Costs and limits of phenotypic plasticity

The costs and limits of phenotypic plasticity are thought to have important ecological and evolutionary consequences, yet they are not as well understood as the benefits of plasticity. At least nine ideas exist regarding how plasticity may be costly or limited, but these have rarely been discussed together. The most commonly discussed cost is that of maintaining the sensory and regulatory machinery needed for plasticity, which may require energy and material expenses. A frequently considered limit to the benefit of plasticity is that the environmental cues guiding plastic development can be unreliable. Such costs and limits have recently been included in theoretical models and, perhaps more importantly, relevant empirical studies now have emerged. Despite the current interest in costs and limits of plasticity, several lines of reasoning suggest that they might be difficult to demonstrate.

Adaptation and Natural Selection revisited

In Adaptation and Natural Selection, George C. Williams linked the distinction between group and individual adaptation with the distinction between group and individual selection. Williams' Principle, as we will call it, says that adaptation at a level requires selection at that level. This is a necessary but not a sufficient condition; for example, group adaptation requires group selection, but the fact that group selection influences a trait's evolution does not suffice for the resulting trait frequency to be a group adaptation. What more is required? In this paper, we describe an answer to this question that has been developed in multilevel selection theory. We also discuss an alternative framework for defining units of adaptation that violates Williams' Principle.

Complex foraging polymorphism in bluegill sunfish

The bluegill sunfish (Lepomis macrochirus) is considered a generalist predator, adept at feeding in both the littoral and open-water habitats of North American freshwater lakes. We demonstrate adaptive intraspecific variation in morphology and foraging behaviors within single lakes. This variation appears to make individual fish specialized for feeding in either the littoral or open-water habitat. Discovery of a complex polymorphism in such a well-studied species suggests that adaptive variation may be more common than is currently perceived.

Social semantics: toward a genuine pluralism in the study of social behaviour

Pluralism is the coexistence of equivalent theoretical frameworks, either because they are historically entrenched or because they achieve separate insights by viewing the same process in different ways. A recent article by West et al. [Journal of Evolutionary Biology (2007) vol. 20, 415-432] attempts to classify the many equivalent frameworks that have been developed to study the evolution of social behaviour. This article addresses shortcomings in the West et al.'s article, especially with respect to multilevel selection, in a common effort to maximize the benefits of pluralism while minimizing the semantic costs.

Use of dry powder inhalers in COPD

INTRODUCTION

This was a study of 30 chronic obstructive pulmonary disease (COPD) patients to assess the ease of use and preference of four dry powder inhalers -- accuhaler, aerolizer, handihaler, turbohaler -- the accuhaler and turbohaler are multidose devices, whereas the aerolizer and handihaler are single dose devices.

METHOD

None of the subjects had previous experience of dry powder inhalers. The correct technique for each inhaler was divided into 12 steps including one critical step that if not performed would result in no drug delivery. Subjects were shown the correct technique for each inhaler in a random order and were assessed immediately and 1 h later. Each subject was asked to rank the four devices for preference and ease of use, as well as to assess how comfortable it felt to inhale through the device using a visual analogue scale.

RESULTS

The numbers of perfect scores were not significantly different between devices, but the number of fatal errors that would result in no drug delivery was significantly more common in single dose devices (p < 0.01). There were significant differences in the rankings of each device (Friedman test, p < 0.005) with the turbohaler being ranked first most often and the handihaler last. The turbohaler scored highest for comfort of inhalation and the accuhaler lowest, but differences were small.

CONCLUSIONS

In COPD patients starting on dry powder inhalers, multidose devices appear to be preferred, have fewer problems and are easier to use effectively.

Replica Ornstein-Zernike self-consistent theory for mixtures in random pores

We present a self-consistent integral equation theory for a binary liquid in equilibrium with a disordered medium, based on the formalism of the replica Ornstein-Zernike (ROZ) equations. Specifically, we derive direct formulas for the chemical potentials and the zero-separation theorems (the latter provide a connection between the chemical potentials and the fluid cavity distribution functions). Next we solve a modified-Verlet closure to ROZ equations, which has built-in parameters that can be adjusted to satisfy the zero-separation theorems. The degree of thermodynamic consistency of the theory is also kept under control. We model the binary fluid in random pores as a symmetrical binary mixture of nonadditive hard spheres in a disordered hard-sphere matrix and consider two different values of the nonadditivity parameter and of the quenched matrix packing fraction, at different mixture concentrations. We compare the theoretical structural properties as obtained through the present approach with Percus-Yevick and Martinov-Sarkisov integral equation theories, and assess both structural and thermodynamic properties by performing canonical standard and biased grand canonical Monte Carlo simulations. Our theory appears superior to the other integral equation schemes here examined and provides reliable estimates of the chemical potentials. This feature should be useful in studying the fluid phase behavior of model adsorbates in random pores in general.

Extra-articular migration of the patellar component following total knee arthroplasty

Complications related to patellar resurfacing are well recognized. We present an unusual case where the patellar button, after separating from the patella, extruded from the knee joint to lie within the extra-articular soft tissues.

