Thermal responses of oriental fruit fly (Diptera: Tephritidae) late third instars: mortality, puparial morphology, and adult emergence

Responses of late third instars of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), to high temperatures (43, 46, and 48 degrees C) were investigated. The different heat exposures not only affected the timing of death but also induced different quantities of malformed puparia and changed the average eclosion time. A majority of larvae died immediately (as larvae) after 30 min at 46 degrees C and > or =15 min at 48 degrees C, whereas most individuals died as pupae after 10-25 min of 46 degrees C, 5-10 min of 48 degrees C, and 40-60 min of 43 degrees C treatments. Lethal times estimated by immediate mortality were longer than those estimated by delayed mortality at the same high temperature. Surviving larvae formed four types of puparial morphology (normal, bottlenose, larviform, and peanut form). The percentage of normal puparia showed a negative correlation with exposure time at all test temperatures. The number of bottlenose was more than the larviform and the peanut at 46 degrees C for < or =20 min and at 48 degrees C for < or =10 min, respectively, whereas the number of larviform was more than the bottlenose and the peanut at 46 degrees C and 48 degrees C for longer exposure times. The average eclosion time increased at first, then decreased as the exposure time prolonged, and the longest average eclosion time occurred in the 40-min exposure at 43 degrees C, 15-min exposure at 46 degrees C, and 10-min exposure at 48 degrees C.     

Effect of alcohol on thermal balance of man in cold water.

The effects of alcohol on core cooling rates (rectal and tympanic), skin temperatures, and metabolic rate were determined for 10 subjects rendered hypothermic by immersion for 45 min in 10 degrees C water. Experiments were duplicated with and without a 20-min period of exercise at the beginning of cold water immersion. Measurements were continued during rewarming in a hot bath. With blood alcohol concentrations averaging 82 mg 100 mL-1, core cooling rates and changes in skin temperatures were insignificantly different from controls, even if the exercise period was imposed. Alcohol reduced shivering metabolic rate by an overall mean of 13%, insufficient to affect cooling rate. Alcohol had no effect on metabolic rate during exercise. During rewarming by hot bath, the amount of 'afterdrop' and rate of increase in core temperature were unaffected by alcohol. It was concluded that alcohol in a moderate dosage does not influence the rate of progress into hypothermia or subsequent, efficient rewarming. This emphasizes that the high incidence of alcohol involvement in water-related fatalities is due to alcohol potentiation of accidents rather than any direct effects on cold water survival, although very high doses of alcohol leading to unconsciousness would increase rate of progress into hypothermia.     

A pig model of hepatic cryotherapy. In vivo temperature distribution during freezing and histopathological changes

We aimed to assess the temperature distribution in the cryolesion during hepatic cryotherapy and the association with postoperative histological changes to optimise the technique and allow better preoperative planning. Hepatic cryolesions were produced in 22 pigs following laparotomy using a CMS-cryosystem and 8mm-AccuProbe-Cryoprobes. The temperature was measured in 1 min intervals at different distances from the probe during freezing. The animals were treated in 5 groups: (i) single freezing of 20 min; (ii) double freezing of 20 min each; (iii) single freezing of 40 min; (iv) single freezing of 20 min (n=4), histology at 1 week p.o., and (v) single freezing of 20 min and Pringle manoeuvre; [(i)-(iii) and (v): histology at 24 h p.o.]. The mean diameter of the -38 degrees C isotherm, i.e., the zone of effective treatment for colorectal metastases was 37 mm for group (i) with a mean iceball diameter of 59 mm and about 46 mm for groups (ii, iii, and v) with mean iceball diameters of 78, 75, and 75 mm, respectively. At 7 days postoperatively secondary necrosis was seen in the largest central part of the lesion, wherever temperatures of -15 degrees C or lower were achieved during cryosurgery. Under the hypothesis that -38 degrees C is the effective temperature for the destruction of colorectal liver metastases, a lesion of 37-mm diameter may be effectively treated with a single 8mm-AccuProbe-Cryoprobe and a 20 min single freeze cycle and a lesion of 46 mm may be effectively treated when a double freeze-thaw cycle of 20 min each, a single freeze cycle of 40 min, or a 20 min single freeze cycle with additional Pringle manoeuvre is used, when it is perfectly placed in the lesion.     

