Evolution of a predator-prey Volterra-Lotka ecosystem with saturation effect

This paper has studied the evolution of a predator-prey Volterra-Lotka ecosystem with saturation effect for the general case where both predator and prey evolve. We have interesting results under the evolutional condition, as follows: (1) the predator population and the ratio of predator to prey populations increase; (2) the parameters of the prey drift in the direction of increasing multiplication rate and saturation level, while the parameters of the predator drift in the direction of decreasing death rate.     

Interleukin-6 triggers the association of its receptor with a possible signal transducer, gp130

Interleukin-6 mediates pleiotropic functions in various types of cells through its specific receptor (IL-6-R), the cDNA of which has already been cloned. We report here that an 80 kd single polypeptide chain (IL-6-R) is involved in IL-6 binding and that IL-6 triggers the association of this receptor with a non-ligand-binding membrane glycoprotein, gp130. The association takes place at 37 degrees C within 5 min and is stable for at least 40 min in the presence of IL-6, but does not occur at 0 degree C. Human IL-6-R can associate with a murine gp130 homolog and is functional in murine cells. Mutant IL-6-R lacking the intracytoplasmic portion is functional, suggesting that the two polypeptide chains interact to involve their extracellular portion. In fact, a soluble IL-6-R lacking the transmembrane and intracytoplasmic domains can associate with gp130 in the presence of IL-6 and mediate its function. These findings indicate that the complex of IL-6 and IL-6-R can interact with a non-ligand-binding membrane glycoprotein, gp130, extracellularly and can provide the IL-6 signal.     

Degradation of 125I-glucagon, -pancreatic polypeptide and -insulin by acid saline extract of rat submaxillary gland and their protection by proteinase inhibitors

The acid saline extract (ASE) of rat submaxillary gland exerts a powerful degrading effect on 125I-glucagon. In order to study the degradation of other 125I-peptides by ASE and the effects of their inhibitors, 125I-pancreatic polypeptide (PP) and 125I-insulin were used together with 125I-glucagon. The degradation studies were done by the trichloroacetic acid (TCA) method or gel filtration. Besides 125I-glucagon, 125I-PP was found to be destroyed by ASE in the ordinary immunoassay system using the TCA method, but 125I-insulin was intact in the presence of ASE. Leupeptin, and to a lesser extent p-chloromercuriphenyl-sulfonic acid (PCMS) and N-ethylmaleimide, inhibited the destruction of 125I-glucagon or -PP under the TCA method. PCMS was especially protective at high concentrations, for example 16 mM. These findings were confirmed by gel filtration of the assay mixture. In the presence of leupeptin (0.4 mM) and PCMS (16 mM), no shift in the peak of labelled glucagon or PP occurred. Thus ASE degrades not only 125I-glucagon but -PP, and thiol proteinase inhibitors have a strong inhibitory action on them.     

Effect of endothelin-1 on release of arginine-vasopressin from perifused rat hypothalamus

Endothelin-1 (ET-1) is an endothelium-derived vasoconstrictor peptide with potent pressor activity. We studied the effect of ET-1 on release of arginine-vasopressin (AVP) from perifused rat hypothalamus. ET-1 (10(-10) to 10(-8) M) significantly stimulated AVP release. The ET-1-induced AVP release was completely blocked in the presence of nicardipine. Our results suggest a possible involvement of ET in the regulation of AVP release.     

Sequence and over-expression of subunits of adenosine triphosphate synthase in thermophilic bacterium PS3

The primary structures of all the subunits of thermophilic ATP synthase were determined, and its alpha, beta and gamma subunits could be over-expressed in Escherichia coli, because these subunits were stable and reconstitutable. DNA of 7500 base pairs in length was found to contain a cluster of nine genes for subunits of ATP synthase. The order of their reading frames (size in base pairs) was: I(381): a(630): c(216): b(489): delta(537): alpha(1507): gamma(858): beta(1419): epsilon(396), I being a gene for a small hydrophobic, basic protein expressed in vitro. All the termini of TF0F1 subunits were confirmed by peptide sequencing. Large quantities of the overexpressed thermophilic alpha, beta and gamma subunits were prepared from the extract of E. coli, by a few purification steps.     

A novel opioid peptide, leumorphin, acts as an agonist at the kappa opiate receptor

The primary structure of the common precursor of porcine beta-neo-endorphin and dynorphin (preproenkephalin B) has shown the existence of a third leucine-enkephalin (leu-enkephalin) sequence with a C-terminal extension of 24 amino acids. This nonacosapeptide, named leumorphin, was approximately 70 times more potent than leu-enkephalin in inhibiting the contraction of the myenteric plexus-longitudinal muscle preparation of the guinea pig ileum. This action of leumorphin, like those of beta-neo-endorphin and dynorphin, was antagonized less effectively by naloxone than that of leu-enkephalin, but more effectively by Mr2266, an antagonist relatively specific for the kappa type opiate receptor. The inhibitory action of leumorphin or beta-neo-endorphin on the contraction of the guinea pig ileum muscle strip was reduced in a dose-dependent manner by pretreatment with dynorphin and vice versa. Leumorphin as well as beta-neo-endorphin and dynorphin inhibits the contraction of the rabbit vas deferens which is known to have only the kappa type opiate receptor. This action was also effectively antagonized by Mr2266. It is concluded that leumorphin has potent opioid activity and acts at the kappa receptor, like other opioid peptides derived from preproenkephalin B.     

Guinea pig alveolar eosinophils and macrophages produce leukotriene B4 but no peptido-leukotriene

The metabolism of arachidonic acid (AA) was investigated in purified guinea pig alveolar eosinophils and macrophages. Alveolar eosinophils produced 12S-hydroxy-5,8,10-heptadecatraenoic acid (HHT) and small amounts only of 5-lipoxygenase products when stimulated by AA (10 microM) or ionophore A23187 (2 microM). However, when the cell suspensions were stimulated with both AA and A23187, the cells produced HHT, leukotriene (LT) B4, and 5S-hydroxy-6,8,11,14-eicosatetraenoic acid, whereas LTC4, D4, and E4 were undetectable. Similarly, alveolar macrophages stimulated with A23187 produced HHT, 5-hydroxy-6,8,11,14-eicosatetraenoic acid, and LTB4 but no peptido-leukotrienes. When LTA4 was added to suspensions of eosinophils and macrophages, only LTB4 was formed, whereas in parallel experiments, intact human platelets incubated with LTA4 produced LTC4. These data suggest that guinea pig alveolar eosinophils and macrophages contain both cyclooxygenase and 5-lipoxygenase, but do not produce peptido-leukotrienes, probably lacking LTA4 glutathione transferase activity. These studies demonstrate that guinea pig eosinophils differ from eosinophils of other animal species which have been shown to be major sources of leukotriene C4. The present data imply that eosinophils and macrophages are not the source of peptido-leukotrienes in anaphylactic guinea pig lungs.     

Total DNA 5-methylcytosine level of rice calli derived from protoplasts is independent of regeneration ability

To study the roles of m⁵C in the differentiation of rice calli derived from protoplasts (protoclones), the m⁵C level of the total DNA was analyzed using the³²P post-labeling method. The level of m⁵C in regenerable and nonregenerable protoclones was similar, as was in calli and leaves of plants regenerated from the same protoclones. Treatment with 0.5 mM 5-azacytidine caused significant reduction of the level of m⁵C and of the regeneration frequency of callus. Significantly increased m⁵C levels were observed during prolonged culture.