Darwin and Mendel: who was the pioneer of genetics?

Although Mendel is now widely recognized as the founder of genetics, historical studies have shown that he did not in fact propose the modern concept of paired characters linked to genes, nor did he formulate the two "Mendelian laws" in the form now given. Furthermore, Mendel was accused of falsifying his data, and Mendelism has been met with scepticism because of its failure to provide scientific explanation for evolution, to furnish a basis for the process of genetic assimilation and to explain the inheritance of acquired characters, graft hybridization and many other facts. Darwin was the first to clearly describe almost all genetical phenomena of fundamental importance, and was the first to present a developmental theory of heredity--Pangenesis, which not only greatly influenced many subsequent theories of inheritance, particularly those of de Vries, Galton, Brooks and Weismann, but also tied all aspects of variation, heredity and development together, provided a mechanism for most of the observable facts, and is supported by increasing evidence. It has also been indicated that Darwin's influence on Mendel, primarily from The Origin, is evident. The word "gene" was derived from "pangen", itself a derivative of "Pangenesis" which Darwin had coined. It seems that Darwin should have been regarded as the pioneer, if not of transmissional genetics, of developmental genetics and molecular genetics.     

Crepidula fornicata is not a first intermediate host for trematodes: who is?

Trematode larvae must generally invade a molluscan intermediate host, usually a gastropod, before they can reach reproductive maturity in another definitive host. The research literature to date has focused almost exclusively on the documented specificity between particular trematode species and particular molluscan hosts; little attention has been paid to gastropod species that do not appear to serve as hosts. We sampled Rhode Island and Massachusetts populations of the marine gastropod Crepidula fornicata to determine whether this widespread species serves as a first intermediate host for trematodes. We also sampled from the same habitat populations of Littorina littorea and Ilyanassa obsoleta, gastropods known to serve as first intermediate hosts for several trematode species. All individuals were examined by dissection for the presence of sporocysts, rediae, or developing cercariae. Although 4-28% of L. littorea (N=112) and I. obsoleta (N=84) were infected by larvae of at least one trematode species, no individuals of C. fornicata sampled from the same locations were so infected (N=136). A survey of the Biological Abstracts computer database indicates that snails in only about 10% of marine gastropod families are known to serve as first intermediate hosts for trematodes. We suggest that more attention be paid to marine gastropods that appear not to be infected by trematode miracidia. Such species may productively serve as new models for understanding trematode host specificity and gastropod resistance to infection.     

Cell polarity, auxin transport, and cytoskeleton-mediated division planes: who comes first?

In plants, cell polarity is an issue more recurring than in other systems, because plants, due to their adaptive and flexible development, often change cell polarity postembryonically according to intrinsic cues and demands of the environment. Recent findings on the directional movement of the plant signalling molecule auxin provide a unique connection between individual cell polarity and the establishment of polarity at the tissue, organ, and whole-plant levels. Decisions about the subcellular polar targeting of PIN auxin transport components determine the direction of auxin flow between cells and consequently mediate multiple developmental events. In addition, mutations or chemical interference with PIN-based auxin transport result in abnormal cell divisions. Thus, the complicated links between cell polarity establishment, auxin transport, cytoskeleton, and oriented cell divisions now begin to emerge. Here we review the available literature on the issues of cell polarity in both plants and animals to extend our understanding on the generation, maintenance, and transmission of cell polarity in plants.     

Virulence factors of Trypanosoma cruzi: who is who?

The aim of this review is to gather the current knowledge of Trypanosoma cruzi's virulence factors described to date in an integrative way, relating these with the parasite's life cycle and trying to elucidate their importance in each process. Several aspects relevant for the parasite's survival, such as invasion, resistance to oxidative damage, escape from the phagolysosomal vacuole and differentiation, among others, will be discussed. However, there is still a lot to learn about what virulence really means in T. cruzi and which parasite molecules are absolutely required to make T. cruzi one of the most successful pathogens to invade, survive and persist in a mammalian host.     

Heme oxygenase: who needs it?

Heme is a molecule that is synthesized by the sequential actions of eight enzymes and is ubiquitous throughout nature. For many years it has been known that heme is also catabolized to yield biliverdin (which is subsequently reduced to bilirubin), one atom of iron, and one molecule of carbon monoxide. There has been a recent explosion of interest in this degradative process that is catalyzed by the rate-limiting enzyme, heme oxygenase. In particular, there has been a special interest in the potential physiological and pathological roles that may be played by these breakdown products. This minireview will examine some of these potential functional correlates, with special emphasis on potential oxidant and antioxidant effects of the bilirubin, carbon monoxide, and iron that result from the activity of heme oxygenase.     