Cryopreservation of channel catfish sperm: effects of cryoprotectant exposure time, cooling rate, thawing conditions, and male-to-male variation

The purpose of this study was to extend previous work on the cryopreservation of channel catfish (Ictalurus punctatus) sperm. The objectives were to compare the effects of freezing and thawing on motility of sperm for: (1) 1 or 48-h exposure before freezing to 5% methanol and use of 0.5 or 0.25 mL straws; (2) 1 h or 5-day exposure before freezing to 5% methanol; (3) cooling at 45 or 3 degrees C/min; (4) thawing at 30, 40 or 50 degrees C using 5 or 10 s duration, and (5) cryopreservation with 5 or 10% methanol of samples from 50 males to analyze male-to-male variation. No differences were found in motility reduction for 1 or 48 h exposure times in 5% methanol, for use of 0.5 or 0.25 mL straws, or for 1 h or 5-day exposures in 5% methanol. A cooling rate of 45 degrees C/min resulted in lower motility reduction (33+/-9%) than a rate of 3 degrees C/min (83+/-13%) (P=0.002). A thawing temperature of 50 degrees C resulted in lower motility reduction (25+/-14%) than 30 degrees C (51+/-21%) or 40 degrees C (59+/-11%) (P=0.001). A thawing duration of 10 s resulted in lower motility reduction (38+/-12%) than a duration of 5 s (52+/-12%) (P=0.005), and there was an interaction between thawing temperature and duration (P=0.050). A concentration of 5% methanol resulted in lower motility reduction (43+/-17%) than 10% methanol (67+/-14%) (P=0.001). Regression analysis showed no relationship between motility before freezing and after thawing for 5% methanol (r2=0.012) or 10% methanol (r2=0.011).     

Influence of skeletal muscle glycogen on passive rewarming after hypothermia

To examine the influence of muscle glycogen on the thermal responses to passive rewarming subsequent to mild hypothermia, eight subjects completed two cold-water immersions (18 degrees C), followed by 75 min of passive rewarming (24 degrees C air, resting in blanket). The experiments followed several days of different exercise-diet regimens eliciting either low (LMG; 141.0 +/- 10.5 mmol.kg.dry wt-1) or normal (NMG; 526.2 +/- 44.2 mmol.kg.dry wt-1) prewarming muscle glycogen levels. Cold-water immersion was performed for 180 min or to a rectal temperature (Tre) of 35.5 degrees C. In four subjects (group A, body fat = 20 +/- 1%), postimmersion Tre was similar to preimmersion Tre for both trials (36.73 +/- 0.18 vs. 37.26 +/- 0.18 degrees C, respectively). Passive rewarming in group A resulted in an increase in Tre of only 0.13 +/- 0.08 degrees C. Conversely, initial rewarming Tre for the other four subjects (group B, body fat = 12 +/- 1%) averaged 35.50 +/- 0.05 degrees C for both trials. Rewarming increased Tre similarly in group B during both LMG (0.76 +/- 0.25 degrees C) and NMG (0.89 +/- 0.13 degrees C). Afterdrop responses, evident only in those individuals whose body core cooled during immersion (group B), were not different between LMG and NMG. These data support the contention that Tre responses during passive rewarming are related to body insulation. Furthermore these results indicate that low muscle glycogen levels do not impair rewarming time nor alter after-drop responses during passive rewarming after mild-to-moderate hypothermia.     

Effect of submaximal exercise at low temperatures on pulmonary function in healthy young men

In order to understand more fully the effect on pulmonary function of whole body exposure to cold during submaximal exercise, we measured pulmonary function indices in ten healthy male students and ten healthy male forestry workers of similar age following submaximal treadmill walking at different temperatures in a climatic chamber. After measuring the maximal aerobic capacity with a cycle ergometer test, the subjects had to walk on four separate occasions in the climatic chamber at an intensity of 70%-75% of their individual maximal heart rate; the first at normal room temperature and then randomly, either at 0 degrees C or at -20 degrees C, and vice versa. The duration of each walk was 8 min. Finally, each subject had to walk in the chamber at -20 degrees C for 17 min. Flow volume spirometry was performed at room temperature 1, 5, 10, and 20 min after exercise and the values were compared to baseline values taken prior to the last walking test. There were only minor changes in pulmonary function indices following exercise at different temperatures. Only one student showed a reduction of over 15% in peak expiratory flow rate after an 8-min walk at -20 degrees C. It seems that submaximal exercise of short duration, even at a temperature as low as -20 degrees C, does not impair pulmonary function in healthy young men.     

