Rheological and structural properties of starches from γ-irradiated and stored potatoes

Starch was extracted from irradiated and stored potato tubers and the properties were compared to CIPC (chlorpropham) treated tubers. The granule properties and dynamic viscoelasticity in temperature ramp and frequency sweep modes were studied while heating the samples. Starch structural characteristics were investigated by high performance anion exchange chromatography (HPAEC) and Fourier transform infrared spectroscopy (FTIR). Gamma-irradiation of potato tubers at a dosage of 0.1 kGy induced some degradation of starch molecules, resulting in earlier swelling of starch granules, and greater extents of amylose and total carbohydrate leaching. The early swelling phenomenon was also enhanced with tuber storage time. The retrogradation rate and extent for a concentrated starch gel also increased with tuber storage time whereas γ-irradiation delayed the gel retrogradation. Sprout inhibiting methods could be selected based on the specific processing and texture requirements of the end products.     

Immunomodulatory and cytoprotective role of RP-1 in γ-irradiated mice

RP-1 has been reported to provide protection against lethal -irradiation in mice. The present study was undertaken to understand its mechanism of action, especially with respect to modulation of radiation-induced changes in immune cell function, plasma antioxidant potential, cell cycle perturbations, apoptosis in mouse bone marrow cells, and micronuclei frequency in mice reticulocytes. 2 Gy reduced mitogenic response of splenic lymphocytes significantly at 48 h. Pre-irradiation RP-1 treatment significantly countered the radiation-induced loss of splenocyte proliferation. RP-1 treatment, with or without radiation, suppressed macrophage activation as compared to control. Irradiation decreased plasma antioxidant status significantly (p < 0.05) at 1 and 2 h (4.8 ± 0.224 and 4.9 ± 0.057 mM Fe²⁺) as compared to control (6.29 ± 0.733 mM Fe²⁺) that was countered by RP-1 pre-treatment significantly (p < 0.05). RP-1 and irradiation individually caused G₂ delay in bone marrow cells. RP-1 pre-treatment augmented radiation-induced G₂ delay and elicited significant (p < 0.05) recovery in S phase fraction at 48 h in comparison to irradiated group. Radiation-induced apoptosis (3%) was significantly higher than the control. RP-1 pre-treatment further enhanced apoptosis frequency (7.2%) in bone marrow cells. RP-1 pre-treatment significantly (p < 0.05) reduced (1.23%) the radiation-induced MN frequency (2.9%) observed at 48 h post-irradiation interval. Since the radioprotective manifestation of RP-1 is mediated through multiple mechanisms, needs further investigation.     

Alterations in carbohydrate metabolism of γ-irradiated cavendish banana

γ-Irradiation of preclimacteric banana resulted in a gradual increase in fructose content, which reached a maximum in 6 days. Although the catabolism of glucose-U-¹⁴C was less in irradiated banana, incorporation of label into fructose was high. Initial fructose accumulation in irradiated banana may be due to a shift in glucose utilization from the glycolytic to the pentose phosphate pathway. The ratio of resporatory CO₂ from glucose-6-¹⁴C and glucose-1-¹⁴C was halved in irradiated bananas indicating predominance of the pentose phosphate pathway. The radioactivity of fructose derived from glucose-6-¹⁴C was almost twice that from glucose-1-¹⁴C in irradiated bananas, whilst in control both fruit the labelled precursors yielded equal amounts. Studies on individual enzymes in these two pathways showed an increase in phosphorylase, phosphoglucomutase, glucose-6-phosphate dehydrogenase and fructose-6-phosphatase and a decrease in hexokinase in irradiated banana.     

Antiatherogenic and radioprotective role of folic acid in whole body γ-irradiated mice

Free radical mediated oxidative damage is one of the prime factors for atherogenic changes in humans. We have shown that the folic acid administration reduced the risk of the atherogenic factors induced by γ -radiation. Folic acid administration prevented the radiation induced increase in the plasma lipoprotein lipase activity and also prevented the radiation-induced increase in the hepatic cholesterol and triglycerides levels. These results indicate the role of folic acid as an antiatherogenic agent. Further, we also report the radioprotective property of folic acid as demonstrated by reduction in the radiation induced membrane damage as measured by lipid peroxidation products and DNA damage, which was measured by alkaline comet assay.     