One-step purification of recombinant proteins using a nanomolar-affinity streptavidin-binding peptide, the SBP-Tag

We describe the use of the SBP-tag, a new streptavidin-binding peptide, for both the one-step purification and the detection of recombinant proteins. The SBP-tag sequence is 38 amino acids long and binds to streptavidin with an equilibrium dissociation constant of 2.5 nM. We demonstrate that a single-step purification of SBP-tagged proteins from bacterial extract yields samples that are more pure than those purified using maltose-binding protein or the His-tag. The capacity of the immobilized streptavidin used to purify SBP-tagged proteins is about 0.5 mg per milliliter of matrix, which is high enough to isolate large quantities of proteins for further study. Also, the elution conditions from the streptavidin column are very mild and specific, consisting of the wash buffer plus biotin. This combination of high-affinity, high-yield, mild elution conditions, and simplicity of use makes the SBP-tag suitable for high-throughput protein expression/purification procedures, including robotically manipulated protocols with microtiter plates. Additionally, the SBP-tag can be used for detection since a wide variety of streptavidin-conjugated fluorescent and enzymatic systems are commercially available. We also present a new, rapid, method for the measurement of protein-protein, protein-peptide, or protein-small molecule equilibrium dissociation constants that require as little as 1 fmol of labeled protein. We call this method the spin-filter binding inhibition assay.

Random mutagenesis by PCR

Error-prone PCR (EP-PCR) is the method of choice for introducing random mutations into a defined segment of DNA that is too long to be chemically synthesized as a degenerate sequence. Using EP-PCR, the 5' and 3' boundaries of the mutated region may be defined by the choice of PCR primers. Accordingly, it is possible to mutagenize an entire gene or merely a segment of a gene. The average number of mutations per DNA fragment can be controlled as a function of the number of EP-PCR doublings performed. The EP-PCR technique described here is for a 400-bp sequence, and an Alternate Protocol is for a library. EP-PCR takes advantage of the inherently low fidelity of Taq DNA polymerase, which may be further decreased by the addition of Mn2+, increasing the Mg2+ concentration, and using unequal dNTP concentrations.

The use of mRNA display to select high-affinity protein-binding peptides

We report the use of "mRNA display," an in vitro selection technique, to identify peptide aptamers to a protein target. mRNA display allows for the preparation of polypeptide libraries with far greater complexity than is possible with phage display. Starting with a library of approximately 10(13) random peptides, 20 different aptamers to streptavidin were obtained, with dissociation constants as low as 5 nM. These aptamers function without the aid of disulfide bridges or engineered scaffolds, yet possess affinities comparable to those for monoclonal antibody-antigen complexes. The aptamers bind streptavidin with three to four orders of magnitude higher affinity than those isolated previously by phage display from lower complexity libraries of shorter random peptides. Like previously isolated peptides, they contain an HPQ consensus motif. This study shows that, given sufficient length and diversity, high-affinity aptamers can be obtained even from random nonconstrained peptide libraries. By engineering structural constraints into these ultrahigh complexity peptide libraries, it may be possible to produce binding agents with subnanomolar binding constants.

Religious groups as adaptive units

This essay provides a sketch of religion as a set of biologically and culturally evolved adaptations that enable human groups to function as adaptive units. Recent developments in evolutionary biology make such a group-level interpretation of religion more plausible than in the past. A brief survey of relevant concepts is followed by a relatively detailed interpretation of Calvinism as a religious system in which explicit behavioral prescriptions, beliefs about God and his relationship with people, and numerous social control mechanisms combined to change the city of Geneva from a collection of warring factions to a unified population.

Artificial selection of microbial ecosystems for 3-chloroaniline biodegradation

We present a method for selecting entire microbial ecosystems for bioremediation and other practical purposes. A population of ecosystems is established in the laboratory, each ecosystem is measured for a desired property (in our case, degradation of the environmental pollutant 3-chloroaniline), and the best ecosystems are used as 'parents' to inoculate a new generation of 'offspring' ecosystems. Over many generations of variation and selection, the ecosystems become increasingly well adapted to produce the desired property. The procedure is similar to standard artificial selection experiments except that whole ecosystems, rather than single individuals, are the units of selection. The procedure can also be understood in terms of complex system theory as a way of searching a vast combinatorial space (many thousands of microbial species and many thousands of genes within species) for combinations that are especially good at producing the desired property. Ecosystem-level selection can be performed without any specific knowledge of the species that comprise the ecosystems and can select ensembles of species that would be difficult to discover with more reductionistic methods. Once a 'designer ecosystem' has been created by ecosystem-level selection, reductionistic methods can be used to identify the component species and to discover how they interact to produce the desired effect.

Artificial ecosystem selection

Artificial selection has been practiced for centuries to shape the properties of individual organisms, providing Darwin with a powerful argument for his theory of natural selection. We show that the properties of whole ecosystems can also be shaped by artificial selection procedures. Ecosystems initiated in the laboratory vary phenotypically and a proportion of the variation is heritable, despite the fact that the ecosystems initially are composed of thousands of species and millions of individuals. Artificial ecosystem selection can be used for practical purposes, illustrates an important role for complex interactions in evolution, and challenges a widespread belief that selection is most effective at lower levels of the biological hierarchy.

In vitro selection of functional nucleic acids

In vitro selection allows rare functional RNA or DNA molecules to be isolated from pools of over 10(15) different sequences. This approach has been used to identify RNA and DNA ligands for numerous small molecules, and recent three-dimensional structure solutions have revealed the basis for ligand recognition in several cases. By selecting high-affinity and -specificity nucleic acid ligands for proteins, promising new therapeutic and diagnostic reagents have been identified. Selection experiments have also been carried out to identify ribozymes that catalyze a variety of chemical transformations, including RNA cleavage, ligation, and synthesis, as well as alkylation and acyl-transfer reactions and N-glycosidic and peptide bond formation. The existence of such RNA enzymes supports the notion that ribozymes could have directed a primitive metabolism before the evolution of protein synthesis. New in vitro protein selection techniques should allow for a direct comparison of the frequency of ligand binding and catalytic structures in pools of random sequence polynucleotides versus polypeptides.

