bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Pectinmethylesterase Infusion Methods and Processing Techniques on Strawberry Firmness
Authors: Duvetter Thomas , Fraeye Ilse , Hoang Tuyen Van , Buggenhout Sandy Van , Verlent Isabel , Smout Chantal , Loey Ann Van , Hendrickx Marc 
Published: August 2010

ABSTRACTStrawberry halves were pretreated with fungal pectinmethylesterase (PME) and calcium chloride using, respectively, passive osmotic infusion, vacuum‐assisted infusion, and pressure‐assisted infusion with the aim to improve the firmness. The vacuum‐assisted procedure was observed to be the only method able to accomplish an uptake of infusion solution and hence capable of improving the firmness of the strawberries. Significantly less firmness increase was realized when tomato PME was vacuum‐infused instead of fungal PME. Strawberry halves were pretreated by vacuum‐assisted infusion with fungal PME and calcium chloride and were subsequently subjected to thermal treatments at 60 °C and 80 °C and pressure treatments at about 400 MPa and 550 MPa. For all treatments studied, the pretreated sample was significantly firmer compared with the reference sample. For the thermal processes, the residual firmness relative to the initial value before treatment was depending on the temperature of the treatment and not on the pretreatment. However, vacuum‐assisted infusion of PME and calcium could limit the portion of firmness loss due to pressure treatment to 30% compared with 80% for non‐pretreated fruits.
Evaluation of Front‐face Fluorescence for Assessing Thermal Processing of Milk
Authors: Schamberger Gerry P. , Labuza Theodore P. 
Published: August 2010

ABSTRACTThe use of front‐face fluorescence spectroscopy (FFFS) was assessed for its ability to monitor the development of Maillard browning in milk during thermal processing. Skim milk was processed using a Microthermics thermal processing system for a range of conditions from 70 °C to 140 °C from 3 to 30 s. Milk was analyzed using FFFS Hunter L*, a*, b*, hydroxymethylfurfural (HMF), tryptophan, and optical density. FFFS and HMF were found to be the most sensitive methods for distinguishing the heat treatment of milk. Activation energies of 126 and 190 kJ/ mol were found for HMF and FFFS, respectively. A strong correlation was found between these 2 methods. As a fast nonpreparatory method, FFFS is quite useful for evaluating the effect on the 1st stages of the Maillard reaction caused by the heat processing of milk. This work indicates that FFFS with no sample preparation has the potential to be of use as an online instrument for monitoring and control of thermal processing of milk; it can be applied as a process analytical technology (PAT) as is being done in the pharmaceutical industry with other methods.
Effects of Salts and Preheating Temperature of Brine on the Texture of Pickled Cucumbers
Authors: Yoo Kyung Mi , Hwang In Kyeong , Eog Geun , Moon BoKyung 
Published: August 2010

ABSTRACTThe effects of salt type and preheating temperature on the texture and quality of pickled cucumber were studied. Four types of salt were used: bay salt, purified salt, and 2 prepared salts, 1 containing the same amount of Ca2+ and Mg2+ as those of bay salt, and the other containing a 3‐fold higher concentration of Ca2+ and Mg2+ than bay salt. Two different temperatures were used for the salt solutions: 98 °C and 65 °C. All samples were fermented for 30 d at 25 °C. To evaluate the quality of the pickled cucumber with fermentation, the pH level, total acidity, alcohol insoluble solids, and mineral contents were analyzed. Texture and sensory evaluation as well as a microscopic observation were performed to observe the textural change of the pickled cucumber during fermentation. Pickled cucumbers with 98 °C of preheated brine showed better texture than the ones with 65 °C. The pickled cucumbers brined with prepared salt, 1 which had the same amount of Ca2+ and Mg2+ to bay salt, displayed the best result among the samples tested, in terms of sensory, textural, and physical properties.
Mechanical and Thermal Characteristics of Pea Starch Films Plasticized with Monosaccharides and Polyols
Authors: Zhang Yachuan , Han J. H. 
Published: August 2010

