Why Is the Substomatal Chamber as Large as It Is?

The rate of CO(2) uptake by the mesophyll is examined as a function of the size of the substomatal chamber. Using the techniques of classical electric circuit analysis and a model in which the uptake is linear in the ambient CO(2) concentration, it is shown that the optimal chamber radius is several times larger than is the pore radius. This is somewhat larger than necessary for the reduction of transpirational water loss, and it offers an explanation for the otherwise inexplicably large size of the chamber.     

Sex: Is Giardia Doing It in the Dark?

The protist Giardia has long been considered strictly asexual. Now genes specific for meiotic recombination have been found in the Giardia genome, but their consequences for genetics, epidemiology and evolution remain unknown.     

Data Acquisition for Conservation Assessments: Is the Effort Worth It?

When identifying conservation priorities, the accuracy of conservation assessments is constrained by the quality of data available. Despite previous efforts exploring how to deal with imperfect datasets, little is known about how data uncertainty translates into errors in conservation planning outcomes. Here, we evaluate the magnitude of commission and omission error, effectiveness and efficiency of conservation planning outcomes derived from three datasets with increasing data quality. We demonstrate that investing in data acquisition might not always be the best strategy as the magnitude of errors introduced by new sites/species can exceed the benefits gained. There was a trade-off between effectiveness and efficiency due to poorly sampled rare species. Given that data acquisition is limited by the high cost and time required, we recommend focusing on improving the quality of data for those species with the highest level of uncertainty (rare species) when acquiring new data.     

Clathrin‐Dependent or Not: Is It Still the Question?

Whether the endocytic uptake of a given molecule is mediated through clathrin-coated pits or not is a classical criterion used to characterize its endocytic pathway(s). Hence, clathrin-dependent endocytosis has been associated with highly selective and efficient uptake, whereas clathrin-independent endocytosis appeared to be confined to bulk uptake of fluid-phase markers. This scholastic view has recently been challenged using newly developed molecular tools that allow for the first time a functional and mechanistic analysis of these less well-characterized clathrin-independent pathways, including caveolar uptake and macropinocytosis. Furthermore, several studies point to a critical role of lateral lipid asymmetry – lipid rafts/microdomains – in membrane sorting. We will discuss the potential role of these structures in endocytosis and the possibility that differential sorting at the plasma membrane predisposes the ensuing intracellular fate of a given molecule as well as its physiological function.     

Is It Worth the Risk? Food Deprivation Effects on Tadpole Anti-Predatory Responses

Predation risk affects foraging behavior and, particularly, the amount of time devoted to the search for food. When exposed to predation risk, food deprived animals should be risk prone and relax behavioral defenses to a wider extent than well fed individuals. To test for this prediction, we used a 2?×?2 factorial design experiment, manipulating both the energetic state (fed vs. fasted) and exposure to an attack-released cue (injured vs. uninjured conspecifics) of common water frog tadpoles (Pelophylax kl. esculentus). Contrary to expectations, food deprivation significantly lowered the activity level of predator-exposed tadpoles. As in this experiment no food resource was added to test containers, energy conserving behavior might have both delayed starvation and lowered the probability of encountering the potential predator. To test for the effect of food availability on behavioral responses, we performed a second experiment, using the same protocol and procedures, except for adding food to all test containers. All tadpoles showed similar levels of activity, while fed tadpoles exposed to alarm cues tended to swim farther from the cage containing the stimulus than in the first experiment. As many anuran larvae can feed on dead conspecifics, prey-borne cues may have been interpreted as the potential presence of both a food source and a predator, fed tadpoles possibly being more confident than fasted tadpoles in their ability to escape predation in case an actual attack occurs.     

Genomic Heritability: What Is It?

Whole-genome regression methods are being increasingly used for the analysis and prediction of complex traits and diseases. In human genetics, these methods are commonly used for inferences about genetic parameters, such as the amount of genetic variance among individuals or the proportion of phenotypic variance that can be explained by regression on molecular markers. This is so even though some of the assumptions commonly adopted for data analysis are at odds with important quantitative genetic concepts. In this article we develop theory that leads to a precise definition of parameters arising in high dimensional genomic regressions; we focus on the so-called genomic heritability: the proportion of variance of a trait that can be explained (in the population) by a linear regression on a set of markers. We propose a definition of this parameter that is framed within the classical quantitative genetics theory and show that the genomic heritability and the trait heritability parameters are equal only when all causal variants are typed. Further, we discuss how the genomic variance and genomic heritability, defined as quantitative genetic parameters, relate to parameters of statistical models commonly used for inferences, and indicate potential inferential problems that are assessed further using simulations. When a large proportion of the markers used in the analysis are in LE with QTL the likelihood function can be misspecified. This can induce a sizable finite-sample bias and, possibly, lack of consistency of likelihood (or Bayesian) estimates. This situation can be encountered if the individuals in the sample are distantly related and linkage disequilibrium spans over short regions. This bias does not negate the use of whole-genome regression models as predictive machines; however, our results indicate that caution is needed when using marker-based regressions for inferences about population parameters such as the genomic heritability.     

Is the Naturalistic Fallacy Dead (and If So,Ought It Be?)

