Lipase-catalyzed acylation of naringin with palmitic acid in highly concentrated homogeneous solutions

Acylation reactions of naringin with palmitic acid were performed by a lipase after formation of highly concentrated homogeneous solutions. Their initial naringin concentration was 840–950 mM, which is 20–60 times greater than that in organic solvent media. The overall productivity of highly concentrated solutions was more than 15 times greater than those of organic phase media. The addition of DMSO (20–40%, w/w) to substrate mixtures lowered the melting temperature of a naringin–palmitic acid mixture (1:1 molar ratio) to about 40 °C. Reactions at 80 °C apparently followed Michaelis–Menten kinetics despite extremely high substrate concentrations. As the temperature increased from 60 °C to 80 °C, the apparent viscosity of the highly concentrated solution decreased remarkably from 4.31 Pa s to 0.063 Pa s. An activation energy of 7.65 kcal/mol obtained in a range of 60–75 °C suggests a diffusion-control. On the other hand, an activation energy of 17.09 kcal/mol in a range of 75–90 °C indicates a reaction-control. The highest product conversion yield of 33% (mol/mol) was obtained in a 10 h reaction at 80 °C. Addition of activated molecular sieves to the highly concentrated solution increased the product conversion yield by 7% (mol/mol), suggesting that the original equilibrium was disrupted by removing water and then a new equilibrium was reached.     

Effect of individual characteristics on a mathematical model of human thermoregulation

A multi-segmental mathematical model of human thermoregulation was tested for its capability to predict individualized physiological responses. We compared the model predictions obtained for an average person with measured individual responses of subjects exposed to mild cold. Secondly, body composition (BC) data, the resting metabolic rate (MR), and the actual measured MR during the test were used as input into the model.

The data was obtained from 20 subjects (age: 19–36 years; BMI: 17–32 kg/m²). BC, MR, rectal and skin temperatures were measured for 1 h at 22 °C, followed by 3 h at 15 °C.

A mean bias of 1.8 °C, with a standard error of 0.7 °C, resulted for the mean skin temperature of an average person at 15 °C. When subjective BC and measured MR were incorporated the bias was −0.2±0.9 °C. For the hand-back skin temperature the bias ± standard error fell from 5.3±2.8 °C for an average person to 2.0±2.5 °C, when using individualized characteristics. Trunk skin temperatures were not significantly affected by the adjustments.

In conclusion, this study shows that on a group level predictions of skin temperatures can be improved when adopting individualized body characteristics and measured MR, but the predictions on an individual level were not improved.     

Finger temperatures during military field training at 0 to −29 °C

1. Skin and rectal temperatures were recorded continuously in 70 measurements during typical tasks of infantry and artillery training at 0 to −29 °C. The duration of the measurements varied from 55 min to 9.5 h.

2. The distribution of finger skin temperatures was quite similar at ambient temperature ranges 0 to −10 °C and −10 to −20 °C, while at −20 to −30 °C the finger temperatures were clearly lower.

3. At different ambient temperature ranges, 20–69% of finger temperatures were low enough to cause cold thermal sensations.

4. Sensation of cold was experienced at a finger temperature of 11.6±3.7 °C (mean±SD).     

Thermoregulatory behavior and critical thermal limits of the angelfish Pterophyllum scalare (Lichtenstein) (Pisces: Cichlidae)

(1)Final temperature preferendum of juvenile (0.9–1.9 g) and adult (5.2–12.5 g) angelfish Pterophyllum scalare were determined with acute and gravitation methods. The final preferenda were similar, independent of the method and development stage (29.0–31.1°C).

(2)The critical thermal maxima (CTMax) for juveniles were 36.9°C, 37.6°C, 40.6°C, 40.8°C and for adults 38.4°C, 38.6°C, 41.0°C, 42.1°C. Adult angelfish CTMax was slightly higher than in juveniles (1°C; P<0.05); the endpoint of CTMax was the onset of spasms.

(3)The acclimation response ratio for both stages had an interval of 0.33–0.44; these values are in agreement with results for subtropical and tropical fishes.

(4)Therefore it is recommended that angelfish cultivation should be consistent with temperatures that do not change abruptly throughout the year and temperature maximum does not exceed 30°C.