ABSTRACTEdible starch films were produced from pea starch and various plasticizers (mannose, glucose, fructose, and glycerol and sorbitol) at the ratio of 4.34, 6.50, 8.69, and 10.87 mmol plasticizer per gram of starch. After film specimens were conditioned at 50% relative humidity, mechanical properties (tensile strength, elongation, and modulus of elasticity), water vapor permeability (WVP), moisture content, and thermomechanical properties (G’ and tan8) were determined as a function of plasticizer concentration. At all concentration levels, monosaccharides (mannose, glucose, and fructose) made the starch films stronger (higher tensile strength) and more stretchable than polyols (glycerol and sorbitol), while WVP of monosaccharide‐plasticized starch films were lower than those of polyol‐plasticized starch films, especially at higher plasticizer concentration levels. Except for 4.34 mmol/g of mannose‐plasticized film, all the other films showed similar modulus of elasticity at the same plasticizer concentration. Polyol‐plasticized films had lower T than the monosaccharide‐plasticized films. Glucose‐ and sorbitol‐plasticized films needed more activation energy to go through glass transition than others. After all, research results showed that not only the polyols but also the monosaccharides were effective in plasticizing starch films. It is concluded that molecular size, configuration, total number of functional hydroxyl group of the plasticizer as well as its compatibility of the plasticizers with the polymer could affect the interactions between the plasticizers and starch molecules, and consequently the effectiveness of plasticization.
Effects of Water‐Glycerol and Water‐Sorbitol Interactions on the Physical Properties of Konjac Glucomannan Films
Authors: Cheng Lai Hoong , Karim Alias Abd , Seow Chee Choon 
Published: August 2010

ABSTRACTKonjac glucomannan (KGM)‐edible films were prepared with different amounts of glycerol or sorbitol as a plasticizer. Films were characterized by moisture sorption isotherm, and following conditioning at different relative humidities, by differential scanning calorimetry and tensile tests. Moisture and polyols (sorbitol and glycerol) were found to plasticize KGM‐based films with respect to their tensile properties. However, thermal properties and water sorption capacity (WSC) of polyolplasticized KGM films were found to vary with water activity (aw), namely at low aw (< 0.6), WSC and melting enthalpy were decreased with increasing in polyol content and the opposite was true at higher aw (>0.6). This was attributed to extensive interactions between plasticizer and KGM that reduced the available active site (‐OH groups) for water adsorption. The presence of polyols at low aw appeared to suppress crystalline structures due probably to restricted molecular mobility. These effects were diminished when the moisture content was >20%.
Rapid and Reversible Inhibition of Brain Aromatase Activity
Authors: Balthazart J. , Baillien M. , Ball G. F. 
Published: August 2010

AbstractMany actions of androgens require their conversion via the enzyme aromatase into oestrogens. Changes in brain aromatase activity are thought to take place via changes in enzyme concentration mediated by effects of sex steroids on aromatase transcription. These changes are relatively slow which fits in well with the fact that oestrogens are generally viewed as slow‐acting messengers that act via changes in gene transcription. More recently, fast actions of oestrogens, presumably at the level of the cell membrane, have been described both in the female brain and in the male brain after the conversion of testosterone to oestradiol. It is difficult to reconcile the slow regulation of oestrogen synthesis (that occurs via changes in aromatase concentration) with a rapid action at the membrane level. Even if fast transduction mechanisms are available, this will not result in rapid changes in brain function if the availability of the ligand does not also change rapidly. Here, we report that aromatase activity in neural tissue of male Japanese quail (Coturnix japonica) is rapidly downregulated in the presence of Mg2+, Ca2+ and ATP in hypothalamic homogenates and in brain explants exposed to high Ca2+ levels following a K+‐induced depolarization or the stimulation of glutamate receptors. The K+‐induced inhibition of aromatase activity is observed within minutes and reversible. Given that aromatase is present in presynaptic boutons, it is possible that rapidly changing levels of locally produced oestrogen are available for nongenomic regulation of neuronal physiology in a manner more akin to the action of a neuropeptide than previously hypothesized.
Involvement of N‐Methyl‐D‐Aspartic Acid Receptor Activation in Oxytocin and Vasopressin Release After Osmotic Stimuli in Rats
Authors: Onaka T. , Yagi K. 
Published: August 2010

