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On the basis that multiple interactions exist between thyroid hormones and immune system, and ageing is accompanied by changes in thyroid hormone secretion, it seems possible that thyroid hormones may be involved in the age-related immune dysfunction. The present study was conducted to evaluate in vivo and in vitro effects of thyroxine (T(4)) treatment on both cell-mediated and humoral immune responses of aged mice. In a trial to improve age-associated immune dysfunction, T(4) (0.2, 1.0 and 5.0 microg) was subcutaneously supplemented to BALB/c mice (over 18 months old) for 30 consecutive days. The present results showed that exogenous treatment of aged mice with T(4) was associated with a marked increase in serum T(4) level, and the total number of peripheral blood leukocytes as well as the total cellularity of thymus, spleen, peripheral lymph nodes (PLNs), mesenteric lymph nodes (MLNs) and bone marrow (BM). T(4) treatment also caused a significant increase in the total and differential numbers of peritoneal exudate cells (PECs), while it caused a slight increase in macrophages' phagocytic activity of PEC. Moreover, T(4) treatment elicited a statistically significant increase in both plaque-forming cell and rosette-forming cell responses. In vitro results showed that the addition of T(4) at concentrations of 0.001, 0.005 and 0.025 microg/well substantially potentiated the ability of splenocytes from aged mice to proliferate in the presence of concanavalin-A mitogen. Histological examination of thymuses from T(4)-treated aged mice revealed that the cortex was preferentially enlarged and repopulated with immature thymocytes. The present study postulates that thyroid hormones may be involved in the observed decrease in the immune responsiveness during ageing, and that T(4) treatment to aged mice is able to restore the age-related decline of the immune efficiency.

The present study aimed to screen for antibacterial activities in soft corals of the eastern Red Sea coast. Specimens of different species were surveyed, collected, preserved, extracted and assayed according to standard protocols. Bioactive materials were extracted using a dichloromethane/methanol mixture, and the activity was determined using the well diffusion and microdilution assay methods. All extracts demonstrated variable activity against marine bacteria previously isolated from the sea water (in situ near the soft corals). Among soft corals, Sarcophyton spp. and Sinularia polydactyla showed the highest activity (MIC = 30-50 g/ml), while the crude extract of Xenia spp. showed the lowest activity (MIC = 200-250 g/ml) against the isolated marine bacterial strains.Antibacterial activity was observed for five out of the seven soft coral extracts (72%) against two Gram-positive (Staphylococcus aureus and Bacillus spp.) bacterial pathogens, while none of the extracts inhibited Gram-negative (Escherichia coli) bacteria. The most potent (MIC = 40-75 g/ml) crude extracts were obtained from S. polydactyla and Sarcophyton spp., while the crude extract of Xenia spp. was the least effective (MIC ≥ 200 g/ml) against the tested Gram-positive bacteria. The results from the current study suggest that soft corals of the Red Sea (Yunbu, SA) are a potential source of novel antibiotics.

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