Sympatric speciation: when is it possible?

This paper is written to compare the results of theoretical investigations of sympatric speciation with the relevant experimental data. We understand sympatric speciation as a formation of species out of a population whose spatial structure is not important genetically. A necessary prerequisite for speciation is an action of disruptive selection on sufficiently polymorphic traits. The present analysis confirms the view that such a selection is ecologically realistic. The genetical part of speciation begins with a development of reproductive isolation between those individuals that are opposed in some characters. It is shown that selection for reproductive isolation may be quite strong. Extinction of intermediate individuals, which completes speciation, proceeds under a wide range of conditions, including those when the newly formed species differ in quantitative characters, though most of the genes arc likely to remain the same in both species. The whole process seems possible if differences in several (up to 10) loci are sufficient to adapt the forming species to different niches and to establish reproductive isolation. It is shown that populations with bimodal distributions of some genetically determined quantitative characters can have a considerable life-time. Such distributions may be formed either as a transition stage of sympatric speciation or represent a stationary state under conditions close to those necessary to complete speciation. They are very important for experimental investigations. Sympatric speciation always follows the same principal course; it does not contradict the idea of a genome coadaptedness. The occurrence of sympatric speciation is different for different taxa depending rather on how frequently populations are subjected to the appropriate kind of selection than on their ability to obey it.     

Cellulase recycling in biorefineries—is it possible?

On a near future, bio-based economy will assume a key role in our lives. Lignocellulosic materials (e.g., agroforestry residues, industrial/solid wastes) represent a cheaper and environmentally friendly option to fossil fuels. Indeed, following suitable processing, they can be metabolized by different microorganisms to produce a wide range of compounds currently obtained by chemical synthesis. However, due to the recalcitrant nature of these materials, they cannot be directly used by microorganisms, the conversion of polysaccharides into simpler sugars being thus required. This conversion, which is usually undertaken enzymatically, represents a significant part on the final cost of the process. This fact has driven intense efforts on the reduction of the enzyme cost following different strategies. Here, we describe the fundamentals of the enzyme recycling technology, more specifically, cellulase recycling. We focus on the main strategies available for the recovery of both the liquid- and solid-bound enzyme fractions and discuss the relevant operational parameters (e.g., composition, temperature, additives, and pH). Although the efforts from the industry and enzyme suppliers are primarily oriented toward the development of enzyme cocktails able to quickly and effectively process biomass, it seems clear by now that enzyme recycling is technically possible.     

Remission in psoriatic arthritis: is it possible and how can it be predicted?

Introduction

Since remission is now possible in psoriatic arthritis (PsA) we wished to examine remission rates in PsA patients following anti tumour necrosis factor alpha (TNFα) therapy and to examine possible predictors of response.

Methods

Analysis of a prospective patient cohort attending a biologic clinic, between November 2004 and March 2008, was performed prior to commencing therapy and at regular intervals. Baseline clinical characteristics including demographics, previous disease-modifying antirheumatic drug (DMARD) response, tender and swollen joint counts, early morning stiffness, pain visual analogue score, patient global assessment, C reactive protein (CRP) and health assessment questionnaire (HAQ) were collected.

Results

A total of 473 patients (152 PsA; 321 rheumatoid arthritis (RA)) were analyzed. At 12 months remission, defined according to the disease activity score using 28 joint count and CRP (DAS28-CRP), was achieved in 58% of PsA patients compared to 44% of RA patients, significant improvement in outcome measures were noted in both groups (P < 0.05). Analysis of a subgroup of PsA and RA patients matched for DAS28-CRP at baseline also showed higher numbers of PsA patients achieving remission. Linear regression analysis identified the HAQ at baseline as the best predictor of remission in PsA patients (P < 0.001).

Conclusions

DAS28 remission is possible in PsA patients at one year following anti-TNF therapy, at higher rates than in RA patients and is predicted by baseline HAQ.     

Additivity in protein-DNA interactions: how good an approximation is it?

Man and Stormo and Bulyk et al. recently presented their results on the study of the DNA binding affinity of proteins. In both of these studies the main conclusion is that the additivity assumption, usually applied in methods to search for binding sites, is not true. In the first study, the analysis of binding affinity data from the Mnt repressor protein bound to all possible DNA (sub)targets at positions 16 and 17 of the binding site, showed that those positions are not independent. In the second study, the authors analysed DNA binding affinity data of the wild-type mouse EGR1 protein and four variants differing on the middle finger. The binding affinity of these proteins was measured to all 64 possible trinucleotide (sub)targets of the middle finger using microarray technology. The analysis of the measurements also showed interdependence among the positions in the DNA target. In the present report, we review the data of both studies and we re- analyse them using various statistical methods, including a comparison with a multiple regression approach. We conclude that despite the fact that the additivity assumption does not fit the data perfectly, in most cases it provides a very good approximation of the true nature of the specific protein–DNA interactions. Therefore, additive models can be very useful for the discovery and prediction of binding sites in genomic DNA.     

Knowledgebase for addiction-related genes: is it possible an extrapolation to rational multi-target drug design?