AbstractThe present study aimed to examine roles of N‐methyl‐D‐aspartic acid (NMDA) receptors in oxytocin and vasopressin release after osmotic stimuli. A noncompetitive NMDA receptor antagonist, MK‐801 (0.2 mg/kg body weight, i.p.), significantly decreased plasma concentrations of oxytocin and vasopressin after hypertonic saline injection (0.3 or 0.6 M NaCl, i.p., 20 ml/kg). By contrast, oxytocin release induced by injection of cholecystokinin octapeptide (20 µg/kg, i.p.) was not significantly changed by MK‐801. Hypertonic saline injection increased the number of cells expressing Fos in the supraoptic nucleus and in the regions anterior and ventral to the third ventricle (AV3V) regions [the organum vasculosum of the lamina terminalis (OVLT) and median preoptic nucleus]. MK‐801 decreased the number of cells expressing protein in these areas after hypertonic saline injection. A microdialysis method showed that a hypertonic saline injection (0.6 M NaCl, 20 ml/kg, i.p.) facilitated glutamic acid release in and near the OVLT. The results support the view that NMDA receptor in the AV3V region modulates in a facilitative fashion the AV3V inputs to the supraoptic neurosecretory neurones.
cAMP Stimulation of Vasopressin and Oxytocin Release and Regulation of Vasopressin mRNA Stability: Role of Auto‐Facilitation
Authors: Song Z. , Sidorowicz H. E. , Sladek C. D. 
Published: August 2010

AbstractThe effects of cycloheximide and actinomycin on 8‐bromo‐cAMP (8‐Br‐cAMP) stimulated vasopressin and oxytocin release from the posterior pituitary and vasopressin mRNA content of the supraoptic nucleus were studied with perifused explants of the hypothalamo‐neurohypophyseal system. 8‐Br‐cAMP stimulated vasopressin and oxytocin release from the explant for up to 6 h. Inhibition of protein synthesis by cycloheximide completely suppressed the response to 8‐Br‐cAMP. When gene transcription was inhibited by actinomycin, vasopressin release was stimulated by 8‐Br‐cAMP for approximately 2 h, but the response was not sustained. Vasopressin mRNA content was not changed by 8‐Br‐cAMP in the absence or presence of cycloheximide, but it was significantly decreased by simultaneous exposure to 8‐Br‐cAMP and actinomycin. Actinomycin alone did not change vasopressin mRNA content. Since other studies have demonstrated that cAMP stimulates vasopressin gene transcription, and since vasopressin mRNA content reflects the balance between gene transcription and mRNA degradation, the effect of actinomycin and 8‐Br‐cAMP on vasopressin mRNA content suggests that 8‐Br‐cAMP also decreased vasopressin mRNA stability and thereby induced a rapid turnover of vasopressin mRNA. The effects of cycloheximide and actinomycin on vasopressin and oxytocin release suggest that ongoing protein synthesis is required for stimulation of hormone release. Since the posterior pituitary hormone stores are not depleted with a stimulus for release that is even more potent than cAMP, it is possible that cycloheximide and actinomycin depleted smaller pools of the peptides such as those responsible for intranuclear vasopressin and oxytocin release. Further evidence that intranuclear release of vasopressin and oxytocin is a prerequisite for cAMP stimulation of vasopressin and oxytocin release was obtained by demonstrating that d(CH2)5‐D‐Tyr(Me)VAVP, a potent combined V1a/V2/oxytocin receptor antagonist blocked stimulation of vasopressin and oxytocin release by 8‐Br‐cAMP.
Stimulating Effect of Glycoprotein Hormone Free α‐Subunit and Daily Gonadotropin Releasing Hormone Treatment on Prolactin Release from 50‐Day Ovine Foetal Pituitary Explants
Authors: Chabot V. , Gauthier C. , Combarnous Y. , Taragnat C. 
Published: August 2010