     

Influence of incubation temperature and time on resistant starch type III formation from autoclaved and acid-hydrolysed cassava starch

Raw cassava starch, having 74.94 and 0.44 g/100 g resistant starch type II and III (RS II and RS III), respectively, was autoclaved at 121 °C in water, 1, 10 or 100 mmol/L lactic acid. The formation of RS III was evaluated in relation to variable incubation temperature (−20 to 100 °C), incubation time (6–48 h) and autoclaving time (15–90 min). Negligible to low quantities of RS III (0.59–2.42 g/100 g) were formed from autoclaved starch suspended in 100 mmol/L lactic acid, whereas intermediate to high quantities (2.68–9.97 g/100 g) were formed from autoclaved starch suspended in water, 1 or 10 mmol/L lactic acid, except for treatments with water or 10 mmol/L lactic acid incubated at 100 °C for 6 h (1.74 g/100 g). Autoclaving times corresponding to maximum RS III contents were 15 and 45 min for water and 10 mmol/L lactic acid, respectively. Whereas, the RS III fractions from cassava starch suspended in water had melt transitions between 158 and 175 °C with low endothermic enthalpies (0.2–1.6 J/g), the thermal transitions of the acid treated samples were indistinct.     

Temperature and carbon source affect the production and secretion of a thermostable β-xylosidase by Aspergillus fumigatus

The effect of the temperature of growth and carbon source on the production and secretion of β-xylosidase (EC 3.2.1.37) by the thermotolerant fungi Aspergillus fumigatus was studied in submerged cultures. In cultures developed at optimal temperature (30 °C), the enzyme was predominantly cell-bound, while in cultures developed at higher temperature (42 °C), the β-xylosidase activity was predominantly found in the cell-free filtrates. The use of corn cob powder instead of xylan as substrate increased considerably the secretion of enzyme. The highest level of extracellular β-xylosidase (45 U/ml or 360 U/mg protein) was obtained in 3% corn cob cultures grown at 42 °C for 72 h. The partially purified enzyme was active and stable at high temperatures. The presence of high titres of β-xylosidase activity in association with xylanase in the culture filtrates enhanced the efficiency of the pulp hydrolysis process.     

Uracil-DNA N-glycosylase (UNG) from the marine, psychrophilic bacterium Vibrio salmonicida shows cold adapted features: A comparative analysis to Vibrio cholerae uracil-DNA N-glycosylase

The genes encoding uracil-DNA N-glycosylase (UNG) from the marine, psychrophilic bacterium Vibrio salmonicida and the mesophilic counterpart Vibrio cholerae have been cloned and expressed in Escherichia coli. The purified proteins have been characterized in order to reveal possible cold adapted features of the V. salmonicida UNG (vsUNG) compared to the V. cholerae UNG (vcUNG). Characterization experiments demonstrated that both enzymes possessed the highest activities at pH 7.0–7.5 and at salt concentrations in the range of 25–50 mM NaCl. Temperature optima for activity were determined to approximately 30 °C for vsUNG and 50 °C for vcUNG. Temperature stability of the enzymes was compared at 4 °C and 37 °C, and vsUNG was found to be more temperature labile than vcUNG. Kinetic studies performed at three different temperatures, 15 °C, 22 °C and 37 °C, demonstrated higher catalytic efficiency for vsUNG compared to vcUNG due to lower K_M-values. The increased substrate affinity of vsUNG is probably caused by an increased number of positively charged residues in the DNA-binding site of the enzyme compared to vcUNG. Thus, activity and stability measurements reveal typical cold adapted features of vsUNG.     

