variation, the frequency of a recessive modifier allele could be as high as 0.3 before being detected.

Electrophoresis↗
PubMed1988

Differential effect of food on kinetics of bromocriptine in a modified release capsule and a conventional formulation.

The influence of food on release of drug from a modified release capsule of bromocriptine 5 mg (Parlodel SRO) and a conventional formulation of bromocriptine 5 mg has been studied in 8 healthy male volunteers. Both formulations produced objective and subjective effects, such as orthostatic reactions, nausea, dizziness, vomiting and nasal congestion. The modified release capsule caused fewer side-effects than the normal capsule. Both formulations had less cardiovascular effect in the fed than in the fasting state. There was no significant difference between the normal and the modified release capsules taken fasting or after a meal in terms of the AUC extrapolated to infinity. The relative bioavailability of the 5 mg modified release capsule was 84.6% of the normal capsule under fasting conditions and 107.5% after food. In contrast to the virtually unchanged extent of absorption, the rate of absorption was markedly affected by food, especially from the conventional capsule. The mean time of 50% absorption increased from 1.06 h (fasting) to 3.2 h (fed), whereas for the modified release capsule food mainly resulted in an increased lag time of absorption. The almost instantaneous dissolution of bromocriptine from the normal capsule in vitro (both in HCl and fasting human gastric juice) and the delay of absorption after a meal in vivo suggest that the rate limiting step in absorption of the normal capsules is delivery of released drug from the stomach to the small intestine, which is delayed by food. Both the modified release 5-mg capsule and the normal 5-mg capsule showed extended suppression of prolactin over 36 h, in all subjects, both fasted and after a meal.

Adult↗
PubMed1988

Pharmacokinetics of low-dose oral modified release, soluble and intravenous aspirin in man, and effects on platelet function.

The pharmacokinetics of low-dose aspirin and the resulting salicylic acid were studied in 6 healthy volunteers. Each received a single 50-mg dose of (1) oral modified release capsules, (2) oral solution and (3) intravenous solution. The volunteers also received 50 mg modified release capsules daily for 6 days to determine the effect on collagen, ADP and arachidonate induced platelet aggregation and thromboxane production, and to compare the pharmacokinetics after repeated dosing with the parameters obtained after the single dose. The formulation and route of administration profoundly influenced several pharmacokinetic parameters for aspirin: the maximum concentration (Cmax, ng.ml-1) was 221 and 191 after modified release for single and chronic dosing respectively, 1323 after the oral solution and 6000 after intravenous injection; the time to achieve this maximum concentration (tmax, h) was 3.42 and 3.02 after modified release for single and chronic dosing respectively, and 0.29 after the oral solution; the area under the plasma drug concentration versus time curve (AUC, microgram.h.ml-1) was 0.38 and 0.27 after modified release single and chronic dosing respectively, 0.68 after the oral solution and 1.57 after intravenous injection. The elimination of aspirin after the two solutions was at least biphasic. The terminal phase rate constant ranged from 1.52 h-1 after intravenous injection to 1.88 h-1 after the oral modified release form. The absorption of the oral forms of aspirin was complete as reflected by the total recovery of the doses as salicylic acid in urine.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1981

Effect of chemical modifiers of amino acid residues on proton conduction by the H+-ATPase of mitochondria.