Biochemical changes involved in stress response and ripening behaviour of γ-irradiated mango fruit

The stress response of ripening mango fruits treated in the pre-climacteric phase with radiation doses of 0.75, 1.25 and 1.75 kGy was investigated. L-Phenylalanine ammonialyase, polyphenol oxidase, peroxidase and catalase activities were determined and significant differences were observed. Differences in the patterns of total phenolics, flavanols and proteins were also observed. Malic enzyme activity was used as an indicator of the ripening stage (climacteric rise, climacteric peak and post-climacteric phase) as well as a measure of the effect of γ-irradiation on fruit ripening. It seems that radiation treatment causes a stress condition in the fruit which, depending on the dose, may lead to browning of the tissue or necrotic decay.     

Relationship between kinetic properties of γ-glutamyl transpeptidase and the structure of its saccharide moiety

Gamma-glutamyl transpeptidase (EC 2.3.2.2; GGT) is a plasma-membrane bound glycoenzyme, the saccharide moiety of which is rather heterogeneous and organ specific. It has been stated that GGT catalyses three types of reactions, i.e., hydrolysis, transpeptidation and autotranspeptidation. The initial velocity equation, involving all these reactions, is shown in the present report. Mathematical analysis of the equation resulted in a. definition of the constant of half saturation (K_hs). The value of K_hs was used for characterization of kinetics of GGT from rat organs differing in the structure of GGT oligosaccharide chains. No significant organ differences were found, when the K_hs values of GGT from the brain, kidney and pancreas equalled 0.61 mM, 0.68 mM and 0.68 mM, respectively. On the contrary, when two different glycoforms of GGT from the pancreas were compared, distinct values of K_hs were obtained (l.43 mM and 0.67 mM, respectively). It is therefore being suggested that the saccharide chains of GGT are involved in its kinetic properties. However, this effect is masked when the enzyme, non-fractionated into glycoforms, is analysed, even though the saccharide moiety is specific for the organ studied.     

Functional and structural features of γ-zeathionins, a new class of sodium channel blockers

γ1- and γ2-zeathionins (γ1-Z and γ2-Z) are members of a family of small and basic peptides involved in plant protection. These plant defensins exhibit remarkable structural similarity to scorpion neurotoxins and insect defensins. In the present report, we used the whole-cell patch clamp technique to investigate the inhibition of the sodium current (I_Na) by γ1-Z and γ2-Z in the GH3 cell line. Both γ1-Z and γ2-Z rapidly and reversibly inhibited I_Na without changing the kinetics or voltage dependence of activation or inactivation. To our knowledge, this is the first example of a plant protein that inhibits the sodium channel. From structural comparisons with the μ-conotoxins, a family of peptides that block the sodium channel, we detected some similar features that could provide the basis of inhibition of sodium channels by γ-zeathionins.     

Enhanced operation of 4-aminobutyrate shunt in γ-irradiated potato tubers

γ-Radiation at a sprout inhibiting dose of 100 Gy enhanced the operation of the 4-aminobutyrate shunt by about 3-fold 48 hr after irradiation, but there was no accumulation of the amino acid in irradiated potatoes during storage up to 6 months. γ-Radiation increased the activity of the first enzyme of the 4-aminobutyrate shunt, glutamate decarboxylase and the maximum increase of 2.6-fold was found on the fourth day after irradiation. γ-Radiation had no pronounced effect on the activity of the other two enzymes of the pathway, 4-aminobutyrate transaminase and succinate semialdehyde dehydrogenase. Based on the results obtained, a possible role for the 4-aminobutyrate shunt in potato tuber physiology was suggested.     

L-methionine γ-lyase from Citrobacter freundii: Cloning of the gene and kinetic parameters of the enzyme

It is shown for the first time for the Enterobacteriaceae family that a gene encoding L-methionine gamma-lyase (MGL) is present in the genome of Citrobacter freundii. Homogeneous enzyme has been purified from C. freundii cells and its N-terminal sequence has been determined. The hybrid plasmid pUCmgl obtained from the C. freundii genomic library contains an EcoRI insert of about 3000 bp, which ensures the appearance of MGL activity when expressed in Escherichia coli TG1 cells. The nucleotide sequence of the EcoRI fragment contains two open reading frames. The first frame (the megL gene) encodes a protein of 398 amino acid residues that has sequence homology with MGLs from different sources. The second frame encodes a protein with sequence homology with proteins belonging to the family of permeases. To overexpress the megL gene it was cloned into pET-15b vector. Recombinant enzyme has been purified and its kinetic parameters have been determined. It is demonstrated that a presence of a hybrid plasmid pUCmgl, containing the megL gene in the E. coli K12 cells, leads to a decrease in efficiency of EcoKI-restriction. It seems likely that decomposition of L-methionine under the action of MGL leads to a decrease in the intracellular content of S-adenosylmethionine. Expression of the megL gene in the C. freundii genome occurs only upon induction by a significant amount of L-methionine.     

