Adenosine diphosphoribosylation of certain basic chromosomal proteins in isolated trout testis nuclei.

Isolated trout testis nuclei rapidly incorporate [alpha-32P]NAD+ into chromosomal proteins. Three proteins, very-lysine-rich histone (H1), a specific trout chromosomal protein (H6) and the sperm-specific protamines, incorporate the label as adenosine diphosphoribosyl (ADP-Rib) residues. No significant labeling of the nucleosomal 'core' histones H2A, H2B, H3 and H4 was observed. The linkage of the [32P](ADP-Rib) residues to each protein was very labile at pH values greater than 7.0 but by working at acidic pH and low temperatures the ADP-Rib label could be shown to be covalently bound to protein by gel electrophoresis and ion-exchange chromatography. The [32P]ADP-Rib chains could be removed by digestion with snake venom phosphodiesterase with the formation of AMP and phosphoribosyl-AMP.     

Effects of low-chloride solutions on action potentials of sheep cadiac purkinje fibers

The rapid repolarization during phase 1 of the action potential of sheep cardiac purkinje fibers has been attributed to a time- and voltage-dependent chloride current. In part, this conclusion was based on experiments that showed a substantial slowing of phase 1 when larger, presumably impermeant, anions were substituted for chloride in tyrode’s solution. We have re- examined the electrical effects of low-chloride solutions. We recorded action potentials of sheep cardiac purkinje fibers in normal tyrode’s solution and in low-chloride solutions made by substituting sodium propionate, acetylglycinate, methylsulfate, or methanesulfonate for the NaCl of Tyrode’s solution. Total calcium was adjusted to keep calcium ion activity of test solutions equal to that of control solutions. Propionate gave qualitatively variable results in preliminary experiments; it was not tested further. Low-chloride solutions made with the other anions gave much more consistent results: phase 1 and the notch that often occurs between phases 1 and 2 were usually unaffected, and the action potential duration usually increased. The only apparent change in the resting potential was a transient 3-6 mV depolarization when low-chloride solution was first admitted to the chamber, and a symmetrical transient hyperpolarization when chloride was returned to normal. If a time- and voltage-dependent chloride current exists in sheep cardiac purkinje fibers, our results suggest that it plays little role in generating phase 1 of the action potential.     

Number of ovarioles and fecundity in the black bean aphid, Aphis fabae

The number of ovarioles in the gonads of the host alternating aphid, Aphis fabae Scop., is not constant. The apterous generations on spindle, emigrants and initial apterous colonists of the secondary host each have a characteristic range of number of ovarioles; subsequent generations in the yearly life cycle have twelve, except for alate exules which have a range and the lowest average number of ovarioles. Ovariole number is programmed and is not a function of adult weight or food quality. The generations with the largest number of ovarioles have the greatest fecundity, highest reproductive rate and smallest offspring, and develop early in the season when the environment is favourable. Later generations have a low fecundity and proportionately more fat, a possible adaptation to the harsher environment these aphids experience.

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Zusammenfassung Die Anzahl der Ovariolen in den Eierstöcken ist bei der wirtswechselnden Bohnenlaus, Aphis fabae, nicht konstant. Bei Läusen der ungeflügelten Generationen auf Pfaffenhütchen, sowie bei Migrantes und den ersten apteren Aphiden auf dem Sekundärwirt variiert die Anzahl der Ovariolen in einem charakteristischen Bereich. Die folgenden Generationen im jährlichen Zyklus haben stets zwölf Ovariolen, ausgenommen alate Exsules, bei denen ebenfalls ein charakteristischer Bereich nachzuweisen war, allerdings mit einem sehr niedrigen Durchschnitt. Die Anzahl der Ovariolen ist programmiert. Ihre Anzahl ist konstant und nicht vom Gewicht der Imagines oder der Nahrungsqualität abhängig. Die Generationen mit der höchsten Anzahl von Ovariolen sind am fruchtbarsten, sie haben die höchste Reproduktionsrate und gebären die kleinsten Läuse. Sie entwickeln sich frühzeitig, wenn die Bedingungen günstig sind. Spätere Generationen zeigen eine niedrigere Fruchtbarkeit, lagern jedoch verhältnismäßig mehr Fett ein, wahrscheinlich eine Anpassung an die schlechteren Bedingungen, denen diese Läuse ausgesetzt sind.