Much of modern moral philosophy argued that there are is's in this world, and there are oughts, but that the two are entirely independent of one another. What this meant was that morality had nothing to do with man's biological nature, and could not be derived from it. Any such attempt was considered to be a categorical mistake, and plain foolish. Most philosophers still believe this, but a growing group of neo-naturalist thinkers are now challenging their assumptions. Here I consider the latest work of one of them, Patricia Churchland, on what neurobiology teaches us about morality, and ask whether her challenge means that the naturalistic fallacy, as it is known, should be laid to rest. I argue that while there may be no such thing as a human trait divorced from human biology, this does not necessarily mean that our natures produce constraints that are relevant to specific moral dilemmas.     

A Review of Transplantation Practice of the Urologic Organs: Is It Only Achievable for the Kidney?

Transplantation is a viable treatment option for failure of most major organs. Within urology, transplantation of the kidney and ureter are well documented; however, evidence supporting transplantation of other urologic organs is limited. Failure of these organs carries significant morbidity, and transplantation may have a role in management. This article reviews the knowledge, research, and literature surrounding transplantation of each of the urologic organs. Transplantation of the penis, testicle, urethra, vas deferens, and bladder is discussed. Transplantation attempts have been made individually with each of these organs. Penile transplantation has only been performed once in a human. Testicular transplantation research was intertwined with unethical lucrative pursuits. Interest in urethra, bladder, and vas deferens transplantation has decreased as a result of successful surgical reconstructive techniques. Despite years of effort, transplantations of the penis, testicle, urethra, vas deferens, and bladder are not established in current practice. Recent research has shifted toward techniques of reconstruction, tissue engineering, and regenerative medicine.Key words: Urology, Transplantation, Reconstruction, Tissue engineeringOrgan transplantation is still a relatively novel treatment modality; its practice only developed in the latter half of the 20th century, in part due to the advent of immunosuppressive drugs. Key questions driving progress in transplant surgery is how far this science can be pushed, and if any part of the human body can be transplanted.In urology, transplantation of the kidney was previously inconceivable, but is now well established, following the first successful renal transplant performed in 1950. However, there is minimal evidence in the scientific literature of the successful transplantation of other urologic organs.There has, in the past, been great interest in exploring this lesser-known area of urologic transplantation, as the morbidity for patients with failure or damage to urologic organs such as the penis, testicle, or bladder is considerable. There is renewed interest in recent years due to the increased prevalence of devastating injuries to the genitalia caused by improvised explosive devices among soldiers stationed in Afghanistan.¹ There is minimal evidence in the literature addressing how these injuries should be best managed or whether transplantation may have a role in helping such patients.Remarkable progress in transplantation surgery has allowed development of new strategies of treatment for many urologic patients. Greater insight into the practice of transplantation may lead to improved management of other urologic pathologies. We comprehensively reviewed the historical evidence for transplantation of those urologic structures for which the practice is not well established. To our knowledge, no such review exists in the literature.     

Contrast Enhancement of the Right Ventricle during Coronary CT Angiography – Is It Necessary?

Purpose

It is unclear if prolonged contrast media injection, to improve right ventricular visualization during coronary CT angiography, leads to increased detection of right ventricle pathology. The purpose of this study was to evaluate right ventricle enhancement and subsequent detection of right ventricle disease during coronary CT angiography.

Materials and Methods

472 consecutive patients referred for screening coronary CT angiography were retrospectively evaluated. Every patient underwent multidetector-row CT of the coronary arteries: 128x 0.6mm coll., 100-120kV, rot. time 0.28s, ref. mAs 350 and received an individualized (P3T) contrast bolus injection of iodinated contrast medium (300 mgI/ml). Patient data were analyzed to assess right ventricle enhancement (HU) and right ventricle pathology. Image quality was defined good when right ventricle enhancement >200HU, moderate when 140-200HU and poor when <140HU.

Results

Good image quality was found in 372 patients, moderate in 80 patients and poor in 20 patients. Mean enhancement of the right ventricle cavity was 268HU±102. Patients received an average bolus of 108±24 ml at an average peak flow rate of 6.1±2.2 ml/s. In only three out of 472 patients (0.63%) pathology of the right ventricle was found (dilatation) No other right ventricle pathology was detected.

Conclusion

Right ventricle pathology was detected in three out of 472 patients; the dilatation observed in these three cases may have been picked up even without dedicated enhancement of the right ventricle. Based on our findings, right ventricle enhancement can be omitted during screening coronary CT angiography.     

What Is the Good of It—Ethical Controls of Human Subject Health Research?

The term “ethics” covers a multitude of virtues and possibly some sins where ethical perspectives differ. Given the diversity of ethical philosophies there is a question about what common ground can, or should, inform health research ethics. At a minimum it must be consistent with the law. Beyond that, ethics embraces a variety of possible approaches. This raises the question—what criteria are applied in determining the appropriate approach and what standards by way of quality control are applied to its decisional application by ethics committees or other authorities exercising responsibility in this difficult area. The particular issue of ethical perspectives on the use of “big data” in medical research also raises complex issues for consideration.     

Microtubule Flux: What Is It Good for?

During mitosis in a eukaryotic cell, microtubule subunits continuously move towards spindle poles. A new study has revealed that inhibiting this microtubule flux in mammalian cells has no major effects on chromosome movements; it does, however, increase the probability of erroneous chromosome segregation.