Some biochemical aspects of the protective effect of strontium chloride on γ-irradiated rats

The effect of treatment with SrCl₂ (10 mg 100 g^–) on rats 15 min prior to whole body -irradiation (7.5 Gy) was studied. The hazardous effects of irradiation were greatly corrected in the treated group. The hyperglycemic effect and liver glycogen accumulation in the untreated group decreased to normal level. The enzymatic activities of serum alkaline phosphatase, alanine and aspartate aminotransferases, and lactate dehydrogenase were greatly affected, showing insignificant changes in the treated group of animals. Life span calculated on 50% survival was also significantly elongated by 36.3%. These results show the potentiality of SrCl₂ as a radioprotective agent. A proposed mechanism is discussed.     

Molecular activation of NF-κB, pro-inflammatory mediators, and signal pathways in γ-irradiated mice

The effects of γ-irradiation on inflammatory gene expression, including NF-κB activation, in the kidney of C57/BL6 mice exposed to 1–9 Gy doses of ⁶⁰Co γ-irradiation. Radiation enhanced the NF-κB activation and oxidative stress caused a dose-dependent disruption in the redox balance. The significance of this study is the new molecular information gained on γ-irradiation effects through the activation of pro-inflammatory genes by NF-κB via the MAPK signaling pathway. Considering the exquisite sensitivity of NF-κB and other pro-inflammatory mediators to the redox status, we conclude that the activation of inflammatory processes by irradiation is likely initiated by increased oxidative stress.     

Cytokine expression and ultrastructural alterations in fresh-frozen,freeze-dried and γ-irradiated human amniotic membranes

The aim of this work was to compare the effects on human amniotic membrane of freeze-drying and γ-irradiation at doses of 10, 20 and 30 kGy, with freezing. For this purpose, nine cytokines (interleukin 10, platelet-derived growth factor-AA, platelet-derived growth factor-BB, basic fibroblast growth factor, epidermal growth factor, transforming growth factor beta 1, and tissue inhibitors of metalloproteinase-1, -2, and -4) were titrated in 5 different preparations for each of 3 amniotic membranes included in the study. In addition, the extracellular matrix structure of each sample was assessed by transmission electron microscopy. While freeze-drying did not seem to affect the biological structure or cytokine content of the different amniotic membrane samples, γ-irradiation led to a significant decrease in the tissue inhibitors of metalloproteinase-4, basic fibroblast growth factor and epidermal growth factor, and induced structural damage to the epithelium, basement membrane and lamina densa. The higher the irradiation dose the more severe the damage to the amniotic membrane structure. In conclusion, the Authors recommend processing amniotic membrane under sterile conditions to guarantee safety at every step rather than final sterilization with γ-irradiation, thereby avoiding alteration to the biological characteristics of the amniotic membrane.     

Inhibition of copper-induced aggregation of human γD-crystallin by a diimine molecule and investigations on their molecular interactions

Communicated by Ramaswamy H. Sarma     

Role of polymer–protein interaction on partitioning pattern of bovine pancreatic trypsinogen and alpha-chymotrypsinogen in polyethyleneglycol/sodium tartrate aqueous two-phase systems