Conceptual model of seagrass die-off in Florida Bay: Links to biogeochemical processes

Seagrasses are recognized as important plant communities in coastal estuaries and lagoons across both tropical and temperate climes; thus, large-scale seagrass die-off events worldwide are of general concern. In Florida Bay, at the southern terminus of the Florida peninsula, seagrass die-off events up to 4000 ha have been reported and smaller scale mortality events are noted annually. In the present study, we examined several hypothesized causative factors (high temperature, hypersalinity, sulfide toxicity) of seagrass (Thalassia testudinum) mortality in Florida Bay. To test sulfide effects, in situ sulfide production was stimulated by applying a labile carbon source (glucose) to sulfate reducers in the sediment at five sites across the bay (northeastern, northcentral, and southwestern basins). During the one year study, high temperature (32–36 °C) and salinity (> 50 psu) were recorded in the bay associated with a regional drought. We also experienced major seagrass die-off events at two of our southwestern bay sites. These field conditions provided an excellent opportunity to closely examine cause–effect relationships among stressors and die-off events in the field, and verify results of our previous mesocosm experiments. Even though glucose amendments stimulated porewater sulfides in bay sediments (4–8 mmol L^− 1), no significant differences in biomass, short shoot density or final growth rates were found between control and glucose plots. In addition, the highest growth rates and shoot densities were concomitant with maximum water column salinity (> 50 psu) and temperature (32–36 °C), when porewater sulfides were also in the millimolar range. Large-scale seagrass mortality events, encompassing  50% of the entire meadow at one site, occurred at southwestern bay sites when plants were down regulating (slower growth and shoot density), probably in response to shorter day length and lower temperature (30–34 to 23–26 °C) from October, 2004 to January, 2005. Sulfate reduction rates (SRR) were also 2-fold higher in the southwestern (214–488 nmol cm^− 3 d^− 1) versus northcentral and northeastern (97–240 nmol cm^− 3 d^− 1) bay sites, possibly limited by labile carbon, which we found to stimulate SRR 3-fold in northeastern and northcentral bay sites (461–708 nmol cm^− 3 d^− 1) and 4-fold at southwestern bay sites (1211–2036 nmol cm^− 3 d^− 1). Based on a synthesis of the field data reported herein, our mesocosm experiments to date, and contributions by others, we present a conceptual model of seagrass die-off in Florida Bay outlining a cascade of stressors, stimulated by P enrichment, which leads to high O₂ consumption in the system triggering a seagrass die-off event.     

CNS thermosensitivity and control of latent heat dissipation in the pigeon

Thermoregulatory responses to heat exposure were studied in 12 hand-reared, acclimated pigeons (Columbia livia). Measurements of body temperature (Tcl), brain temperature (Tbr), cutaneous water evaporation (CWE) and respiratory frequency (fr) were carried out in intact conscious heat exposed birds. In a second group of lightly restrained birds, fr and CWE were taken when temperatures of the trunk, brain and air (Ta) were independently changed. Increasing Tbr to 43.5–43.8°C induced a pronounced polypnea (deep and fast, (300 breaths min⁻¹) when Tcl regulated at 42.4°C. Moreover, when hyperthermia (Tcl = 43.0°C) was combined with increased Tbr (43.0–43.8°C) shallow and fast panting (>500 breaths min⁻¹) was evoked. CWE was probably elicited by inputs generated by the skin warm receptors as a result of increased Ta. Moreover it was demonstrated that warming the brain to 42.5°C elicits cutaneous water evaporation in birds exposed to 26°C. When a high Ta (60°C) is accompanied by a high relative humidity (17%), the combined effect generates inputs eliciting intensive panting. The integration of the present and earlier data allows us to generate a model demonstrating the distinguished significance of the trunk, skin and brain thermosensors in the regulation of both respiratory and cutaneous latent heat dissipation. The present model also emphasizes the fact that the highly thermosensitive pigeon brain responds in a similar pattern to that found in mammals     

Effect of dietary polyunsaturated/saturated fatty acid ratio on heat production and growth performance of chicks under different ambient temperature

Two trials were conducted to investigate the influence of dietary polyunsaturated/saturated fatty acid ratio (P/S) on growth performance and heat production (HP) of chicks under different ambient temperature (Ta). With the exception of Ta, all other treatment processes for two trials were the same. In each trial, 120 Arbor Acres 1-day-old male chicks were allotted to 2 (P/S, 0.6 or 2.4) × 2 (high or low Ta) factorial design with six replicates of five chicks each treatment. Chicks were reared in wire-floored metabolism cages in two temperature-controlled chambers, and were exposed to high Ta (37 and 38 °C at the first day for trial 1 and 2, respectively, and decreased 0.2 °C/day) or low Ta (33 and 28 °C at the first day for trial 1 and 2, respectively, and decreased 0.3 °C/day), for 3 weeks. Chicks were fed ad libitum. Body weight, feed intake and gain:feed were recorded. Excreta were collected for determining metabolizable energy. Energy retention was measured by the comparative slaughter technique; HP was calculated as the difference between metabolizable energy intake and body energy retention.

