Dynamical properties of a hydrated lipid bilayer from a multinanosecond molecular dynamics simulation

A fully hydrated dimiristoylphosphatidylcholine (DMPC) bilayer has been studied by a molecular dynamics simulation. The system, which consisted of 64 DMPC molecules and 1792 water molecules, was run in the NVE ensemble at a temperature of 333 K for a total of 10 ns. The resulting trajectory was used to analyze structural and dynamical quantities. The electron density, bilayer spacing, and order parameters (S(CD)), based on the AMBER forcefield and SPCE water model are in good agreement with previous calculations and experimental data. The simulation reveals evidence for two types of lateral diffusive behavior: cage hopping and that of a two-dimensional liquid. The lateral diffusion coefficient is 8 x 10(-8) cm(2)/s. We characterize the rotational motion, and find that the lipid tail rotation (D(rot_tail) = -0.04 rad(2)/ns) is slower then the head group rotation (D(rot_hg) = 2.2 rad(2)/ns), which is slower than the overall in plane (D(rot) = 3.2 rad(2)/ns) for the lipid molecule.     

The effects of cage size and pair housing on exercise of beagle dogs

One of the requirements of the 1985 amendments to the Animal Welfare Act is the establishment of an exercise program for dogs. Assumptions have been made by some that larger cages or the presence of a companion animal will motivate exercise. To examine how cage size, pair housing and human contact affect exercise, a study was conducted using a computerized video-data acquisition system that measured distance traveled and time spent moving in 1 x 1 m, (single only) and 1 x 2 m (single and paired) and 1 x 1.5 m cage (paired only) cages. Male beagle dogs (n = 6) housed singly in the 1 m2 cage traveled an average of 55 m/hr spending only 8% (57 min) of the 12 h photo period in motion. When the cage size was doubled, the average distance traveled decreased to 13 m/hr and the time spent moving increased to 11% (77 min/day). When dogs were pair housed in a regulation size cage, the average distance traveled decreased to 8.6 m/hr and they spent less than 6% of the day in exercising (42 min/12 hrs). The greatest amount of exercise was seen when dogs were housed as a pair in a cage less than recommended size (an average of 109 m/hr and 8.8 min/hr). Therefore, these data indicate that larger cages or pair housing in regulation size cages have little or no effect on the activity of purpose bred male beagle dogs. There was, however, a direct correlation between activity, time and distance, and the presence of humans in the animal room.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of Metabolic Cage Housing on Rat Behavior and Performance in the Social Interaction Test

Although the metabolic cage is commonly used for housing nonhuman animals in the laboratory, it has been recognized as constituting a unique stressor. Such an environment would be expected to affect behavioral change in animals housed therein. However, few studies have specifically addressed the nature or magnitude of this change. The current study sought to characterize the behavioral time budget of rats in metabolic cage housing in comparison to that of individually housed animals in standard open-top cages. Rats in metabolic cages spent less time moving, manipulating enrichment, and carrying out rearing behaviors, and there was a corresponding shift toward inactivity. In an applied Social Interaction Test, behavioral scoring implied that metabolic cage housing had an anxiogenic effect. In conclusion, metabolic cage housing produces measurable effects on spontaneous and evoked behavior in rats in the laboratory. These behavioral changes may lead to a negative emotional state in these animals, which could have negative welfare consequences. Further research is needed to quantify the existence and magnitude of such an effect on rat well being.     

Calibration and evaluation of field cage for oviposition study with Aedes (Stegomyia) aegypti female (L.) (Diptera: Culicidae)

Differences among results gathered from insect behavior studies conducted in laboratory and field situations are due to ambient variables that differ greatly between both environments. In laboratory studies the environmental conditions can be controlled whereas in field temperature, humidity and air velocity vary uncontrollably. The objective of this study was to calibrate and evaluate an experimental area (field cage) (14 x 7 x 3.5 m) subdivided into eight test cages (2.5 x 2.5 x 2 m) for use in behavioral oviposition tests of Aedes aegypti (L.) mosquitoes for developing a new methodology to assess attractants and oviposition traps. Test cage calibration involved: (1) minimal experiment duration tests; (2) optimal female release number per traps test and (3) trap placement tests. All tests used gravid A. aegypti females; 3-4 days post blood meal and the sticky trap MosquiTRAP to catch adults. Ninety percent of the females released were recaptured 2h after the beginning of the experiment, and this allowed up to 32 test repetitions/day to be conducted in the field cage. The minimum number of females necessary to conduct statistical analyses was 20 females/trap/test per cage. No significant difference was found in the behavioral response of gravid females to four different trap positions within test cages. Field trapping results with attractant were similar to those in the field cage. Therefore, the field cage could replace field trapping for evaluating at least mosquito traps and oviposition attractants for A. aegypti.     

