Direct radioimmunoassay of estradiol-17β in defatted bovine milk

A radioimmunoassay was developed for rapid determination of estradiol-17β concentrations in unextracted defatted bovine milk. The assay was dependent on the use of a highly specific anti-estradiol-17β antiserum. Application of a formula to correct for the interference associated with individual milk samples and use of appropriate assay blanks facilitated interpolation on a buffer standard curve. The assay offered a high degree of sensitivity (0.6pg/ml milk) and a precision (within-assay coefficient of variation: 0.196; between-assay CV:0.191) comparable with contemporary extraction methods.     

Amine modulation of the neurogenic Limulus heart

(1) The biogenic amines octopamine (OCT), dopamine (DA), epinephrine (E), and norepinephrine (NE) cause dose-dependent increases in both the rate and amplitude of contractions of the isolated Limulus heart-cardiac ganglion. Their relative ability to produce this excitation is OCT greater than DA approximately the same as E greater than NE. (2) The excitatory effects of all these amines are antagonized by the alpha-adrenergic blocker phentolamine and the dopaminergic antagonist haloperidol. The beta-adrenergic antagonist dichloroisoproterenol slightly reduces amine excitation, but is also a partial agonist. The beta-adrenergic antagonist propanolol, the alpha-blocker phenoxybenzamine, and the serotonin antagonist metergoline are ineffective. (3) In addition to their excitatory effects, DA and, to a lesser extent, NE initially reduce contraction rate and amplitude. (4) The transient inhibition is eliminated selectively by metergoline and is unaffected by the other antagonists. (5) The amines all increase the frequency of cardiac ganglion electrical bursting activity, whether ganglia are isolated or attached to cardiac muscle. Dopamine and NE also transiently inhibit the cardiac ganglion. (6) The amines do not alter myocardial resting tension, contractility, or membrane potential. (7) These amines appear to exert their modulatory effects on Limulus heart by altering the properties of the neurons which comprise its cardiac ganglion.     

Detection and characterization of agarose-binding, capsid-like particles produced during assembly of a bacteriophage T7 procapsid.

It has previously been shown that: (i) during infection of its host, the DNA bacteriophage T7 assembles a DNA-free procapsid (capsid I), a capsid with an envelope differing physically and chemically from the capsid of the mature bacteriophage, and (ii) capsid I converts to a capsid (capsid II) with a bacteriophage-like envelope as it packages DNA. Lysates of phage T7-infected Escherichia coli contained a particle (AG particle) which copurified with capsid II during buoyant density sedimentation, velocity sedimentation, and solid support-free electrophoresis, but was distinguished from capsid II by its apparent diversity during electrophoresis in agarose gels. Treatment of AG particles with trypsin converted most of them to particles that comigrated with trypsin-treated capsid II during electrophoresis in agarose gels. Irreversible binding of AG particles to agarose gels was shown to contribute to the apparent diversity of AG particles during agarose gel electrophoresis. The results of quantitation of AG particles and of capsid I and capsid II in lysates of a nonpermissive host infected with T7 amber mutants suggested that, in site of their capsid II-like properties, most AG particles were produced during assembly of capsid I and not during DNA packaging. The presence of AG particles in T7 lysates explains contradictions in previous data concerning the pathway of T7 assembly.     

Function of an internal bacteriophage T7 core during assembly of a T7 procapsid.

A DNA-free, proteinaceous procapsid of bacteriophage T7 (capsid I) has been shown in previous studies to consist of an external, spherical shell (envelope) and an internal, cylindrical core with fibrous projections that connect the core to the envelope. To determine the role of the core in assembly of the envelope of capsid I, the kinetics of appearance of capsid I and possible intermediates in capsid I assembly (AG particles) were determined in the presence and absence of the core. For obtaining these data, agarose gel electrophoresis was used and appeared to be a technique more accurate and efficient than techniques used for obtaining similar data in the past. The results of these experiments were: (i) in the presence of the core, AG particles behaved kinetically as intermediates in the assembly of capsid I; (ii) in the absence of the core, assembly of capsid I terminated prematurely and AG particles accumulated. These and other data have been interpreted by assuming that: AG particles are breakdown products of precursors of capsid I; these precursors have uncorrected errors in the assembly of their envelope; and a function of the core is to correct these errors.     