The effect of chemical modifiers of amino acid residues on the proton conductivity of H+-ATPase in "inside out" submitochondrial particles has been studied. Treatment of submitochondrial particles prepared in the presence of EDTA (ESMP) with the arginine modifiers, phenylglyoxal or butanedione, or the tyrosine modifier, tetranitromethane, caused inhibition of the ATPase activity. Phenylglyoxal and tetranitromethane also caused inhibition of the anaerobic release of respiratory delta micro H+ in ESMP as well as in particles deprived of F1 (USMP). Butanedione treatment caused, on the contrary, acceleration of anaerobic proton release in both particles. The inhibition of proton release caused by phenylglyoxal and tetranitromethane exhibition in USMP a sigmoidal titration curve. The same inhibitory pattern was observed with oligomycin and with N,N'-dicyclohexylcarbodiimide. In ESMP, relaxation of delta micro H+ exhibited two first-order phases, both an expression of the H+ conductivity of the ATPase complex. The rapid phase results from transient enhancement of H+ conduction caused by respiratory delta micro H+ itself. Oligomycin, N,N'-dicyclohexylcarbodiimide, and tetranitromethane inhibited both phases of H+ release, and butanedione accelerated both. Phenylglyoxal inhibited principally the slow phase of H+ conduction. In USMP, H+ release followed simple first-order kinetics. Oligomycin depressed H+ release, enhanced respiratory delta micro H+, and restored the biphasicity of H+ release. Phenylglyoxal and tetranitromethane inhibited H+ release in USMP without modifying its first-order kinetics. Butanedione treatment caused biphasicity of H+ release from USMP, introducing a very rapid phase of H+ release. Addition of soluble F1 to USMP also restored biphasicity of H+ release. A mechanism of proton conduction by Fo is discussed based on involvement of tyrosine or other hydroxyl residues, in series with the DCCD-reactive acid residue. There are apparently two functionally different species of arginine or other basic residues: those modified by phenylglyoxal, which facilitate H+ conduction, and those modified by butanedione, which retard H+ diffusion.

Adenosine Triphosphatases↗
PubMed2000

Modifier effects on supercritical CO2 extraction efficiency of cephalotaxine from Cephalotaxus wilsoniana leaves.

The effects of modifiers such as methanol, water, diethylamine in methanol (10 v/v %), and diethylamine in water (10 v/v %) were investigated at three different concentrations (1, 5, and 10 v/v %) of the modifiers in supercritical CO2 (SC-CO2) in order to enhance the supercritical fluid extraction (SFE) efficiency of cephalotaxine from Cephalotaxus wilsoniana leaves. Among the modifiers employed, methanol basified with diethylamine was found to greatly enhance the extraction efficiency relative to any other modifiers employed. The results suggest that cephalotaxine in plant matrices may be readily changed from SC-CO2-insoluble salt to SC-CO2-soluble free base by basified modifiers. In addition, SC-CO2 modified with basified methanol could enhance the extraction efficiency of cephalotaxine more than 30% when compared to the conventional organic solvent extraction.

Antineoplastic Agents, Phytogenic↗
PubMed1993

Ultrafiltration and modified ultrafiltration in pediatric open heart operations.

The capillary leak associated with cardiopulmonary bypass results in an increase in content of water in the tissues measurable by an increase in total body water after cardiac operation. Following work by Magilligan in the 1970s, ultrafiltration was introduced during bypass as a means of hemoconcentrating patients and potentially removing water from the tissues. Conventional methods proved inconsistent; thus, we modified the technique to ultrafilter the patients immediately after cessation of bypass. Modified ultrafiltration takes 10 minutes and results in an elevation of the on-bypass hematocrit to about 35% or 40%. In pilot studies comparing bypass in absence of ultrafiltration with conventional ultrafiltration and modified ultrafiltration, only the modified technique was seen reliably to reduce the elevation in total body water to only 4%, within a narrow range. Subsequent prospective studies confirmed the reduction in accumulation of total body water and also demonstrated a reduction in blood loss and in requirements for blood transfusion. Systolic blood pressure was observed to increase uniformly in all patients undergoing modified ultrafiltration. This effect was investigated and found to be associated with a marked increase in cardiac index, no change in systemic vascular resistance, a decrease in heart rate, and a marked decrease in pulmonary vascular resistance. Recently, we have demonstrated an increase in contractility and a decrease in myocardial wall volume. The modified technique of ultrafiltration has been employed successfully in more than 400 patients in our institution, and represents an excellent option for perioperative management of both accumulation of fluid in the tissues and hemodynamics after hypothermic bypass.

Adolescent↗
PubMed1996

Effective 30-hour preservation of canine lungs with modified ET-Kyoto solution.

