l-threonine production by l-aspartate- and l-homoserine-resistant mutant of Escherichia coli

Summary Growth and l-threonine productivity of l-threonine producer Escherichia coli H-4290 were inhibited by precursor amino acids, l-homoserine and l-aspartate. l-Threonine hyper-producers were isolated among the mutants resistant to l-homoserine and l-aspartate. Mutants H-4351 (Hom^r) and H-4578 (Hom^r, Asp^r) accumulated 22.2 g/l and 24.3 g/l of l-threonine in test tube cultures, while the parental strain H-4290 accumulated 18.2 g/l. The enzyme level of aspartokinase I (first enzyme of the threonine operon) was enhanced 2.3 times (H-4351) and 3 times (H-4578) that of H-4290. Mutant H-4578 accumulated 76 g/l of l-threonine in a 2-l jar fermentor after 75 h cultivation.Abbreviations DAP diaminopimeric acid - Met ^l poor growth in methionine-free medium - AHV -amino--hydroxyvaleric acid - Thr-N^- lack of ability to utilize l-threonine as a nitrogen source - Rif rifampicin - Lys+Met^r resistant to l-lysine and dl-methionine     

Induction of interdigitating reticulum cell-like differentiation in human monocytic leukemia cells by conditioned medium from IL-2-stimulated helper T-cells

Monocytic leukemia (MoL) cells were obtained from the peripheral blood of a patient in whom the leukemic cells infiltrating various lymphoreticular organs exhibited features intermediate between interdigitating reticulum cells (IDC) and ordinary phagocytic macrophages, whereas the leukemic cells in the peripheral blood were essentially monocytic and lacked such features. Peripheral blood CD4+ T-cells were established as an interleukin-2-dependent T-cell line. When the MoL cells were exposed for a few days to conditioned medium from the T-cell line, they extended several dendritic cytoplasmic projections and became intensely positive for HLA-DR antigen, cytoplasmic S-100β protein, and CD1 antigen. Functionally, the conditioned medium significantly down-regulated Fc-mediated and Fc-independent phagocytic activities, and the levels of lysosomal enzymes such as lysozyme and nonspecific esterase in the MoL cells. Moreover, the conditioned medium significantly up-regulated the accessory cell function of the MoL cells as measured by the primary allogenic mixed leukocyte reaction (MLR). Furthermore, the conditioned medium significantly down-regulated the expression of CD14 antigen. Biochemical analysis indicated that the factor responsible for these changes is a protein which is distinct from known human cytokines and whose molecular weight is approximately 31 kDa. These findings suggest that IDC are closely related the monocytic lineage and that helper T-cells play an important role in constructing the microenvironment of T-lymphoid tissues which is necessary for the differentiation and maturation of IDC.     

Maternal care in the red-headed spruce web-spinning sawfly,Cephalcia isshikii (Hymenoptera: Pamphiliidae)

We describe oviposition and maternal behavior in the sawfly Cephalcia isshikiiand examine the adaptive significance of this behavior. Females deposited eggs in a single but loose cluster on needles of terminal twigs of spruces, Piceaspp., and remained with the eggs usually on the underside of the twig facing toward the tip. The female attended her eggs until death without taking food but did not follow the first-instar larvae that moved from natal needles even if she survived until then. When the female was disturbed, she usually moved toward the source and attempted to bite it. Though at much lower frequencies, this aggressive behavior was also observed in gravid females and even in males. Field observations and female removal experiments indicated that the female enhanced the survival of the eggs through the reduction of arthropod prédation.     

Construction of a fusion gene comprising the Taka-amylase A promoter and the Escherichia coli β-glucuronidase gene and analysis of its expression in Aspergillus oryzae

Summary Northern blot analysis of glucose-grown and starch-grown mycelia of Aspergillus oryzae R11340 was conducted using the cloned Taka-amylase A (TAA) gene as a probe. The amount of mRNA homologous to the TAA gene was increased when this fungus was grown with starch as a sole carbon source. In order to analyze the induction mechanism, we inserted the Escherichia coli uidA gene encoding -glucuronidase (GUS) downstream of the TAA promoter and introduced the resultant fusion gene into the A. oryzae genome. Production of a functional GUS protein was induced by starch, but not by glucose. When the effects of various sugars on expression of the fusion gene were examined, the results suggested that the expression of the fusion gene was under control of the TAA gene promoter.     

Destruction and reorganization of the receptor membrane in labellar chemosensory cells of the blowfly. Recovery of responses to sugar after destruction

Recovery from destruction by sodium deoxycholate (DOC) was studied with the receptor membrane of the blowfly, Phormia regina. The recovery can be divided into two processes, colchicine dependent and colchicine independent. The colchicine-dependent process was completely depressed by pretreatment with colchicine at 5 mM for 2 min (partially at 0.1 mM for 10 min), but the colchicine-independent one persisted. Vinblastine also caused depression but lumicolchicine did not. Records of responses obtained from the DOC-treated sugar receptor showed long response latencies that gradually became indistinct with recovery. Colchicine also affected this change in response latency after the DOC treatment. These results suggest that the colchicine-dependent recovery process is related to microtubules in the distal process of the receptor cell. The recovery time course and the change in response latency could be quantitatively explained by the simple assumptions that DOC underwent desorption from the receptor membrane (colchicine-independent recovery process) and that regeneration of the disrupted distal process of the receptor cell accompanied recovery in the number of available receptor sites (colchicine-dependent recovery process).     

Interaction of palytoxin and cardiac glycosides on erythrocyte membrane and (Na+ + K+) ATPase

Palytoxin (PTX), at extremely low concentrations (0.01-1 nM), caused K+ release from rabbit erythrocytes. Among the various chemical compounds tested, cardiac glycosides potently inhibited the PTX-induced K+ release. The order of inhibitory potency (IC50) was cymarin (0.42 microM) greater than convallatoxin (0.9 microM) greater than ouabain (2.3 microM) greater than digitoxin (88 microM) greater than digoxin (90 microM). Their corresponding aglycones, even at 10 microM, did not inhibit the K+ release, but competitively antagonized the inhibitory effect of the glycosides. All these cardiotonic steroids inhibited the activity of (Na+ + K+)-ATPase prepared from hog cerebral cortex in narrow concentration ranges (IC50 = 0.15-2.4 microM), suggesting that the inhibition of K+ release is not related to their inhibitory potency on the (Na+ + K+)-ATPase activity, and the sugar moiety of cardiac glycosides is involved in the inhibition. On the other hand PTX, at higher concentrations (greater than 0.1 microM), inhibited the (Na+ + K+)-ATPase activity. However, this inhibitory effect of PTX was not antagonized by ouabain. It is suggested that, compared with ouabain, PTX has additional binding site(s) on the (Na+ + K+)-ATPase.     

The standardization of the candidate national standard anti-D blood-typing serum with the Groupamatic MG50 system

The utility of the Groupamatic MG50 system for quantitative expression of agglutination in terms of continuous response was studied. By use of the characteristics of the design of this system, in which the change in voltage reflects the degree of agglutination, a linear regression relationship between the log ratio of light flux obtained by transformation of the voltage and the log dilution factor of the serum was demonstrated. The availability of the parallel line assay method to the standardization of the blood grouping antisera was also described.