Effects of high CO₂ levels on fermentation, peroxidation, and cellular water stress in Fragaria vesca stored at low temperature in conditions of unlimited O₂

To better understand the tolerance of strawberries (Fragaria vesca L.) to high CO2 in storage atmospheres, fermentation and cellular damage were investigated. Fruits were stored for 3 and 6 days at 0 °C in the presence of different CO2 levels (0, 20, or 40%) with 20% O2. Changes in pyruvate decarboxylase (PDC) and alcohol dehydrogenase (ADH) gene expression and in fermentative metabolites, as well as in bound water and malondialdehyde (MDA) concentrations, were analyzed. In strawberries stored without added CO2, up-regulation of PDC and ADH was not associated with an increase in fermentative metabolites. By contrast, moderate ethanol fermentation in fruits exposed to 20% CO2 seems to be essential to maintain fruit metabolism, reducing both lipid peroxidation and cellular water stress. However, if the CO2 concentration increases (40%), the excess acetaldehyde and ethanol produced were closely correlated with a decrease in bound water and production of MDA.

Two cold-induced family 19 glycosyl hydrolases from cherimoya (Annona cherimola) fruit: an antifungal chitinase and a cold-adapted chitinase

Two cold-induced chitinases were isolated and purified from the mesocarp cherimoyas (Annona cherimola Mill.) and they were characterised as acidic endochitinases with a Mr of 24.79 and 47.77kDa (AChi24 and AChi48, respectively), both family 19 glycosyl hydrolases. These purified chitinases differed significantly in their biochemical and biophysical properties. While both enzymes had similar optimal acidic pH values, AChi24 was enzymatically active and stable at alkaline pH values, as well as displaying an optimal temperature of 45°C and moderate thermostability. Kinetic studies revealed a great catalytic efficiency of AChi24 for oligomeric and polymeric substrates. Conversely, AChi48 hydrolysis showed positive co-operativity that was associated to a mixture of different functional oligomeric states through weak transient protein interactions. The rise in the AChi48 kcat at increasing enzyme concentrations provided evidence of its oligomerisation. AChi48 chitinase was active and stable in a broad acidic pH range, and while it was relatively labile as temperatures increased, with an optimal temperature of 35°C, it retained about 50% of its maximal activity from 5 to 50°C. Thermodynamic characterisation reflected the high kcat of AChi48 and the remarkably lower ΔH(‡), ΔS(‡) and ΔG(‡) values at 5°C compared to AChi24, indicating that the hydrolytic activity of AChi48 was less thermodependent. In vitro functional studies revealed that AChi24 had a strong antifungal defence potential against Botrytis cinerea, whereas they displayed no cryoprotective or antifreeze activity. Hence, based on biochemical, thermodynamic and functional data, this study demonstrates that two acidic endochitinases are induced at low temperatures in a subtropical fruit, and that one of them acts in an oligomeric cold-adapted manner.

Increasing catechin and procyanindin accumulation in high-CO2-treated Fragaria vesca strawberries

This paper deals with the impact of low temperature and high CO2 levels on flavonols, proanthocyanidins, and anthocyanins, synthesized via branched pathways from common precursors, in strawberries (Fragaria vesca L.). Flavonoids were identified with Q-TOF equipment and quantified by HPLC-quadrupole. Proanthocyanins B1 and B3 accumulated in CO2-treated strawberries, whereas in untreated (air) fruit, flavonoid production was redirected toward anthocyanin accumulation with a sharp decrease in catechin and procyanidin B3 levels. Moreover, in CO2-treated fruit, mainly in those with 20% CO2, anthocyanin accumulation did not decline. Due to its antifungal activity, catechin induction in CO2-treated strawberries could explain the capacity of high CO2 treatments to reduce fungal decay. Ascorbic acid content increased in 40% CO2-treated fruits, whereas in those treated with 20% CO2 an increase in flavonol content was observed. Despite these differences, similar antioxidant capacities were found in untreated and CO2-treated Mara de Bois strawberries.

A cryoprotective and cold-adapted 1,3-β-endoglucanase from cherimoya (Annona cherimola) fruit

A 1,3-β-glucanase with potent cryoprotective activity was purified to homogeneity from the mesocarp of CO2-treated cherimoya fruit (Annona cherimola Mill.) stored at low temperature using anion exchange and chromatofocusing chromatography. This protein was characterized as a glycosylated endo-1,3-β-glucanase with a Mr of 22.07kDa and a pI of 5.25. The hydrolase was active and stable in a broad acidic pH range and it exhibited maximum activity at pH 5.0. It had a low optimum temperature of 35°C and it retained 40% maximum activity at 5°C. The purified 1,3-β-glucanase was relatively heat unstable and its activity declined progressively at temperatures above 50°C. Kinetic studies revealed low k(cat) (3.10±0.04 s(-1)) and Km (0.32±0.03 mg ml(-1)) values, reflecting the intermediate efficiency of the protein in hydrolyzing laminarin. Moreover, a thermodynamic characterization revealed that the purified enzyme displayed a high k(cat) at both 37 and 5°C, and a low Ea (6.99 kJ mol(-1)) within this range of temperatures. In vitro functional studies indicated that the purified 1,3-β-glucanase had no inhibitory effects on Botrytis cinerea hyphal growth and no antifreeze activity, as determined by thermal hysteresis analysis using differential scanning calorimetry. However, a strong cryoprotective activity was observed against freeze-thaw inactivation of lactate dehydrogenase. Indeed, the PD50 was 8.7 μg ml(-1) (394 nM), 9.2-fold higher (3.1 on a molar basis) than that of the cryoprotective protein BSA. Together with the observed accumulation of glycine-betaine in CO2-treated cherimoya tissues, these results suggest that 1,3-β-glucanase could be functionally implicated in low temperature-defense mechanism activated by CO2.