The results showed that high Ta decreased weight gain (P < 0.01) and feed intake (P < 0.01) in both trials, improved gain:feed in trial 2 (P < 0.01), and decreased HP in trial 2 (P < 0.01) of chicks during 0–3 weeks of age. Increasing dietary P/S did not affect the growth performance and HP of chicks during 0–3 weeks of age. No Ta × dietary P/S interaction among growth performance and HP in chicks was observed.

In summary, increasing dietary P/S did not affect HP, therefore, it is neither detrimental to the growth of chicks reared under high Ta nor is beneficial to the growth of chicks reared under low Ta.     

Influence of pregnancy on locomotor and feeding performances of the skink, Mabuya multifasciata: why do females shift thermal preferences when pregnant?

It has been documented in the many-lined sun skink (Mabuya multifasciata) that pregnant females select lower body temperatures (27.6–30.8 °C) than do nonpregnant females and adult males (29.7–35.7 °C). We therefore used the skink to test the hypothesis that the maximization of reproductive benefits should be achieved in pregnant females by shifting thermal preferences towards the levels optimal for embryonic development but entailing relatively small costs of reproduction. Data on adult males showed that temperatures maximizing swimming stamina (indicative of locomotor endurance) fell within the range of body temperatures selected by nonpregnant females and adult males. Data on swimming stamina and feeding performance of pregnant females, nonpregnant females and adult males measured at 26 and 30 °C showed that: (1) pregnancy impaired locomotor and feeding performances, but such impairments did not persist after parturition; (2) the degree of locomotor impairment during pregnancy was greater at 26 °C than at 30 °C, but the degree of feeding impairment during pregnancy was greater at 30 °C than at 26 °C. Pregnant females of M. multifasciata selecting body temperatures at about 29 °C could not only produce good-quality offspring in a relatively short gestation length but also reduce reproductive costs associated with locomotor and feeding impairments to some extent. Thus, data from M. multifasciata validate the above hypothesis.     

Cheek skin temperature and thermal resistance in active and inactive individuals during exposure to cold wind

1. The present study examined the effect of the thermal state of the body (as reflected by rectal temperature) on cheek skin temperature and thermal resistance in active and inactive subjects.

2. Active subjects were exposed to a 30 min conditioning period (CP) (0 °C air with a 2 m/s wind), followed immediately by a 30 min experimental period (EP) (0 °C with a 5 m/s wind). Inactive subjects were exposed to a 30 min CP (22 °C air with no wind), followed immediately by a 45 min EP (0 °C air with a 4.5 m/s wind). The CP period was used to establish a core temperature difference between the active and inactive subjects prior to the start of EP. The 0 °C exposure was replaced with a −10 °C ambient air exposure and the experiment was repeated on a separate day. Subjects were comfortably dressed for each ambient condition.

3. Cheek skin temperature was not significantly higher in active subjects when compared to inactive subjects, but thermal resistance was higher in active subjects.

4. Cheek skin temperature and thermal resistance both decreased as ambient temperature decreased from 0 to −10 °C. The lower cheek thermal resistance at −10 °C may have been due to a greater cheek blood flow as a result of cold-induced vasodilation.

The effect of arsenic on the thermal tolerance of newly hatched muskellunge fry (Esox masquinongy)

1. 1.The temperature tolerance, Critical Thermal Maxima (CTM), was significantly reduced when newly hatched muskellunge fry were reared in tanks containing 0.05, 1.0 and 5.0 ppm arsenic as sodium arsenite (NaAsO₂).

2. 2.During swim-up (days 8–14 post hatch), CTM decreased from 32.5°C, 30.5°C for fry exposed to 0.05 ppm As. from 32.2°C to 30.°C for fry in 1.0 ppm As and from 31.3°C to 29.3°C for fry in 5.0 ppm. The CTM for the fry exposed to As remained depressed from the onset of swim-up until the experiment was terminated.

