Tissue distribution,metabolism, and elimination of perfluorooctanoic acid in male and female rats

The elimination, tissue distribution, and metabolism of [1-¹⁴C]perfluorooctanoic acid (PFOA) was examined in male and female rats for 28 days after a single ip dose (9.4 μmol/kg, 4 mg/kg). A sex difference in urinary elimination of PFOA-derived ¹⁴C was observed. Female rats eliminated PFOA-derived radioactivity rapidly in the urine with 91% of the dose being excreted in the first 24 hr. In the same period, male rats eliminated only 6% of the administered ¹⁴C in the urine. The sex-related difference in urinary elimination resulted in the observed difference in the whole-body elimination half-life (t_1/2) of PFOA in males (t_1/2 = 15 days) and females (t_1/2 < 1 day). Analysis of PFOA-derived ¹⁴C in tissues showed that the liver and plasma of male rats and the liver, plasma, and kidney of female rats were the primary tissues of distribution. The relatively high concentration of PFOA in the male liver was further examined using an in situ nonrecirculating liver perfusion technique. It was shown that 11% of the PFOA infused was extracted by the liver in a single pass. The ability of the liver to eliminate PFOA into bile was examined in rats whose renal pedicles were ligated to alleviate sex differences in the urinary excretion of PFOA. In a 6-hr period following IP administration of PFOA, there was no apparent difference in biliary excretion, where both males and females eliminated less than 1% of the PFOA dose via this route. We hypothesized that the sex difference in the persistence of PFOA was due to a more rapid formation of a PFOA-containing lipid (i.e., a PFOA-containing mono-, di-, or triacylglycerol, cholesteryl ester, methyl ester, or phospholipid) in the male rat. Also, the increased urinary elimination of PFOA in females may have been due to increased metabolism to a PFOA-glucuronide or sulfate ester. However, no evidence that PFOA is conjugated to form a persistent hybrid lipid was obtained, nor were polar metabolites of PFOA in urine or bile detected. In addition, daily urinary excretion of fluoride in male and female rats before or after PFOA treatment were similar, suggesting that the parent compound is not defluorinated. Thus, the more rapid elimination of PFOA from female rats is not due to formation of a PFOA metabolite.     

Yearly maps of summer temperatures in Western Europe from A.D. 1750 to 1975 and Western North America from 1600 to 1982:

The primary purpose of this publication is to make available two series of historical maps showing summer (April–September mean) temperatures over western Europe from A.D. 1750 and western North America from A.D. 1600. These maps have been reconstructed using networks of temperature-sensitive tree-ring chronologies as part of a continuing collaboration between the Swiss Federal Institute for Forest, Snow and Landscape Research (FSL) at Birmensdorf, Switzerland and the Climatic Research Unit (CRU) at the University of East Anglia, Norwich, U.K. The maps were reconstructed using relatively long maximum latewood density chronologies selected from the extensive networks of tree-ring data produced at the FSL. The reconstructions were produced using a spatial regression technique developed at CRU.The basis for the reconstructions are wood samples from various conifers growing at cool-moist sites close to the alpine or boreal timberlines. This material was analysed by x-ray densitometry and the resulting maximum latewood density chronologies were calibrated against meteorological data over a 100-year calibration period.These results emphasize the value of dendroclimatological research which can provide continentalscale reconstructions of past climate which represent a potential resource for climatologists, biologists, and historians with an interest in the spatial variability of summer temperatures over the middle to high latitudes.     

Similarity of maize and sorghum genomes as revealed by maize RFLP probes

Summary Densely saturated genetic maps of neutral genetic markers are a prerequisite either for plant breeding programs to improve quantitative traits in crops or for evolutionary studies. cDNA and genomic clones from maize were utilized to initiate the construction of a RFLP linkage map in Sorghum bicolor. To this purpose, an F₂ population was produced from starting parental lines IS 18729 (USA) and IS 24756 (Nigeria) that were differentiated with regard to many morphological and agronomical traits. A total of 159 maize clones were hybridized to the genomic DNA of the two parents in order to detect polymorphism: 154 probes hybridized to sorghum and 58 out of these were polymorphic. In almost all of the cases hybridization patterns were similar between maize and sorghum. The analysis of the segregation of 35 polymorphic clones in an F₂ population of 149 individuals yielded five linkage groups. The three principal ones recall regions of maize chromosomes 1, 3 and 5: in general, colinearity was maintained. A possible inversion, involving a long region of maize chromosome 3, was detected. Simulations were also performed to empirically obtain a value for the lowest number of individuals of the F₂ population needed to obtain the same linkage data.Prof. E. Ottaviano, to whom this paper is dedicated, suddenly died on June 7^th, 1991     

The effects of selective fish predation on the horizontal distribution of pelagic Cladocera in a southern French reservoir