BACKGROUND: With the aim of developing a preservation solution that can preserve donor lungs reliably for a long time, we prepared a modified ET-Kyoto solution by adding N-acetylcysteine, nitroglycerin, and dibutyryl adenosine 3', 5'-cyclic phosphate to the previously reported ET-Kyoto solution, which contains trehalose, gluconate, and hydroxyethyl starch. In this study, we examined the efficacy of modified ET-Kyoto solution in 30-hour lung preservation. METHODS: Twenty five pairs of adult mongrel dogs were divided into four groups. Donor lungs were flushed with modified ET-Kyoto solution (n = 9), with ET-Kyoto solution (n = 6), with University of Wisconsin solution group (n = 6), or with ET-Kyoto solution plus the solvents of nitroglycerin (ethanol and propylene glycol) (n = 4), then stored at 4 degrees C for 30 hours. All animals were treated with prostaglandin E1. Left lungs were transplanted and reperfused for 6 hours. RESULTS: With respect to arterial oxygen tension, peak inspiratory pressure, and wet-to-dry lung weight ratio, modified ET-Kyoto solution was significantly superior to ET-Kyoto solution. The modified ET-Kyoto solution was significantly superior to University of Wisconsin solution with respect to survival rate, arterial oxygen tension, and wet-to-dry lung weight ratio. Ultrastructural findings supported these results. CONCLUSIONS: These results suggest that modified ET-Kyoto solution is superior to University of Wisconsin solution for 30-hour lung preservation.

Acetylcysteine↗
PubMed1980

The sulphatase of ox liver. XXIII. The nature of substrate-modified sulphatase A.

An improved method is described for the preparation of milligram quantities of substrate-modified sulphatase A. The latter has the same molecular weight and the same ability to form a tetramer as has native sulphatase A. It has been shown that the modified enzyme prepared with nitrocatechol [35S]sulphate as substrate contains 1 mol 35SO24- per mol enzyme and that any treatment which causes reversion of the modified enzyme to native enzyme is accompanied by the loss of the bound SO24-. Dialysis of the 35S-modified enzyme against a solution containing SO24- causes a loss of 35SO24- with no change in the amount of modified enzyme in the preparation. It has been shown that the activation of the substrate-modified enzyme by SO24- does not lead to the formation of a third stable form of sulphatase A.

Animals↗
PubMed1977

Preparation and enzymatic hydrolysis of dinucleoside monophosphates and DNA modified with aromatic residues.

The following procedures have been used to prepare fifteen modified dinucleoside monophosphates: (a) bisulfite-catalyzed transamination with aniline to give an N4-phenylcytidine (CPh), (b) bisulfite-catalyzed transamination with beta-naphthylamine to give an N4-beta-naphthylcytidine (CbetaN), (c) alkylation with 7-bromomethylbenz[a] anthracene to afford a 7(benz[a]anthryl-7-methyl)guanosine (GMBA), and (d) reaction with N-acetoxy-2-acetylaminofluorene to give an 8-(N-2-fluorenylacetamido)guanosine (GAAF). The compounds prepared were A-CPh, CPh-A, CPh-G, U-CPh, CPh-U, A-CbetaN, CbetaN-A, G-CbetaN, CbetaN-G, U-CbetaN, CbetaN-U, GMBA-U, U-GMBA, GAAF-U, and U-GAAF. All of the modified compounds were hydrolyzed to the expected monomers with venom and spleen exonucleases. Hydrolysis by micrococcal nuclease was inhibited in the following cases: A-CPh, A-CbetaN, U-GMBA, and U-GAAF. The first three reactions above were applied to denatured calf thymus DNA to prepare modified DNA samples containing from 0.3 to 2.0% bound aromatic residues. The modified nucleic acids were completely hydrolyzed to nucleosides by the combination of venom exonuclease, deoxyribonuclease I and alkaline phosphatase. The same results were obtained with a combination of spleen exonuclease, deoxyribonuclease II, and alkaline phosphatase. Hydrolysis of the modified nucleic acids by micrococcal nuclease and alkaline phosphatase afforded primarily nucleosides, with some dinucleoside monophosphates. The amount of the latter did not exceed that found in the hydrolysis of control DNA, however. Other workers have observed inhibition of enzymatic hydrolysis of nucleic acids modified by aromatic carcinogens. We postulated that their results may have been caused by cross-links, which were avoided in our studies.

Animals↗
PubMed1991

Survival and differentiation within the adult mouse striatum of grafted rat pheochromocytoma cells (PC12) genetically modified to express recombinant beta-NGF.

