Changes in the Activity of the Maturation-Promoting Factor Are Correlated with Those of a Major Cyclic AMP and Calcium-Independent Protein Kinase During the First Mitotic Cell Cycles in the Early Starfish Embryo

Many studies suggest that MPF activation depends on protein phosphorylation or that MPF is itself a protein kinase. In the present report, cyclic variations of MPF activity have been correlated in vivo with changes in the extent of protein phosphorylation or in vitro with changes of a major protein kinase during the first cell cycles of fertilized starfish eggs. This cycling protein kinase neither requires cAMP nor Ca²⁺. Neither colchicine nor aphidicoline, which inhibits cleavage and chromosome replication respectively, was found to suppress the synchronous and cyclic variations of both MPF and protein kinase activities. Protein synthesis was found to be required for both MPF and protein kinase activities to reappear after their simultaneous drop at the time of mitotic or meiotic cleavages. Production of either MPF or protein kinase activities is not the immediate result of protein synthesis since there is a delay at each cell cycle between the time when protein synthesis is required and the time when both MPF and protein kinase activities are produced. This suggests that both MPF and protein kinase activities might involve some post-translational modification of a precursor protein synthesized during the preceeding cell cycle.     

Rapid determination of antimicrobial susceptibility patterns ofListeria monocytogenes isolates by the autobac AIS and MIC procedures

A total of 34 isolates ofListeria monocytogenes were tested against ampicillin, cephalothin, chloramphenicol, erythromycin, tetracycline, and penicillin-G using the Autobac 3-h AIS and the Autobac 5-h MIC procedures. The results were compared to susceptibility category interpretations and MICs determined using the Sceptor system. With the Sceptor System, all isolates were interpreted to be moderately susceptible to ampicillin and penicillin-G, and susceptible to the four other antibiotics. With the Autobac AIS, all isolates were interpreted to be susceptible to all the antibiotics except penicillin-G. All but one of the 34 isolates were interpreted to be resistant to penicillin-G with the Autobac AIS test. The remaining isolate was interpreted to be indeterminant. The Autobac AIS test was unsatisfactory for determining the susceptibility ofL. monocytogenes isolates to penicillin-G. The Autobac MIC results correlated well with the MIC results of the Sceptor system provided that the Autobac was programmed as though it were testing enterococci. The Autobac MIC reported penicillin-G MICs in units per milliliter and required the use of a conversion factor to obtain micrograms per milliliter, and did not allow for the testing of erythromycin. The Autobac MIC susceptibility category interpretations must not be used, as they were derived from an outdated susceptibility standard. The Autobac MIC test may be used if the limitations given above are observed.     

中国平脉树螽属五新种记述：直翅目：螽斯科：树螽亚科

本文报道中国平脉树螽属5个新种。每个新种皆有详细的形态描述和形态特征图。所有模式标本存于北京农业大学昆虫标本室。     

Synthesis and secretion of mucous glycoprotein by the gill of Mytilus edulis. I. Histochemical and chromatographic analysis of [14C]glucosamine bioincorporation

The ability of the isolated gill epithelium of Mytilus edulis to incorporate [14C]glucosamine as a precursor in the biosynthesis and secretion of mucous glycoproteins was investigated. Localization of mucous cells in the gill filament was achieved using histochemical staining techniques. Mucus cells containing neutral and acidic mucins were found in the lateral region, whereas mucus cells containing primarily neutral or sulfated mucins were found in the abfrontal region. Autoradiographic results showed that in both regions, the mucous cells were rich in content of the incorporated radiolabel. The secreted glycoproteins containing the incorporated radiolabel were analyzed by column chromatography using Bio-Gel P-2 and P-6. Two populations of the glycoproteins differing in molecular size were isolated. Upon alkaline reductive borohydride cleavage of the O-glycosidic linkages of the high molecular weight protein, about 70% of the radiolabel and 85% of the carbohydrate content were removed from the protein. The alkaline borohydride cleavage resulted in the formation of at least six oligosaccharide chains of various lengths of sugar units. Gas chromatographic analysis of the carbohydrate composition shows that the glycoproteins contain N-acetylglucosamine, N-acetylgalactosamine, and galactose, fucose, and mannose as the neutral monosaccharides. The above results indicate that the isolated gill epithelium of M. edulis is capable of incorporating [14C]glucosamine in the synthesis of secretable mucin-type glycoproteins.     