Fructo-oligosaccharides in table grapes and response to storage

Fructo-oligosaccharides (FOS) have been recognized as health food ingredients with a protective effect against environmental stresses in plants. We have analyzed the profiles of individual FOS in Cardinal table grape pulp, until now undetected, and quantified their changes in response to low temperature and high CO2 levels. FOS separation and quantification was carried out using anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD), and the glucose, fructose and sucrose content of the grapes was also determined. Five FOS were identified and quantified: 1-kestose, neokestose, nystose, nystose b and kestopentaose. While in non-treated table grapes the endogenous FOS remained at steady state levels during storage at 0°C, exposure to 20% CO2 for 3days significant increases the levels of 1-kestose and kestopentaose, members of the inulin series. Considering the competitive advantage afforded by CO2-treated grapes, this transitory FOS accumulation could provide protection against damage caused by low temperature storage.

Potent cryoprotective activity of cold and CO2-regulated cherimoya (Annona cherimola) endochitinase

A cryoprotective chitinase (BChi14) was isolated and purified from the mesocarp of CO(2)-treated cherimoya fruit (Annona cherimola Mill.) stored at chilling temperature by anion exchange and chromatofocusing chromatography. This hydrolase was characterized as an endochitinase with a M(r) of 14.31 kDa and a pI of 8.26, belonging to the family 19 of glycosyl hydrolases (GH19). While it was stable over a wide pH range and active in a broad acidic pH range, it had an optimum pH of 7.0. Its optimum temperature was low, 35 degrees C, and it retained about 30% of its maximum activity at 5 degrees C. Moreover, BChi14 was relatively heat unstable and its activity was progressively lost at temperatures above 50 degrees C. Kinetic studies revealed many similarities with other plant endochitinases. However, BChi14 had high k(cat) (6.93 s(-1)) value for the fluorogenic substrate 4-MU-(GlcNAc)(3), reflecting its great catalytic efficiency. Moreover, a thermodynamic characterization revealed that the purified enzyme displayed a high k(cat) at 37 and 5 degrees C, and a low E(a) (11.32 kJ mol(-1)). In vitro functional studies indicated that BChi14 had no effect on the inhibition of Botrytis cinerea hyphal growth and no antifreeze activity, as shown by the thermal hysteresis analysis using differential scanning calorimetry. However, the purified endochitinase showed very strong cryoprotective activity against freeze-thaw inactivation of lactate dehydrogenase. The PD(50) was 12.5 times higher than that of the cryoprotective protein BSA, and 2 or 3 orders of magnitude greater than sucrose, comparable with that of most cryoactive plant dehydrins. These results, together with the consolidated microstructure and the integrity of CO(2)-treated mesocarp tissue, indicate that BChi14 is functionally implicated in the mechanisms underlying chilling tolerance activated by high CO(2) concentrations.

Regulation of defense and cryoprotective proteins by high levels of CO(2) in Annona fruit stored at chilling temperature

This study focuses on how the length of exposure to chilling temperature and atmosphere storage conditions regulate the hydrolytic activity and expression of chitinase (PR-Q) and 1,3-beta-glucanase (PR-2) isoenzymes in cherimoyas (Annona cherimola Mill.). Storage at 6 degrees C modified the expression of constitutive isoenzymes and induced the appearance of novel acidic chitinases, AChi26 and AChi24, at the onset of the storage period, and of a basic chitinase, BChi33, after prolonged storage. The induction of this basic isoenzyme was concomitant with the accumulation of basic constitutive 1,3-beta-glucanases. These low-temperature-induced chitinases modified the growth inhibition in vitro of Botrytis cinerea. Short-term high CO(2) treatment activated a coordinated response of acidic chitinases and 1,3-beta-glucanases after prolonged storage at chilling temperature. Moreover, the high in vitro cryoprotective activity of CO(2)-treated protein extracts was associated with the induction of two low molecular mass isoenzymes, AGlu19 and BChi14. Thus, exposure to high concentrations of CO(2) modified the response of fruit to low temperature, inducing the synthesis of cryoprotectant proteins such as specific pathogenesis-related isoenzymes that could be functionally associated with an increase in chilling tolerance in vivo.