Rat pheochromocytoma PC12 cells were genetically modified in vitro to express recombinant beta-nerve growth factor (beta-NGF) using a replication-deficient retroviral vector carrying the mouse beta-NGF gene and subsequently implanted into the striatum of a mouse model of Parkinson's disease. The fate of the genetically modified PC12 cells (PC12N.8) was assessed at varying times postimplantation by studying immunoreactivity (IR) to tyrosine hydroxylase (TH) or the rat NGF receptor (NGFR). In vitro, the genetically modified PC12 cells displayed a neuronal morphology in the absence of exogenous NGF which was characterized by extensive neurite outgrowth. In addition, the genetically modified PC12 displayed a catecholaminergic phenotype in vitro as assessed by TH-IR. Following implantation into the striatum, the survival of PC12N.8 cells was limited. Surviving cells could be identified by NGFR-IR, but not by TH-IR. In addition, PC12N.8 cells with a neuronal morphology similar to that observed in vitro were only rarely observed in vivo. No tumors were observed in PC12N.8 graft recipients up to 30 days postimplantation. In contrast, intrastriatal tumors were observed in 50% of the PC12 cell recipients. These data demonstrate that PC12 cells genetically modified in vitro to synthesize beta-NGF do not revert to the mitotic phenotype of the parent PC12 cell line following implantation into the adult striatum, an observation that suggests that these cells may continue to express recombinant beta-NGF in vivo. The data further suggest that the genetically modified PC12 cells lose the catecholaminergic phenotype following implantation into the striatal parenchyma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Gland Neoplasms↗
PubMed1988

Quantification of plasma lipids and apolipoproteins in British Halflop rabbits. A comparison between normocholesterolemic rabbits, hypercholesterolemic rabbits (modified WHHL rabbits) and rabbits fed an atherogenic diet.

We have established isolation methods and developed electroimmunoassays for rabbit apolipoprotein A-I (apo A-I), apo B, apo C-III and apo E. The assays were used to characterize a hyperlipidemic strain of the British Halflop rabbits (BHL rabbits), obtained after cross-breeding with WHHL rabbits and referred to as modified WHHL rabbits, and to investigate the changes in the apolipoprotein levels induced by feeding normal BHL rabbits an atherogenic diet (0.25% cholesterol and 3% coconut oil). The modified WHHL rabbits were characterized by increased levels of apo B, apo C-III and apo E as well as cholesterol, phospholipids and triacylglycerol as compared to chow-fed BHL rabbits, while the apo A-I levels were only half of those found in the chow-fed animals. The modified WHHL rabbits had virtually no low density lipoprotein (LDL) receptor activity and a low fractional catabolic rate (FCR) of LDL. These results indicate that the modified WHHL rabbit has the homozygous form of the LDL receptor deficiency. The BHL rabbits fed the atherogenic diet showed increased levels of cholesterol, triacylglycerol, apo B, apo C-III and apo E, as compared to those of the chow-fed BHL rabbits. The apo E and apo C-III reached levels in the range of or even higher than those of the modified WHHL rabbits. The apo A-I levels on the other hand did not differ from those of the chow-fed rabbits. Feeding an atherogenic diet led to a decrease in the FCR of LDL to a level similar to that found in the modified WHHL rabbits.

Animals↗
PubMed1986

The standardisation of gauge length: its influence on the relative extensibility of natural and chemically modified pericardium.

Cyclic uniaxial load tests were performed on natural and chemically modified bovine pericardium which is used in the construction of heart valve substitutes. A template was employed to select specimens from the same sites in different pericardial sacs. When the pericardium was chemically modified by glutaraldehyde fixation as an entire sac the tissue showed increased extensibility after modification compared with the natural tissue. The undeformed stress-free length (gauge length) in both the natural and modified tissue was determined by a highly reproducible experimental method giving a coefficient of variation of less than 0.5%. Specimens excised from a natural pericardial sac demonstrated a significant increase (p less than 0.03) in length, 4.97 +/- 3.49%, after a single load cycle, compared with controls placed in isotonic saline but not mechanically tested. The test pieces had returned to their original length by 8.5 h after the mechanical test. After fixation the same specimens decreased significantly in length (p less than 0.001) by 11.18 +/- 4.28%. This shrinkage was not significantly different to that of the control specimens (11.09 +/- 2.47%) which had not been tested. Uniaxial loading of these chemically modified strips demonstrated a similar increase in tissue extensibility compared to the natural tissue if the undeformed length of the test specimen after shrinkage was used as the gauge length. After mechanical conditioning the chemically modified tissue also demonstrated a significant increase (p less than 0.001) in stress-free length (5.35 +/- 0.59% after 36 cycles, 8.92 +/- 1.50% after 2085 cycles). These deformations were not permanent. The tissue had returned to its original length after 38 h in its normal buffered glutaraldehyde storage medium. On the basis of these observations, recommendations for the clarification and standardisation of gauge length definitions were made in natural, chemically modified and mechanically conditioned tissue.