A four-year study showed a clear seasonal succession of species within the cladoceran community of the large, oligotrophic Sainte-Croix reservoir (S.E. France). Diaphanosoma brachyurum and Ceriodaphnia pulchella were strictly limited to the warm stratified period (July to October), whereas Bosmina longirostris and Bosmina coregoni were dominant during spring and autumn. Daphnia longispina was the only species to occur throughout the year with higher densities in spring.In spring and late autumn, the discharge of the inflowing river Verdon was high and the abundance of all species showed a gradient over the whole lake with lower densities close to the inflow. During the stratified period, water inflow was very low and species showed different patterns. Densities of the small form Ceriodaphnia pulchella were similar all along the long axis of the lake, whereas Daphnia densities were significantly higher near the dam. The distribution pattern of Diaphanosoma, an intermediate-sized species, showed similar trends to that of Daphnia. The only planktivorous fish in the pelagic zone, the bleak (Alburnus alburnus), fed mostly on large-bodied species (> 1.0 mm) and was more abundant close to the inflow current. A comparison between the length frequency distributions of cladocera upstream and downstream provided a clear demonstration of the effects of size-selective predation on prey populations. Finally, the interactions between spatial heterogeneity and long-term development of the zooplankton community and the indirect effects of predation are discussed.     

Broad-host-range cloning vectors derived from the W-plasmid Sa

Four nonconjugative broad-host-range cloning vectors were derived from the W-plasmid Sa. They are small (M_r 5.6?7.2 × 10⁶), carry several drug-resistance markers, and allow constructing and screening for recombinant plasmids generated by the restriction enzymes EcoRI, PstI, BglII, HindIII, BamHI and SalI,     

Variation between mouse major urinary protein genes isolated from a single inbred line

We describe ten Charon 4A genomic DNA clones from BALB/c mice which include at least seven different major urinary protein (MUP) genes. We have established the orientation of all seven sequences, and have placed six of them in precise register by means of restriction site maps and Southern blot hybridization with cloned cDNA sequences. Four of the seven genomic sequences (family I sequences) form hybrids with six independent cDNA clones that have a high thermal stability and hybridize more strongly with mRNA from three inbred mouse lines. Hybrids between the remaining three genomic sequences and the cDNA clones have a lower thermal stability and hybridize less strongly with mRNA from the three inbred lines. Homologies between different cloned sequences extend over as much as 15 kb. No clone contains parts of two MUP genes, and no homology has been detected between the 3' flanking region of one MUP gene and the 5' flanking region of another.     

Brazilian vegetation on maps

The development and current status of mapping the vegetation of Brazil is discussed. This includes the manner of portraying the vegetation on maps, especially with regard to physiognomy and structure, the floristic composition and ecological relations. A slow beginning has given way to a rapid though uneven development. Recent government efforts tend to correct this.     

Identification, Development, and Regional Distribution of Thymidylate Synthetase in Adult Rabbit Brain

Abstract: The development and regional distribution of thymidylate synthetase (TS) (EC 2.1.1.45) in rabbit brain were determined. After optimization of the assay for brain, TS activity in brain was measured by a nonspecific (³H₂O release) and specific method. The specific method involved the conversion of [6-³H]deoxyuridine monophosphate (dUMP) to [³H]thymidine phosphate and the subsequent identification of [³H]thymidine. The specific activity of the enzyme in whole brain of newborn rabbits declined from 10.35 ± 1.17 units/mg protein to 0.71 ± 0.09 units/mg protein at 10–12 weeks of age. Two-year-old rabbits had 0.81 ± 0.04 units/mg protein. The decline in specific activity with age was not due to an inhibitor of TS activity or a change in the K_m for dUMP. The K_m for dUMP of the unpurified enzyme in the brains of both 10-day-old and young adult rabbits was 0.8 μ m . In young adult rabbits (3 months) the specific activity of TS was similar in the various regions of the brain tested except for the cerebellum, which had 40% higher specific activity than the whole brain. The results show that TS is widely distributed in adult rabbit brain, and, although the activity declines with age, it stabilizes at adult levels at 3 months of age.     

Rat Brain 3-Hydroxy-3-Methylglutaryl-CoA Reductase: Subcellular Distribution and Cold Lability

Abstract: Data are provided indicating that the rat brain 3-hydroxy-3-methyl-glutaryl-CoA reductase is similar to the enzyme from other tissues as far as diurnal rythmicity, cold lability and half-life measurements at 0°C are concerned. The enzyme activity in the brain decreased with age of the animals. Subcellular fractionation studies demonstrate that while 77% of the activity was associated with the microsomal fraction, 19% of the enzyme activity was recovered in the mitochondrial fraction. The possible function of such a mitochondrially located 3-hydroxy-3-methylglutaryl-CoA reductase in rat brain is discussed.