The partitioning pattern of bovine trypsinogen (TRPz) and alpha-chymotrypsinogen (ChTRPz) was investigated in a low impact aqueous two-phase system formed by polyethyleneglycol (PEG) and sodium tartrate (NaTart) pH 5.00. ChTRPz exhibited higher partition coefficients than TRPz did in all the assayed systems. The decrease in PEG molecular weight and the increase in tie line length were observed to displace the partitioning equilibrium of both proteins to the top phase, while phase volume ratios in the range 0.5–1.5 showed not to affect protein partitioning behaviour. Systems formed by PEG of molecular weight 600 with composition corresponding to a high tie line length (PEG 12.93%, w/w and NaTart 21.20%, w/w) are able to recover most of both zymogens in the polymer-enriched phase. A crucial role of PEG–protein interaction in the partitioning mechanism was evidenced by isothermal calorimetric titrations. The major content of highly exposed tryptophan rests, present in ChTRPz molecule, could be considered to be determinant of its higher partition coefficient due to a selective charge transfer interaction with PEG molecule. A satisfactory correlation between partition coefficient and protein surface hydrophobicity was observed in systems formed with PEGs of molecular weight above 4000, this finding being relevant in the design of an extraction process employing aqueous two-phase systems.     

Effect of protein synthesis inhibition on recovery of UV- and γ-irradiated Schizosaccharomyces pombe from repair inhibition by caffeine

Summary The progress of repair in Schizosaccharomyces pombe may be followed during post-irradiation incubation by measuring, after various intervals, the ability of UV- or -irradiated cells to avoid enhanced lethality when exposed to the repair inhibitor caffeine (Gentner and Werner, 1975). This technique has now been used to investigate the effect of inhibition of protein synthesis on repair of UV- and -irradiation-induced damage in this organism.When protein synthesis was inhibited with cycloheximide in UV-irradiated wild-type cells, only a small amount of recovery from caffeine inhibition occurred; this indicated that post-irradiation protein synthesis was required for repair, and in particular for the recombinational repair pathway, which is a major mechanism for repair of UV damage in this organism.In -irradiated wild-type cells, inhibition of post-irradiation protein synthesis reduced the rate of recovery from repair inhibition by caffeine, but full recovery from caffeine-sensitive damage did occur at longer incubation times. We attribute the reduction in rate to the effect of protein synthesis inhibition on the recombinational repair pathway, because this pathway is known to be involved in the repair of both -ray and UV damage. The recovery that took place at the slower rate must reflect a caffeine-sensitive pathway which is involved only in repair of -ray damage and which does not require post-irradiation protein synthesis for activity.AECL Reference No. 5402     

Somatic hybridization in potato: use of γ-irradiated protoplasts of Solanum pinnatisectum in genetic reconstruction

Summary Leaf mesophyll protoplasts of Solanum pinnatisectum (2n=24) -irradiated at doses of 200 Gy and consequently unable to divide were fused with untreated protoplasts of genomic chlorophyll deficient mutant IvP 841-1 (2n=24) containing the germplasms of S. tuberosum and S. phureja. Two types of plants differing in their pigmentation characteristics were selected. The regenerants of one group were identified as true somatic hybrids by using isozyme analyses of esterase and aspartate aminotransferase. The anthocyanin marker of S. pinnatisectum was phenotypically expressed in these regenerants and could be used as an additional selection trait for hybrid screening in this species combination. The regenerants of the second group were corrected for the gene controlling chlorophyll deficiency but contained species-specific isozymes of the potato cultivar only. Restriction analysis of chloroplast DNA revealed chloroplasts of the S. pinnatisectum type in all but one of the plants tested. The fusion experiments involving -irradiated protoplasts show that this approach in potato reconstruction has the advantage of producing a wide range of genetically novel plants.Dedicated to Prof. H. F. Linskens on his 65th birthday     

Probiotic-mediated biotransformation of monosodium glutamate to γ-aminobutyric acid: differential production in complex and minimal media and kinetic modelling

Lactic cultures were screened for their ability to accumulate γ-aminobutyric acid (GABA) in the culture medium. Lactobacillus bulgaricus CFR 2028 produced the highest yields of GABA (22.7 mM) from the substrate monosodium glutamate (MSG). Instrumental characterization by high-performance liquid chromatography and structural characterization by mass spectrometry confirmed GABA production by L. bulgaricus CFR 2028. The differential production of GABA in complex and minimal media indicated that minimal medium (modified tryptone, yeast extract and glucose; TYG) supported the highest production of GABA (37 mM), thereby signifying that the acidic pH alone could have a significant bearing on the yield of GABA. This observation opens up avenues for the optimization of the medium components for yield maximization. The biotransformation kinetics of MSG was examined in batch experiments by varying initial MSG concentration (1–5 %). The Monod model was fitted to determine the kinetic parameters under the MSG uninhibited domain, and the MSG inhibited domain was represented well by Briggs–Haldane model.