Preface

The legal process is often invoked to resolve scientific or economic problems such as may arise when a bridge collapses, or an aeroplane crashes, or a ship sinks; or when a mishap occurs on the operating table; or when patent protection is sought for an invention claimed to be novel; or when it is necessary to assess the effect of a commercial practice on competition in a market; or when a baby dies, for no apparent reason, in its cot; or when it is sought to identify a fingerprint on a murder weapon.     

Influence of body position on pulmonary diffusing capacity in yound and old men.

Steady-state diffusing capacity (DLCOSS2), studied in healthy nonsmokers, was significantly higher in five old men when seated than when supine, but was unchanged in five young men. However, "corrected" for the increased ventilation, it decreased in the young--but not in the old--when erect compared with when supine. The change of DLCOSS2 in the young during the first 20 min when seated was related to a change of the fractional dead space ventilation (VD/VT)mThe old showed less venous admixture when seated than when supine, whereas VD/VT and regional ventilation-perfusion index of the lung bases was the same in both positions. The decrease in venous admixture was probably due to the closing capacity (CC) being less than the functional residual capacity (FRC) when seated. The elimination of closed off regions when seated made more pulmonary capillaries available for diffusion.     

Management of Transient Cerebral Ischemic Attacks

Transient ischemic attacks (TIAs) are brief reversible episodes of neurological dysfunction due to temporary focal cerebral ischemia. Angiography should be performed only when operation is indicated or when the diagnosis is in doubt. Surgical treatment is recommended when the patient is a good surgical risk, when the stenosis is more than 70 per cent in the appropriate vessel and in certain patients with less severe stenotic lesions that appear to be a probable source of emboli. Anticoagulant therapy is indicated when there are recurrent TIAs, when the patient is not a good surgical candidate and when no appropriate surgically remediable lesion is found by angiography. If there is any significant contraindication to anticoagulants they should not be given. Discontinuance of anticoagulant therapy when the patient has been symptom-free for six months is recommended. In the experience of the authors the TIA syndrome is more benign in its course than was originally suspected and a conservative approach to surgical and anticoagulant therapy is recommended.     

Enhanced vigilance in monogamous pairs of the lizard, Tiliqua rugosa

The Australian sleepy lizard, Tiliqua rugosa, forms monogamouspairs for up to 8 weeks each spring before mating. We observedthat males had food in their mouths significantly less oftenwhen they were in pain than when they were alone. Females hadfood in the mouth independent of the presence or absence ofmales. Among females that had been feeding, indicated by foodin the mouth, we observed them feeding, as we approached, lessoften when they were in pairs than when they were alone. Amongfemales in pairs with food in their mouths, we observed themfeeding less often when their male partners were not feedingthan when their partners were feeding. This suggests that femalesare alerted to approaching danger earlier when they are in apair, and alerted earlier in a pair when their male partneris not feeding. Enhanced vigilance may be one function of pairingbehavior.     

Overestimating resource value and its effects on fighting decisions

Much work in behavioral ecology has shown that animals fight over resources such as food, and that they make strategic decisions about when to engage in such fights. Here, we examine the evolution of one, heretofore unexamined, component of that strategic decision about whether to fight for a resource. We present the results of a computer simulation that examined the evolution of over- or underestimating the value of a resource (food) as a function of an individual's current hunger level. In our model, animals fought for food when they perceived their current food level to be below the mean for the environment. We considered seven strategies for estimating food value: 1) always underestimate food value, 2) always overestimate food value, 3) never over- or underestimate food value, 4) overestimate food value when hungry, 5) underestimate food value when hungry, 6) overestimate food value when relatively satiated, and 7) underestimate food value when relatively satiated. We first competed all seven strategies against each other when they began at approximately equal frequencies. In such a competition, two strategies--"always overestimate food value," and "overestimate food value when hungry"--were very successful. We next competed each of these strategies against the default strategy of "never over- or underestimate," when the default strategy was set at 99% of the population. Again, the strategies of "always overestimate food value" and "overestimate food value when hungry" fared well. Our results suggest that overestimating food value when deciding whether to fight should be favored by natural selection.     

