Synthesis and storage of a neurohormone in insect brains in vitro

The build-up of neurosecretory material in the median neurosecretory cells and fibre tracts of cultured cockroach brains was demonstrated by staining and bioassay. Examination of the cultured brains by electron microscopy showed active production of neurosecretory granules after 3 days in vitro. The close correlation of the results obtained by these different methods of assay leaves little doubt that a neurohormone is being synthesized and stored.     

Biodistribution and pharmacokinetics of vanadium following intraperitoneal administration of vanadocene dichloride to mice

The biodistribution and pharmacokinetics of vanadium following i.p. administration of vanadocene dichloride (VDC), a representative of a new class of organometallic anticancer agents, is reported for Strain A mice. A convenient flameless atomic absorption spectroscopic assay is described and is used to determine kinetic profiles for vanadium in blood, kidney, liver, small intestine and brain tissue for times up to 24 h after administration. For a VDC dose of 80 mg/kg, vanadium concentration decreases rapidly from both the blood and small intestine, and the data can be fit to a phenomenological exponential function (blood: t1/2 = 118 +/- 43 min; small intestine: t1/2(alpha) = 18.10 +/- 0.14 min, t1/2(beta) = 341 +/- 45 min). In contrast, vanadium accumulates in both the kidney and liver up to a maximal concentration (1.12 +/- 0.06 mM and 0.56 +/- 0.06 mM after 12 and 8 h, respectively), and is then excreted with estimated half-lives of 7.9 +/- 0.7 and 12.1 +/- 0.1 h, respectively. No detectable levels of vanadium are found in the brain tissue over the temporal course of the experiment. These results are compared to previous mammalian studies with cis-dichlorodiammineplatinum(II) (CDDP) and related 'second generation' platinum derivatives; there are both qualitative similarities between the vanadium and platinum systems as well as important quantitative differences.     

Molecular cloning and physical characterization of a Brassica linear mitochondrial plasmid

Summary A linear mitochondrial plasmid reported to be associated with cytoplasmic male sterility in the genus Brassica was analyzed. A protein was found to be associated with the 5 ends of the plasmid. The entire plasmid was cloned by the homopolymer tailing technique via free hydroxyl groups present at its 3 ends. DNA sequence analysis of the cloned plasmid revealed a perfect terminal inverted repeat of 325 base pairs. Southern hybridization and restriction enzyme mapping analysis confirmed colinearity of the native plasmid and the clone, which showed significant homology with organelle DNA but not with nuclear DNA. Under high-stringency hybridization conditions, an internal 4.6 kb fragment of the 11.5 kb plasmid hybridized to the main mitochondrial genome in several species. Although the hybridization signal was weaker, the chloroplast genome also showed homology to the mitochondrial plasmid. The plasmid was undetectable at a molar ratio of less than 1/10 000 of the main mitochondrial genome in some lines of Brassica and Raphanus that contain the Ogura male sterile cytoplasm (cms). The absence of the plasmid in these sterile lines demonstrates that the plasmid is not required for the expression and maternal inheritance of male sterility.     

Sex- and species-related differences in the biotransformation of isosorbide dinitrate by various tissues of the rabbit and rat

The biotransformation of isosorbide dinitrate (ISDN) by various tissues of the rabbit and rat was examined. Incubation of 2 X 10(-7) M ISDN at 37 degrees C with tissue homogenates of liver, lung, kidney, intestine, skeletal muscle, aorta, and erythrocytes from the rabbit and rat resulted in a significant disappearance of ISDN after a 30-min incubation (also, 5-min incubation for liver). The disappearance of ISDN in each tissue homogenate was accompanied by an equimolar production of the mononitrate metabolites, isosorbide-2-mononitrate (2-ISMN) and isosorbide-5-mononitrate (5-ISMN), with the exception of liver homogenates where the loss of ISDN could not be accounted for by mononitrate formation. The relative rate of ISDN disappearance in various tissue homogenates was for the male rabbit, liver greater than lung approximately intestine greater than kidney greater than erythrocytes approximately skeletal muscle approximately aorta; for the female rabbit, liver greater than kidney approximately lung approximately intestine greater than erythrocytes approximately skeletal muscle approximately aorta; and for the male rat, liver greater than intestine greater than erythrocytes greater than skeletal muscle greater than lung approximately kidney. A sex difference in the percent disappearance of ISDN was observed in homogenates of lung and intestine from male and female rabbits. In addition, a sex difference in the ratio of metabolite (2-ISMN/5-ISMN) formed by denitration of ISDN was seen in homogenates of lung, skeletal muscle, and erythrocyte lysate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Organization of hindbrain segments in the zebrafish embryo

To learn how neural segments are structured in a simple vertebrate, we have characterized the embryonic zebrafish hindbrain with a library of monoclonal antibodies. Two regions repeat in an alternating pattern along a series of seven segments. One, the neuromere centers, contains the first basal plate neurons to develop and the first neuropil. The other region, surrounding the segment boundaries, contains the first neurons to develop in the alar plate. The projection patterns of these neurons differ: those in the segment centers have descending axons, while those in the border regions form ventral commissures. A row of glial fiber bundles forms a curtain-like structure between each center and border region. Specific features of the individual hindbrain segments in the series arise within this general framework. We suggest that a cryptic simplicity underlies the eventual complex structure that develops from this region of the CNS.