Animals↗
PubMed1983

The fate of autosomal modifiers of the sex-ratio trait in drosophila and other sex-linked meiotic drive systems.

A model is proposed to analyze the behavior of autosomal suppressor modifiers of "Sex-Ratio" meiotic drive in drosophila. These modifiers, if neutral in fitness, are expected to increase because they tend to be associated with the rare sex (males). However, selection operating on the sex-linked drive locus will sometimes act against autosomal modifiers as well because the two loci are always in gametic phase disequilibrium. Conditions under which modifiers will not increase are presented in terms of the relative fitness of the sex-linked drive locus. To prevent the increase of modifiers, the fitness of Sex-Ratio males relative to Standard males has to be no greater than 0.3 and there has to be overdominance in females. This model integrates findings from the search for modifiers and results from the measurement of fitness.

Animals↗
PubMed1996

Hepatocyte culture on carbohydrate-modified star polyethylene oxide hydrogels.

We describe the synthesis and in vitro biological characterization of a new class of carbohydrate-modified hydrogels based on radiation-cross-linked star polyethylene oxide (PEO). Hydrogels were synthesized from either of two types of PEO star molecules in order to vary the terminal hydroxyl content of the gels while keeping other gel properties such as molecular weight between cross-links and water content constant. The resulting gels were covalently modified with monosaccharide ligands and the behaviour of primary rat hepatocytes on the modified gels was evaluated under culture conditions. Hepatocytes exhibited a sugar-specific adhesion to the modified gels, adhering to gels bearing galactose but not glucose. Cell spreading was observed on both types of galactose-modified PEO star gels; moreover, the gels supported long-term (6 d) culture and differentiated function of primary hepatocytes. Further, on comparing the cell spreading behaviour observed on the PEO star gels with that reported previously for galactose-modified polyacrylamide, we find that our gels elicit spreading at ligand concentrations lower by an order of magnitude. A simple mechanistic analysis indicates that this enhanced ability of PEO star gels to support spreading of primary hepatocytes on low concentrations of immobilized galactose derives from freedom of the immobilized ligands to come within sufficiently close proximity to mimic a high-affinity branched oligosaccharide.

Animals↗
PubMed1991

Quantitative analysis of carbodiimide modified DNA and immunoprobing by adduct specific antibodies.

Antibodies have been raised against N-cyclohexyl-N-(4-methylmorpholinium)ethyl carbodiimide (CMC) modified single-stranded DNA and characterized by competitive and non-competitive immunoassays to be highly specific for CMC base adduct in homopolymers poly(dG), poly(dT) and DNA. The antibodies recognize picogram concentrations of CMC treated DNA with no cross reactivity to at least 1000-fold excess of unmodified DNA or CMC treated poly(dA). The detection limit of antibodies at 1.4 fmol CMC adduct allows quantitation at a CMC/base ratio of 4.6.10(-7). Based upon single modified base-containing synthetic oligomers, a 7-fold higher binding preference is observed for CMC modified thymine than guanine bases. CMC binding to supercoiled DNA is found to depend upon reaction temperature and ionic strength. CMC-modified supercoiled SV40 and ColE1 DNA, exhibit specific antibody binding proportional to the DNA concentration and extent of CMC modification. However, antibody binding observed is independent of the conformation or strandedness of CMC-modified DNA. DNA extensively modified with CMC retains its inherent capacity to specifically and quantitatively hybridize with complementary DNA immobilized to membranes upon direct blotting or Southern transfers from gels. Hybridized CMC-DNA, through antibody binding, provides for the sensitive and non-isotopic detection of the target DNA sequences.

