A sexually dimorphic distribution pattern of the novel estrogen receptor G-protein-coupled receptor 30 in some brain areas of the hamster

The isolation of the G-protein-coupled receptor 30 (GPR30), an orphan membrane receptor unrelated to nuclear estrogen receptors (ERs), has become a key factor towards the unraveling of rapid estrogen action. This membrane receptor together with cellular signaling intermediaries, i.e., extracellular signal-dependent kinases 1 and 2, may promote neuronal proliferation and differentiation activities. In the present study, an evident gene expression pattern of GPR30 characterized postnatal 7 (young) and 60 (adult) days of age hamsters as shown by its heterogeneous mRNA distribution in hypothalamic, amygdalar and cerebellar areas of both sexes. In particular, most of the brain areas considered in the adult hamster plus only the amygdala and cerebellum of young animals behaved in a sexually dimorphic fashion. This similar pattern was also detected for the ERα and β, as shown by the latter receptor prevailing in young and adult females, while the former predominated in young females. Even for the two kinases, a sexually dimorphic distribution was featured above all for young hamsters. Overall, the findings of the present study established a distinct expression pattern of the novel ER (GPR30) that may operate differently in some brain areas of the hamster and this may provide interesting insights regarding its probable neuroprotective role during the execution of some hibernating states, which are typical of our rodent model.

In Vitro and In Vivo Activities of Nitazoxanide against Clostridium difficile

ABSTRACT We have used the hamster model of antibiotic-inducedClostridium difficile intestinal disease to evaluate nitazoxanide (NTZ), a nitrothiazole benzamide antimicrobial agent. The following in vitro and in vivo activities of NTZ in the adult hamster were examined and compared to those of metronidazole and vancomycin: (i) MICs and minimum bactericidal concentrations (MBCs) againstC. difficile, (ii) toxicity, (iii) ability to preventC. difficile-associated ileocecitis, and (iv) propensity to induce C. difficile-associated ileocecitis. The MICs and MBCs of NTZ against 15 toxigenic strains of C. difficilewere comparable to those of vancomycin or metronidazole. C. difficile-associated ileocecitis was induced with oral clindamycin and toxigenic C. difficile in a group of 60 hamsters. Subgroups of 10 hamsters were given six daily intragastric treatments of NTZ (15, 7.5, and 3.0 mg/100 g of body weight [gbw]), metronidazole (15 mg/100 gbw), vancomycin (5 mg/100 gbw), or saline (1 ml/100 gbw). Animals receiving saline died 3 days post-C. difficile challenge. During the treatment period, NTZ (≥7.5 mg/100 gbw), like metronidazole and vancomycin, prevented outward manifestations of clindamycin-induced C. difficileintestinal disease. Six of ten hamsters on a scheduled dose of 3.0 mg of NTZ/100 gbw survived for the complete treatment period. Of these surviving animals, all but three died of C. difficiledisease by between 3 and 12 days following discontinuation of antibiotic therapy. Another group of hamsters received six similar daily doses of the three antibiotics, followed by an inoculation with toxigenic C. difficile. All of the NTZ-treated animals survived the 15-day postinfection period. Upon necropsy, all hamsters appeared normal: there were no gross signs of toxicity or C. difficile intestinal disease, nor was C. difficiledetected in the cultures of the ceca of these animals. By contrast, vancomycin and metronidazole treatment induced fatal C. difficile intestinal disease in 20 and 70% of recipients, respectively.

Chromatin remodelling of the cardiac β-myosin heavy chain gene

To investigate the role of chromatin structure in cardiac gene expression, we used the DNase I and micrococcal nuclease to probe the chromatin structure of the hamster cardiac β-MyHC gene. Two cardiac-specific DNase I hypersensitive sites (DHS) were identified, one of which was mapped to the -2.3 kb (β-2.3 kb) region and the other to the proximal promoter region of the β-MyHC gene. The two sites were readily detectable using nuclei from neonatal hamster heart; however, the proximal promoter site disappeared when adult hamster heart nuclei were used, and the -2.3 kb site decreased in intensity. We were able to demonstrate the gradual disappearance of this proximal promoter DHS by comparing heart nuclei isolated from animals at late-gestation and 1-day-old stages. Furthermore, injecting thyroid hormone caused the disappearance of the proximal promoter DHS in late gestational fetal ventricular nuclei. Digestion of nuclei from various tissues by micrococcal nuclease revealed that the β-MyHC gene proximal promoter exists in an array of three specifically-positioned nucleosomes only in fetal heart chromatin. The β-MyHC gene proximal promoter is DNase I hypersensitive within one of the nucleosomal particles. Our data suggest that chromatin structure may participate actively in cardiac gene expression.