AbstractThe aim of our study was to determine whether free α of glycoprotein hormones (free α) plays a role in lactotroph function during early pituitary development in the sheep foetus. Detection and quantification of free α, luteinzing hormone β‐subunit (LHβ) and prolactin immunolabelling were determined by immunocytochemistry at days 32, 37, 42, 50 and 63 of gestation. Free α‐ and LHβ‐containing cells were first detected in the ovine foetal pituitary gland on day 37 of gestation, while prolactin‐containing cells were first identified on day 42. Analysis of serial sections suggested that free α immunoreactive cells were also LHβ‐positive, indicating that free α was mainly synthesized by gonadotrophs. In early foetal stages, free α occurred in the antero‐medio ventral region of the pituitary gland, whereas prolactin‐containing cells were more dorsally and more caudally localized. The free α‐, LHβ‐ and prolactin‐immunostained area increased markedly between days 50 and 63 of gestation. To evaluate a possible functional relationship between gonadotrophs and lactotrophs, the effects of free α or gonadotropin releasing hormone (GnRH) on prolactin release were assayed. Chronic treatment of pituitary explants from male and female 42‐day‐old ovine foetuses for 8 days with 10−9 or 10−7 M ovine free α did not affect prolactin release. By contrast, free α administration on pituitary explants from male and female 50‐day‐old foetuses resulted in enhanced prolactin release. At this age, a daily (2 h per day) treatment with 10−8 M GnRH had similar stimulatory effect to free α whereas a ‘first day’ treatment (24 h on the first day) reduced prolactin release throughout the culture in males and had no effect in females. These results indicate that, despite early detection of free α at day 37 in the ovine foetal pituitary, its stimulatory effect on prolactin release occurs from day 50 of gestation, corresponding to the first period of lactotroph development in vivo. A daily treatment with GnRH mimics the effect of free α on prolactin release.
Expression of mRNA for Prolactin Receptor (Long Form) in Dopamine and Pro‐Opiomelanocortin Neurones in the Arcuate Nucleus of Non‐Pregnant and Lactating Rats
Authors: Kokay I. C. , Grattan D. R. 
Published: August 2010

AbstractUnder most conditions, prolactin secretion from the pituitary gland is subject to negative‐feedback regulation. Prolactin stimulates dopamine release from tuberoinfundibular (TIDA) neurones in the arcuate nucleus of the hypothalamus, which in turn suppresses the production of prolactin. However, during late pregnancy and continuing into lactation, this feedback mechanism becomes less responsive to prolactin and, as a result, a hyperprolactinaemic state develops. We investigated whether long‐form prolactin receptor (PRL‐RL) mRNA is present on TIDA neurones in nonpregnant and lactating rats. In addition, we examined whether PRL‐RL mRNA is colocalised on hypothalamic pro‐opiomelanocortin (POMC) neurones. Dual‐label in situ hybridisations using an 35S‐labelled cRNA probe specific for long‐form PRL‐R, together with a digoxigenin‐labelled RNA probe that encoded either tyrosine hydroxylase (TH) or POMC mRNA, were performed on brain sections. In both nonpregnant and lactating rats, the majority of TH mRNA‐positive cells (> 90%) were found to express long‐form PRL‐R mRNA. In sections from nonpregnant rats, few non‐TH positive cells expressed PRL‐RL mRNA. By contrast, during lactation, the proportion of PRL‐RL mRNA‐positive cells that were not TH mRNA‐positive increased to approximately 70%. Only a small number of neurones in this subpopulation of PRL‐RL mRNA‐positive neurones were found to be positive for POMC mRNA. These data show that the loss of responsiveness to prolactin occuring during lactation is not due to down regulation of long‐form PRL‐R gene expression on TIDA neurones. Moreover, the persistent expression of PRL‐RL in arcuate neuroendocrine circuits suggests that PRL‐R‐mediated signalling continues to be important in these neurones during lactation.
MOLECULAR PARAMETERS OF C‐PEPTIDE FROM BOVINE PROINSULIN
Authors: Markussen Jan , Schiff Hans Erik 
Published: August 2010

