Lessons and revelations from biomimetic syntheses

Biomimetic synthesis describes the field of organic chemistry that aims to emulate the natural, biosynthetic processes toward natural products. As well as providing insight into how molecules are formed in nature, the benefits of this approach to total synthesis are numerous and extend beyond the gains typical of traditional synthesis. For example, using biosynthetic proposals to design a synthetic route can highlight alternative methods to the desired target. The pursuit of biomimetic syntheses also promotes the development of new reactions to prove or disprove a biosynthetic proposal or to unravel mechanistic implications of a proposed biosynthesis and can lead to the identification of new natural products. Here we look at some recent compelling examples and examine how biomimetic synthesis has led to the discovery of new procedures and principles that would not have been found by other approaches.     

Castration attenuates myelin repair following lysolecithin induced demyelination in rat optic chiasm: an evaluation using visual evoked potential, marker genes expression and myelin staining

Multiple sclerosis (MS) is a demyelinating disease that affects the central nervous system. MS is the most common neurological disorder in young adults with a greater incidence among females. Male gonadal hormones have a protective effect on neural system development and myelin maturation. In this study, we investigate the effect of castration on lysolecithin-induced demyelination and remyelination processes using visual evoked potentials, in addition to measuring the expressions of Olig2, MBP, Nogo-A and GFAP mRNAs as oligodendrocyte or astrocyte markers; and histological assessments by myelin-specific staining. We observed more expanded demyelination with delayed repair process in castrated rats. Expression levels of the aforementioned marker genes confirmed histological and electrophysiological observations. Our results showed a pivotal role for endogenous male hormones in the context of demyelinating insults. It may also account for the different prognosis of MS between male and female genders and provide new insights for therapeutic treatments.     

Four fish species new to the Omo-Turkana basin,with comments on the distribution ofNemacheilus abyssinicus (Cypriniformes: Balitoridae) in Ethiopia

Four fish species,Pollimyrus isidori (Mormyridae),Barbus paludinosus, Labeo forskalii (Cyprinidae), andNemacheilus abyssinicus (Balitoridae), new to the Omo-Turkana basin, were recorded from the Gojeb River, a tributary of the Omo River (south-western Ethiopia). Occurrence of the latter species in the upper reaches of the Blue Nile and of the Omo drainage substantiates the belonging of the upper parts of these water systems to the Abyssinian highlands ichthyofaunal province.     

Individual ontogenetic trajectories and ontogenetic channels of three forms of large African barbs (<Emphasis Type="Italic">Barbus intermedius</Emphasis> complex). Analysis of experimental data

Changes of external morphological characters in three forms (morphotypes) of African barbs from Lake Tana (Ethiopia) belonging to Barbus intermedius complex were traced using electronic tags. It was shown that within age interval from two to four years individual ontogenetic allometric curves often cannot be described with a single power function equation. Individual ontogenetic trajectories in the principal components space within this interval strongly differ in shape meandering within ontogenetic channels outlined on the basis of cross-sectional data. Morphological differences between siblings are found that do not allow to classify some of them with the morphotype of their parents.     

Restraint Stress Potentiated Morphine Sensitization: Involvement of Dopamine Receptors within the Nucleus Accumbens

Sensitization to psychostimulant drugs, as well as morphine, subjected to cross-sensitization with stress. The development of morphine sensitization is associated with enhancements in dopamine overflow in the Nucleus accumbens (NAc). This study aimed to examine the role of accumbal D1/D2-like dopamine receptors in restraint stress (RS) induced sensitization to morphine antinociceptive effects. Adult male Wistar rats weighing 220–250 g underwent stereotaxic surgery. Two stainless steel guide cannulae were bilaterally implanted, 1 mm above the NAc injection site. Different solutions of SCH-23390, as a D1-like receptor antagonist or sulpiride, as a D2-like receptor antagonist, were microinjected into the NAc five min before exposure to RS. Restraint stress lasted for 3 h, 10 min after RS termination; animals received a subcutaneous injection of morphine (1 mg/kg) for 3 consecutive days. The procedure was followed by a 5-day drug and/or stress-free period. After that, on the 9th day, the nociceptive response was evaluated by the tail-flick test. The results revealed that intra-NAc administration of D1/D2-like dopamine receptor antagonists, SCH-23390 or sulpiride, respectively, blocked morphine sensitization-induced by RS and morphine co-administration in rats for three consecutive days. This work provides new insight into the determinant role of accumbal dopamine receptors in morphine sensitization produced by RS-morphine co-administration.