Photosynthesis: what color was its origin?

Recent studies using geological and molecular phylogenetic evidence suggest several alternative evolutionary scenarios for the origin of photosynthesis. The earliest photosynthetic group is variously thought to be heliobacteria, proteobacteria or a precursor of cyanobacteria, organisms whose photosynthetic pigments make them different colors.     

Thrombocytopenia in malaria: who cares?

Despite not being a criterion for severe malaria, thrombocytopenia is one of the most common complications of both Plasmodium vivax and Plasmodium falciparum malaria. In a systematic review of the literature, platelet counts under 150,000/mm3 ranged from 24-94% in patients with acute malaria and this frequency was not different between the two major species that affected humans. Minor bleeding is mentioned in case reports of patients with P. vivax infection and may be explained by medullary compensation with the release of mega platelets in the peripheral circulation by megakaryocytes, thus maintaining a good primary haemostasis. The speculated mechanisms leading to thrombocytopenia are: coagulation disturbances, splenomegaly, bone marrow alterations, antibody-mediated platelet destruction, oxidative stress and the role of platelets as cofactors in triggering severe malaria. Data from experimental models are presented and, despite not being rare, there is no clear recommendation on the adequate management of this haematological complication. In most cases, a conservative approach is adopted and platelet counts usually revert to normal ranges a few days after efficacious antimalarial treatment. More studies are needed to specifically clarify if thrombocytopenia is the cause or consequence of the clinical disease spectrum.     

Brain donation: who and why?

Understanding what influences people to donate, or not donate, body organs and tissues is very important for the future of transplant surgery and medical research (Garrick in J Clin Neurosci 13:524–528, 2006). A previous web-based motivation survey coordinated by the New South Wales Tissue Resource Centre found that most people who participated in brain donation were young, female, educated Australians, not affiliated with any particular religion, and with a higher prevalence of medical illness than the general Australian population. It discussed the main motivating factors for brain donation to be “the benefits of the research to medicine and science”. This study has been replicated in a paper-based version to capture a broader cross-section of the general population, to find out who they are and what motivates them to donate. All consented and registered brain donors (n = 1,323) were sent a questionnaire via the post and recipients were given 3 months to complete the questionnaire and return it in a reply paid envelope. Results were entered into the original web-based survey and analyzed using SPSS version 10. Six hundred and fifty-eight questionnaires were returned completed, a response rate of 53%. The results show that people from all age groups are interested in brain donation. The over 65’s are the largest of the groups (30.7%). The majority of the participants were female (60.6%), married (49.2%) with children (65.8%), employed (52.9%) and have a tertiary education (73.3%). They were either non-religious (48.2%) or Christian (41.6%) and were mostly Australian (65.4%). Most (81%) had pledged to donate other organs and tissues for transplantation. The most commonly cited reasons for the donation were to benefit science (27.6%), to benefit medicine (23.9%), a family illness (17.5%) and to benefit the community (16.6%). This study demonstrates that people across all age groups are interested in brain donation. Recruitment of new brain donors could target the over 65 female Australians, who are not religious or Christian and who have also donated other organs and tissues for transplant purposes. It also indicates the need to make donation for research part of the national transplant donation program.     

The osteocutaneous free fibula flap: is the skin paddle reliable?

This clinical and anatomic study was undertaken to see if the skin paddle of the osteocutaneous fibula flap could be made more reliable. Eighty cadaver limbs were dissected to evaluate the type, number, and location of the cutaneous perforators supplying the lateral leg. Three types of perforators were identified: septocutaneous, musculocutaneous, and a type we termed septomuscular, which does not actually run within the muscle substance but is adherent to the muscle. Although not a true musculocutaneous perforator, it should be treated as such clinically. Musculocutaneous perforators were found to be more numerous and more proximal than the septocutaneous perforators. Eighteen clinical cases demonstrate a 33 percent skin paddle survival when dissected as a septocutaneous flap and a 93 percent skin paddle survival when dissected as a septomusculocutaneous flap. In using the osteocutaneous fibula flap, it is recommended that a cuff of soleus and flexor hallucis longus be incorporated into the flap to help ensure flap viability.     

Chromatin methylation: who's on first?

Two recent studies have exploited Arabidopsis mutants and chromatin immunoprecipitation to reveal the complexity of the interaction between histone H3 methyl K9 and cytosine methylation, two epigenetic marks that characterize silent chromatin.