Effects of ecdysterone, inokosterone and eyestalk ablation on limb regeneration in the fiddler crab,Uca pugilator

Medicinal plants from the Himalayan region for potential novel antimicrobial and anti-inflammatory skin treatments

BACKGROUND AND OBJECTIVES

Adequate treatment of wounds remains one of the major medical needs globally, most notably in the regions with poor or limited access to health care. In many local and traditional systems of medicine, plants are often widely used for treating infected wounds.

AIM AND OBJECTIVES

The overarching aim of this project was selection of potential species for use in a future treatment by combining with plant resources with aspects of antimicrobial photodynamic therapy (aPDT). Specifically, we focussed on species used locally in the Himalayan region for the treatment of skin disorders and then assessed the existing pharmacological evidence for key species based on the published evidence available.

METHODS

Database searches were performed to identify relevant publications describing local and traditional uses of plants in the Himalayan region of Bhutan, PR China, India, Nepal and Pakistan. Using the Global Biodiversity Information Facility (GBIF), species were researched in terms of their distribution including in different climatic regions, focussing on species mostly found in higher climatic zones (based on the Köppen-Geiger climate classification). For species used in three or more countries and restricted to the higher altitudes, data on safety, pharmacology, as it relates to dermatological conditions, and phytochemistry were retrieved.

KEY FINDINGS

The study identified a total of 606 species that are used in the treatment of various skin conditions often associated with infections reported in 84 articles. Common weeds like Ageratum conyzoides and Bidens pilosa, widely used and cultivated species like Centealla asiatiaca and Prunus armenica were excluded. This ultimately led to the identification of a core group of five widely used species restricted to the Himalayan region (Cedrus deodara, Nardostachys jatamansi, Pinus wallichiana, Pinus roxburghii and Valeriana jatamansi).

CONCLUSIONS

Here we apply a novel approach comprising an assessment of the published information on the use of medicinal plants (i.e. local and traditional knowledge) in the context of their potential to be used in a biomedical form of clinical treatment - aPDT. Then, once sustainable sourcing based on access and benefit-sharing arrangements is in place, these species are investigated for their potential in wound treatment. Ultimately, the goal is to develop a new baseline for primary health care in some of the regions of the world with poor or limited access to health care.

Cloning of crustacean ecdysteroid receptor and retinoid-X receptor gene homologs and elevation of retinoid-X receptor mRNA by retinoic acid

We report the cloning and analysis of ecdysteroid receptor (bpEcR) and retinoid-X receptor (UpRXR) cDNA homologs from the fiddler crab Uca pugilator. The deduced amino acid sequence of this crustacean EcR most closely resembles the insect EcRs within the DNA binding and ligand binding domains (LBDs). For UpRXR, the DNA binding domain (DBD) shares greatest identity to the insect USPs. The ligand binding domain, however, is closer to vertebrate RXRs but may have a nonfunctional AF-2 domain. Probes derived from these clones were used to examine transcript levels in blastemas during early limb regeneration. Both UpEcR and UpRXR transcripts were detected in low amounts 1 day after limb loss, but increased during the next 4 days. Immersion of crabs in sea water containing all-trans retinoic acid increased the steady state concentrations of UpRXR transcript and altered the pattern of circulating ecdysteroids. These effects correlate with the disruptive effects of retinoic acid on blastemal differentiation observed in earlier studies.

Expression of the genes encoding the ecdysteroid and retinoid receptors in regenerating limb tissues from the fiddler crab, Uca pugilator

Using sequence information derived from the Drosophila melanogaster (Dm) ecdysteroid receptor (EcR)- and retinoid X receptor (RXR)-encoding gene homologs, we have isolated cDNA clones corresponding to the DNA-binding domains (DBD) for these two nuclear receptors from the fiddler crab, Uca pugilator (Up). Both genes appear to be represented in 1-2 copies in the Up genome, and unlike Dm, contain an intron within the DBD-encoding region. Sequence comparisons to the Dm EcR and RXR homologs indicate 76 and 82% nucleotide identity, respectively, corresponding to 6 and 4 single-amino acid substitutions which primarily cluster in the region of the molecule involved in dimerization. RT-PCR analysis indicates that both the EcR and RXR homologs are expressed during the initial stages of limb regeneration, temporally concomitant with early blastema formation and the secretion of a flexible sac cuticle at the site of limb loss.

Role of ecdysone and eyestalk factors in regulating regeneration in larval crustaceans

Megalopae of the mud crab Rhithropanopeus harrisii can regenerate autotomized limbs. Regeneration during the megalopal stage required a significant delay in ecdysis to the first crab. Megalopae that failed to initiate regeneration complete ecdysis significantly faster than do controls. Exposure of intermolt- and premolt-stage megalopae to exogenous ecdysone significantly reduced (greater than or equal to 30%) the number of animals completing regeneration. The regeneration-induced delay in ecdysis was not significantly different in animals exposed to ecdysone. The molt cycle of nonregenerating megalopae exposed to ecdysone was further accelerated. Eyestalk ablation did not significantly reduce the molt cycle duration of regenerating animals. Eyestalkless nonregenerating animals did not display accelerated ecdysis. It is hypothesized that two additional hormonal factors are involved in "fine tuning" the molt cycle of regenerating animals. One located outside the eyestalks extends the molt cycle to accommodate regeneration. The second factor accelerates ecdysis in nonregenerating animals and appears to be produced in the eyestalks.

Effect of Y-organ removal on limb regeneration and molting in the terrestrial crab, Sesarma haematocheir

The effect of Y-organ removal on limb regeneration and molting was investigated in the crab, Sesarma haematocheir. Basal growth of regenerating limb bud was achieved independently of the Y-organs. However, bilateral removal of the Y-organ inhibited premolt growth and molting. It was also found that removal of the Y-organs from crabs at stage D2 inhibited further premolt growth of regenerating limb bud and molting. Ecdysterone injections in Y-organless crabs induced premolt growth of regenerating limb bud and gastrolith formation, but were insufficient to induce molting.

Patterns of serum ecdysteroids during induced and uninduced proecdysis in the fiddler crab, Uca pugilator

Eyestalk-intact and eyestalkless fiddler crabs, Uca pugilator, have similar temporal patterns of circulating serum ecdysteroids during proecdysis. Both groups of animals showed two distinct transient peaks of radioimmunoassay (RIA)-active ecdysteroids. Peak 1 occurred 3 weeks prior to ecdysis and preceded the onset of rapid proecdysial limb bud growth. Peak 2 was a larger peak that occurred a few days prior to ecdysis. Thin-layer chromatography profiles of the two peaks showed at least seven RIA-active compounds common to both peaks. The relative abundance of these compounds differed between the two peaks. The role of the eyestalks in control of circulating ecdysteroids was limited to maintenance of intermolt conditions. During proecdysis, the control of circulating ecdysteroid levels was located outside of the eyestalks. There was no correlation between limb bud growth rates and serum ecdysteroid levels during proecdysis.