Neuron differentiation and axon growth in the developing wing of Drosophila melanogaster

Sensory neurons in the wing of Drosophila originate locally from epithelial cells and send their axons toward the base of the wing in two major bundles, the L1 and L3 nerves. We have estimated the birth times of a number of identified wing sensory neurons using an X-irradiation technique and have followed the appearance of their somata and axons by means of an immunohistochemical stain. These cells become immunoreactive and begin axon growth in a sequence which mirrors the sequence of their birth times. The earliest ones are born before pupariation and begin axonogenesis within 1 to 2 hr after the onset of metamorphosis; the last are born and differentiate some 12 to 14 hr later. The L1 and L3 nerves are formed in sections, with specific neurons pioneering defined stretches of the pathways during the period between 0 and 4 hr after pupariation (AP), and finally joining together around 12 hr AP. By 16 hr AP the adult complement of neurons is present and the adult peripheral nerve pattern has been established. Pathway establishment appears to be specified by multiple cues. In places where neurons differentiate in close proximity to one another, random filopodial exploration followed by axon growth to a neighboring neuron soma might be the major factor leading to pathway construction. In other locations, filopodial contact between neighboring somata does not appear to occur, and axon pathways joining neural neighbors by the most direct route are not established. We propose that in these cases additional factors, including veins which are already present at the time of axonogenesis, influence the growth of axons through non-neural tissues.     

Intraneuronal amyloid precursor protein (APP) and appearance of extracellular β‐amyloid peptide (aβ) in the brain of aging kokanee salmon

Antibodies to human amyloid precursor protein (APP₆₉₅) and beta‐amyloid peptide (Aβ_1‐42) were used to determine timing of amyloidosis in the brain of kokanee salmon (Oncorhynchus nerka kennerlyi) in one of four reproductive stages: immature (IM), maturing (MA), sexually mature (SM), and spawning (SP), representing a range of aging from somatically mature but sexually immature to spawning and somatic senescence. In IM fish, immunoreactive (ir) intracellular APP occurred in 18 of 23 brain regions. During sexual maturation and aging, the number of neurons expressing APP increased in 11 of these APP‐ir regions. Aβ‐ir was absent in IM fish, present in seven regions in MA fish, moderately abundant in 15 regions in SM fish, and was most abundant in all brain regions of SP fish exhibiting Aβ‐ir. Intracellular APP‐ir was observed in brain regions involved in sensory integration, olfaction, vision, stress responses, reproduction, and coordination. Intra‐ and extracellular Aβ_1‐42 immunoreactivity (Aβ‐ir) was present in all APP‐ir regions except the nucleus lateralis tuberis (hypothalamus) and Purkinje cells (cerebellum). APP‐ir and Aβ deposition increase during aging. APP‐ir is present in IM fish; Aβ‐ir usually appears first in MA or SM fish and increases in SM fish as does APP‐ir. Extracellular Aβ deposition dramatically increases between SM and SP stages (1–2 weeks) in all fish, indicating an extremely rapid and synchronized process. Rapid senescence observed in pacific salmon could make them a useful model to investigate timing of amyloidosis and neurodegeneration during brain aging. © 2002 Wiley Periodicals, Inc. J Neurobiol 53: 11–20, 2002     

The effect of sodium chlorate and nitrapyrin on the nitrification mediated nitrosation process in soils

Summary The influence of total nitrification to nitrate or partial nitrification to nitrite on the soil organic nitrogen status was examined. NH ₄ ⁺ –¹⁵N was added to the soil in the absence and the presence of NaClO₃, respectively nitrapyrin. The first chemical inhibits only nitrate formation, the second inhibits total nitrification. The accumulation of nitrite nitrogen in the soil at levels up to 5 mg kg^–1 increased the loss of nitrogen. Yet, it did not increase the binding of mineral nitrogen into soil organic matter, relative to the control soil. The data suggest that the biochemistry of the nitrite formation process, rather than the levels of nitrite ions formed, are of primary importance in the role of nitrification mediated nitrosation of soil organic matter.     

Specific localization of 2′,3′-cyclic nucleotide 3′-phosphohydrolase, (Ca2+/Mg2+)-ATPase,and acetylcholinesterase in human erythyrocyte membrane

A procedure was developed for the detection of 2′,3′-cyclic nucleotide 3′-phosphohydrolase in myelin. This assay was sufficiently sensitive to detect the low levels of 2′,3′-cyclic nucleotide 3′-phosphohydrolase in human erythrocytes. The 2′,3′-cyclic nucleotide 3′-phosphohydrolase of human erythrocytes was determined to be exclusively associated with the inner (cytosolic) side of the membrane. Leaky ghostsand resealed ghosts were assayed for 2′,3′-cyclic nucleotide 3′-phosphohydrolase, (Ca²⁺/Mg²⁺-ATPase, and acetylcholinesterase activity, and the 2′,3′-cyclic nucleotide 3′-phosphohydrolase profile is the same as that of the (Ca²⁺/Mg²⁺)-ATPase, an established inner membrane maker.     