Evaluation of the preference to and behavioral effects of an enriched environment on male rhesus monkeys.

Two environments were provided to laboratory rhesus monkeys to determine if the animals spent more time (for the purposes of this study, defined as the cage side preference) in an enriched cage side than an unenriched cage side. The side (right or left) of a double-wide cage in which the animal spent the most time (as determined by Chi square analysis) was initially determined during baseline observations. The "nonpreferred" side was then enriched during the experimental phase of the study. The enrichment consisted of a perch, a Tug-A-Toy suspended inside the cage, a Kong toy suspended on the outside of the cage, and a grooming board mounted on the outside of the cage. No statistically significant changes in use of the enrichments were detected over time. Fifty percent of the animals switched cage side preference to the enriched side during the study. All subjects showed reduced behavioral pathology during exposure to the enriched environment with a return of behavioral pathology when the enrichments were removed.     

Effects of voluntary resistance exercise and high-protein snack on bone mass, composition, and strength in rats given glucocorticoid injections

We examined the effects of a voluntary resistance exercise (climbing) together with high-protein snacks (60% protein) on bone mass and strength in rats given glucocorticoid-injections (2 mg/kg/day) as a model of age-related osteopenia. Fifty-two male Sprague-Dawley rats, 8 weeks age, were assigned to exercise or sedentary groups. These groups were further divided into groups that received no snack, snack during activity or a snack during rest. All groups were meal-fed 7:30-8:30 h and 19:30-20:30 h and the snack was fed 23:30-0:30 h (active) or 11:30-12:30 h (resting). Energy and protein intake were approximately equal in all groups. The exercise groups were allowed to climb a wire-mesh tower cage (phi 20 cm x 200 cm) to drink water from a bottle set at the top. Weight gain during the 8-week experimental period was inhibited by a glucocorticoid-injection. Bone mass and strength were increased by climbing exercise with a high-protein snack, while no effect of snack nor any effect of snack timing was observed. Bone weight, calcium content and protein content were positively correlated to maximum load or structural stiffness. These results suggest that resistance exercise and high-protein supplementation may be a preventive therapy for osteoporosis associated with aging.     

Effects of under- and overcrowding on exploratory behavior in the elevated plus-maze

The present work investigated whether the number of rats housed in a cage affects exploration of an elevated plus-maze. Male Wistar-derived rats were kept 1, 2, 3, 4, 6, 8, 12, 16, or 24 to same size cages either for 1 or 14 days and tested in the elevated plus-maze. Rats kept 6 to a cage were arbitrarily considered controls because this is the housing condition adopted in many laboratories, ours included. In comparison to controls, 1-day housed rats kept 1, 2, 16, and 24 to a cage decreased the percentage of entries into the open arms. Similar decreases were also found in the time spent in the open arms, the only exception being the group with rats kept 16 to a cage which failed to show significant differences from the control group. Fourteen-day housed rats kept 1, 2, 16, or 24 to a cage decreased the percentage of entries and time spent in the open arms. We found plus-maze exploration to be similar in groups in which rats were kept from 4 to 12 to a cage. The present data indicate that anxiogenic effects resulting from under- and overcrowding should be taken into consideration in behavioral studies.     

