Epinephrine: A Potential Neurotransmitter in Retina

Abstract: Dopamine (DA), norepinephrine (NE), and epinephrine (EPI) are present in rat retina. DA is the major catecholamine, whereas NE and EPI represent ∼5% of the DA content. DA is contained in a subpopulation of amacrine cells and has been the subject of numerous studies. We investigated the origin and properties of NE and EPI in retina. Following superior cervical ganglionectomy, there was a decrease in NE content, but no decrease in EPI or phenylethanolamine- N -methyltransferase (PNMT) activity. PNMT in retina has many of the substrate-specificity and inhibitor-sensitivity characteristics of other tissues. Enzyme activity is enhanced in newborn rats by treatment with dexamethasone. Exposure to a lighted environment increases retinal EPI in normal and superior cervical ganglionectomized rats. EPI content increased for more than 2 h in a lighted environment. We conclude that most of the NE is contained within the sympathetic neurons that innervate the eye from the superior cervical ganglion, whereas EPI is contained in retinal elements that are responsive to photic stimulation.     

Neuronal perikarya and astroglia of rat brain: chemical composition during myelination

Cells isolated by a new technique from 10-, 20-, and 30-day-old rat brains have been analyzed for total lipid, cholesterol, galactolipid, individual phospholipids, gangliosides, DNA, and RNA. The lipid composition does not vary appreciably in either neurons or astrocytes during this period of rapid myelination. Moreover, the lipid compositions of the two cell types are surprisingly similar, both having very low galactolipid concentrations, high phospholipid content, and cholesterol concentrations lower than whole brain. Astrocytes have a higher ganglioside content than neuronal perikarya, a finding ascribed to the higher ratio of surface membrane to mass in the astrocytes, and considered as evidence that gangliosides are normal glial constituents. Compared with an average astrocyte, the individual neuron soma has less mass, a lower total lipid content, and a much higher RNA content.     

A collection of maize from Darien,Panama

A collection of maize obtained from the Chocó Indian tribe of Darien, Panama, differs from published accounts of maize reported as typical for the area in size and in methods of cultivation. The collection may represent a segregating population from crosses occurring between the racesChococeño andCoastal Tropical Flint. Implications of this hypothesis with regard to problems of introduction, present geographical occurrence, and transportation of these races by nomadic human vectors are briefly discussed.     

Molecular requirements for T cell activation by the staphylococcal toxic shock syndrome toxin-1

The activation of Ag-specific, Ia molecule-restricted, TCR V beta 3+ T cell clones by staphylococcal toxic shock syndrome toxin-1 (TSST-1), was investigated. The results show that although Ag- and TSST-1-induced activation of T cell clones both require TCR expression and similar biologic activation signals, the Ia molecule requirement for TSST-1 recognition was much less stringent than that observed for antigenic peptide recognition. In addition, T cell clones recognized TSST-1 without processing by APC. These results suggest that the ability of TSST-1 to polyclonally activate T cells is dependent on TCR recognition of the intact toxin molecule bound to a nonpolymorphic region(s) of the Ia molecule resulting in the same activation events induced by Ag recognition.     

Presence of glyoxalase II in mitochondria from spinach leaves: comparison with the enzyme from cytosol

Glyoxalase II has been purified from cytosol and mitochondria of spinach leaves. Electrophoresis and isoelectric focussing have resolved cytosolic and mitochondrial glyoxalase II in multiple forms: pl 5.3, 5.8 and 6.2 (cytosol) and pl 4.8 (mitochondria). The enzyme of both localizations is a monomer showing a relative molecular mass of about 26 kDa. The values of kinetic constants using several glutathione thiolesters as substrates, are similar for the enzymes from cytosol and mitochondria. These results extend also to plant the presence in mitochondria of peculiar forms of glyoxalase II, likewise recently demonstrated in mammalians.     

The fate of the fusarium mycotoxin zearalenone in maize cell suspension cultures

The fusarium mycotoxin zearalenone was transformed in cell suspension cultures of Zea mays giving α- and β-zearalenol and the β-D-glu cos ides of zearalenone and α- and β-zearalenol. The structure of zearalenone-4-β-D-glucopyranoside was determined by liquid — chromatography-mass spectrometry and specific hydrolysis with β-glucosidase. α- and β-zearalenol and their glucosides were identified by co chromatography using tic and HPLC and glucosidase — treatment Up to 50% of the mycotoxin added was bound to a non extractable or “bound” residue fraction. After treating this residue by a sequential cell wall fractionation procedure, zearalenone was found to be bound mainly to starch, hemicellulose, and lignin fractions.     

Polypyrimidine tract sequences direct selection of alternative branch sites and influence protein binding.

IVS1, an intron derived from the rat fibronectin gene, is spliced inefficiently in vitro, involving the use of three alternative branch sites. Mutation of one branch point site, BP3, so as to increase complementarity to U2 snRNA resulted in exclusive use of that site and improved splicing efficiency, indicating that the wild type BP3 site is one determinant of poor IVS1 splicing. Deletions within the polypyrimidine tract had a variable effect on splicing efficiency and altered the pattern of branch site usage. Selection of each branch site was influenced negatively by purine substitutions ca. 20 nucleotides downstream. It is proposed that all three IVS1 branch sites are pyrimidine tract-dependent. Pyrimidine tract deletions also influenced the crosslinking of PTB (the polypyrimidine tract-binding protein), hnRNP C, and splicing factor U2AF65. All three proteins bound preferentially to distinct regions within the polypyrimidine tract and thus are candidates for mediating pyrimidine tract-dependent branch site selection. The findings indicate the complexity of the IVS1 polypyrimidine tract and suggest a crucial role for this region in modulating branch site selection and IVS1 splicing.     

Allozyme diversity in Chinese,Seguin and American chestnut (Castanea spp.)

Allozyme genetic variability in three chestnut (Castanea) species was investigated using 19 loci from ten enzyme systems. G-tests of heterogeneity of isozymic allele distribution showed significant differences between the three species at 15 of the 19 loci, and between the 13 C. mollissima populations at 13 of the 19 loci examined. C. mollissima was found to possess a significantly-higher value of mean gene heterozygosity (H=0.3050±0.0419), the percentage of polymorphic loci (P=84.21%) and the average number of alleles per locus (A=2.05), than any other species in the Castanea section Eucastanon. When the genetic variability of populations of C. mollissima from four regions in China was investigated, the population from the Changjiang river region showed a markedly higher mean gene heterozygosity (H=0.3480±0.0436) than populations from the other regions. Genetic relationships among the four regions were assessed by Nei's genetic identity I and standard genetic distance D. An approximately-identical distance between the population from the Changjiang river region and populations from the three other regions was observed, while populations from the latter regions showed almost the same genetic distance from each other. These data, when considered with information existing prior to this study, contribute to an understanding of the possible origin and progenitor of the chestnut species.