Alcohol dehydrogenase isozymes in the mouse: Genetic regulation, allelic variation among inbred strains and sex differences of liver and kidney A2 isozyme activity

Genetic analysis of a proposed cis-acting temporal locus ( Adh-3t ), which regulates alcohol dehydrogenase C₂ (ADH-C₂) acitivity in mouse epididymis extracts, among F₁ (ddN × BALB/c) × ddN male backcross progeny provided evidence for genetic distinctness between the structural ( Adh-3 ) and temporal ( Adh-3t ) loci on chromosome 3. Genetic analysis also confirmed the close, linkage of Adh-1 (encoding liver and kidney ADH-A₂) and Adh-3 (encoding stomach ADH-C₂) to within 0.3 centimorgans on the mouse genome. Evidence is presented for a proposed closely linked cis-acting temporal locus (designated Adh-1t ) for the A₂ isozyme (encoded by Adh-1 ) controlling the activity of this enzyme in mouse kidney extracts, but having no apparent affect on liver and intestine ADH-A₂ activities. An extensive survey of the distribution of Adh-1, Adh-3 and Adh-3t alleles among 65 strains of mice is reported — with the exception of two Japanese strains (ddN and KF), linkage disequilibrium between Adh-3 and Adh-3t was observed. Sex differences in mouse liver and kidney ADH-A₂ activities were observed, with male/female ratios of approximately 0.6 and 3 respectively for these tissue extracts.     

Origin of bombesin-like peptides in human fetal lung

Four different forms of bombesin-like immunoreactive peaks were detected in extracts of human fetal lung by the use of reversed-phase high performance liquid chromatography (HPLC). Peaks I, II, III and IV, (increasing retention time), were eluted using a 14-38% of acetonitrile gradient containing 0.1% trifluoroacetic acid (TFA). Peak II was the major material found in the extract of human fetal lung obtained at 16-20 weeks gestation. None of the four compounds contained in the eluted peaks had the same retention time as amphibian bombesin or porcine gastrin releasing peptide (GRP). On reversed-phase HPLC using two different solvent systems TFA or heptafluorobutyric acid (HFBA) as a hydrophobic counter ion, and in gel filtration chromatography, the chromatographic behavior of the main peak (peak II) was the same as that of the carboxyl terminal fragments of GRP, GRP18-27 or GRP19-27. This suggested that the peptide(s) in peak II resembled in composition the carboxy terminal 9 or 10 amino acids of porcine GRP. Following tryptic digestion the material in peak IV was converted to the more polar compound present in peak II. Two other peptide peaks were eluted close to peak II and these were presumed to be a modification of this main peak. One of the possible biosynthetic steps in the formation of bombesin-like peptides in human fetal lung could be a tryptic conversion of a less polar peptide to a more polar form (peak IV to II).     

Sample preparation and high-resolution separation of mycotoxins possessing carboxyl groups

The chromatographic analysis of carboxyl-containing mycotoxins, such as fumonisin B₁, ochratoxin A, and citrinin, presents a continual challenge. Toxins must first be extracted from foods or tissues and then cleaned up before chromatographic separation and detection. Liquid–liquid extraction efficiencies for some carboxylic mycotoxins are marginal for spiked samples and uncertain for incurred residues. Immunoaffinity columns may be useful for concentrating mycotoxins from samples before chromatography. In almost every case, more than one analytical method must be used to confirm the identification of the mycotoxin. The fumonisins are especially troublesome to analyze because they are relatively insoluble in organic solvents, they are not separated easily by gas chromatography, and they do not respond to the usual absorbance or fluorescence detectors used in liquid chromatography. Fluorescence derivatization and electrospray liquid chromatography–mass spectrometry have now made it possible to detect trace levels of mycotoxins. The purity of mycotoxin standards for toxicological studies can be determined by liquid chromatography with either an evaporative light scattering detector or electrospray mass spectrometer. New developments in capillary electrophoresis, nonporous microsphere liquid chromatography, and detection methods for low-volatility compounds show promise for improving the analysis of mycotoxins in the future.