Effect of low ambient temperature on protein turnover and heat production in chicks

1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks.     

Requirement of caspase and p38MAPK activation in zinc-induced apoptosis in human leukemia HL-60 cells.

Zinc (Zn), an endogenous regulator of apoptosis, and has abilities both to induce apoptosis and inhibit the induction of apoptosis via the modulation of caspase activity. Due to the multifunctions of Zn, the intracellular Zn level is strictly regulated by a complex system in physiological and pathological conditions. The commitment of Zn to the regulation of apoptosis is not fully understood. In the present study, we investigated the role of intracellular Zn level in the induction of apoptosis in human leukemia cells (HL-60 cells) using a Zn ionophore [pyrithione (Py)]. Treatment of HL-60 cells with Zn for 6 h in the presence of Py (1 micro m) exhibited cytotoxicity in a Zn dose-dependent manner (25-200 micro m). Necrotic cells, assayed by trypan blue permeability, increased in number in a Zn dose-dependent fashion (50-100 micro m), but the appearance of apoptotic cells, assayed by formation of a DNA ladder and terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end-labeling method, peaked at 25 micro m, suggesting the dependence of intracellular Zn level on the execution of apoptosis. In fact, treatment with Py resulted in increases in intracellular Zn levels, and N,N,N',N'-tetrakis (2-pyridylmethyl)ethylenediamine, a cell-permeable Zn chelator, inhibited DNA ladder formation induced by Py/Zn treatment (1 micro m Py and 25 micro m Zn). Py/Zn treatment activated the caspases, as assessed by the proteolysis of poly(ADP-ribose) polymerase (PARP), which is a substrate of caspase, and activated p38 mitogen-activated protein kinase (p38MAPK), which is a transducer of apoptotic stimuli to the apparatus of the apoptosis execution. Z-Asp-CH2-DCB, a broad-spectrum inhibitor of caspase, attenuated proteolysis of PARP and DNA ladder formation by Py/Zn, indicating that apoptosis induced by Py/Zn is mediated by caspase activation. The p38MAPK-specific inhibitor SB203580 also inhibited induction of apoptosis by Py/Zn. Although SB203580 suppressed the proteolysis of PARP, Z-Asp-CH2-DCB did not inhibit the phosphorylation of p38MAPK, raising the possibility that apoptosis triggered by Py/Zn might be mediated by the p38MAPK/caspase pathway.     

Influence of the gut microflora on protein synthesis in tissues and in the whole body of chicks.

1. The influence of the gut microflora on protein synthesis in individual tissues and in the whole body of young chicks was investigated by the large-dose injection of [3H]phenylalanine. 2. Growth of germ-free chicks was significantly better than that of conventional controls. Wet weights of liver, spleen, duodenum, jejunum + ileum and caeca were heavier in conventional birds than in germ-free counterparts. 3. Fractional rates of protein synthesis were higher in jejunum + ileum and whole body of conventional birds than in those of germ-free birds. Amounts of protein synthesized were larger in liver, jejunum + ileum and caeca in the presence of the gut microflora. 4. When tissues were classified into gut + liver and the remainder of the carcass, in the presence of the gut microflora an enhanced protein synthesis in fractional and absolute rate was found in the gut + liver, which is in direct contact or in close association with micro-organisms, whereas virtually no effect of the gut micro-organisms was detected in the remainder of the carcass. 5. The contribution of protein synthesis of gut + liver to that of the whole body was larger in conventional chicks than in germ-free birds, whereas the reverse was true for the remainder of the carcass.     

FINE STRUCTURE OF THE OCTOPUS RETINA

The fine structure of the visual and the supporting cells and of the blood capillaries in the octopus retina is described. Lamellated structures contained in the proximal segment of the visual cell consist of compact arrays of dense membranes each of which is quintuple-layered and divides at its margins into two thinner sheets or membranes which are connected directly with the agranular or granular endoplasmic reticulum. Proximal to the deeper extremities of the rhabdomeres, the lateral plasma membranes of two adjoining visual cells contact each other forming a quintuple-layered compound membrane, which results in occlusion of the intercellular space. The central layer of the compound membrane is of high density, so that the membrane, as a whole, appears to be a single thick layer at low magnifications. The supporting cells are connected with the neighboring visual cells by two types of junctions. Long slender processes extend from the supporting cells to the surface of the retina through narrow spaces among the distal segments of the visual cells. The capillary endothelial cells are characterized by luminal surfaces irregularly contoured and by lateral surfaces elaborately interdigitated. The functional significance of the close contact between adjoining visual cells is discussed.     

Multiple roles of the mitogen-activated protein kinase kinase/mitogen-activated protein kinase cascade in Xenopus laevis

Mitogen-activated protein kinase (MAPK) was originally identified as a serine/threonine protein kinase that is rapidly activated in response to various growth factors and tumor promoters in mammalian cultured cells. The kinase cascade including MAPK and its direct activator, MAPK kinase (MAPKK), is now believed to transmit various extracellular signals into their intracellular targets in eukaryotic cells. It has been reported that activation of MAPKK and MAPK occurs during the meiotic maturation of oocytes in several species, including Xenopus laevis . Studies with neutralizing antibodies against MAPKK, MAPK phosphatases and constitutively active MAPKK or MAPK have revealed a crucial role of the MAPKK/MAPK cascade in a number of developmental processes in Xenopus oocytes and embryos.     

Effect of Z-100, an immunomodulator extracted from human type tubercle bacilli,on the pulmonary metastases of lewis lung carcinoma in attempt to regulate suppressor T cells and suppressor factor,IL-4

In the present study, anti-metastatic effect of Z-100 on the spontaneous pulmonary metastases of Lewis lung carcinoma (3LL) was examined in an attempt to regulate suppressor T cells. When Z-100 (10 mg/kg) was daily injected i.p. after 3LL inoculation, survival rate of these mice was increased significantly (p<0.05). In addition, the number of pulmonary metastatic colonies of 3LL in Z-100-treated mice were significantly decreased by 38% at 21 days, as compared with that of control mice (p<0.05). Along with the decrease of pulmonary metastases, suppressor cell activity was also gradually reduced in these mice, as compared with that of control mice. When splenic suppressor cells (5×10⁷ cells) from 3LL-bearing mice were adoptively transferred into normal mice (recipients) just before inoculation of 3LL, the development of pulmonary metastases in recipients was significantly accelerated. However, splenocytes from 3LL-bearing mice treated with Z-100 did not affect the development of pulmonary metastasis. The potential to accelerate the metastasis of splenic mononuclear cells from 3LL-bearing mice was decreased significantly by the treatment with anti-Thy 1.2 monoclonal antibody (mAb), anti-Lyt 2.2 mAb or anti-CD11b mAb followed by complement. IL-4 activity in the sera of 3LL-bearing mice was detected 15 days after tumor inoculation (13 pg/ml) and gradually increased (18 pg/ml) 20 days after tumor inoculation. However, when Z-100 (10 mg/kg) was daily injected i.p., IL-4 activity in sera was decreased significantly, and the IL-4 activity was not detected in these mice on day 20. These results suggest that Z-100 could inhibit the pulmonary metastases in 3LL-bearing mice through the inhibition of suppressor T cell activity and a possible candidate of its effector molecule, IL-4.