Influence of availability of perches on the behavioral well-being of captive,group-living mangabeys

Environmental enrichment is expected to increase the well-being of animals. Changes in well-being can be measured by variations in behavioral patterns. This study reports on behavioral changes induced, in arboreal monkeys, by progressively increasing the number of perches, from none to five, in an “experimental cage.” A cage equipped with five perches was used as the control cage. The behaviors of a group of seven gray-cheeked mangabeys in the control cage and in the “experimental” cage were compared. A total deprivation of perches yielded an increase in aggressive behaviors and locomotion, and a decrease in cohesiveness. Placing perches progressively in the experimental cage restored the level of all the variables to levels found in the control cage. This restoration to control levels actually occurred only when the number of perches in the experimental cage was close or equal to that in the control cage. Therefore perches constitute a necessary feature of an adequate environment for mangabeys. We suggest that this restoration is a consequence of providing appropriate structure of the utilizable space for the monkeys. This structure might increase the control and the predictability that monkeys should have over social events. © 1996 Wiley-Liss, Inc.     

Correlation of scrotal circumference and age in American Brahman bulls

Scrotal circumference (SC) measurements were taken of 921 American Brahman bulls located on two ranches in southcentral Texas. Measurements were taken at various seasons of the year over an 11-yr time span. Body condition scores, as reflected by fat cover, and a subjective estimate of overall nutritional status were 4 or better, based upon a 1 to 9 scoring system, with 5 representing an animal with an average amount of body fat. Associated body weights were not measured and semen evaluations were not performed. Ages were calculated from exact birthdates and rounded to the nearest whole month. Ages from 8 mo to more than 36 mo were reported. SC measurements ranged from 16.0 cm to 42.5 cm. The relationship of SC and age was positively correlated (r=0.74) (P<0.0001) and could be predicted using the equation y=0.525x + 18.702 where y=SC in centimeters and x=age in months. These data provide evidence that the relationship of scrotal circumference and age of American Brahman bulls is similar to that of other cattle breeds.     

对虾综合养殖生态系底泥细菌的数量动态

1997年5～9月于山东海阳市黄海集团公司养虾场,用5个实验围隔研究了对虾综合养殖生态系底泥细菌的数量动态.结果表明,底泥细菌数量波动在4.10×108～12.36×108cells·g-1之间,平均为8.09×108±2.17×108cells·g-1.随着养殖时间的推移,底泥细菌数量逐渐增加.底泥细菌数量最大值出现在表层1cm之内,2～3cm以下泥层,细菌数量明显减小     

Mice Do Not Habituate to Metabolism Cage Housing–A Three Week Study of Male BALB/c Mice

The metabolism cage is a barren, non-enriched, environment, combining a number of recognized environmental stressors. We investigated the ability of male BALB/c mice to acclimatize to this form of housing. For three weeks markers of acute and oxidative stress, as well as clinical signs of abnormality were monitored. Forced swim tests were conducted to determine whether the animals experienced behavioral despair and the serotonergic integrity was tested using an 8-OH-DPAT challenge. The metabolism cage housed mice excreted approximately tenfold higher amounts of corticosterone metabolites in feces throughout the study when compared to controls. Urinary biomarkers confirmed that these mice suffered from elevated levels of oxidative stress, and increased creatinine excretions indicated increased muscle catabolism. Changes in the core body temperature (stress-induced hyperthermia) and the fur state of the mice also indicated impaired well-being in the metabolism cage housed mice. However, monitoring body weight and feed intake was found misleading in assessing the wellbeing of mice over a longer time course, and the forced swim test was found poorly suited for studying chronic stress in mice in the present setup. In conclusion, the mice were found not to acclimatize to the metabolism cages whereby concern for animal welfare would dictate that mice should be housed in this way for as short periods as possible. The elevated degree of HPA axis activity, oxidative stress, and increased overall metabolism warrant caution when interpreting data obtained from metabolism cage housed mice, as their condition cannot be considered representative of a normal physiology.     

The efficiency and direction of thymus changes after whole-body exposure of mice to the weak electromagnetic field are determined by the initial status of the thymus

The work presents results of the experimental study on thymus changes developing after whole-body exposure of mice to ultralow power pulse-modulated electromagnetic field (carrying frequency 2.39 GHz, modulating pulses with frequency 4 Hz, duration of impulses 0.025 sec, average power density 60 mW/cm2, absorbed dose 0.086 J/g or 0.172 J/g). It was shown that a percent of the microwave induced increase or decrease of thymus mass and the number of cells in the organ (y) are determined by the initial mass or number of cells in thymus accordingly to equation of linear regression: (yx = 215-2.25x, where x is the thymus mass of control animals (in a range 31-63 mg) and (yx = 178.6-41x, where x is the initial number of cells in thymus (in a range 0.6 x 10(8)-2.6 x 10(8)) reduced by a factor of 10(8).     