Population viscosity and the evolution of altruism

The term population viscosity refers to limited dispersal, which increases the genetic relatedness of neighbors. This effect both supports the evolution of altruism by focusing the altruists' gifts on relatives of the altruist, and also limits the extent to which altruism may emerge by exposing clusters of altruists to stiffer local competition. Previous analyses have emphasized the way in which these two effects can cancel, limiting the viability of altruism. These papers were based on models in which total population density was held fixed. We present here a class of models in which population density is permitted to fluctuate, so that patches of altruists are supported at a higher density than patches of non-altruists. Under these conditions, population viscosity can support the selection of both weak and strong altruism.

Constructing high complexity synthetic libraries of long ORFs using in vitro selection

We present a method that can significantly increase the complexity of protein libraries used for in vitro or in vivo protein selection experiments. Protein libraries are often encoded by chemically synthesized DNA, in which part of the open reading frame is randomized. There are, however, major obstacles associated with the chemical synthesis of long open reading frames, especially those containing random segments. Insertions and deletions that occur during chemical synthesis cause frameshifts, and stop codons in the random region will cause premature termination. These problems can together greatly reduce the number of full-length synthetic genes in the library. We describe a strategy in which smaller segments of the synthetic open reading frame are selected in vitro using mRNA display for the absence of frameshifts and stop codons. These smaller segments are then ligated together to form combinatorial libraries of long uninterrupted open reading frames. This process can increase the number of full-length open reading frames in libraries by up to two orders of magnitude, resulting in protein libraries with complexities of greater than 10(13). We have used this methodology to generate three types of displayed protein library: a completely random sequence library, a library of concatemerized oligopeptide cassettes with a propensity for forming amphipathic alpha-helical or beta-strand structures, and a library based on one of the most common enzymatic scaffolds, the alpha/beta (TIM) barrel.

Kinetics of selenium incorporation into tissues of female mallard ducks

Selenium is essential for both mammalian and avian species, although its metabolism in birds has been less thoroughly studied. Little information has been available on the kinetics of selenium in birds, especially as it relates to the teratogenicity seen in waterfowl consuming excessive amounts. This study describes the pharmacokinetics of small amounts of 75Se as selenious acid injected into female mallard ducks. Labeled selenium was injected into a wing vein of restrained animals and tissues taken at five different time points up to 24 h post-injection. Selenium levels as percent of injected dose were determined in liver, kidney, heart, lung, adrenals, thyroid, spleen, pancreas, ovaries, intestine, muscle and plasma. Estimates of kinetic parameters (uptake and elimination rates, time of maximum concentration and maximum concentration) were obtained with a non-linear kinetics computer program (PCNONLIN, SCI Software, Lexington, KY). Results showed four basic patterns of distribution, uptake and elimination. Visceral tissues exhibited a triphasic pattern with a rapid rise, a decline followed by a distinctive increase in levels between the last two time points. Brain uptake was continuous over the 24 h. Plasma rose rapidly and then declined to a constant level. The ovaries as a tissue of interest relating to the teratogenic effects of selenium showed the greatest relative increase at 24 h, suggesting kinetic mechanisms consistent with a pathway that might lead to accumulation of toxic levels and teratogenic effects during embryo development.

Direct regulation of rhodopsin 1 by Pax-6/eyeless in Drosophila: evidence for a conserved function in photoreceptors

Pax-6 is a transcription factor containing both a homeodomain (HD) and a Paired domain (PD). It functions as an essential regulator of eye development in both Drosophila and vertebrates, suggesting an evolutionarily conserved origin for different types of metazoan eyes. Classical morphological and phylogenetic studies, however, have concluded that metazoan eyes have evolved many times independently. These apparently contradictory findings may be reconciled if the evolutionarily ancient role of Pax-6 was to regulate structural genes (e.g., rhodopsin) in primitive photoreceptors, and only later did it expand its function to regulate the morphogenesis of divergent and complex eye structures. In support of this, we present evidence that eyeless (ey), which encodes the Drosophila homolog of Pax-6, directly regulates rhodopsin 1 (rh1) expression in the photoreceptor cells. We detect ey expression in both larval and adult terminally differentiated photoreceptor cells. We show that the HD of Ey binds to a palindromic HD binding site P3/RCS1 in the rh1 promoter, which is essential for rh1 expression. We further demonstrate that, in vivo, P3/RCS1 can be replaced by binding sites specific for the PD of Ey. P3/RCS1 is conserved in the promoters of all Drosophila rhodopsin genes as well as in many opsin genes in vertebrates. Mutimerized P3 sites in front of a basal promoter are able to drive the expression of a reporter gene in all photoreceptors. These results suggest that Pax-6/Ey directly regulates rhodopsin 1 gene expression by binding to the conserved P3/RCS1 element in the promoter.