3. 3.The control group also displayed a drop in CTM during swim-up from 32.4°C to 30.3°C but the CTM then slowly recovered and increased to 31.8°C on day 15.

4. 4.Swim-up began in all tanks on day 8 and was accompanied by a rapid increase in mortality in those fry exposed to As. 50% mortality was reached 2 days after swim-up began at 5.0 ppm As, 4 days after swim-up began at 1.0 ppm and 5 days after the onset of swim-up for 0.05 ppm. All fish exposed to As died within 7 days after the onset of swim-up.

5. 5.Control fish completed swim-up in 3 days (11 days after hatching), began to feed and appeared normal.

Effects of aging on functional properties of caprine milk made into Cheddar- and Colby-like cheeses

The effects of cheese milk obtained at three times during lactation (weeks 4–5, 12–15, and 21–23) and cheese storage (up to 16 or 24 weeks) on meltability, sliceability, and color changes upon heating (232 °C for 5 min, high baking temperature, HT, or 130 °C for 75 min, low baking temperature, LT) of caprine milk cheeses were evaluated. The cheeses were manufactured from milk from Alpine goats and based on the procedures of Cheddar and Colby cheese manufacture. In Cheddar-like cheese, the sliceability (force required to slice sample) was at its highest when the cheese was made with milk from weeks 12–15 into lactation. Color change was variable although it tended to be lowest in cheese made at weeks 4–5 into lactation. In Colby-like cheeses, meltability was at its highest and sliceability was very poor (after 8 weeks of aging) when made with milk obtained later in lactation. Color changes were variable at the two different baking temperatures. As expected during aging, the meltability of the cheeses increased and the force required to slice the cheeses decreased with the significant changes occurring within the first 16 weeks for Cheddar-like and the first 8 weeks for Colby-like cheeses. The color changes upon heating were variable for aged Cheddar-like cheeses and did not change significantly for aged Colby-like cheeses. Color changes were highly correlated with proteolysis occurring during storage. Cheese milk obtained at different times of lactation and aging of the cheese impact the functional properties of caprine milk cheeses and will affect their optimal utilization.     

Pharmacological studies on the behavioral thermoregulation in the salamander necturus maculosus

The aquatic salamander Necturus maculosus was tested as a model for investigations of behavioral thermoregulatory responses to drugs which modify thermoregulation in endotherms. Animals were acclimatized to 15°C and an LD 12:12 photoperiod and placed in linear thermal gradients (5° to 30–35°C). Drugs were given each day for two days and deep body temperature monitored with trailing thermocouples. Prostaglandin E₁ produced a pronounced long-lasting behavioral hyperthermia. Melatonin and chlorpromazine caused significant falls in mean selected temperature (MST). Oxotremorine and ethanol were without effect on MST, while scopolamine treatment resulted in decreased MST on Day 1 and a increase on Day 2. Neurotensin produced hyperthermia on Day 2, but not on Day 1, an effect opposite that found with mammals. Capsaicin caused a pronounced decreased in MST on Day 1, followed by hyperthermia on Day 2, a response similar to that observed in mammals. The use of ectothermic animal models for investigation of behavioral thermal responses to those pharmacological agents which influence thermoregulation in endotherms may lead to a better understanding of the evolution of vertebrate temperature regulation.     

Spherulitic crystallization of gelatinized maize starch and its fractions

Binary systems of polymers often display spherulitic morphologies after cooling from the melt, but these phenomena have rarely been reported among food polymers of native-size. Here we report the observation of spherulitic and other morphologies in gelatinized maize starch. The morphology could be manipulated by choosing polymer compositions and kinetic regimes. Spherulites (10 μm diameter) formed from gelatinized high-amylose maize starches and purified amylose at cooling rates of order of magnitude 100 °C/min. They were more numerous and exhibited a higher melting point the greater the ratio of amylose to amylopectin. Rapid cooling rates (150–500 °C/min) resulted in a more even distribution of smaller spherulites. Very rapid (liquid nitrogen quench) or slow (0.1–1 °C/min) cooling rates resulted in mixed morphology, as did addition of 15 or 60% (w/w) sucrose to a 10% (w/w) dispersion of high-amylose starch (HAS). Spherulites were observed in aqueous suspensions of high-amylose maize starch between 5 and 30% (w/w). Lower starch concentrations resulted in a broader size distribution and spherulites of more distinct shape. WAXS patterns of B-type were observed. Negatively birefringent spherulites predominated, but positive spherulites were found. The spherulite melting range overlapped with that for amylose–lipid complex. Evidence indicated that micro-phase separation takes place when a holding period at 95 °C follows gelatinization at 180 °C. Despite the high maximum temperature of treatment (180 °C) there was evidence for a memory effect in samples of 30% HAS. Spherulite morphology closely resembled that of native starch granules in very early stages of development.     

