THE TOXIC EFFECT OF SODIUM GLUTAMATE AND DL-α-AMINOADIPIC ACID ON RAT RETINA: CHANGES IN HIGH AFFINITY UPTAKE OF PUTATIVE TRANSMITTERS

Subcutaneous administration of high doses of sodium glutamate to new born rats was used to destroy retinal interneurons and ganglion cells. Such treatment was accompanied by 90% reduction in the high affinity uptake of choline, 60–70% reductions in the uptakes of GABA, diamino-n-butyric acid and glycine and 30–40% reductions in the uptakes of asparatate and glutamate measured on retinal homogenates from 30-day-old rats. The high affinity uptakes of β-alanine and taurine were unchanged. Preincubation of retinal homogenates with 1 mM β-alanine or 100 μM diamino-n-butyric acid severely reduced the high affinity GABA uptake in control and experimental animals. In intact retinae, however, the glutamate treatment increased the high affinity uptake of β-alanine by 70%, whereas that of diamino-n-butyric acid was reduced by 40% and the high affinity uptakes of GABA and glutamate were unchanged. Four hours after injection of the gliotoxic compound DL-α-aminoadipic acid into the vitreous body of 30-day-old rats, the Müller cells could no longer be identified. This lesion was accompanied by 55% reduction in the high affinity uptake of β-alanine and 25% reduction in the uptakes of GABA and glutamate on intact retinae. The high affinity uptakes of diamino-n-butyric acid, choline and the enzyme activities of choline acetyltransferase and glutamate decarboxylase were unchanged under these conditions. After 24 h, however, the Müller cells could be recognized again, and the β-alanine uptake had normalized.     

Correlations Between Acetylcholinesterase Activity in Guinea-Pig Iris and Pupillary Function: A Biochemical and Pupillographic Study

: Acetylcholinesterase (AChE) in guinea pig iris was inhibited by methylisocyclopentylfluorophosphate (soman) administered topically or parenterally, and enzyme activity was correlated to pupillary diameter by infrared pupillography. After a single topical soman instillation into the conjunctival sac there was an almost linear relationship between the reduction in AChE activity and pupillary diameter. Topical administration of soman at 24-h intervals in doses capable of almost complete inhibition of AChE in iris was accompanied by a reduced miotic effect of this drug. This was indicated by a reduced rate of the soman-induced pupillary constriction, a less pronounced reduction in pupillary diameter, and a more rapid return of the pupillary diameter to normal size. The change in pupillary diameter occurred after three daily administrations and remained constant during 31 days of treatment. These observations were seen irrespective of inhibition of blood AChE. The decrease in response to repeated administration could not be explained by a reduced inhibitory effect of soman on AChE, by a more rapid de novo synthesis of AChE, or by a change in the number of the muscarinic receptors as determined by quinuclidinyl benzilate binding. When soman or DFP was administered subcutaneously in high doses a severe AChE inhibition was obtained in iris without any concomitant miosis.     

Genetic comparison of salmon from the White Sea and north-western Atlantic Ocean

Samples of salmon Salmo salar from the River Kachkovka and the River Nilma in northern Russia were analysed by starch gel electrophoresis and compared to three Norwegian stocks, the Neiden river in northern Norway and Øyreselv and Hopselv rivers on the west coast. The comparison included the following polymorphic loci: AAT-4 *, IDDH-2 *, IDHP-3 *, MDH- 3,4 *, MEP-2 *, ESTD * as well as the newly discovered polymorphic loci FBALD-3 * and TPI-3 *. Samples were run side by side on gels, and the alleles found in the Russian stocks were the same as those found in the Norwegian stocks, although the electrophoretic methods used lead to differences in designations of alleles. A polymorphism in ESTD * which involves a slow allele was commonly observed in the three northern populations of the Nilma, Kachkovka and Neiden rivers. This allele was absent in the other Norwegian stocks and in a major brood stock of farmed salmon in Norway. The IDHP-3 * 116 allele was found in unusually high frequencies in the northern populations. Thus, the variability observed at these two loci indicates a barrier to gene flow between the northern salmon stocks and the more southern stocks in the East Atlantic area.     

Lipids as indicators of eutrophication in marine coastal sediments.