Isolation of an Hfr donor of Pseudomonas aeruginosa PAO by insertion of the plasmid RP1 into the tryptophan synthase gene

Summary A derivative of the IncP-1 plasmid RP1, temperature-sensitive for maintenance, was inserted into the Pseudomonas aeruginosa chromosome by selection for a plasmid marker (carbenicillin resistance) at nonppermissive temperature. In one strain, PAO 1000, the plasmid was stably integrated in the trpA, B gene cluster mapped at 27 min, as shown by the following evidence. (i) Trp⁺ transductants lost all plasmid markers. (ii) Cleared lysates of PAO 1000 showed no plasmid band typical of the autonomous RP1 in agarose gel electrophoresis. (iii) No transfer of carbenicillin resistance by PAO 1000 was detectable. (iv) PAO 1000 mobilised the chromosome from an origin at, or very near, the plasmid insertion site with high frequency (recovery of proximal markers 10^–3 per donor). Matings on the plate with and without interruption of conjugation showed that chromosome transfer was unidirectional. (v) Recombinants from PAO 1000-mediated crosses did not inherit plasmid markers or the trpA, B mutation. A derivative of PAO 1000 was obtained which had lost the Hfr property and all plasmid markers except carbenicillin resistance. This strain (PAO 1001), when carrying the autonomous RP1 plasmid, was capable of unidirectional chromosome mobilisation like PAO 1000, but with 50-fold lower efficiency. We propose that integration of the temperature-sensitive RP1 plasmid in PAO 1000 occurred via transposition of Tnl, the element specifying carbenicillin resistance.     

Systematic variation in amino acid compositions of grass caryopses

Variation in amino acid patterns of 121 species (72 genera) of grass caryopses is extensively consistent with taxonomic groupings. The patterns of pooids and chloridoids are distinguishable from one another and from those of eu-panicoids and andropogonoids; the bamboos, Oryza, Stipeae, Ehrharta and Microlaena, which share certain morphological and anatomical features, also share a characteristic amino acid profile, while profiles of danthonoioids, Triodia and Aristida are clearly non-pooid. Caryopsis amino acid patterns vary independently of photosynthetic pathway. Embryos from taxonomically diverse genera all show very similar amino acid profiles, which differ strikingly from those of the endosperms, and the amino acid patterns of whole caryopses are dominated by their endosperms, which are responsible for the taxonomic variation. ‘Chemical scores’ of the caryopsis proteins, but not total protein contents, correlate to some extent with taxonomic groupings.     

Variations in Kinetic Properties of Ribulose-1,5-bisphosphate Carboxylases among Plants

Studies of ribulose-1,5-bisphosphate (RuBP) carboxylase from taxonomically diverse plants show that the enzyme from C(3) and crassulacean acid metabolism pathway species exhibits lower K(m)(CO(2)) values (12-25 micromolar) than does that from C(4) species (28-34 micromolar). RuBP carboxylase from aquatic angiosperms, an aquatic bryophyte, fresh water and marine algae has yielded consistently high K(m)(CO(2)) values (30-70 micromolar), similar in range to that of the enzyme from C(4) terrestrial plants. This variation in K(m)(CO(2)) is discussed in relation to the correlation between the existence of CO(2)-concentrating mechanisms for photosynthesis and the affinity of the enzyme for CO(2). The K(m)(RuBP) of the enzyme from various sources ranges from 10 to 136 micromolar; mean +/- sd = 36 +/- 20 micromolar. This variation in K(m)(RuBP) does not correlate with different photosynthetic pathways, but shows taxonomic patterns. Among the dicotyledons, the enzyme from crassinucellate species exhibits lower K(m)(RuBP) (18 +/- 4 micromolar) than does that from tenuinucellate species (25 +/- 7 micromolar). Among the Poaceae, RuBP carboxylase from Triticeae, chloridoids, andropogonoids, Microlaena, and Tetrarrhena has yielded lower K(m)(RuBP) values (29 +/- 11 micromolar) than has that from other members of the grass family (46 +/- 10 micromolar).     

Unsaturated fatty acid but not ergosterol is essential for high ethanol production in Saccharomyces

Summary The membrane lipid composition of Saccharomyces was manipulated by growing cells anaerobically with or without ergosterol and unsaturated fatty acid. Cells low in ergosterol but enriched in unsaturated fatty acid residues on membrane phospholipids produced high concentrations, 13–15.5% w/v, of ethanol at substrate conversion efficiencies of around 90%.