Sperm cryopreservation of green swordtail Xiphophorus helleri, a fish with internal fertilization

Sperm cryopreservation for fishes with internal fertilization is essentially unexplored although many species of these fishes are valuable biomedical research models. To explore methods for sperm cryopreservation within the live-bearing genus Xiphophorus, this study used X. helleri to evaluate the effects of cryoprotectant, osmotic pressure, cooling rate, equilibration time, and sperm-to-extender ratio. Sperm motility and survival duration after thawing showed significant differences among different cryoprotectants with the highest motility at 10 min after thawing obtained with 14% glycerol. With subsequent use of 14% glycerol as the cryoprotectant, the highest motility after thawing was observed with Hanks' balanced salt solution (HBSS) at 300 mOsmol/kg. Samples cooled from 5 to -80 degrees C at 20 degrees C/min yielded the highest post-thaw motility although no significant difference was found in the first 4h after thawing for cooling rates across the range of 20-35 degrees C/min. Evaluation of equilibration time revealed no significant difference between 20 min and 2h, but the highest motility at 10 min after thawing was found with a 20-min equilibration. Dilution ratios of sperm-to-extender at 1:20, 1:60, and 1:120 showed no significant differences in motility and survival duration after thawing, but the dilution of sperm solutions with HBSS (320 mOsmol/kg) immediately after thawing reduced the decline of sperm motility, and significantly prolonged the survival duration. Based on these findings, the highest average sperm motility (77%) at 10 min after thawing was obtained when sperm were suspended in HBSS at 300 mOsmol/kg with 14% glycerol as cryoprotectant, diluted at a ratio of sperm to HBSS-glycerol of 1:20, equilibrated for 10 min, cooled at 20 degrees C/min from 5 to -80 degrees C before being plunged in liquid nitrogen, and thawed in a 40 degrees C water bath for 7s. If diluted immediately after thawing, sperm frozen by the protocol above retained continuous motility after thawing for more than 8 days when stored at 4 degrees C.     

Plasma catecholamines in rats during rewarming from induced hypothermia

The present study sought to quantitate the levels of plasma catecholamines [norepinephrine (NE), epinephrine (E), and dopamine (DA)] during induction and rewarming from hypothermia. Male rats (317 +/- 8 g) were made hypothermic by exposure to 0.9% halothane at -10 to -15 degrees C while blood pressure (carotid artery), heart rate, and colonic temperature (Tc) were monitored. Anesthesia was discontinued when Tc reached 28 degrees C. Tc continued to fall but was held at 20-20.5 degrees C for 30 min. Rewarming was then initiated by raising ambient temperature to 22 degrees C. Arterial blood samples were taken 1) before cooling, 2) just before rewarming, 3) when Tc reached 22 degrees C during rewarming, and 4) when Tc reached 27 degrees C during rewarming. Plasma was assayed radioenzymatically for catecholamines using both phenylethanolamine-N-methyltransferase and catechol-O-methyltransferase procedures, and hypothermic induction resulted in significant increases in NE, E, and DA above control levels (P less than 0.01). With rewarming to Tc = 22 degrees C, all catecholamines increased above the level observed during hypothermia (P less than 0.01), and NE and DA increased still further (P less than 0.01) when Tc reached 27 degrees C. The levels of plasma catecholamines observed during hypothermia and during the rewarming phase indicate a role of the sympathoadrenal medullary system in the metabolic adjustments associated with hypothermia and recovery. During rewarming, the levels of E and NE attained exceed those at which both substances may be expected to act as circulating hormones.     

Freeze-induced membrane damage in ram spermatozoa is manifested after thawing: observations with experimental cryomicroscopy.

