Purification and characterization of macrolide 2''-phosphotransferase type II from a strain of Escherichia coli highly resistant to macrolide antibiotics

Hyperimmune and high-titered polyclonal pneumococcal antisera, specific for cross-reactive types within groups, were produced in adult rabbits. Purified capsular polysaccharide was injected intravenously into adult rabbits. One week later, these rabbits were given multiple intravenous injections of formalin-inactivated pneumococci of the cross-reactive type by an established method. Each of the resultant antisera were specific for the cross-reactive type indicating that the previous injection of the polysaccharide had induced epitope-specific tolerance. This method was successful for production of antisera against pneumococcal types 6A, 6B, 9N, 9V, 19F and 19A. Polyclonal rabbit pneumococcal antisera have some advantages over murine monoclonal antibodies for serologic studies and this method should be applicable for producing type-specific antibodies to cross-reactive polysaccharides of clinical interest. Further, this method is simpler and generally produces higher titered monovalent (factor) reagents than absorbed antisera.     

The Epstein-Barr Virus BDLF4 Gene Is Required for Efficient Expression of Viral Late Lytic Genes

Epstein-Barr virus (EBV) is a gammaherpesvirus, associated with infectious mononucleosis and various types of malignancy. We focused here on the BDLF4 gene of EBV and identified it as a lytic gene, expressed with early kinetics. Viral late gene expression of the BDLF4 knockout strain was severely restricted; this could be restored by an exogenous supply of BDLF4. These results indicate that BDLF4 is important for the EBV lytic replication cycle, especially in late gene expression.     

The Association of Ascorbate and Ascorbate Oxidase in the Apoplast with IAA-Enhanced Elongation of Epicotyls from Vigna angularis

The level of (ascorbic acid (AA) plus dehydroascorbic acid (DHA))and the ratio of the level of AA to that of AA plus DHA in intercellularwashing fluid (IWF) of epicotyl segments from Vigna angularisdecreased from 2.8±0.3 to 1.2±0.5nmol (g fr wt)^–1and from 0.23±0.03 to 0.13±0.01, respectively,after incubation of the segments without IAA for 20 h at 27°C.However, these values changed to 5.3±1.7 nmol (g fr wt)^–1and 0.07±0.05 after incubation with 0.1 mM IAA. The activityof cell wall-bound ascorbate oxidase increased by about 20%and 70% after incubation without IAA and with IAA, respectively.However, the activity of cell wall-bound peroxidase was notaffected by incubation with or without IAA. The activities ofascorbate oxidase and peroxidase in IWF decreased by about 85and 75% after incubation without IAA. IAA did not affect thesedecreases to any great extent. A lignin-like compound was formedduring the incubation of epicotyl segments in the absence ofIAA. Formation of this compound was inhibited by IAA. The resultssuggest that one of the causes of the enhancement of elongationgrowth by IAA is the inhibition of peroxidase-dependent lignificationas a result of increases in levels of AA and DHA and in ascorbateoxidase activity. (Received August 16, 1993; Accepted December 6, 1993)     

Ontogenetic change in the relationship between metabolic rate and body mass in a sea bream Pagrus major (Temminck & Schlegel)

Ontogenetic changes in the relationship between resting rate of oxygen consumption and wet body mass were examined at 20° C with the sea bream Pagrus major ranging from 0.00020 g (weight just after hatching) to 270 g (weight at 530 days old). There was a triphasic relationship between oxygen consumption of an individual fish M (μl min⁻¹) and body mass W (g). During a very early stage (weight 0.00020–0.00025 g), corresponding to the pre-larval stage and with the transitional period to the post-larval stage, there was no substantial change in body mass. The mass–specific metabolic rate M/W (μl g⁻¹ min ¹) showed no clear relationship to body mass as expressed by the equation M/ W =4.86 + 1.47 D , where D is age in days. During the post-larval stage (weight 0.00031–0.005 g), M/W remained almost constant independent of body mass following the expression M = 12.5 W0 .949. During the juvenile and later stages (weight 0.005–270 g), M/ W decreased with increasing body mass following the expression M = 6.3 W ^0.821 which is significantly different from the expression for the post-larval stage ( P < 0.001). Ontogenetic changes in the metabolism-body mass relationship are discussed from the viewpoint of relative growth of organs with different metabolic activities.     

Tidal effects on the organic carbon mineralization rate under aerobic conditions in sediments of an intertidal estuary

Laboratory experiments and field measurements were conducted to examine the effect of tide on the organic carbon mineralization rate in sediments under aerobic conditions of an intertidal estuary. Core samples of surface sediments were collected from an intertidal estuary of the Kurose River, Hiroshima, Japan. To mimic low and high tide in the intertidal estuary, organic carbon mineralization rates in the samples were measured in the laboratory under both air-exposed and submerged conditions. Mineralization rates under air-exposed conditions were two to five times higher than those under submerged conditions. Field measurements of the rate of CO₂ emission from the sediment surface revealed a rapid increase in the rate as the sea level fell during ebb tide. The estimated amount of daily organic carbon mineralization assuming a constantly submerged condition was 30% less than that estimated when considering the semi-diurnal fluctuation in sea level. These results indicate that tide has a marked impact on the organic carbon mineralization rate in sediments under aerobic conditions on an intertidal estuary, and tidal effects need to be considered when the amount of mineralized organic carbon is estimated.     

Circular dichroism studies of native and chemically modified Ca2+-dependent protein modulator.

The structural features of the native Ca2+-dependent protein modulator and two chemically modified derivatives, namely, nitrotyrosyl modulator and alkylated modulator, were examined by circular dichroism. The binding of Ca2+ to the native molecule was accompanied by an increase in helical content from 40 to 49%, with little effect on the local environments of aromatic residues in the modulator. The Mg2+ and Mn2+ do not elicit the conformational change induced by the binding of Ca2+, which also stabilizes the modulator against urea denaturation. The overall secondary structure of nitrotyrosyl modulator is indistinguishable from that of the native protein and undergoes a similar conformational change upon binding Ca2+. These observations are in agreement with the fact that nitration has no effect on modulator functions. Furthermore, nitrotyrosyl modulator interacts with troponin I only in the presence of Ca2+, as detected by circular dichroism (cd). On the other hand, alkylation of five methionine residues on the modulator with benzyl bromide affects protein conformation, as evidenced by a reduced helical content of only 35%. Alkylated modulator retains the ability of the native protein to bind Ca2+ although the affinity of this derivative for Ca2+ is reduced some three orders of magnitude relative to the native protein, with Kd = 3.2 X 10(-4) M. The results with the alkylated modulator, in conjunction with previous cd studies on N-chlorosuccinimide oxidized modulator are utilized to advance a model for the Ca2+ activation of modulator protein, based on three conformational states of the molecule.