Diene chirality and cotton effects of nonhomoannular cisoid conjugated dienes: circular dichroism and crystal structure of a steroidal 19-nor-1(10),9(11)-diene derived from Westphalen's diol diacetate

Nonhomoannular cisoid conjugated dienes exhibit negative lowest energy pi-->pi* Cotton effects when they have P diene chirality and positive CEs when they have M diene chirality. We investigated this relationship further with a variety of such dienes by MM2 conformational energy-minimization calculations and by an X-ray crystal structure of a steroidal 19 nor 1(10),9(11) diene. CEs are stronger when each double bond of the diene is endocyclic in a different ring and weaker when only one of the double bonds is endocyclic or when neither double bond is endocyclic. They are also stronger when axial allylic and homoallylic substituents with CH/pi interactions are present that exert consignate chirality contributions.     

Conflict and co-operation in White Cloud Mountain minnow schools

Schooling fish do not always behave co-operatively, and conflict is particularly evident when individuals compete for limited resources. In White Cloud Mountain minnows, Tanichrhys albonubes , aggression is associated with the defence of potential spawning sites. Agonistic encounters between males are more prevalent when available habitat is reduced and when the number of spawning sites (patches of weed) is restricted. Conversely, competition diminishes when the fish are in a potentially threatening situation, e.g. when they are exploring a new environment.     

Frequency‐dependent fitness in gynodioecious Lobelia siphilitica

Selection is frequency dependent when an individual's fitness depends on the frequency of its phenotype. Frequency‐dependent selection should be common in gynodioecious plants, where individuals are female or hermaphroditic; if the fitness of females is limited by the availability of pollen to fertilize their ovules, then they should have higher fitness when rare than when common. To test whether the fitness of females is frequency dependent, we manipulated the sex ratio in arrays of gynodioecious Lobelia siphilitica. To test whether fitness was frequency dependent because of variation in pollen availability, we compared open‐pollinated and supplemental hand‐pollinated plants. Open‐pollinated females produced more seeds when they were rare than when they were common, as expected if fitness is negatively frequency dependent. However, hand‐pollinated females also produced more seeds when they were rare, indicating that variation in pollen availability was not the cause of frequency‐dependent fitness. Instead, fitness was frequency dependent because both hand‐ and open‐pollinated females opened more flowers when they were rare than when they were common. This plasticity in the rate of anthesis could cause fitness to be frequency dependent even when reproduction is not pollen limited, and thus expand the conditions under which frequency‐dependent selection operates in gynodioecious species.     

Visual motion retards alternations between conflicting perceptual interpretations

When the visual system is faced with conflicting or ambiguous stimulus information, visual perception fluctuates over time. We found that perceptual alternations are slowed when inducing stimuli move within the visual field, constantly engaging fresh, unadapted neural tissue. During binocular rivalry, dominance durations were longer when rival figures moved compared to when they were stationary, yielding lower alternation rates. Rate was not reduced, however, when observers tracked the moving targets, keeping the images on approximately the same retinal area. Alternations were reliably triggered when rival targets passed through a local region of the visual field preadapted to one of the rival targets. During viewing of a kinetic globe whose direction of rotation was ambiguous, observers experienced fewer alternations in perceived direction when the globe moved around the visual field or when the globe's axis of rotation changed continuously. Evidently, local neural adaptation is a key ingredient in the instability of perception.     

The relative advantages of plasticity and fixity in different environments: when is it good for a plant to adjust?

Plant populations and species differ greatly in phenotypic plasticity. This could be because plasticity is advantageous under some conditions and disadvantageous or not advantageous under others. We distinguish adaptive from injurious and neutral plasticity and discuss when selection should favor adaptive plasticity over genetic differentiation or lack of phenotypic variation. It seems reasonable to hypothesize that selection is likely to favor plasticity when an environmental factor varies on the same spatial scale as the plant response unit, when the plant can respond to an environmental factor faster than the level of the factor changes, and when environmental variation is highly but not completely predictable. Phenotypic plasticity might also tend to be more advantageous when mean resource availability is high rather than low, when a response can occur late in development rather than early, and when a response is reversible rather than irreversible. There is substantial evidence for the hypothesis that predictability favors plasticity. However, available evidence does not support the hypothesis that high mean resource availability necessarily favors plasticity. Testing hypotheses about when it is good for a plant to adjust is central to understanding the diversity of plasticity in plants.     