In recent years the single-probe-single-target approach in drug design has started to be smoothly replaced by the single-probe-multiple-target (or multi-target) one, where a single drug is able to tackle different, but disease-related targets in a selective manner. However, the design of multi-target drugs has been hindered by a lack of a systematic network of disease-related common pathways. The recent development of the knowledgebase of addiction-related genes (KARG) has provided important hints on how to rationally design multi-target probes by connecting experimental techniques with available network models. In this perspective, the use of KARG as a template to build knowledgebases of disease-related genes for the rational multi-target drug design is suggested. Moreover, it is proposed that building knowledgebases of disease-related genes will become a necessary and ubiquitous tool in the rational design of multi-target drugs.     

Antitumor vaccines: is it possible to prevent a tumor?

The main medical use of vaccines is to induce a state of immunity in healthy individuals to protect them from deadly or dangerous diseases. In the field of cancer immunology, however, vaccines are being used in patients as therapy, often with a very poor success rate against advanced disease. This paper reviews recent preclinical evidence in favor of the prophylactic use of immunological approaches to cancer. Successful attempts at immunological cancer prevention in HER-2/neu transgenic mice are described as an example. The specific properties of the HER-2/neu gene product as a tumor antigen, and the nature of the immune responses induced by effective preventive treatments are reviewed. Although the very high rate of mammary carcinoma prevention in mice has generated enthusiasm, it should not be forgotten that such treatments, when administered to healthy humans at risk of cancer, may carry the risk of inducing autoimmunity. These issues can be addressed in preclinical studies in appropriate animal models.     

Antigenic polymorphism in malaria: is it an important mechanism for immune evasion?

Malarial infections do not readily evoke an effective protective immunity against re-infection. Possible reasons for this include the ability of the parasites to interfere with the host's immune response and to evade the response in an immune host, by, for example, exploiting antigenic polymorphism or variation. Antigenic polymorphism undoubtedly exists in malaria parasite populations but does this polymorphism actually contribute to immune evasion by the parasite? Here, Kamini Mendis and colleagues examine the evidence for this and its implications for future malaria vaccines.     

Acoustic and magnetic communication in plants: Is it possible?

Over the last two decades, important insights into our understanding of plant ecology and the communicative nature of plants have not only confirmed the existence of a wide range of communication means used by plants, but most excitingly have indicated that more modalities remain to be discovered. In fact, we have recently found that seeds and seedlings of the chili plant, Capsicum annuum, are able to sense neighbors and identify relatives using alternative mechanisms beyond previously studied channels of plant communication. In this addendum, we offer a hypothetical mechanistic explanation as to how plants may do this by quantum-assisted magnetic and/or acoustic sensing and signaling. If proven correct, this hypothesis prompts for a re-interpretation of our current understanding of plasticity in germination and growth of plants and more generally, calls for developing a new perspective of these biological phenomena.     

Limb regeneration in axolotl: is it superhealing?

The ability of axolotls to regenerate their limbs is almost legendary. In fact, urodeles such as the axolotl are the only vertebrates that can regenerate multiple structures like their limbs, jaws, tail, spinal cord, and skin (the list goes on) throughout their lives. It is therefore surprising to realize, although we have known of their regenerative potential for over 200 years, how little we understand the mechanisms behind this achievement of adult tissue morphogenesis. Many observations can be drawn between regeneration and other disciplines such as development and wound healing. In this review, we present new developments in functional analysis that will help to address the role of specific genes during the process of regeneration. We also present an analysis of the resemblance between wound healing and regeneration, and discuss whether axolotls are superhealers. A better understanding of these animals' regenerative capacity could lead to major benefits by providing regenerative medicine with directions on how to develop therapeutic approaches leading to regeneration in humans.     

Whitefly control in cut gerbera: is it possible to control Trialeurodes vaporariorum with Encarsia formosa?

We investigated the impact of inundative releases of the parasitoid, Encarsia formosa Gahan (Hymenoptera: Aphelinidae), for control of greenhouse whitefly, Trialeurodes vaporariorum (Westwood), on cut gerbera (Gerbera jamesonii L.) under controlled greenhouse conditions. Experimental units consisted of ten plants covered and separated from other units by gauze tents. We assessed three release rates of the aphelinid parasitoid: a 7-week experiment with a standard release rate (10 m⁻²/14 days), and a subsequent 3-month trial with high (100 m⁻²/week) and very high (1,000 m⁻²/week) release rates. Experimental units without release of parasitoids served as control treatment. Gerbera plants were infested initially with 50–100 juvenile and 50–70 adult whiteflies in the first experiment, and in the second experiment with less than 50 juveniles per plant and 50–70 adults. Whitefly and parasitoid population density were assessed in weekly intervals using infestation and activity categories. Results show that parasitized whiteflies were present in all treatments within 2 weeks after initial release. Unfortunately, it was not possible to control whiteflies with standard release rates of E. formosa. Although parasitism rates slightly increased, the effect on whitefly populations was negligible. Large amounts of honeydew and growth of sooty mold fungi caused the termination of the first experiment. In a second experiment, E. formosa was tested at 10–100 times higher release densities. In contrast to the first experiment, whitefly densities increased steadily during the first 8 weeks, but remained constant until the end of the experiment in both treatments. Parasitism by E. formosa reached its maximum after 8 weeks. We discuss possible reasons for the low efficiency of E. formosa as a whitefly antagonist in greenhouse production of gerbera.