Phosphoenolpyruvate carboxylase from cherimoya fruit: properties, kinetics and effects of high CO(2)

Phosphoenolpyruvate carboxylase (PEPC, EC 4.1.1.31) regulatory properties were studied in non-photosynthetic (mesocarp) and photosynthetic (peel) tissues from cherimoya (Annona cherimola Mill.) fruit stored in air, in order to gain a better understanding of in vivo enzyme regulation. Analyses were also performed with fruit treated with 20% CO(2)-20% O(2) to define the role of PEPC as part of an adaptive mechanism to high external carbon dioxide levels. The results revealed that the special kinetic characteristics of the enzyme from mesocarp--high V(max) and low sensibility to L-malate inhibition - are related to the active acid metabolism of these fruits and point to a high rate of reassimilation of respired CO(2) into keto-acids. With respect to fruit stored in air, PEPC in crude extracts from CO(2)-treated cherimoyas gave a similar V(max) (1.12+/-0.03 microkat x mg(-1) protein), a lower apparent K(m) (68+/-9 microM for PEP) and a higher I(50) of L-malate (5.95+/-0.3 mM). These kinetic values showed the increase in the affinity of this enzyme toward one of its substrate, PEP, by elevated external CO(2) concentrations. The lower K(m) value and lower sensitivity to L-malate are consistent with higher in vivo carboxylation reaction efficiency in CO(2)-treated cherimoyas, while pointing to an additional enzyme regulation system via CO(2).

Putrescine uptake regulation in response to alpha-difluoromethylornithine treatment in Leishmania infantum promastigotes

The putrescine uptake/efflux regulation and their regulatory role on intracellular polyamine pools have been studied in the parasitic protozoa Leishmania infantum. Putrescine uptake was age-dependent with maximal values in logarithmic phase promastigotes and minimal in stationary phase. Moreover, putrescine uptake was activated in response to depletion of intracellular polyamines by alpha-difluoromethylornithine (DFMO)--a well known irreversible enzyme-activated inhibitor of ornithine decarboxylase. Kinetic studies of putrescine uptake induction showed a notable rise in Vmax without Km changes, suggesting a de novo synthesis of putrescine carriers. Putrescine uptake was able to replenish polyamine content and also to recover the proliferative rate in cells treated during 24 hours with DFMO.

Leishmania infantum: polyamine biosynthesis and levels during the growth of promastigotes

1. Decarboxylation of polyamine precursors: L-ornithine and L-methionine was determined along the growth curve of Leishmania infantum promastigotes in vivo, reaching maximum values on day 2 post-inoculum (mid-logarithmic phase). 2. Maximum values of L-ornithine and L-methionine decarboxylation were: 1.97 +/- 0.28 nmol CO2/hr/10(7) promastigotes and 3.18 +/- 0.34 nmol CO2/hr/10(7) promastigotes, respectively. 3. Total (free + conjugated) polyamine content was closely related with the proliferative stage of Leishmania infantum promastigotes. 4. D,L-alpha-difluoromethylornithine (DFMO) and Berenil depleted putrescine levels in a concentration-dependent manner. 5. Total and free putrescine/spermidine ratio varied significantly with the proliferative stage. Minimum values were found in late logarithmic phase (day 3 post-inoculum). 6. Small but detectable amounts of free spermine were detectable along the growth curve of Leishmania infantum promastigotes.

High performance liquid chromatography of the dansyl derivatives of putrescine, spermidine, and spermine

A high performance liquid chromatographic (HPLC) method, based on dansylation and fluorescence detection, is described for the estimation of putrescine, spermidine, and spermine in lichen (Evernia prunastri [L.]) samples. Because of the high concentrations of phenols and salts, dansylation was followed by a pre-HPLC purification step. Both flow rate and mobile phase (methanol:water) followed a gradient for optimum resolution on a reverse-phase column. Amounts as small as 0.3 picomole of standard polyamines could be detected. In applying the method to lichens, it was found that 5.45% (w/w) of the exogenous putrescine taken up by the thallus was unbound in the algal partner and that 60% (w/w) was conjugated in the thallus, perhaps to lichen phenolics.

[Obstetrical behaviour in diabetes. Perinatal mortality (author's transl)]

Ever today diabetes and pregnancy constitute a high risk situation of the mother as well for the fetus, since still high maternal-fetal mortality rates are observed. A series of 134 diabetic women (99 type A, 15 type B, and 20 type C) were evaluated during pregnancy and delivery, and the results obtained during two different periods of time (1972-1975 and 1976-1978) are analyzed. From the results obtained the reduction of the indexes of perinatal mortality (before and after birth) stands out. These facts could probably be related to a change in the protocol applied during the last years and consisting in the administration of a carbohydrate supplement at night in order to avoid nocturnal hypoglycemias, admission of patients after the 32nd-34th week of pregnancy, complete rest in bed, control of the maturity of the fetus, etc. Likewise, there was a lack of significant rise in the presence of macrosomias, premature births, or urinary infection in the mother. As it was to be expected, the incidence of hydramnios as well as toxemia was higher than normal. The evaluation of the newborns through the Apgar score proved that 20 percent of the neonates in the type C diabetes were still partially or seriously depressed after 5 minutes of birth. A protocol of assistance in this special situation affords an evident reduction in perinatal mortality.