Local alternated temperature gradients as footprints of cortical functional activation

Heat liberation in the brain was utilized as a direct signature of functional activation. We hypothesize that both temporal and spatial uncoupling between local cerebral blood flow (lCBF) and metabolic temperature components can be explored through the imaging of brain thermal gradients evoked by functional stimulation.

Surface cortical infrared (IR) images were obtained from 34 patients undergoing surgery for brain lesions under baseline conditions following peripheral nerve stimulation and, in some patients, during active behavioral tasks such as finger apposition and repetitive hand movements. An IR camera (0.02 °C sensitivity, 3–5 μm wavelength) was used to image local thermal gradients across the cerebral cortex by passively detecting IR emission.

Neural activation elicited reproducible temperature changes (0.04–0.09 °C) within the primary somatosensory cortex during median nerve stimulation and in the sensorimotor cortex during repetitive hand movements and finger tapping. The initial temperature responses were detected as early as 100–200 ms, the peak IR response occurred 5–7 s after stimulus onset.

Models of the relationship between evoked thermal gradients, lCBF and metabolic heat are proposed. Since the latencies of local metabolic and lCBF responses to stimulation vary by more than an order of magnitude, we are able to separate vascular-dependent and metabolic-dependent temperature components and thus create two discrete brain images, each reflecting distinct physiological mechanisms of functional activation. The resultant temperature profile reflects the balance between metabolism and lCBF, and therefore the degree of their functional uncoupling for the exposed and (possibly) for the intact normal human brain.     

High temperature-induced changes in exopolysaccharides, lipopolysaccharides and protein profile of heat-resistant mutants of Rhizobium sp. (Cajanus)

A thermosensitive wild-type strain (PP201) of Rhizobium sp. (Cajanus) and its 14 heat-resistant mutants were characterized biochemically with regard to their cell surface (exopolysaccharides (EPSs) and lipopolysaccharides (LPSs)) properties and protein profile. Differences were observed between the parent strain and the mutants in all these parameters under high temperature conditions. At normal temperature (30 °C), only half of the mutant strains produced higher amounts of EPSs than the parent strain, but at 43 °C, all the mutants produced higher quantities of EPS. The LPS electrophoretic pattern of the parent strain PP201 and the heat-resistant mutants was almost identical at 30 °C. At 43 °C, the parent strain did not produce LPS but the mutants produced both kinds of LPSs. The protein electrophoretic pattern showed that the parent strain PP201 formed very few proteins at high temperature, whereas the mutants formed additional new proteins. A heat shock protein (Hsp) of 63–74 kDa was overproduced in all mutant strains.     

Study on response surface methodology (RSM) of lipase-catalyzed synthesis of palm-based wax ester

The synthesis of wax ester using refined, bleached and deodorized (RBD) palm oil and oleyl alcohol catalyzed by lipozyme IM was carried out. Response surface methodology (RSM) based on a five-level, four-variable central composite rotatable design (CCRD) was used to evaluate the interactive effects of synthesis, of reaction time (2.5–10 h), temperature (30–70 °C), amount of enzyme (0.1–0.2 g) and substrate molar ratio (palm oil to oleyl alcohol, 1:1–1:5) on the percentage yield of wax esters. The optimum conditions derived via RSM were: reaction time 7.38 h, temperature 53.9 °C, amount of enzyme 0.149 g, and substrate molar ratio 1:3.41. The actual experimental yield was 84.6% under optimum condition, which compared well to the maximum predicted value of 85.4%.