The potential for and constraints on the evolution of compensatory ability in Asclepias syriaca

To investigate the potential for and constraints on the evolution of compensatory ability, we performed a greenhouse experiment using Asclepias syriaca in which foliar damage and soil nutrient concentration were manipulated. Under low nutrient conditions, significant genetic variation was detected for allocation patterns and for compensatory ability. Furthermore, resource allocation to storage was positively, genetically correlated both with compensatory ability and biomass when damaged, the last two being positively, genetically correlated with each other. Thus, in the low nutrient environment, compensatory ability via resource allocation to storage provided greater biomass when damaged. A negative genetic correlation between compensatory ability and plant biomass when undamaged suggests that this mechanism entailed an allocation cost, which would constrain the evolution of greater compensatory ability when nutrients are limited. Under high nutrient conditions, neither compensatory ability nor allocation patterns predicted biomass when damaged, even though genetic variation in compensatory ability existed. Instead, plant biomass when undamaged predicted biomass when damaged. The differences in outcomes between the two nutrient treatments highlight the importance of considering the possible range of environmental conditions that a genotype may experience. Furthermore, traits that conferred compensatory ability did not necessarily contribute to biomass when damaged, demonstrating that it is critical to examine both compensatory ability and biomass when damaged to determine whether selection by herbivores can favor the evolution of increased compensation. Received: 2 April 1999 / Accepted: 21 September 1999     

Reliability and the value of information

When animals lack the ability to discriminate between correct and incorrect information, they must choose to either respond to or ignore an information source. I define the reliability of information as the probability that information is correct and introduce reliability into the value of information to explore the level of risk information consumers should incur when using information. I find that when information consumers do not control the reliability of information, they should be more discriminating as the benefit of correct information declines, as the cost of misinformation increases and when acquisition costs are greater. However, when consumers pay for reliability, I find that consumers should be more discriminating as the benefit of correct information increases, the cost of misinformation increases, and when acquisition is cheaper. Application of this theory suggests that: (1) selection for individual recognition should be stronger when the cost of misinformation (deception) is high; (2) mimics can outnumber models when models are very noxious or alternative prey are abundant; and (3) memory about predators should be longer than memory about prey.     

Facultative parthenogenesis and sex-ratio evolution

Summary Phenotypic models of selection are used to determine the effect of facultative parthenogenesis on the production of males in a spatially variable environment when (i) sex determination is under strict genetic control, and (ii) when sex may be environmentally determined. The results show that when sex is under strict genetic control and there is some chance of maturing in isolation, selection favors a female-biased sex ratio. When sex can be environmentally induced by cues which indicate high density, selection favors a mixture of genetic and environmental control, such that half the individuals always become female and the other half become females when isolated and become males when not isolated.     

Effect of acclimation temperature on Km values towards GDP-mannose of the microsomal dolichol phosphate mannosyltransferase activity of trout liver (Salmo gairdnerii)

Apparent Km value for GDP-mannose remained stable when trout were raised and when enzyme activity was assayed at temps corresponding to the natural biological temp (between 5 and 15 degrees C). The Km value increased when the temperature of the assay was higher than 21 degrees C. Marked increase of the Km value was observed when trout were acclimated at 21 degrees C, whatever the temperature of the assay between 5 and 30 degrees C.     

Evolution of learning capacities and learning levels

Humans strongly depend on individual and social learning, both of which are highly effective and accurate. I study the effects of environmental change on the evolution of the effectiveness and accuracy of individual and social learning (individual and social learning levels) and the number of pieces of information learned individually and socially (individual and social learning capacities) by analyzing a mathematical model. I show that individual learning capacity decreases and social learning capacity increases when the environment becomes more stable; both decrease when the environment becomes milder. I also show that individual learning capacity increases when individual learning level increases or social learning level decreases, while social learning capacity increases when individual or social learning level increases. The evolution of high learning levels can be triggered when the environment becomes severe, but a high social learning level can evolve only when a high individual learning level can simultaneously evolve with it.     

Improved separation of bacteria with a dual flocculant hydrocol™ system

Summary Polyelectrolyte flocculants are inefficient at flocculating Z. mobilis and B. subtilis in a complex medium, when administered singly or when combined with an oppositely charged polymer. However, when polymer dosing is followed by bentonite addition, particularly when chitosan constitutes the soluble polymer, effective flocculation occurs. High broth clarities can be attributed to chitosan interaction with cells, extracellular polymer and bentonite.     