The molecular parameters of bovine C‐peptide, which is a single‐chain peptide of 26 amino acids, were studied in aqueous solution. The partial specific volume δ was found to be 0.708 cm 3/g, the sedimentation coefficient s o20,w was found to be 0.53 S and the diffusion coefficient D o20,w was found to be 18.4 F. From these data, the frictional ratio f/f o was calculated at 1.31, and the molecular weight at 2421. The true molecular weight is 2383.Hydration disregarded, the frictional ratio of 1.31 is equivalent to that obtained from a prolate ellipsoid of rotation with a ratio of 1:5.9 between the axes. The axes are calculated at 28.5 and 4.8 Å, making the total length 57 Å. For an oblate ellipsoid of rotation, the ratio between the axes becomes 1:6.7, and the axes become 16.5 Å and 2.5 Å, making the diameter 33 Å.In insulin crystals, the terminals B 30 and A 1 are 10 Å apart. In proinsulin, these terminals are connected to the C‐peptide terminals through the basic dipeptides Arg‐Arg and Arg‐Lys, allowing, at maximum, a distance of 24 Å between the C‐peptide terminals. Assuming that free C‐peptide takes on the same conformation in solution as when proinsulin‐bound, one may combine the crystallographic and the hydrodynamic data to the following models: (a) A linear peptide chain of 26 amino acids having a bend near the middle, the two halves running antiparallel and close to each other, or (b) A peptide chain forming a planar ring with the terminals closing the loop.
CONFORMATIONAL STUDIES ON ALKALINE PROTEASE FROM Bacillus Mesentericus
Authors: Genov Nicolay , Jori Giulio 
Published: August 2010

The alkaline protease from Bacillus mesentericus (E‐30‐III) is soluble in acidic media up to pH 4. Below this pH the protein precipitates. The difference ultraviolet spectra showed that in the pH‐range from 6.0 to 4.1 gradual changes in the environment of the aromatic chromophores in E‐30‐III take place which depend on pH.On the basis of photooxidation kinetics the following subdivision of the methionyl and tryptophyl residues in E‐30‐III was made: at pH 6.85 two methionyl residues were “slowly reactive”, one tryptophyl residue was “reactive”, and four methionyl and two tryptophyl residues were “unreactive”. At pH 4.10 all six methionyl and one tryptophyl residues were “slowly reactive” and two tryptophyl residues were “reactive”. The comparison between subtilisin BPN‘, subtilisin Carlsberg and protease E‐30‐III showed some differences in the state of methionyl and tryptophyl residues.Circular dichroism spectra showed that E‐30‐III possesses about 26% α‐helix structure at pH 6.85. At pH 4.10 the protein preserved about 11% α‐helix content.Gradual but not complete unfolding of the protein molecule occurred when the pH was lowered from 6.0 to 4.1.
PROTEIN SOLUBILITY: PHASE SEPARATION IN ARACHIN‐SALT‐WATER SYSTEMS
Authors: Tombs M. P. , Newsom B. G. , Wilding P. 
Published: August 2010