CD18 antibody treatment limits early myocardial reperfusion injury after initial leukocyte deposition

Following myocardial ischemia, initial reperfusion with whole blood impairs the recovery of ventricular function. The exact mechanisms underlying early myocardial reperfusion injury are not clear, but leukocytes play an important role. In this study, we tested if treating the initial blood reperfusate with a monoclonal antibody (CL26) against the leukocyte adhesion protein (CD18 would reduce the leukocyte contribution to early reperfusion injury. We reasoned that blocking CD18 would reduce the initial retention of leukocytes in the heart and thereby limit the inflammatory response. Rat hearts were isolated and perfused at constant flow with a red cell-rich solution (K2RBC). The perfusate was not recirculated. Baseline measures were made of coronary flow, perfusion pressure, and ventricular pump function. No-flow, normothermic ischemia was induced for 30 min, followed immediately by reperfusion, at the preischemic flowrate, with diluted whole blood (DWB, treated with either vehicle or CL26). Reperfusion was continued with K2RBC for 40 min more, during which postischemic measures were made. We found that the cardiac retention of leukocytes was not significantly different for the two groups, nor were the recoveries of ventricular function. Later in reperfusion (R35), the coronary blood flowrate and the coronary vascular resistances were not different; however, the recoveries of ventricular pump function were significantly different (+dP/dt @ R35 (%Pre-I): Vehicle: 27 +/- 9% (n = 8); CL26: 51 +/- 6% (n = 7); P < 0.05). Also, at R35, the voltage required to capture and pace the vehicle-treated hearts was significantly greater than the voltage required to pace the CL26 hearts (P < 0.05). Because the coronary flowrate and leukocyte retention were similar for both groups, the improved recovery observed in the CL26-treated group was not due to either improved flow or to reduced leukocyte retention. Rather, the findings suggest that the beneficial effect of antibody treatment was to attenuate step(s) in the acute inflammatory response that occurred after the initial deposition of leukocytes in the heart.

Conservation and diversification in homeodomain-DNA interactions: a comparative genetic analysis

Nearly all metazoan homeodomains (HDs) possess DNA binding targets that are related by the presence of a TAAT sequence. We use an in vitro genetic DNA binding site selection assay to refine our understanding of the amino acid determinants for the recognition of the TAAT site. Superimposed upon the conserved ability of metazoan HDs to recognize a TAAT core is a difference in their preference for the bases that lie immediately 3' to it. Amino acid position 50 of the HD has been shown to discriminate among these base pairs, and structural studies have suggested that water-mediated hydrogen bonds and van der Waals contacts underlie for this ability. Here, we show that each of six amino acids tested at position 50 can confer a distinct DNA binding specificity.

Pentoxifylline reduces leukocyte retention in the coronary microcirculation early in reperfusion following ischemia

Using direct visualization techniques, we recently confirmed earlier histologic studies that leukocytes accumulate primarily in the coronary capillaries of ischemic hearts during early reperfusion. The purpose of this study was to determine if pentoxifylline (PTX) would reduce leukocyte trapping in postischemic hearts. Isolated rat hearts were subjected to 30 min of 37 degrees C, no-flow ischemia. Hearts were initially reperfused with diluted whole blood containing fluorescent leukocytes. At 5, (R5), 20, and 35 min of reperfusion, the deposition of leukocytes in the coronary capillaries and venules was observed directly using intravital fluorescence microscopy. Three groups were studied: a non-ischemic control group (group I) and postischemic groups reperfused with diluted whole blood treated with vehicle group II or PTX (5 mM; group III). Postischemic reperfusion with unactivated blood caused a significant trapping of leukocytes in coronary capillaries throughout reperfusion (R5, group I = 2.0 +/- 0.3 vs. group II = 5.7 +/- 0.6 leukocytes/capillary field, p < 0.05). The addition of PTX reduced capillary leukocyte trapping below control values throughout reperfusion (R5, group III = 1.6 +/- 0.2 leukocytes/capillary field, p < 0.05). At R5, there was no statistically significant difference in leukocyte accumulation in venules for all groups (group I = 1.5 +/- 0.6, group II = 3.2 +/- 0.4, group III = 3.3 +/- 0.4 leukocytes/100 microns venule). During the reperfusion period, leukocyte persistence in the capillaries of postischemic hearts (36%) was greater than in the venules (13%). These data indicate that early in reperfusion after myocardial ischemia, leukocyte trapping occurs primarily in the coronary capillaries. PTX reduced early leukocyte trapping in the capillaries. The results also demonstrate that during reperfusion, the mechanisms affecting capillary retention are more persistent than those in the venule. These findings suggest that attempts to attenuate the damaging potential of early leukostasis in capillaries consider the biophysical properties of the leukocyte.

Machiavellianism: a synthesis of the evolutionary and psychological literatures

Manipulative strategies of social conduct (Machiavellianism) have been studied by both psychologists and evolutionary biologists. The authors use the psychological literature as a database to test evolutionary hypotheses about the adaptive advantages of manipulative social behavior. Machiavellianism does not correlate with general intelligence and does not consistently lead to real-world success. It is best regarded as 1 of several social strategies, broadly similar to the "defect" strategy of evolutionary game theory, which is successful in some situations but not others. In general, human evolutionary psychology and evolutionary game theory provide useful frameworks for thinking about behavioral strategies, such as Machiavellianism, and identify a large number of specific hypotheses that have not yet been tested by personality and social psychologists.

Early in reperfusion following myocardial ischemia, leukocyte activation is necessary for venular adhesion but not capillary retention

OBJECTIVE

The pathobiology of leukocyte sequestration in the coronary microcirculation following ischemia is unclear. We examined the location(s) and persistence of leukocyte sequestration of unactivated and preactivated blood in the coronary microcirculation early during reperfusion following ischemia.