Antibody Affinity↗
PubMed1986

Gly-Pro-Arg-Pro modifies the glutamine residues in the alpha- and gamma-chains of fibrinogen: inhibition of transglutaminase cross-linking.

During blood clotting Factor XIIIa, a transglutaminase, catalyzes the formation of covalent bonds between the epsilon-amino group of lysine and the gamma-carboxamide group of peptide-bound glutamine residues between fibrin molecules. We report that glycyl-L-prolyl-L-arginyl-L-proline (GPRP), a tetrapeptide that binds to the fibrin polymerization sites (D-domain) in fibrin(ogen), inhibits transglutaminase cross-linking by modifying the glutamine residues in the alpha- and gamma-chains of fibrinogen. Purified platelet Factor XIIIa, and tissue transglutaminase from adult bovine aortic endothelial cells were used for the cross-linking studies. Gly-Pro (GP) and Gly-Pro-Gly-Gly (GPGG), peptides which do not bind to fibrinogen, had no effect on transglutaminase cross-linking. GPRP inhibited platelet Factor XIIIa-catalyzed cross-linking between the gamma-chains of the following fibrin(ogen) derivatives: fibrin monomers, fibrinogen and polymerized fibrin fibers. GPRP functioned as a reversible, noncompetitive inhibitor of Factor XIIIa-catalyzed incorporation of [3H]putrescine and [14C]methylamine into fibrinogen and Fragment D1. GPRP did not inhibit 125I-Factor XIIIa binding to polymerized fibrin, demonstrating that the Factor XIIIa binding sites on fibrin were not modified. GPRP also had no effect on Factor XIIIa cross-linking of [3H]putrescine to casein. This demonstrates that GPRP specifically modified the glutamine cross-linking sites in fibrinogen, and had no effect on either Factor XIIIa or the lysine residues in fibrinogen. GPRP also inhibited [14C]putrescine incorporation into the alpha- and gamma-chains of fibrinogen without inhibiting beta-chain incorporation, suggesting that the intermolecular cross-linking sites were selectively affected. Furthermore, GPRP inhibited tissue transglutaminase-catalyzed incorporation of [3H]putrescine into both fibrinogen and Fragment D1, without modifying [3H]putrescine incorporation into casein. GPRP also inhibited intermolecular alpha-alpha-chain cross-linking catalyzed by tissue transglutaminase. This demonstrates that the glutamine residues in the alpha-chains involved in intermolecular cross-linking are modified by GPRP. This is the first demonstration that a molecule binding to the fibrin polymerization sites on the D-domain of fibrinogen modifies the glutamine cross-linking sites on the alpha- and gamma-chains of fibrinogen.

Animals↗
PubMed1990

Growth of Listeria monocytogenes Scott A, serotype 4 and competitive spoilage organisms in raw chicken packaged under modified atmospheres and in air.

The development of Listeria monocytogenes Scott A, serotype 4 and aerobic plate counts on minced raw chicken were determined independently at 4, 10 and 27 degrees C. Samples were packaged in flexible film under two modified atmospheres (one containing oxygen and one containing no oxygen) or air. The anaerobic modified atmosphere (75:25, CO2:N2) resulted in the failure of both the aerobic plate counts and L. monocytogenes to grow at all temperatures. Both the L. monocytogenes and aerobic plate counts grew in air at all temperatures. The aerobic modified atmosphere (72.5:22.5:5, CO2:N2:O2), which more closely duplicates commercial practice, inhibited the increase in aerobic plate counts by more than 4 log10 cfu/g compared to air at 4 degrees C. However, the L. monocytogenes was not affected by this atmosphere and increased in numbers by nearly 6 log10 cfu/g at 4 degrees C in 21 days. Regression analysis of the log10 growth and 95% confidence intervals showed that the differences between aerobic plate counts and L. monocytogenes in modified atmosphere were large. The ability of L. monocytogenes to grow in the aerobic modified atmosphere was not affected by level of the L. monocytogenes inoculum nor by the initial level of aerobic plate counts. These data show that modified atmosphere packaging of raw chicken (and probably other meats) can substantially inhibit the aerobic spoilage flora while allowing pathogenic L. monocytogenes to increase.

Animals↗