Binding mode transitions of Escherichia coli single strand binding protein-single-stranded DNA complexes. Cation, anion, pH, and binding density effects

We have extended our investigations of the multiple binding modes that form between the Escherichia coli single strand binding (SSB) protein and single-stranded DNA (Lohman, T. M. & Overman, L. B. (1985) J. Biol. Chem. 260, 3594-3603; Bujalowski, W. & Lohman, T. M. (1986) Biochemistry 25, 7799-7802) by examining the effects of anions, pH, BaCl2, and protein binding density on the transitions among these binding modes. "Reverse" titrations that monitor the quenching of the intrinsic tryptophan fluorescence of the SSB protein upon addition of poly(dT) have been used to measure the apparent site size of the complex at 25 degrees C in pH 8.1 and 6.9 as a function of NaF, NaCl, NaBr, and MgCl2 concentrations. Under all conditions in which "reverse" titrations were performed, we observe three distinct binding modes with site sizes of 35 +/- 2, 56 +/- 3, and 65 +/- 3 nucleotides/SSB tetramer; however, the transitions among the three binding modes are strongly dependent upon both the cation and anion valence, type, and concentration as well as the pH. A net uptake of both cations and anions accompanies the transitions from the (SSB)35 to the (SSB)56 binding mode at pH 6.9, whereas at pH 8.1 this transition is anion-independent, and only a net uptake of cations occurs. The transition from the (SSB)56 to the (SSB)65 binding mode is dependent upon both cations and anions at both pH 6.9 and 8.1 (25 degrees C), and a net uptake of both cations and anions accompanies this transition. We have also examined the transitions by monitoring the change in the sedimentation coefficient of the SSB protein-poly(dT) complex as a function of MgCl2 concentration (20 degrees C, pH 8.1) and observe an increase in s20,w, which coincides with the increase in apparent site size of the complex, as measured by fluorescence titrations. The frictional coefficient of the complex decreases by a factor of two in progressing from the (SSB)35 to the (SSB)65 binding mode, indicating a progressive compaction of the complex throughout the transition. The transition between the (SSB)35 and the (SSB)56 complex is dependent on the protein binding density, with the lower site size (SSB)35 complex favored at higher binding density. These results indicate that the transitions among the various SSB protein-single-stranded DNA binding modes are complex processes that depend on a number of solution variables that are thermodynamically linked.(ABSTRACT TRUNCATED AT 400 WORDS)     

Changes in Abscisic Acid Content in Axis and Cotyledons of Developing Phaseolus vulgaris Embryos and their Physiological Consequences

Prevost, I. and Le Page–Degivry, M. Th. 1985. Changesin absicisic acid content in axis and cotyledons of developingPhaseolus vulgaris embryos and their physiological consequences.—J.exp. Bot. 36: 1900–1905.Changes in abscisic acid (ABA)content with time were measured in embryonic axes and in cotyledonsof Phaseolus vulgaris embryos using a radio–immunoassay.During embryogenesis, a similar pattern was observed in bothtissues: ABA increased to a maximum 29 d after an thesis, followedby a decrease as the seed matured. The level of ABA in the cotyledonswas always much higher than that in the axes. In in vitro cultures,the duration of the lag phase before germination of isolatedembryonic axes increased with ABA content. The presence of cotyledonsalways lengthened the lag phase; longer lag phases were associatedwith greater concentrations of ABA in the cotyledons. Moreoverthe presence of cotyledons stimulated the growth of seedlings. Key words: ABA distribution, embryo maturation, axis and embryo germinability