Monte Carlo simulations of supercoiling free energies for unknotted and trefoil knotted DNAs.

A new Monte Carlo (MC) algorithm is proposed for simulating inextensible circular chains with finite twisting and bending rigidity. This new algorithm samples the relevant Riemann volume elements in a uniform manner, when the constraining potential vanishes. Simulations are performed for filaments comprising 170 subunits, each containing approximately 28 bp, which corresponds to a DNA length of 4770 bp. The bending rigidity is chosen to yield a persistence length, P = 500 A, and the intersubunit potential is taken to be a hard-cylinder potential with diameter d = 50 A. This value of d yields the same second virial coefficient as the electrostatic potential obtained by numerical solution of the Poisson-Boltzmann equation for 150 mM salt. Simulations are performed for unknotted circles and also for trefoil knotted circles using two different values of the torsional rigidity, C = (2.0 and 3.0) x 10(-19) dyne cm2. In the case of unknotted circles, the simulated supercoiling free energy varies practically quadratically with linking difference delta l. The simulated twist energy parameter ET, its slope dET/dT, and the mean reduced writhe <w>/delta l for C = 3 x 10(-19) dyne cm2 all agree well with recent simulations for unknotted circles using the polygon-folding algorithm with identical P, d, and C. The simulated ET vs. delta l data for C = 2.0 x 10(-19) dyne cm2 agree rather well with recent experimental data for p30 delta DNA (4752 bp), for which the torsional rigidity, C = 2.07 x 10(-19) dyne cm2, was independently measured. The experimental data for p30 delta are enormously more likely to have arisen from C = 2.0 x 10(-19) than from C = 3.0 x 10(-19) dyne cm2. Serious problems with the reported experimental assessments of ET for pBR322 and their comparison with simulated data are noted. In the case of a trefoil knotted DNA, the simulated value, (ET)tre, exceeds that of the unknotted DNA, (ET)unk, by approximately equal to 1.40-fold at magnitude of delta l = 1.0, but declines to a plateau about 1.09-fold larger than (ET)unk when magnitude of delta l > or = 15. Although the predicted ratio, (ET)tre/(ET)unk approximately equal to 1.40, agrees fairly well with recent experimental measurements on a 5600-bp DNA, the individual measured ET values, like some of those reported for pBR322, are so large that they cannot be simulated using P = 500 A, d = 50 A, and any previous experimental estimate of C.     

Social Communication in Mice – Are There Optimal Cage Conditions?

Social communication is heavily affected in patients with neuropsychiatric disorders. Accordingly, mouse models designed to study the mechanisms leading to these disorders are tested for this phenotypic trait. Test conditions vary between different models, and the effect of these test conditions on the quantity and quality of social interactions and ultrasonic communication is unknown. The present study examines to which extent the habituation time to the test cage as well as the shape / size of the cage influence social communication in freely interacting mice. We tested 8 pairs of male mice in free dyadic social interactions, with two habituation times (20 min and 30 min) and three cage formats (rectangle, round, square). We tested the effect of these conditions on the different types of social contacts, approach-escape sequences, follow behavior, and the time each animal spent in the vision field of the other one, as well as on the emission of ultrasonic vocalizations and their contexts of emission. We provide for the first time an integrated analysis of the social interaction behavior and ultrasonic vocalizations. Surprisingly, we did not highlight any significant effect of habituation time and cage shape / size on the behavioral events examined. There was only a slight increase of social interactions with the longer habituation time in the round cage. Remarkably, we also showed that vocalizations were emitted during specific behavioral sequences especially during close contact or approach behaviors. The present study provides a protocol reliably eliciting social contacts and ultrasonic vocalizations in adult male mice. This protocol is therefore well adapted for standardized investigation of social interactions in mouse models of neuropsychiatric disorders.     