METHODS

Isolated rat hearts were subjected to 30 min of 37 degrees C, no-flow ischemia. Hearts were initially reperfused with diluted whole blood containing fluorescent leukocytes (DWB*). At 5, 20, and 35 min of reperfusion (R), the deposition of leukocytes in the coronary capillaries and venules was observed directly using intravital fluorescence microscopy. Four groups were studied: a nonischemic control group (Gr I), and postischemic groups reperfused with DWB* treated with vehicle (Gr II) or preactivated with 10(-8) M N-formylmethionyl-leucyl-phenylalanine (fMLP) (Gr III) or 10(-6) M fMLP (Gr IV).

RESULTS

At R5, postischemic reperfusion with unactivated blood caused a significant trapping of leukocytes in coronary capillaries (Gr I = 2.2 +/- 0.4 versus Gr II = 5.6 +/- 0.6 leukocytes per capillary field, P < 0.05). Hearts in Gr IV exhibited significantly greater leukocyte retention in capillaries compared to all other groups at R5 (R5, Gr IV = 8.8 leukocytes per capillary field, P < 0.05) and at R35. At R5, although more leukocytes were observed adhered to the venules in Gr II compared to Gr I, the difference was not statistically significant (Gr I = 1.7 +/- 0.7 versus Gr II = 3.4 +/- 0.5 leukocytes per 100 microns venule, P = 0.23). DWB* preactivated with the lower concentration of fMLP (10(-8) M) resulted in a significant increase in venular leukocyte adhesion at R5 compared to Gr I and Gr II (Gr III 6.1 +/- 0.5, P < 0.05). After 35 min of reperfusion, a greater percentage of leukocytes remained in the capillaries than in the venules.

CONCLUSIONS

These direct observations suggest that early in reperfusion after ischemia, both leukocyte and endothelial activation are necessary for venular adhesion, but that ischemia-induced coronary microvascular alterations are sufficient to promote leukocyte retention in coronary capillaries. These results also indicate that during 35 min of reperfusion, the degree of leukocyte washout is greater in the venules than in the capillaries. These results suggest that the mechanisms contributing to leukocyte retention early in reperfusion following myocardial ischemia are, indeed, different in the capillaries and venules and that the mechanisms affecting retention in capillaries are more persistent than those in the venules.

Left ventricular function after extended hypothermic preservation of the heart is dependent on functional coronary capillarity

BACKGROUND

A growing body of knowledge has led to the hypothesis that injury to the microcirculation during hypothermic myocardial preservation may result in decreased contractility of hearts upon reperfusion.

METHODS AND RESULTS

To test this hypothesis, we examined the relationship between no-reflow and left ventricular function after hypothermic cardiac preservation after reperfusion with solutions containing dilute whole blood (DWB) or washed red blood cells (K2RBC). Rat hearts were arrested with high-potassium cardioplegia, then flushed and stored for 6 hours in low-potassium cardioplegia at 4 degrees C. Hearts were reperfused at a constant flow rate (4 mL/min) with K2RBC for 60 minutes (group 1, n = 5) or DWB for 7 minutes followed by 53 minutes of K2RBC (group 2, n = 5). Left ventricular developed pressure (LVDP) was measured with an intraventricular balloon. Immediately after functional assessment, hearts were perfused with an india ink solution to mark flow, then glutaraldehyde. Morphometric techniques were used to determine the degree of capillary compression [delta d(c)], perfused capillary number per fiber area [QA(0)P], and perfused capillary surface area per fiber volume [Sv(c,f)P]. Capillaries were moderately compressed in both groups after reperfusion (group 1, 19 +/- 1%; group 2, 20 +/- 1%). QA(0)P and Sv(c,f)P were highly correlated with delta d(c) in hearts reperfused with K2RBC (r = .92 and r = .92; P < .01). Although statistically significant, the correlation was not as strong in DWB-reperfused hearts (r = .66 and r = .67; P < .05). LVDP was correlated to QA(0)P and Sv(c,f)P (r = .86 and r = .87, respectively) for groups 1 and 2.

CONCLUSIONS

The weaker correlation between capillary perfusion and capillary compression in DWB-reperfused hearts suggests that factors other than compression contribute to no-reflow after hypothermic preservation. Regardless of the composition of the reperfusate, recovery of left ventricular function after hypothermic ischemia is directly related to coronary capillary perfusion upon reperfusion.

High resolution crystal structure of a paired (Pax) class cooperative homeodomain dimer on DNA

The crystal structure of the paired homeodomain bound to DNA as a cooperative dimer has been determined to 2.0 A resolution. Direct contacts between each homeodomain and the DNA are similar to those described previously. In addition, an extensive network of water molecules mediates contacts between the recognition helix and the DNA major groove. Several symmetrical contacts between the two homeodomains underlie the cooperative interaction, and deformations in the DNA structure are necessary for the establishment of these contacts. Comparison with structures of homeodomains bound monomerically to DNA suggests that the binding of a single paired homeodomain can introduce these DNA distortions, thus preparing a template for the cooperative interaction with a second homeodomain. This study shows how the paired (Pax) class homeodomains have achieved cooperativity in DNA binding without the assistance of other domains, thereby enabling the recognition of target sequences that are long enough to ensure specificity.

