Bioscience hypotheses最新文献

A characteristic feature of the life history of humans and some other species of social mammals is a long post-reproductive period. This condition is of a physiological nature in females (menopause), whereas in males it is largely of a behavioral nature. We discuss the hypothesis that old, post-reproductive individuals in these species may act as repositories of acquired knowledge, thereby providing an evolutionary benefit for their group. According to this view, the group's investment into the care for their older members is overcompensated by the benefits gained from the experience of these individuals (“senators”). This phenomenon is suggested to be largely independent from the degree of genetic relatedness within the group. We put forward a list of several necessary preconditions for the senator phenomenon to evolve. The presence or absence of these preconditions can be studied empirically.

Studies have shown that the more iron in a given population, the more that population is vulnerable to intracellular opportunistic infections (OIs) in AIDS, mainly because these microbes make use of the intracellular iron to proliferate, and could render infections deadly. In contrast, macrophages that lack iron are effective in preventing an establishment of infection. We propose that reduction in total body iron could be a valuable treatment option for some intracellular infections, including OIs. We suggest two options to deprive pathogens of using intracellular iron (i) to practice regular blood-letting, an ancient treatment option, and (ii) to down-regulate hepcidin, the key hormone involved in the regulation of iron balance and recycling. This could also deprive transformed cells of metabolizing iron for survival. Whether or these methods serve to curb the onset of OIs/cancers to prolong HIV disease progression remains to be investigated.

Autoimmune disorders are connected with the actions of sex hormones. Clinical observations have shown that especially estrogens are involved in these phenomena. In some cases the administration of estrogens can increase the pathological symptoms of a disorder, while in others they can cause disease remission. In multiple autoimmune diseases, type I interferons, a family of cytokines acting through the common receptor IFNAR1/IFNAR2, seem to have action convergent with that of estrogens. We hypothesize that this coincidence is not accidental and type I interferons can regulate the level of estrogen receptor alpha (ERα) and consequently change the sensitivity of immune cells to estrogen's action. There is evidence that ERα is responsible for the effects exerted by estrogens and that this phenomenon mainly involves antigen-presenting cells. On the other hand, research on IFN-tau, a type I interferon family members, showed that this cytokine can modulate ERα levels in ovine endometrium. Because of the common receptor for these interferons, we suspect that other type I interferons can act in this way not only in endometrial cells, but also in immune cells. If there is such a mechanism, it can be exploited in the therapy of immune disorders, especially autoimmune disease, for example through simultaneous administration of less toxic interferons and estrogens.

The brain's wrong-sidedness, or contralaterality, is one of life's great mysteries. Unlike invertebrates, all vertebrates from fish to mammals possess a forebrain with hemispheres innervated from sense organs on the body's opposite side. The vertebrate chambered eye has long been implicated as the cause for this paradox but no credible or testable theory had previously been postulated to support such an idea. Ramon y Cajal, the founder of neurobiology, made such a claim in the early 1900s but failed to provide adequate evidence. Here we show that the eye indeed appears to be the inverting culprit based on this author's entirely original, but untested, concept of a cyclopean origin to vertebrates at a time when single-eyed chordates were evolving to double-eyed agnathan fish.

This framework of evidence has been entitled The Inversion Hypothesis and was originally based on the author's observation that the primary cortical sensorimotor map in mammals appears to unfold from a prior longitudinal position which was inverted in all three dimensions to the body itself. It postulates a four-stage development of the vertebrate forebrain from primitive to modern whereby a longitudinal primary bodymap (Protomap) unfolds in a predictable caudal direction. As proposed, the initial establishment of the map in the contralateral hemispheres was consequent on the inverting effect of a single frontal imaging eye as it developed in tandem with the early forebrain in ancient fish.

The most conspicuous evidence today of these cyclopean origins is the common fetal abnormality in all vertebrates of cyclopia, the default developmental condition when cyclopia-nulling genes fail to activate. Further, the most exciting and convincing evidence of these origins promises to come from a change in paradigm for explaining the bizarre single circular stain at the anterior snout of primitive agnathan fossils. This circular stain is presently causing much consternation amongst palaeontologists. Unable to ascribe two eyes to these primitive fossils, mainstream palaeontology is bereft of a weltanschauung that allows the interpretation of the circular stain as a single frontal eye. The Inversion Hypothesis offers a very credible solution.

The kidney is a major source of systemic erythropoietin, despite itself showing little angiogenesis. Based on paper by Schumacher VA et-al. [J Am Soc Nephrol 2007;18:719–29] that renal synthesis of an inhibitory VEGF variant (VEGF165b) blocks local angiogenesis, we hypothesise that the chronic hypoxia in the renal medulla, due to limited perfusion through vasa recta stimulates continuous renal erythropoietin secretion.

Because human mesenchymal stem cells (hMSCs) can proliferate indefinitely in an undifferentiated state and differentiate into various cell types, hMSCs are expected to be useful for cell replacement therapy. But the clinic application is limited by its differentiation efficiency of hMSCs. It has been proved that cells can be geometrically switched between gene programs for growth, apoptosis and differentiation. Previous studies showed that hMSCs started showing round when exposed to modeled microgravity (MMG), while their differentiation capability seemed enhanced simultaneously. Thus, this article briefly reviews such studies, and hypothesizes that “spherical shape” could be a potential predictor of hMSCs with potentiated differentiation capability.

Hemoglobin variants are associated with protection from malaria. Stem cell engineering may yield erythrocytes with new modified hemoglobin which might protect against severe malaria.

Cleft lip and palate is multifactorial in aetiology. The elevation of palatal shelves is a key point of palatogenesis. However, there were many different opinions on the explanation of the elevation. In this article, we offered a new explanation. Before sixth week of gestation in humans, Palatal mesenchymal proliferation was along the horizontal direction. Because of the block of the tongue, the palatal shelves had to grow first vertically in the oral cavity. In the process of cells migration, much horizontal stress accumulated in the palatal shelves, meanwhile increased the collagen secretion of the palatal mesenchymal cells in order to strengthen the elasticity of palatal shelf and maintain the integrity to make palatal shelf look like an elastic palate. The intrinsic elevating force and the block of tongue made the palatal shelf curved. After seventh week facial structures grew predominantly in the sagittal plane. The activity of the geniohyoid and genioglossus muscles caused the mandibular retraction and the widening of the angulation between the bilateral hemimandibles. These changes provided the space for palatal shelf elevation. At some moment of the eighth to tenth weeks, the elastic stress center of the palatal shelf was above the horizontal surface because of the drop of the tongue. The palatal shelves might bounce up and elevate in a horizontal position when enough horizontal stress accumulated, and then adhered and fused.