Relationship tenure differentially influences pair-bond behavior in male and female socially monogamous titi monkeys (Callicebus cupreus)

Pair-bonded primates have uniquely enduring relationships and partners engage in a suite of behaviors to maintain these close bonds. In titi monkeys, pair bond formation has been extensively studied, but changes across relationship tenure remain unstudied. We evaluated differences in behavioral indicators of pair bonding in newly formed (~6 months paired, n = 9) compared to well-established pairs (average 3 years paired, n = 8) of titi monkeys (Callicebus cupreus) as well as sex differences within the pairs. We hypothesized that overall males would contribute more to maintenance than females, but that the pattern of maintenance behaviors would differ between newly formed and well-established pairs. Each titi monkey (N = 34) participated in a partner preference test (PPT), where the subject was placed in a middle test cage with grated windows separating the subject from the partner on one side and an opposite-sex stranger on the other side. During this 150-min behavioral test, we quantified four key behaviors: time in proximity to the partner or stranger as well as aggressive displays toward the partner or stranger. Overall, we found different behavioral profiles representing newly formed and well-established pair-bond relationships in titi monkeys and male-biased relationship maintenance. Males spent ∼40% of their time in the PPT maintaining proximity to the female partner, regardless of relationship tenure. Males from well-established bonds spent less time (14%) near the female stranger compared to males from newly formed bonds (21%) at the trend level. In contrast, females from well-established bonds spent less (23%) time near the male partner in the PPT compared to females from newly formed bonds (47%). Aggressive displays were more frequent in newly formed bonds compared to well-established bonds, especially for females. Scan sampling for homecage affiliation showed that newly formed pairs were more likely to be found tail twining than well-established pairs.     

Selection for the predisposition to catalepsy enhances depressive-like traits in mice

Immobility reaction or catalepsy is a natural passive defensive (lurking) behavioral response to the appearance of a predator. Selection for high predisposition to catalepsy has been performed in a population of (CBA x (CBA x AKR)) backcrosses of the crossing between mouse lines sensitive and resistant to catalepsy (VBA and AKR, respectively). A rapid increase in the number of animals with catalepsy has been observed: from 23% in backcrosses to 71% in the S3 generation. Selection for catalepsy does not affect mouse anxiety in the open field and plus-maze tests. However, S8 and S9 mice are characterized by a decreased motor activity in the open-field test and an increased immobility in the forced swim and tail suspension tests, which is interpreted as an increase in "depressiveness." The results indicate that genetically determined catalepsy is related to depressive-like characteristics of defensive behavior.     

Non-steady-state diffusion in a multilayered tissue initiated by manipulation of chemical activity at the boundaries.

Diffusion of ionic and nonionic species in multilayered tissues plays an important role in the metabolic processes that take place in these tissues. To create a mathematical model of these diffusion processes, we have chosen as an example hydrogen-bicarbonate ion pair diffusion within the mammalian cornea. This choice was based on the availability of experimental data on this system. The diffusion coefficient of the hydrogen-bicarbonate ion pair in corneal stroma and epithelium is calculated from the observed change in pH in the stroma when conditions at the corneal anterior epithelial surface are changed while the posterior surface is continually bathed with a Ringer's solution in equilibrium with a CO2-gas air mixture. Matching experimental results to a mathematical model of the cornea as a two-layer diffusion system yields, at 37 degrees C, a diffusion coefficient of the hydrogen-bicarbonate ion pair of 2.5 x 10(-6) cm2/s in the stroma and 0.4 x 10(-6) cm2/s in the epithelium. Application of the Nernst-Einstein equation to these data gives the following diffusion coefficients in the two layers: 1) stroma, D(H+) = 11.8 x 10(-6) cm2/s; D(HCO3-) = 1.5 x 10(-6) cm2/s; and 2) epithelium, D(H+) = 1.9 x 10(-6) cm2/s; D(HCO3-) = 0.22 x 10(-6) cm2/s.     