Cryoinjury in ram sperm was investigated by direct observation, using cryomicroscopy, to validate model hypotheses of freezing injury in such a specialized cell. Fluorescein diacetate was used to determine when during the freeze-thaw cycle the sperm membrane became permeable. In noncryoprotected sperm plasma membrane, integrity was maintained throughout the cooling and freezing process, but fluorescein leakage occurred during rewarming. The temperature of post-thaw permeabilization varied in relation to the minimum temperature reached during freezing; cells cooled to -10 degrees C retained fluorescence into the post-thaw temperature range of 9-24 degrees C (mean +/- SEM; 13.25 +/- 0.91 degrees C), whereas cells cooled to -20 degrees C lost fluorescence shortly after thawing (mean +/- SEM; 2.62 +/- 0.91 degrees C). Sperm cooled to 5 degrees C, but not frozen, retained fluorescence during rewarming up to 20-30 degrees C. The inclusion of glycerol and egg yolk in the freezing medium significantly and independently increased the post-thaw permeabilization temperature. Maintenance of fluorescence was also correlated with ability to resume motility after thawing. Sperm reactivation experiments were undertaken to examine deleterious effects of freezing upon the flagellar microtubular assembly. No direct evidence for such effects was obtained. Instead, a highly significant correlation between minimum freezing temperature and post-thaw temperature of initial reactivation was detected.     

Effects of summer frost exposures on the cold tolerance strategy of a sub-Antarctic beetle

The sub-Antarctic beetle Hydromedion sparsutum (Coleoptera, Perimylopidae) is common locally on the island of South Georgia where sub-zero temperatures can be experienced in any month of the year. Larvae were known to be weakly freeze tolerant in summer with a mean supercooling point (SCP) around -4 degrees C and a lower lethal temperature of -10 degrees C (15min exposure). This study investigated the effects of successive freezing exposures on the SCP and subsequent survival of summer acclimatised larvae. The mean SCP of field fresh larvae was -4.2+/-0.2 degrees C with a range from -1.0 to -6.1 degrees C. When larvae were cooled to -6.5 degrees C on 10 occasions at intervals of 30min and one and four days, survival was 44, 70 and 68%, respectively. The 'end of experiment' SCP of larvae surviving 10 exposures at -6.5 degrees C showed distinct changes and patterns from the original field population depending on the interval between exposure. In the 30min interval group, most larvae froze between -6 and -8 degrees C, a depression of up to 6 degrees C from the original sample; all larvae were dead when cooling was continued below the SCP to -12 degrees C. In the one and four day interval groups, most larvae froze above -6 degrees C, showing no change as a result of the 10 exposures at -6.5 degrees C. As with the 30min interval group, some larvae froze below -6 degrees C, but with a wider range, and again, all were dead when cooled to -12 degrees C. However, in the one and four day interval groups, some larvae remained unfrozen when cooled to -12 degrees C, a depression of their individual SCP of at least 6 degrees C, and were alive 24h after cooling. In a further experiment, larvae were cooled to their individual SCP temperature at daily intervals on 10 occasions to ensure that every larva froze every day. Most larvae which showed a depression of their SCP of 2-4 degrees C from their day one value became moribund or died after six or seven freezing events. Survival was highest in larvae with SCPs of -2 to -3 degrees C on day one and which froze at this level on all 10 occasions. The results indicate that in larvae in which the SCP is lowered following sub-zero exposure, the depression of the SCP is greatest in individuals that do not actually freeze. Further, the data suggest that after successive frost exposures in early winter the larval population may become segregated into two sub-populations with different overwintering strategies. One group consists of larvae that freeze consistently in the temperature range from -1 to -3 degrees C and can survive multiple freeze-thaw cycles. A second group with lower initial SCPs (around -6 degrees C), or which fall to this level or lower (down to -12 degrees C) after freezing on one or more occasions, are less likely to freeze through extended supercooling, but more likely to die if freezing occurs.     