Solutions of arachin, a groundnut protein, show liquid‐liquid phase separations in certain conditions of ionic strength and pH. Phase diagrams show upper, lower and closed boundaries corresponding to salting in and salting out curves of globulins and a hitherto undescribed solubility behaviour. The protein rich liquid phases and protein ‘precipitates’ are similar.As conditions approach the phase boundary, arachin undergoes self‐association, as revealed by the concentration dependence of the sedimentation coefficient and gel chromatography, while in D2O, association is more extensive and the phase boundaries are correspondingly shifted. Oligomer formation could lead to thermodynamic instability of the solutions and hence phase separation. At high protein contents (60%) the protein rich phase produces deformed helical crystalline spherulites.By electron microscopy the protein rich phase contains predominantly oligomers of about 400 Å diameter, but no evidence for long range order could be found.
COMPLETE ENZYMIC DIGESTION OF ACIDIC PROTEINS
Authors: Kay John 
Published: August 2010

Acidic proteins are usually resistant to complete enzymic hydrolysis. The increasing number of “unusual” amino acids, which are unstable to acid hydrolysis, makes it necessary to have a method of enzymic hydrolysis applicable to all proteins.The complete hydrolysis of four acidic proteins by subtilisin plus leucine amino‐peptidase plus prolidase followed by carboxypeptidase C, is described. Recoveries of amino acids were in excellent agreement with the expected content from the known sequences.
COACERVATION OF SEQUENTIAL POLYPEPTIDE MODELS OF TROPOELASTIN
Authors: Rapaka R. S. , Urry D. W. 
Published: August 2010

Syntheses of two sequential polytctrapeptide models, H‐(Val‐Ala‐Pro‐Gly)n‐Val‐OMe and H‐(Val‐Pro‐Gly‐Gly)n‐Val‐OMe via the p‐nitrophenyl ester method are described. The p‐nitrophenyl ester method gave high yields (85%–100%) of large molecular weight polymers. H‐(Val‐Pro‐Gly‐Gly)n‐Val‐OMe exhibited the interesting property of coacervation on raising the temperature of aqueous solutions while H‐(Val‐Ala‐Pro‐Gly)n‐Val‐OMe precipitates irreversibly under similar conditions.Whereas non‐dialyzed lower molecular weight polymers of H‐(Val‐Pro‐Gly‐Gly)n‐Val‐OMe with n = 8 to 40 did not coacervate, but did show a transition to increased intramolecular order on raising the temperature of aqueous solutions above 50°C, the dialyzed higher molecular weight polymer, n > 40, does coacervate beginning at about 50°C. This demonstrates the molecular weight dependence of coacervation and also suggests the importance to coacervation of side chain interactions in the Val‐Pro sequence. The increase in intramolecular order, seen as the formation of a 14‐atom hydrogen‐bonded ring, occurs simultaneously with the Val‐Pro hydrophobic side chain association.
CIRCULAR DICHROISM STUDIES ON NATIVE AND PHENYLMETHANESULFONYL‐MESENTERICOPEPTIDASE
Authors: Genov Nicolay , Shopova Maria 
Published: August 2010

At neutral pH the far ultraviolet circular dichroism (CD) spectrum of alkaline mesentericopeptidase is dominated by two negative bands: at 208 and 220 nm. The near ultraviolet CD spectrum is characterized by a large negative band at 277nm, a shoulder near 286nm and a small positive band at 297nm. The introduction of phenylmethanesulfonyl (PMS) group on the serine residue at the active site does not alter the intensity and the wavelength position of the bands.In contrast to the other alkaline bacterial proteases, which are remarkably resistant to denaturation by urea, mesentericopeptidase was unfolded in the presence of this reagent at neutral pH. The denaturation reactions in the presence of 9.5 M urea of both native and PMS‐mesentericopeptidase followed first order kinetics. The introduction of PMS‐group on the active‐site serine lowered the conformational stability of the enzyme. In the first 3h PMS‐mesentericopeptidase was denaturated 2.5 times faster than native protease.In the presence of 9.5 M urea at natural pH alkaline mesentericopeptidase lost its catalytic activity. The loss of enzymatic activity correlated with the unfolding of the protein molecule and also followed first‐order kinetics.