The initial response of blood leukocytes to incubation with perfluorocarbon blood substitute emulsions

Due to their enhanced oxygen carrying characteristics, perfluorocarbon emulsions are valuable adjuncts to coronary revascularization procedures. However, the effects of perfluorocarbon emulsions on white blood cell function are unclear. The purpose of this study was to determine the effects of three perfluorocarbon emulsions on the adhesion characteristics of leukocytes. Heparinized blood from donor rats was mixed with either Phosphate Buffered Saline (PBS), PFB-1, PFB-2 (both non-complement activating perflubron emulsions, Alliance Pharmaceutical Corp.) or Fluosol (20% w/v PFC, Alpha Therapeutic) in a ratio of one part emulsion to six parts blood. The blood-emulsion mixtures were incubated for ten minutes at 37 degrees C, then passed down nylon wool leukocyte adhesion columns. Blood samples were counted for: Leukocytes, Granulocytes and Lymphocytes. % Cell Adherence was calculated as: (1-[WBC-out]/[WBC-in]). We found that, compared to PBS control, the granulocyte adherence to the nylon fiber was significantly increased for both Fluosol-20 and PFB-1 (P < 0.05). In contrast, PFB-2 (designed for reduced cell surface activity) caused no significant change in leukocyte adhesion. In fact, a modest decrease in granulocyte adhesion was observed with PFB-2. These findings suggest a direct effect of some, but not all, PFC emulsions on blood leukocyte function.

Analysis of explanted silicone implants: a report of 300 patients

Breast implants from 300 consecutive patients during the 35-month period from February 1, 1991 to January 1, 1994 were examined. Of these, 214 (71.3%) patients had disruption (frank rupture or severe silicone bleed or both) of one or both implants. Of the 592 implants removed, 376 (63.5%) had disruption. We found virtually no difference in disruption rates between those patients relating symptoms to their implants and those who did not (71.8% vs. 70.9%). However, disruption was directly related to time since implantation. We observed 103 of 142 patients relating various symptoms to their silicone implants. About half (52) reported improvement after implant removal. We found no direct correlation between disruption and repeated closed capsulotomy. Of 505 implants, 69 of 92 implants having had one or more closed capsulotomies were disrupted (75%). However, 245 of 413 implants never having had a closed capsulotomy also showed disruption (59.3%). We found mammography to be of very limited value in assessing disruption. Our study showed a low 16.2% sensitivity rate. The same was true with magnetic resonance imaging interpretation, especially in the diagnosis of severe silicone bleed. Although our series was quite small, magnetic resonance imaging interpretation was found to be an unreliable tool in our study. A Kaplan-Meier survival curve for mammary implants based on this study has proven very helpful and effective in communicating with patients and has served as a guideline in predicting the presence or absence of implant disruption.(ABSTRACT TRUNCATED AT 250 WORDS)

Homeodomain proteins. Cooperating to be different

The product of the Drosophila extradenticle gene interacts cooperatively with homeodomain proteins encoded by homeotic selector genes, and may account in part for their distinct regulatory properties.

Binding of plasma selenoprotein P to cell membranes

Competitive binding assays were performed to determine the amount of binding of 75Se-labeled plasma selenoprotein P (PSP) to membranes from different rat tissues at physiologic pH. 75Se PSP for use as a ligand in the binding assays was labeled in vivo by injecting rats with 75Se selenious acid. PSP was obtained from plasma by salt precipitation and affinity and ion-exchange chromatography. Membranes for receptor assays were prepared from liver, kidney, testes, and brain of rats fed diets with either 0.01, 0.1, or 2 ppm selenium. At pH 7.4 PSP was bound differentially to tissues in the following order: brain > kidney > testes > liver. Specific binding of PSP to tissue membranes from rats fed the different levels of selenium increased with increasing amounts of dietary selenium. Saturation assays indicated apparent saturation of membrane receptors by the 75Se-labeled PSP. Another significant new finding was a 134-kDa complex of PSP and membrane receptor, identified by gel-filtration chromatography of cross-linked samples from binding assays. This provides evidence for a membrane receptor for PSP in rat tissues.

Single- and multiple-dose pharmacokinetics of clarithromycin, a new macrolide antimicrobial

The pharmacokinetics of clarithromycin and its active 14(R)-hydroxy metabolite were evaluated after single and multiple oral doses of 250 and 500 mg of clarithromycin. Multiple-dose regimens used 12-hour dosing intervals for 7 doses. Plasma and urine concentrations were measured using high-performance liquid chromatography. Appearance of clarithromycin and its metabolite in plasma were rapid, as reflected by mean times to maximum plasma concentration ranging from 1.8 to 2.6 and 1.8 to 2.9 hours, respectively. The rises in clarithromycin peak plasma concentration (Cmax) and area under the plasma concentration versus time curve (AUC) were disproportionate to increase in dose, suggesting nonlinearity in parent compound pharmacokinetics. Clarithromycin terminal disposition half-life (t1/2) also exhibited dose dependency, ranging from harmonic means of 2.7 to 4.8 hours. In contrast, based on Cmax AUC, and predicted/observed accumulation ratios, nonlinearity in metabolite pharmacokinetics was not observed. Plasma accumulation of metabolite occurred to a much lesser degree than that of the parent compound despite a substantially longer t1/2 for the metabolite (metabolite accumulation ratios based on AUC dose 7/AUC dose 1:250-mg regimen = 1.03 +/- 0.33, 500-mg regimen = 0.81 +/- 0.29, parent accumulation ratios: 250-mg regimen = 1.64 +/- 0.47, 500-mg regimen = 1.65 +/- 0.69). This would suggest that formation of this metabolite is capacity-limited and that this may in part account for the nonlinearity observed in clarithromycin pharmacokinetics. Urinary excretion constituted a relatively important route of elimination of clarithromycin, with renal clearance accounting for 17 to 31% of apparent total body clearance.

