Apoptosis In Chickens Research Articles

Early Posthatch Starvation Induces Myonuclear Apoptosis in Chickens

The effect of early posthatch starvation on myonuclear apoptosis was examined in chickens. Male broiler chickens were or were not provided feed for the first 3-d posthatch. Subsequently, all chickens were provided feed for an additional 4-d posthatch. Chickens were killed at 3- and 7-d posthatch, and the pectoralis thoracicus was harvested, fixed and embedded in paraffin. Muscle sections were labeled with the terminal deoxynucleotidyl transferase histochemical staining technique to identify apoptotic nuclei. At 3- and 7-d posthatch, there was a significantly (P < 0.05) smaller myofiber cross-sectional area for the starved compared with the fed chickens. A larger proportion (P < 0.05) of apoptotic nuclei relative to total nuclei was observed in the starved compared to the fed chickens killed at 3-d posthatch, but the proportion of apoptotic nuclei relative to total nuclei did not differ (P > 0.05) between the starved and fed chickens killed at 7-d posthatch. It appears that apoptosis is a mechanism contributing to the smaller myofiber size observed when feed is not provided early posthatch.

Virulent influenza A viruses induce apoptosis in chickens

Virulent avian influenza A viruses produce lethal disease in chickens. Since cell death can be caused by either necrosis or apoptosis, we investigated the types of cell death that occur in natural hosts, chickens, infected with virulent avian viruses. Using biochemical methods, we demonstrate that virulent avian influenza viruses induce apoptosis of vascular endothelial cells in liver, kidney, and brain. Viral antigens were also detected in these organs, suggesting that viral replication induces apoptosis in infected chickens. These results indicate that apoptosis does occur in virulent avian influenza virus infection in a natural host, and may contribute to the lethality of the virus.

Calpain inhibitors, but not caspase inhibitors, prevent actin proteolysis and DNA fragmentation during apoptosis.

Apoptosis, or programmed cell death, involves a cascade of regulatory events leading to the activation of specific proteases. However, the key substrates for these proteases remain to be identified. We previously demonstrated that levels of five unidentified polypeptides were specifically increased in neurons from embryonic chicken ciliary ganglia undergoing apoptosis by trophic deprivation. Here we show by microsequencing of two of these polypeptides that they are fragments of actin. One of them represents cleavage of actin at the site of interaction with DNase I. The same actin fragments are also found at early stages of apoptosis in chicken and rat dorsal root ganglion neurons, chicken spinal motoneurons and rat thymocytes. Actin fragmentation may play a role in the apoptotic process, since calpain inhibitors I and II both inhibit neuronal death and suppress actin fragmentation. In contrast, caspase (ICE family) inhibitors, though effective in delaying neuronal death, do not prevent actin cleavage or DNA fragmentation. These results indicate a key role for calpain-like proteases in neuronal programmed cell death and suggest that actin fragmentation in the cell is correlated with subsequent DNA fragmentation.

In-situ apoptosis in chickens infected with infectious bursal disease virus

Groups of specific pathogen-free chickens aged 3 weeks were inoculated with one of three strains of infectious bursal disease virus (IBDV), namely: (1) a classical virulent strain, IM-IBDV; (2) an antigenic variant-E strain, VE-IBDV; and (3) an attenuated vaccine strain, B2-IBDV. The bursa of Fabricius and thymus were examined 1 to 5 days after inoculation for histopathological lesions, IBDV antigen, and in-situ apoptosis. Infection of chickens with IM-, VE-, or B2-IBDV resulted in the appearance of large numbers of apoptotic bursal lymphocytes, both in IBDV antigen-positive and antigen-negative bursal follicles. B2-IBDV induced a slower increase in the IBDV antigen-positive cells and apoptotic cells than did IM- and VE-IBDV. The results suggested that virulent strains and vaccine strains of IBDV enhance endogenous apoptosis of bursal lymphocytes that are free of detectable IBDV antigen. Infection of chickens with IM-IBDV, but not with VE- or B2-IBDV, caused a significant increase in apoptotic cells in the thymic cortical lymphocytes. The apoptotic lymphocytes in the thymus were negative for IBDV antigen. This result indicated that histopathological lesions in the thymus of IM-IBDV-infected chickens may be due to enhanced endogenous apoptosis of thymic lymphocytes without IBDV antigen production in the cells.

Distinctive functions of Syk and Lyn in mediating osmotic stress- and ultraviolet C irradiation-induced apoptosis in chicken B cells.

By taking advantage of the established chicken B cell line, DT40 cells, which do not express tyrosine kinase Syk or Lyn, functional roles of Syk and Lyn in apoptotic response elicited by cellular stress were investigated. DT40 cells underwent apoptosis after hyperosmotic stress. In Syk-deficient DT40 cells, this apoptotic process was significantly enhanced. Ectopic expression of wild type, but not kinase-inactive, porcine Syk in Syk-deficient cells rescued cells from osmotic stress-induced apoptosis, demonstrating that the presence of functionally active Syk is necessary to protect cells from osmotic stress-induced apoptosis. In comparison, there was no effect on osmotic stress-induced apoptosis in Lyn-deficient DT40 cells. Interestingly, while Syk was not involved in ultraviolet C (UVC)-induced apoptosis, a deficiency of Lyn rendered cells resistant to UVC irradiation. These observations defined Syk and Lyn as important mediators of apoptosis in DT40 cells in response to osmotic stress and UVC irradiation, respectively. Furthermore, osmotic stress, but not UVC irradiation, could activate c-Jun N-terminal kinase (JNK) in DT40 cells. A deficiency in either Syk or Lyn did not affect the osmotic stress-induced activation of JNK. We, therefore, concluded that Syk and Lyn regulate the apoptotic responses to osmotic stress and UVC irradiation independently of the JNK pathway in DT40 cells.

Morphological evidence of apoptosis in chickens infected with infectious bursal disease virus

Two-week-old specific pathogen-free chickens were infected with the infectious bursal disease virus by the ocular route. Immediately, and at 4 and 8 days after infection, groups of three chickens were killed and tissue samples were collected. Under electron microscopical examination, typical apoptotic cells were seen in the bursa of Fabricius (BF) and in the spleen. Tissue sections stained with haematoxylin and eosin were subjected to image analysis to quantify cellular depletion in the follicles of the BF. Unstained sections were treated with a terminal deoxy-transferase-based kit to detect apoptotic cells. The numbers of apoptotic cells at different stages of infection were counted by image analysis. The results revealed a rapid depletion of cells in the BF and a simultaneous increase in apoptotic cells.