Changes in the integrin-mediated adhesion of human neutrophils in the cold and after rewarming

Changes in the mechanical and adhesive properties of neutrophils may modify perfusion of the microcirculation in cooled tissue. We tested how integrin-mediated adhesion of isolated human neutrophils was altered by cooling, or cooling and rewarming. First, adhesion was tested in a static assay. In the presence or absence of integrin-activating agents (formyl peptide, fMLP or Mn(++)), there were significant reductions in adhesion to immobilised albumin at 10 degrees C or 0 degrees C compared to 37 degrees C, although a slight increase in adhesion was induced by fMLP or Mn(++) at 10 degrees C or 0 degrees C. If cells were cooled for 5 or 20 min at 10 degrees C and rewarmed (in the absence of activators) there was >100% increase in adhesion compared to cells held at 37 degrees C. In a flow assay, neutrophils perfused over P-selectin at 37 degrees C formed rolling attachments, but if neutrophils were cooled to 10 degrees C and rewarmed for 1 or 5 min, there was transformation to stationary adhesion, which was reversed by antibody against CD18. After 20 minutes of rewarming, rolling was restored. Cooling and rewarming did not cause de novo expression of CD11b/CD18, and so appears to transiently activate constitutively-expressed integrin. Thus, integrin-mediated adhesion may be impaired in cold tissue but on return to normal temperature, neutrophils may transiently adhere locally or in remote vessels.     

Generic vapor heat treatments to control Maconellicoccus hirsutus (Homoptera: Pseudococcidae)

Vapor heat treatments were developed against life stages of the mealybug Maconellicoccus hirsutus (Green) (Homoptera: Pseudococcidae). Treatments tested were 47 degrees C for 5-50 min in 5-min increments and 49 degrees C for 3, 5, 8, 10, and 12 min. All tests were conducted with mixed age M. hirsutus on Chinese pea, Pisum sativum L. Treatment at 47 degrees C required 45 min to kill all M. hirsutus, whereas treatment at 49 degrees C required 10 min. The adult female and nymphal stages were the most heat tolerant at 47 degrees C, but the egg stage was the most heat tolerant at 49 degrees C. Use of the vapor heat treatments on other commodities will require achieving or exceeding the proper temperature and duration at all locations on the host where M. hirsutus may reside.     

Effect of exercise intensity on the postexercise sweating threshold.

The hypothesis that the magnitude of the postexercise onset threshold for sweating is increased by the intensity of exercise was tested in eight subjects. Esophageal temperature was monitored as an index of core temperature while sweat rate was measured by using a ventilated capsule placed on the upper back. Subjects remained seated resting for 15 min (no exercise) or performed 15 min of treadmill running at either 55, 70, or 85% of peak oxygen consumption (V(o2 peak)) followed by a 20-min seated recovery. Subjects then donned a liquid-conditioned suit used to regulate mean skin temperature. The suit was first perfused with 20 degrees C water to control and stabilize skin and core temperature before whole body heating. Subsequently, the skin was heated ( approximately 4.0 degrees C/h) until sweating occurred. Exercise resulted in an increase in the onset threshold for sweating of 0.11 +/- 0.02, 0.23 +/- 0.01, and 0.33 +/- 0.02 degrees C above that measured for the no-exercise resting values (P < 0.05) for the 55, 70, and 85% of V(o2 peak) exercise conditions, respectively. We did note that there was a greater postexercise hypotension as a function of exercise intensity as measured at the end of the 20-min exercise recovery. Thus it is plausible that the increase in postexercise threshold may be related to postexercise hypotension. It is concluded that the sweating response during upright recovery is significantly modified by exercise intensity and may likely be influenced by the nonthermal baroreceptor reflex adjustments postexercise.     

Metabolic rate and thermoregulation in two species of tuco-tuco, Ctenomys talarum and Ctenomys australis (Caviomorpha, Octodontidae)

1. Resting metabolic rate and body temperature in function of ambient temperature were determined for two species of Ctenomys. 2. Oxygen consumption was lowest between 25 and 30 degrees C and was 0.946 +/- 0.030 and 0.968 +/- 0.022 in Ctenomys talarum (from Mar de Cobo and Necochea, respectively). Resting metabolic rate was 0.343 +/- 0.053 at 30 C in C. australis. 3. Mean rectal temperature at thermoneutrality was 36.1 +/- 0.13 and 37.3 +/- 0.17 in C. talarum and C. australis, respectively. 4. Limited thermoregulation occurred in C. talarum down to 20 degrees C but C. australis maintained body temperature down to 10 degrees C. 5. Both species of tuco-tucos became hyperthermic at ambient temperatures above thermoneutrality.     