Diaphragmatic work of breathing in premature human infants

Present methods of assessing the work of breathing in human infants do not account for the added load when intercostal muscle activity is lost and rib cage distortion occurs. We have developed a technique for assessing diaphragmatic work in this circumstance utilizing measurements of transdiaphragmatic pressure and abdominal volume displacement. Eleven preterm infants without evidence of lung disease were studied. During periods of minimal rib cage distortion, inspiratory diaphragmatic work averaged 5.9 g X cm X ml-1, increasing to an average of 12.4 g X cm X ml-1 with periods of paradoxical rib cage motion (P less than 0.01). Inspiratory work was strongly correlated with the electrical activity of the diaphragm as measured from its moving time average (P less than 0.05). Assuming a mechanical efficiency of 4% in these infants, the caloric cost of diaphragmatic work may reach 10% of their basal metabolic rate in periods with rib cage distortion. When lung disease is superimposed, the increased metabolic demands of the diaphragm may predispose preterm infants to fatigue and may contribute to a failure to grow.     

Transient quinonimines and 1,4-benzothiazines of pheomelanogenesis: new pulse radiolytic and spectrophotometric evidence.

Biosynthetic and model in vitro studies have shown that pheomelanins, the distinctive pigments of red human hair, arise by oxidative cyclization of cysteinyldopas mainly 5-S-cysteinyldopa (1) via a critical o-quinonimine intermediate, which rearranges to unstable 1,4-benzothiazines. To get new evidence for these labile species, fast time resolution pulse radiolytic oxidation by dibromide radical anion of a suitable precursor, the dihydro-1,4-benzothiazine-3-carboxylic acid 7 was performed in comparison with that of 1. In the case of 7, dibromide radical anion oxidation leads over a few microseconds (k = 2.1 x 10(9) M(-1) s(-1)) to a phenoxyl radical (lambda(max) 330 nm, epsilon = 6300 M(-1) cm(-1)) which within tens of milliseconds gives rise with second-order kinetics (2k = 2.7 x 10(7) M(-1) s(-1)) to a species exhibiting an absorption maximum at 540 nm (epsilon = 2200 M(-1) cm(-1)). This was formulated as the o-quinonimine 3 arising from disproportionation of the initial radical. The quinonimine chromophore is converted over hundreds of milliseconds (k = 6.0 s(-1)) to a broad maximum at around 330 nm interpreted as due to a 1,4-benzothiazine or a mixture of 1,4-benzothiazines, which as expected are unstable and subsequently decay over a few seconds (k = 0.5 s(-1)). Interestingly, the quinonimine is observed as a labile intermediate also in the alternative reaction route examined, involving cyclization of the o-quinone (lambda(max) 390 nm, epsilon = 6900 M(-1) cm(-1)) arising by disproportionation (2k = 1.7 x 10(8) M(-1) s(-1)) of an o-semiquinone (lambda(max) 320 nm, epsilon = 4700 M(-1) cm(-1)) directly generated by dibromide radical anion oxidation of 1. Structural formulation of the 540 nm species as an o-quinonimine was further supported by rapid scanning diode array spectrophotometric monitoring of the ferricyanide oxidation of a series of model dihydrobenzothiazines.     

Effects of early weaning and housing conditions on the development of stereotypies in farmed mink

Female mink pups were weaned at 6, 8 or 10 weeks of age and subjected to two different housing conditions. They were either kept together with a single male sibling in traditional mink cages (30x45x90 cm) or housed socially with all litter-mates in an alternative system consisting of three adjoining traditional cages (90x45x90 cm). All cages were supplied with nest boxes. At 5 months of age, the siblings were removed leaving the females socially isolated in the two different cage systems. Females' stereotypies were quantified by repeated scanning observations under the social housing conditions immediately before removal of the siblings, and again at the age of 7 and 9 months, when the animals had stayed solitary in the two systems for 2 and 4 months. Solitary females showed significantly more stereotypies than females under social housing conditions in both cage systems. Stereotypies were more frequent in the smaller traditional cages. Stereotypies declined from 7 to 9 months of age among solitary animals in traditional cages but not in alternative cages. Early-weaned solitary females in traditional cages showed more stereotypies than later-weaned animals, but only when measured at the age of 7 months. It is suggested that early weaning, individual housing and small cages promote the development of stereotypies in farmed mink. The influence of early weaning on stereotypies seems to decline with age, while effects related to individual housing and small cages appear to be more persistent.