Growth Hormone Promotes Hair Cell Regeneration in the Zebrafish (Danio rerio) Inner Ear following Acoustic Trauma

BACKGROUND: Previous microarray analysis showed that growth hormone (GH) was significantly upregulated following acoustic trauma in the zebrafish (Danio rerio) ear suggesting that GH may play an important role in the process of auditory hair cell regeneration. Our objective was to examine the effects of exogenous and endogenous GH on zebrafish inner ear epithelia following acoustic trauma. METHODOLOGY/PRINCIPAL FINDINGS: We induced auditory hair cell damage by exposing zebrafish to acoustic overstimulation. Fish were then injected intraperitoneally with either carp GH or buffer, and placed in a recovery tank for either one or two days. Phalloidin-, bromodeoxyuridine (BrdU)-, and TUNEL-labeling were used to examine hair cell densities, cell proliferation, and apoptosis, respectively. Two days post-trauma, saccular hair cell densities in GH-treated fish were similar to that of baseline controls, whereas buffer-injected fish showed significantly reduced densities of hair cell bundles. Cell proliferation was greater and apoptosis reduced in the saccules, lagenae, and utricles of GH-treated fish one day following trauma compared to controls. Fluorescent in situ hybridization (FISH) was used to examine the localization of GH mRNA in the zebrafish ear. At one day post-trauma, GH mRNA expression appeared to be localized perinuclearly around erythrocytes in the blood vessels of the inner ear epithelia. In order to examine the effects of endogenous GH on the process of cell proliferation in the ear, a GH antagonist was injected into zebrafish immediately following acoustic trauma, resulting in significantly decreased cell proliferation one day post-trauma in all three zebrafish inner ear end organs. CONCLUSIONS/SIGNIFICANCE: Our results show that exogenous GH promotes post-trauma auditory hair cell regeneration in the zebrafish ear through stimulating proliferation and suppressing apoptosis, and that endogenous GH signals are present in the zebrafish ear during the process of auditory hair cell regeneration

Antifungal activity of recombinant thanatin in comparison with two plant extracts and a chemical mixture to control fungal plant pathogens

Abstract The most common method for controlling plant diseases is the application of chemical pesticides and sometimes use of resistant cultivars. Due to the effects of chemical pesticides on human and environmental health, mutation in pathogens and resistance to various toxins besides the challenges with resistant cultivar production, the constant use of these methods are not recommended any longer. Thus, use of biological control agents along with the natural ingredient extracted from plants and application of peptide with antimicrobial activity, have been the focus of many researchers. In the present study, the antifungal activity of two plant extracts named Turmeric and Persian lilac in comparison with a chemical mixture and recombinant thanatin were evaluated against five following fungal plant pathogens; Geotrichum candidum, Botrytis cinerea, Rhizoctonia solani, Alternaria tenuissima and Gibberella fujikuroi. The results showed that, all treatments have antifungal activity against tested fungi. Both plant extracts were shown an acceptable antifungal activity against tested fungi but their inhibition effects was not comparable with chemical mixture. Turmeric showed a higher rate of mycelial inhibition than Persian lilac. Amongst all treatment, thanatin showed a great antifungal activity by its application at µg level under both in vitro and in vivo condition. Considering to the compatibility of thanatin with human health and environmental safety we could imagine a clear perspective for the application of this recombinant peptide in sustainable agriculture