Sperm cryopreservation of African catfish, Clarias gariepinus: cryoprotectants, freezing rates and sperm:egg dilution ratio

Methods for cryopreserving spermatozoa and optimizing sperm:egg dilution ratio in African catfish Clarias gariepinus were developed. Five percent to 25% DMSO and methanol were tested as cryoprotectants, by diluting semen in Ginzburg fish ringer and freezing in 1-milliliter cryovials in a programmable freezer. To avoid an excess of spermatozoa per egg, post-thaw semen was diluted 1:20, 1:200 or 1:2,000 before fertilization. Highest hatching rates were obtained by spermatozoa frozen in 10% methanol and post-thaw diluted to 1:200. Then, slow freezing rates (-2, -5 or -10 degrees C/min) to various endpoint temperatures (range -25 to -70 degrees C) before fast freezing in liquid nitrogen (LN2) were evaluated. Hatching rates equal to control (P > 0.05) were obtained by spermatozoa frozen at -5 degrees C/min to -45 to -50 degrees C and at -10 degrees C/min to -55 degrees C. In 3-step freezing programs, at -5 degrees C/min, the effect of holding spermatozoa for 0, 2 or 5 min at -30, -35 or -40 degrees C before fast freezing in LN2 was analyzed. Hatching rates equal to control (P > 0.05) were produced by spermatozoa frozen to, and held at, -35 degrees C for 5 min and at -40 degrees C for 2 or 5 min. Finally, frozen spermatozoa (10% methanol, -5 degrees C/min, 5-min hold at -40 degrees C, LN2, post-thaw diluted to 1:200) were tested in on-farm fertilization conditions. Again, no difference (P > 0.05) in hatching rate was observed between frozen and fresh spermatozoa. Cryopreservation offers utility as a routine method of sperm storage and management for catfish.     

A second postcooling afterdrop: more evidence for a convective mechanism.

An attempt was made to demonstrate the importance of increased perfusion of cold tissue in core temperature afterdrop. Five male subjects were cooled twice in water (8 degrees C) for 53-80 min. They were then rewarmed by one of two methods (shivering thermogenesis or treadmill exercise) for another 40-65 min, after which they entered a warm bath (40 degrees C). Esophageal temperature (Tes) as well as thigh and calf muscle temperatures at three depths (1.5, 3.0, and 4.5 cm) were measured. Cold water immersion was terminated at Tes varying between 33.0 and 34.5 degrees C. For each subject this temperature was similar in both trials. The initial core temperature afterdrop was 58% greater during exercise (mean +/- SE, 0.65 +/- 0.10 degrees C) than shivering (0.41 +/- 0.06 degrees C) (P < 0.005). Within the first 5 min after subjects entered the warm bath the initial rate of rewarming (previously established during shivering or exercise, approximately 0.07 degrees C/min) decreased. The attenuation was 0.088 +/- 0.03 degrees C/min (P < 0.025) after shivering and 0.062 +/- 0.022 degrees C/min (P < 0.025) after exercise. In 4 of 10 trials (2 after shivering and 2 after exercise) a second afterdrop occurred during this period. We suggest that increased perfusion of cold tissue is one probable mechanism responsible for attenuation or reversal of the initial rewarming rate. These results have important implications for treatment of hypothermia victims, even when treatment commences long after removal from cold water.     

Effect of pre-cooling, with and without thigh cooling, on strain and endurance exercise performance in the heat

Body cooling before exercise (i.e. pre-cooling) reduces physiological strain in humans during endurance exercise in temperate and warm environments, usually improving performance. This study examined the effectiveness of pre-cooling humans by ice-vest and cold (3 degrees C) air, with (LC) and without (LW) leg cooling, in reducing heat strain and improving endurance performance in the heat (35 degrees C, 60% RH). Nine habitually-active males completed three trials, involving pre-cooling (LC and LW) or no pre-cooling (CON: 34 degrees C air) before 35-min cycle exercise: 20 min at approximately 65% VO2peak then a 15-min work-performance trial. At exercise onset, mean core (Tc, from oesophagus and rectum) and skin temperatures, forearm blood flow (FBF), heart rate (HR), and ratings of exertion, body temperature and thermal discomfort were lower in LW and LC than CON (P<0.05). They remained lower at 20 min [e.g. Tc: CON 38.4+/-0.2 (+/-S.E.), LW 37.9+/-0.1, and LC 37.8+/-0.1 degrees C; HR: 177+/-3, 163+/-3 and 167+/-3 b.p.m.), except that FBF was equivalent (P=0.10) between CON (15.5+/-1.6) and LW (13.6+/-1.0 ml.100 ml tissue(-1) x min(-1)). Subsequent power output was higher in LW (2.95+/-0.24) and LC (2.91+/-0.25) than in CON (2.52+/-0.28 W kg(-1), P=0.00, N=8), yet final Tc remained lower. Pre-cooling by ice-vest and cold air effectively reduced physiological and psychophysical strain and improved endurance performance in the heat, irrespective of whether thighs were warmed or cooled.     