     

Comparison of methods for isolation of dematiaceous fungi from nature

Direct plating and animal inoculation techniques were compared for effectiveness in isolating dematiaceous fungi from nature. The direct plating technique involved comparison of aqueous and mineral oil extraction of the samples with subsequent plating on Mycobiotic and Sabhi agar. Twenty four different organisms were recovered from 19 samples using both extraction procedures and both media. Dematiaceous fungi isolated by direct plating were Alternaria alternata, Cladosporium spp., Exophiala jeanselmei, Wangiella dermatitidis and 6 unidentified organisms. Direct plating resulted in more isolations of dematiaceous fungi partly because of the frequent isolations of A. alternata and W. dermatitidis. Both more and a larger variety of organisms were recovered on Mycobiotic than on Sabhi agar. The aqueous extraction of samples resulted in more direct plating isolations of fungi than oil extraction.Only dematiaceous fungi were isolated with the animal inoculation techniques. Fungi isolated from hamsters included Cladosporium spp., Exophiala spinifera, Phialophora verrucosa, Rhinocladiella sp. and 3 unidentified organisms. Fungi isolated by the mouse inoculation technique included Bispora betulina, Cladosporium spp., W. dermatitidis and 1 unidentified organism. In general there was variation in the types of organisms isolated from the same samples depending on the isolation procedure used.     

Taxonomy and morphology of dematiaceous fungi isolated from nature

The Hughes system of classification was applied to the identification of dematiaceous fungi isolated from nature. The majority of the isolates encountered could be identified with this system using brightfield microscopy. However, phase contrast microscopy was needed to determine the mode of conidial ontogeny with some species of Phialophora, Exophiala and Wangiella. The identifications based upon phase contrast microscopy were confirmed using the scanning electron microscope (SEM). Scanning electron photomicrographs are presented for Bispora betulina, Cladosporium trichoides, Exophiala jeanselmei, Phialophora revens, P. verrucosa and Wangiella dermatitidis. SEM observations of W. dermatitidis support the present classification of this organism as proposed by other workers. It is suggested that the Hughes system of classification and phase contrast microscopy be used to facilitate identification of isolates of dematiaceous fungi encountered in the clinical laboratory.     

Aldolase-like imine formation in the mechanism of action of phosphonoacetaldehyde hydrolase.

Phosphonoacetaldehyde hydrolase (EC 3.11.1.1), the bacterial enzyme that catalyses the reaction HCO-CH2-PO(OH)2+H2O leads to HCO-CH3+Pi, is inactivated by borohydride if either phosphonoacetaldehyde or acetaldehyde is present. This supports the suggestion that the substrate forms an imine with an amino group of the enzyme. Such imine formation would labilize the C-P bond in the same way that aldolase and related enzymes labilize C-C and C-H bonds (Scheme 1a).     

The pH-dependence of second-order rate constants of enzyme modification may provide free-reactant pKa values.

1. Reactions of enzymes with site-specific reagents may involve intermediate adsorptive complexes formed by parallel reactions in several protonic states. Accordingly, a profile of the apparent second-order rate constant for the modification reaction (Kobs., the observed rate constant under conditions where the reagent concentration is low enough for the reaction to be first-order in reagent) against pH can, in general, reflect free-reactant-state molecular pKa values only if a quasi-equilibrium condition exists around the reactive protonic state (EHR) of the adsorptive complex. 2. Usually the condition for quasi-equilibrium is expressed in terms of the rate constants around EHR: (formula: see text) i.e. k mod. less than k-2. This often cannot be assessed directly, particularly if it is not possible to determine kmod. 3. It is shown that kmod. must be much less than k-2, however, if kobs. (the pH-independent value of kobs.) less than k+2. 4. Since probable values of k+2 greater than 10(6)M-1.S-1 and since values of kobs. for many modification reactions less than 10(6)M-1.S-1, the equilibrium assumption should be valid, and kinetic study of such reactions should provide reactant-state pKa values. 5. This may not apply to catalyses, because for them the value of kcat./Km may exceed 5 X 10(5)M-1.S-1. 6. The conditions under which the formation of an intermediate complex by parallel pathways may come to quasi-equilibrium are discussed in the Appendix.