Effect of b-c1-site inhibitors on the midpoint potentials of mitochondrial cytochromes b

Anaerobic potentiometric titrations of b cytochromes have been carried out in beef heart submitochondrial particles in the presence of several specific inhibitors of electron transfer through the b-c1-site of the respiratory chain. Whereas antimycin shows no significant effect on the titration curve of cytochrome b-562, NoHOQnO is found to shift the Em of b-562 by 20-30 mV to the positive. Funiculosin raises the Em of b-562 by greater than 100 mV and also appears to bring about a minor shift of b-566 midpoint potential. In the presence of myxothiazol, both b cytochromes titrate with Em values 15-30 mV more positive than in the control.     

Passive Avoidance Training Increases Fucokinase Activity in Right Forebrain Base of Day-Old Chicks

Fucokinase (EC 2.7.1.52) activity was estimated in supernatants of homogenate from day-old chick forebrain. Enzyme kinetic studies gave a Km of 4.5 X 10(-6) M and Vmax of 3.72 nmol fucose converted into fucose-1-phosphate/mg prot/h. The pH optimum was 7.5. The enzyme is thus considerably more active than was reported for other species and tissues. There were no differences in enzyme activity between the four forebrain regions studied. One hour after chicks were trained on a one-trial passive avoidance learning paradigm, enzyme activity in the right forebrain base increased 14% over control values (p less than 0.02). The 11.3% increase in activity in the left forebrain base and 10.3% increase in the left roof were not statistically significant. The relationship of this change to the increased fucose incorporation into glycoproteins known to occur over a similar time period and the significance of the lateralization of the increase are discussed.     

Irreversible Activation of the Opiate Receptor of Neuroblastoma × Glioma Hybrid Cells by an Alkylating Benzomorphan Derivative

The benozomorphan derivative (-)-2-[2-(p-bromoacetamidophenyl)ethyl]-5,9 alpha-dimethyl-2'-hydroxy-6,7-benzomorphan (BAB), capable of reacting with nucleophilic groups, acts on neuroblastoma X glioma hybrid cells as a potent, irreversible opiate agonist. Its potency in inhibiting the increase in cellular cyclic AMP, evoked by prostaglandin E1, is comparable to that of Leu-enkephalin. This also applies to its capacity to compete with [3H]D-Ala2-Met-enkephalinamide ([3H]DAEA) in binding on cell membrane preparations. The comparatively lower potency of (-)-2-[2-(p-acetamidophenyl)-ethyl]-5,9 alpha-dimethly-2'-hydroxy-5,7-benzomorphan (AB), which differs from BAB in the substitution of the bromoacetamido group by an acetamido group, is of the same order of magnitude as that of morphine. The covalent interaction of BAB with the opiate receptors is deduced from the observations that (1) it is not possible to wash away this compound from the receptors, (2) the potency of BAB in inhibiting the specific binding of [3H]DAEA increases with prolonged preincubation time, and (3) AB behaves as a reversible agonist.     

Determination of the region of rDNA involved in polytenization in salivary glands of Drosophila hydei

During the formation of polytene chromosomes in salivary glands of Drosophila hydei, the genes for ribosomal RNA (rDNA) are underreplicated relative to the rest of the genome. We have measured the number of rRNA genes with and without intervening sequences (ivs+ and ivs- genes) in polytene chromosomes of different genotypes. In the group of genotypes having a large number of ivs- rRNA genes polytenization only occurs within the cluster of ivs- genes. In each of these genotypes rDNA polytenization reaches a constant level of 150 ivs- genes per two chromatid sets (2C); X/X constitutions having two nucleolus organizers (NOs) in the diploid set polytenize the same amount of rDNA as X/O constitutions. In the group of genotypes with small ivs- gene numbers, the rDNA region involved in polytenization is longer and has an average length of 1,700 kb per NO, which is constant in these genotypes. Polytenization of rDNA is extended into the cluster of ivs+ genes, in spite of the fact that these genes appear to be nonfunctional. The smaller the number of ivs- genes, the greater the number of ivs+ genes that are polytenized in the NO. In these genotypes, X/X females replicate twice as much rDNA as X/O males, suggesting that both NOs of the diploid set are polytenized. A comparison of the pattern of spacer length heterogeneity in hybrids between different stocks also demonstrates that both NOs are replicated during polytenization.     

Ontogeny of the photoreceptors in the embryonic retina of the viviparous guppy,Poecilia reticulata P. (Teleostei)

Summary Ultrastructural analyses of retinal development in the guppy embryo show that at midgestation all types of photoreceptors are differntiated in the fundus, and at birth differentiation extends over the whole retina. Formation of discs of outer segments is more rapid in rods than in cones. Double cones differentiate simultaneously with long single cones and are formed by the adhesion of two primordial inner segments; short single cones develop last. Wherever cones are differentiated, they are arranged in an adult-type square mosaic. The rods in the embryo, as opposed to the adult, are likewise regularly arranged within the mosaic unit.These results are at variance with the generally held opinion that adult teleosts which possess duplex retinae have larvae with pure cone retinae, and that rods, double cones and mosaics appear in late larval life or only at metamorphosis.In the double cones of the guppy embryo subsurface cisternae develop along the adjoining primordial inner segments. Additionally, regularly distributed subsurface cisternae are formed in the regions of intimate contact of long single cones with double cones and rods.We suggest that the early development of rods and double cones, and a square-mosaic with regular distribution of rods and subsurface cisternae, provide the newly born with a fully functional optical apparatus, especially suited to perception of movements. This is necessary for its survival against predatory, especially maternal, attacks.This work was in part subsidized by a grant from the Medical Research Council of Ireland to Y.W.K.     

Mechanical Method of Inoculating Plates for Antibiotic Sensitivity Testing

A mechanical method of inoculating culture plates for antibiotic sensitivity testing is described. This method, which involves the use of a modified laboratory centrifuge, is rapid and provides a homogeneous distribution of organisms.     

Inheritance of the allele Pr of the red cell acid phosphatase (EC. 3.1.3.2) in a Caucasian family

Summary The occurrence of the allele P^r showing an unexpected atypical isozyme band pattern in a Caucasian family is reported.