Total organic carbon (TOC) and sedimentary lipid contents were investigated in the Bunnefjord, the most inner part of the Oslofjord (Norway). The Bunnefjord is an intermittent anoxic basin and has undergone major eutrophication since the early 1800s. A core from this fjord was collected at 100 m depths under anoxic remnant waters. The first 15 cm corresponding to deposits from 1500 to present were considered for analysis. Lipid classes were quantified by TLC-FID and the molecular composition of selected lipid classes was investigated by GC and GC-MS. Lipids were dominated by two main classes, phospholipids and hydrocarbons. The hydrocarbons represented up to 7.4% of total lipids in the sediment layers covering the period when the most extensive cultural eutrophication took place (1900 to 1970). The higher fluxes of organic carbon produced during this period may have controlled hydrocarbon inputs into the sediments, due to the hydrophobic character of these pollutants. The hydrocarbon concentration reversed toward pre-industrial levels in the more recent layers, which suggests an improvement of the water quality, possibly in response to improved treatment of the sewage in the cities around Bunnefjord.The second most abundant pool of lipids consists in phospholipids, mostly contributed by bacteria. Even though the concentration decreased with depth, their relative proportions to total lipids remained high, mainly in the deepest layers (>80% of total lipids). A rapid decrease of the polyunsaturated fatty acid methyl esters (FAME) from the phospholipid fraction in the upper 4 cm suggests a rapid biodegradation of planktonic inputs and meiofauna. Odd branched fatty acids were more probably contributed by bacteria linked to the high sedimentary hydrocarbon content. The down core distribution of 16:1omega7, 18:1omega7, 18:1omega5 esterified to phospholipids suggests a vertical zonation of the microbial community in relation to redox conditions and available organic matter. In addition to bacterial sulphur biomass, the presence of hopanoic acids in the phospholipids fraction suggests the contribution of bacteria growing on methane. According to the sterol composition, dominated by 4alpha(H)-methylsterols, dinoflagellates represent the major contributors to the organic matter produced in the water column, particularly during the period of extensive eutrophication. Long-chain diols (1,13-C(26), 1,15-C(30) and 1,15-C(32)) and long-chain keto-ols (1,15-C(30) and 1,15-C(32)) are reported for the first time at high latitudes. Their relative distributions (diol and keto-ol indexes of Versteegh et al. [Org. Geochem. 27 (1997)]) have allowed depicting a particular event during the eutrophication period, a freshwater intrusion with inputs of land-derived organic matter. This is in accordance with the downcore distribution of freshwater/terrestrial markers as sitosterol, dehydroabietic acid and iso- and anteiso-pimaric acids. The diol and keto-ol indexes have also underlined the general transition trend from marine to more brackish waters in the Bunnefjord. These last observations provide confidence into the use of these compounds in paleoenvironmental reconstruction.     

A primary screen of the bovine genome for quantitative trait loci affecting twinning rate

An autosomal genome scan for quantitative trait loci (QTL) affecting twinning rate was carried out in the Norwegian Cattle population. Suggestive QTL were detected on Chromosomes (Chr) 5, 7, 12, and 23. Among these, the QTL positions on both Chr 5 and Chr 23 are strongly supported by literature in the field. Our results also confirm previous mapping of a QTL for twinning to Chr 7, but definitely suggest a different location of the QTL on this chromosome. The most convincing QTL peak was observed for a region in the middle part of Chr 5 close to the insulin-like growth factor 1 (IGF1) gene. Since IGF1 plays an important role in the regulation of folliculogenesis, a mutation search was performed by sequencing more than 3.5 kb of the gene in actual families. The sequencing revealed three polymorphisms in noncoding regions of the gene that will be important in fine structure mapping and characterization of the QTL. Received: 14 December 1999 / Accepted: 25 May 2000     

Evaluation of PM3(tm) as a Geometry Generator in Theoretical Studies of Transition-Metal-Based Catalysts for Polymerizing Olefins

The PM3(tm) method has been applied to several systems of relevance to catalytic polymerization of olefins, for catalysts containing Ti, Zr or Cr. With some exceptions, PM3(tm) calculations reproduce experimental geometries of stable, closed-shell, precursors well. For stationary points along the path of monomer insertion into a metal-alkyl bond, the comparison is made to structures obtained by optimization using various first-principle methods. Large errors are uncovered for the transient structures, in particular pertaining to metal-ethylene coordination and agostic interactions. The energy profiles for four insertion reactions are computed by gradient-corrected density functional (DFTG) methods, using molecular structures taken from PM3(tm) and first-principle geometry optimizations, respectively. The chromium case is promising, giving values for the barrier to monomer insertion of 11 and 9 kcal/mol based on PM3(tm) and DFTG geometries, respectively. The Ti- and Zr-based systems are predicted to proceed downhill based on PM3(tm) structures, whereas small barriers are found when using first-principle structures. A hybrid PM3(tm)-DFTG procedure is suggested for geometry optimization, which facilitates an accurate estimate of the barrier when applied to one of the zirconium systems.