Clarithromycin pharmacokinetics in healthy young and elderly volunteers

The pharmacokinetics of clarithromycin and its active 14(R)-hydroxy metabolite were assessed in 12 healthy young and 12 healthy elderly volunteers after oral administration of a multiple dose regimen of oral clarithromycin (500 mg every 12 hours for 5 doses). Plasma and urine clarithromycin and 14(R)-hydroxyclarithromycin concentrations were determined using high-performance liquid chromatography. The elderly subjects exhibited significantly elevated clarithromycin peak (Cmax) and trough (Cmin) plasma concentrations and area under the plasma concentration-time curve (AUC) compared with young subjects. In addition, the elderly group exhibited a significantly reduced apparent total body clearance (300 +/- 97 versus 476 +/- 112 mL/min, respectively) and renal clearance (CLR) (84 +/- 31 versus 168 +/- 35 mL/min, respectively). Similar results were noted for the 14(R)-hydroxy metabolite, with significantly elevated Cmax, Cmin, and AUC and reduced CLR in the elderly compared with the young group. Because the differences in parent and metabolite pharmacokinetic parameters were small and the increase in circulating drug concentrations was well tolerated (no increase in incidence or severity of adverse events), adjustments in clarithromycin dosing regimens may not be necessary solely on the basis of age.

Pharmacokinetics of clarithromycin, a new macrolide, after single ascending oral doses

The pharmacokinetics and safety of single ascending doses of clarithromycin (6-0-methylerythromycin A) were assessed in a placebo-controlled, double-blind, randomized trial with 39 healthy male volunteers. Subjects were randomized to receive single doses of either placebo or 100, 200, 400, 600, 800, or 1,200 mg of clarithromycin. Blood and urine collections were performed over the 24 h following administration of the test preparation. Biological specimens were analyzed for clarithromycin and 14(R)-hydroxyclarithromycin content by a high-performance liquid chromatographic technique. The pharmacokinetics of clarithromycin appeared to be dose dependent, with terminal disposition half-life ranging from 2.3 to 6.0 h and mean +/- standard deviation area under the concentration-versus-time curve from time 0 to infinity for plasma ranging from 1.67 +/- 0.48 to 3.72 +/- 1.26 mg/liter.h per 100-mg dose over the 100- to 1,200-mg dose range. Similar dose dependency was noted in the pharmacokinetics of the 14(R)-hydroxy metabolite. Mean urinary excretion of clarithromycin and its 14(R)-hydroxy metabolite ranged from 11.5 to 17.5% and 5.3 to 8.8% of the administered dose, respectively. Urinary excretion data and plasma metabolite/parent compound concentration ratio data suggested that capacity-limited formation of the active metabolite may account, at least in part, for the nonlinear pharmacokinetics of clarithromycin. No substantive dose-related trend was observed for the renal clearance of either compound. There were no clinically significant drug-related alterations in laboratory and nonlaboratory safety parameters. In addition, there was no significant difference between placebo and clarithromycin recipients in the incidence or severity of adverse events. Clarithromycin appears to be safe and well tolerated.

Drug-food interaction potential of clarithromycin, a new macrolide antimicrobial

To evaluate the effect of food on bioavailability, clarithromycin and 14-hydroxyclarithromycin (active metabolite) pharmacokinetics were assessed in 26 healthy adult volunteers after ingestion of a single oral 500-mg dose of clarithromycin in a fasting state (2 hours before breakfast after an overnight fast) and a nonfasting state (0.5 hours after the start of breakfast). Clarithromycin and 14-hydroxy metabolite plasma concentrations were measured using a high-performance liquid chromatographic technique. Food intake immediately before dosing increased the extent of absorption from the 500-mg tablet formulation by approximately 25%. The mean increase in metabolite area under the plasma concentration-time curve was approximately 9%. These results suggest that clarithromycin can be taken without regard to timing in relation to meals.

Identification of preventable trauma deaths: confounded inquiries?

The published evaluation of methods for identifying preventable trauma deaths contains many unstudied confounding factors. To investigate the reliability of methods for identifying such preventable deaths, we compared three consensus systems using separate five-member general review panels assessing 20 non-central nervous system fatalities: panel A, independent judgments; panel B, discussion of all cases preceding individual judgments; and panel C, independent judgments followed by discussion and equivocal case reassignment. The Kappa concordance index was low for all methods (method A, 0.20; methods B and C, 0.40). Of the 11 deaths judged preventable by at least one panel, only one death was judged preventable by all three panels. Consensus agreement (four of five assessors) was 20% for panel A, 45% for panel B, and 10% for panel C (difference between panels B and C, p less than 0.03). In panel C, discussion affected the rate of equivocal case designation from 30% to 5%. Thus different consensus methods yielded different results. We conclude that individual case review can be severely flawed and therefore should not be used to measure institutional quality of patient care. We recommend that assessment of institutional performance should be based on objective evaluation methods, which require the study of patient population outcomes, rather than on subjective methods in which individual cases are reviewed.

Ubiquinone protects against loss of tocopherol in rat liver microsomes and mitochondrial membranes

Liver microsomes and submitochondrial particles (SMP) were isolated from rats fed on a vitamin E or coenzyme Q10/vitamin E enriched diet in order to clarify the antioxidant interactions between coenzyme Q10 and vitamin E. Electron spin resonance spectrometry shows that the decay of vitamin E radicals (tocopheroxy radicals) generated by the arachidonic acid/lipoxygenase oxidation system proceeded at a higher rate in vitamin E enriched microsomes and SMP than in those enriched with coenzyme Q10/vitamin E. Vitamin E levels determined by high performance liquid chromatography revealed that when subjected to enzymatic oxidation, membranes enriched with vitamin E alone were depleted of vitamin E earlier than those enriched with both coenzyme Q10 and vitamin E. These results show that coenzyme Q10 conserves vitamin E, which would help prolong membrane resistance against oxidative damage.