Inactivation of a norovirus by high-pressure processing

Murine norovirus (strain MNV-1), a propagable norovirus, was evaluated for susceptibility to high-pressure processing. Experiments with virus stocks in Dulbecco's modified Eagle medium demonstrated that at room temperature (20 degrees C) the virus was inactivated over a pressure range of 350 to 450 MPa, with a 5-min, 450-MPa treatment being sufficient to inactivate 6.85 log(10) PFU of MNV-1. The inactivation of MNV-1 was enhanced when pressure was applied at an initial temperature of 5 degrees C; a 5-min pressure treatment of 350 MPa at 30 degrees C inactivated 1.15 log(10) PFU of virus, while the same treatment at 5 degrees C resulted in a reduction of 5.56 log(10) PFU. Evaluation of virus inactivation as a function of treatment times ranging from 0 to 150 s and 0 to 900 s at 5 degrees C and 20 degrees C, respectively, indicated that a decreasing rate of inactivation with time was consistent with Weibull or log-logistic inactivation kinetics. The inactivation of MNV-1 directly within oyster tissues was demonstrated; a 5-min, 400-MPa treatment at 5 degrees C was sufficient to inactivate 4.05 log(10) PFU. This work is the first demonstration that norovirus can be inactivated by high pressure and suggests good prospects for inactivation of nonpropagable human norovirus strains in foods.     

Freezing induces a loss of freeze tolerance in an overwintering insect

Cold-hardy insects overwinter by one of two main strategies: freeze tolerance and freeze avoidance by supercooling. As a general model, many freeze-tolerant species overwinter in extreme climates, freeze above -10 degrees C via induction by ice-nucleating agents, and once frozen, can survive at temperatures of up to 40 degrees C or more below the initial freezing temperature or supercooling point (SCP). It has been assumed that the SCP of freeze-tolerant insects is unaffected by the freezing process and that the freeze-tolerant state is therefore retained in winter though successive freeze-thaw cycles of the body tissues and fluids. Studies on the freeze-tolerant larva of the hoverfly Syrphus ribesii reveal this assumption to be untrue. When a sample with a mean 'first freeze' SCP of -7.6 degrees C (range of -5 degrees C to -9.5 degrees C) were cooled, either to -10 degrees C or to their individual SCP, on five occasions, the mean SCP was significantly depressed, with some larvae subsequently freezing as low as -28 degrees C. Only larvae that froze at the same consistently high temperature above -10 degrees C were alive after being frozen five times. The wider occurrence of this phenomenon would require a fundamental reassessment of the dynamics and distinctions of the freeze-tolerant and freeze-avoiding strategies of insect overwintering.     

Hot-water treatments for control of Planococcus ficus (Homoptera: Pseudococcidae) on dormant grape cuttings

Hot-water immersions were tested for control of mealybug Planococcus ficus (Signoret), on dormant grape cuttings used for nursery stock. A range of hot-water temperatures (47-58 degrees C) were evaluated at immersion periods of 2, 5, 10, or 20 min, by using a total of 353,720 mealybugs across all treatments. A 5-min immersion at 51 degrees C is effective in killing > 99% of P. ficus. At or above this immersion period and temperature, there was no difference in mealybug stage mortality. We evaluated a commercial operation, which used a 5-min immersion in each of three water tanks: preheating (30.0 +/- 3 degrees C), hot-water (52.8 +/- 0.3 degrees C), and cooling (23 +/- 3 degrees C). The commercial procedure provided 99.8-100% mealybug control in each of three separate trials.