Estrogen-sensitive cell lines: uptake of labeled sex steroids and growth properties

Cells of a rat pituitary cell line injected into Wistar/Furth rats produce tumors when inoculated into intact females or estradiol-17β primed males. No tumors are produced when the same number of cells are injected into spayed females, intact males or castrated males. Experiments carried out in animals and in tissue culture indicate the selective uptake of these cells for physiological amounts of estradiol-17β when compared with testosterone and when compared with an undifferentiated cell line.     

Physiological adaptations to head-out aquatic exercises with different levels of body immersion

The purpose of this study was to compare the physiological adaptations to basic head-out aquatic exercises with different levels of body immersion. Sixteen young and clinically healthy subjects (9 women and 7 men) volunteered to participate in this study. Each subject performed 3 repetitions (on land, immersed to the hip, and immersed to the breast) of the aquatic exercise "rocking horse" for 6 minutes. The rating of perceived effort (RPE), the maximal heart rate achieved during the exercitation (HRmax), the percentage of the maximal theoretical heart rate estimated (%HRmax), the peak of oxygen uptake during the exercise (V(.-)O2peak), and the energy expenditure (EE) were evaluated. The RPE was significantly higher when exercising immersed to the hip than on land (p < 0.01) and immersed to the breast (p = 0.03). The HRmax and %HRmax were significantly lower when exercising with immersion to the breast than on land (p < 0.01) and with immersion to the hip (p < 0.01). The V(.-)O2peak was significantly different between all conditions. The lower mean value was verified when exercising immersed to the breast, followed by immersion to the hip and on land. The EE was significantly higher when performing aquatic exercises on land than when immersed to the hip (p = 0.02) and the breast (p < 0.01). So, physiological responses when exercising immersed to the hip are higher than when immersed to the breast. The physiological responses when exercising on land are higher than when exercising with immersion to the hip and to the breast.     

Multiple Roles of Tail Display by the Curly-Tailed Lizard Leiocephalus carinatus: Pursuit Deterrent and Deflective Roles of a Social Signal

The same display may be used in different contexts to convey different messages, or may have other, non-signaling functions. Several lines of evidence suggest that vertical tail curling, a previously documented social display in the lizard Leiocephalus carinatus , has antipredatory functions that may include pursuit deterrence and deflection of attacks from the body to the tail, which can be autotomized. An antipredatory role of tail curling is suggested by its more frequent occurrence when a predator is approaching than moving away, its greater frequency and intensity when a lizard is approached by a predator than when it moves spontaneously, and its greater frequency when the predator approaches directly rather than on a path bypassing the lizard. Evidence is presented contradicting use of tail curling for flash concealment or as an alarm signal to conspecifics. A pursuit-deterrent function of tail curling is suggested by its (1) more frequent use by lizards close to a refuge than those further from a refuge, (2) greater frequency during direct approaches by predators, and (3) much greater frequency when a predator is far enough away for pursuit to be deterred than when the predator is close enough to pose a high risk of capture. Lizards fled into a refuge without tail curling when the predator was very close, but often stopped outside a refuge while displaying the curled tail when the predator was farther away. Tail curling also may deflect attacks to the autotomizable tail, as suggested by its occurrence during spontaneous movements when no predator is approaching and by the high frequency of completely uncurled tails among individuals under bushes. The role of the tail in autotomy may facilitate evolution of pursuit-deterrent signals involving the tail.     

Structure-activity studies on prolactin-releasing peptide (PrRP). Analogues of PrRP-(19-31)-peptide.

An investigation of a series of single replacement analogues of PrRP-(19-31)-peptide has shown that good functional activity was retained when Phe31 was replaced with His(Bzl), Phe(4Cl), Nle, Trp, Cys(Bzl) or Glu(OBzl); when Val28 or Ile25 was replaced with Phg; when Gly24 was replaced with D-Ala, L-Ala, Pro or Sar; when Ser22 was replaced with Gly and when Ala21 was replaced with Thr or MeAla. The results confirm that the functionally important residues are located within the carboxyl terminal segment, -Ile-Arg-Pro-Val-Gly-Arg-Phe-NH2.