Mitochondrial electron transport-linked tocopheroxyl radical reduction

alpha-Tocopherol (vitamin E) is a lipophilic chain-breaking antioxidant which inhibits lipid peroxidation in isolated mitochondrial membranes and protects membranes from oxidative damage. The primary oxidation product of vitamin E is the tocopheroxyl radical. Reduction of the tocopheroxyl radical can occur by reactions with water-soluble anti-oxidants such as ascorbate or glutathione, resulting in the recycling of vitamin E. Physiological concentrations of vitamin E are too low to allow detection of tocopheroxyl radical by ESR. After dietary supplementation with vitamin E, a 10-20-fold increase in the rat liver mitochondrial membrane content of vitamin E was achieved and this allowed for direct detection of the tocopheroxyl radical by ESR, after treatment with an oxidizing system composed of lipoxygenase and arachidonic acid. By using submitochondrial particle membranes, it was shown that NADH, succinate, and reduced cytochrome c-linked oxidation reduce the tocopheroxyl radical, preventing both accumulation of the radical and vitamin E consumption. As the electron transport chain can reduce tocopheroxyl radical it may have an important physiological role in recycling vitamin E.

Acute effects of near ultraviolet and visible light on the cutaneous antioxidant defense system

Reactive oxygen species are considered to play an important role in cutaneous pathology. Enzymic and non-enzymic antioxidants can prevent oxidative damage but may be overcome by strong pro-oxidative stimuli. The acute effect of a single exposure to near ultraviolet (UVA)/visible radiation (greater than 320 nm) on various skin antioxidants was examined in hairless mice immediately after irradiation. Impairment of cutaneous catalase and glutathione reductase activity was observed. Superoxide dismutase and glutathione peroxidase were not significantly influenced. Inhibition of catalase may render skin more susceptible to the damaging effects of hydrogen peroxide and its reaction products such as the hydroxyl radical. Partially diminished glutathione reductase activity is not accompanied by a change in reduced/oxidized glutathione level immediately after irradiation. There was a tendential (not statistically significant) decrease in cutaneous tocopherol, ubiquinol + ubiquinone 9 and ascorbic acid levels, either indicating direct photodestruction or consumption by reaction products of photooxidative stress. This partial impairment of the cutaneous antioxidant defense system by near ultraviolet/visible light, showing that the most susceptible component in skin is catalase, suggests possible pharmacological interventions.

Repletion of folate-depleted rats with an amino acid-based diet supplemented with folic acid

Folate depletion and repletion protocols are not well standardized. Weanling rats were moderately depleted of folate in 28 d with a folate-free purified diet based on 17% amino acids as the nitrogen source. They were then folate repleted for 23 d with the amino acid diet supplemented with either 125, 250, 500, 1000 or 2000 micrograms folic acid/kg. Hematology, growth and tissue folate levels were measured in subsets of the rats when they were 24 (baseline), 52 (depleted) and 75 d old (repleted). The same measurements were made in control rats that had been fed 2 mg folic acid/kg of the amino acid diet for the same period of time. Our findings show that with repletion, growth of previously depleted rats is in direct proportion with the level of supplementation up to 1000 micrograms folic acid/kg diet. Serum folate levels of repleted rats also increased in proportion to supplementation between 500 to 2000 micrograms/kg diet, and liver folate levels increased proportionally with the level of supplement within the range of 125 to 2000 micrograms/kg diet. The 2000 micrograms/kg supplement was sufficient to restore liver folate levels equivalent to that of controls, but body weight and serum folate levels failed to catch up with that of controls in the 23-d repletion period. There was a nonlinear relationship between serum and liver folate levels: serum folate remained constant at about 6 micrograms/l as liver folate increased to about 7 micrograms/g, then serum folate diverged by increasing to 120 micrograms/l with only minor increases in liver folate.(ABSTRACT TRUNCATED AT 250 WORDS)

Impairment of enzymic and nonenzymic antioxidants in skin by UVB irradiation

Antioxidants may play a significant role in ameliorating or preventing photobiologic damage in skin that could lead to cutaneous disorders such as cancer and premature aging. The objective of this study was to assess the acute cutaneous enzymic and nonenzymic antioxidant response to a single exposure of large fluence (300 mJ/cm2) ultraviolet radiation (greater than 280 nm) in hairless mice. This treatment caused an immediate and statistically significant inhibition of glutathione reductase and catalase activity. Glutathione peroxidase and superoxide dismutase were not affected. Glutathione levels decreased and, conversely glutathione disulfide concentrations increased. A slight depletion of the total glutathione was observed, while the content of total ascorbic acid did not change. The lipophilic antioxidants alpha-tocopherol, ubiquinol 9 and ubiquinone 9 also decreased significantly, and the concentration of malondialdehyde remained constant. The free radical scavenging activity of epidermis, as assessed by reduction of the stable, cationic nitroxide radical [2,2,6,6-tetramethyl-1-piperidinoxy-4-(2',4',6'-trimethyl) methylpyridinium perchlorate] was considerably inhibited. The study indicates that immediately after exposure to a large fluence of ultraviolet radiation the enzymic and nonenzymic antioxidant capacity of skin decreases significantly.