Enzymatic deconjugation of catecholamines in human and rat plasma and red blood cell lysate

We have developed a method for enzymatic hydrolysis of both sulfated and glucuronidated catecholamines in plasma and red blood cell lysate. Hydrolysis occurs in the course of the radioenzymatic assay for catecholamines. In human plasma, catecholamines are conjugated almost entirely with sulfate while, in rat plasma, glucuronides are the main conjugates of epinephrine and dopamine but not norepinephrine. Rat plasma contains less percent conjugated catecholamine than human plasma. Human red blood cell lysate contains less conjugated catecholamine than plasma, whereas free E in lysate exceeds that of plasma and free NE has same level both in plasma and lysate. This method is useful in detecting total (free + sulfated + glucuronidated) catecholamines and the nature of conjugated catecholamines.     

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.     

Stimulation of Free Fatty Acid and Diacylglycerol Accumulation in Cerebrum and Cerebellum During Bicuculline-Induced Status Epilepticus. Effect of Pretreatment with α-Methyl-p-Tyrosine and p-Chlorophenylalanine

The pool size and composition of free fatty acids (FFA) and diglycerides (DG) from the cerebrum and cerebellum of rats undergoing bicuculline-induced seizures were studied. A fourfold increase in cerebral FFA occurred 3-4 min after bicuculline injection; arachidonic and stearic acids were the principal fatty acids accumulated. Cerebellar FFA also increased, but to a lesser extent. An increased production of arachidonic acid took place in the cerebrum as a function of time after bicuculline injection. Other fatty acids produced were oleic, palmitic, and docosahexaenoic acids. A twofold increase in cerebral arachidonic acid was seen at the time of the first generalized tonic-clonic convulsion. However, a 13- to 17-fold increase in arachidonic acid was seen approximately 5-6 min after bicuculline injection. The rise in other FFA was much smaller. Stearoyl- and arachidonoyl-DG were also accumulated. The drug alpha-methyl-p-tyrosine was found to (a) potentiate the bicuculline-stimulated release of cerebellar FFA, and (b) inhibit by 70% the production of stearoyl- and arachidonoyl-DG in the cerebrum and cerebellum. Basal production of FFA was stimulated by p-chlorophenylalanine, but the drug had no effect on the bicuculline-induced changes. Hydrolysis of phospholipids enriched in stearoyl-arachidonoyl groups, such as phosphatidylinositol of excitable membranes, may be stimulated during seizures.     

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.