Radiolabelled pyrimidine nucleosides to monitor the expression of HSV-1 thymidine kinase in gene therapy.

Selective radiolabelling and imaging of transduced HSV tk expressing cells was studied using [123I]IVFRU, [125I]FIRU and [125I]FIAU. Although all three radionucleosides accumulated in the KBALB-STK transduced murine tumour line in vitro and in vivo, [125I]FIRU provided optimal performance in terms of selectivity for HSV tk expressing cells and % of injected dose accumulating in the tumor.     

Denitrification in Bahia Darwin (Galapagos Islands) an intermittent anoxic basin in the tropics

Changes in oxygen and nitrate in Bahia Darwin between July 1968 and March 1969 indicate that denitrification occurred in the deeper waters of this tropical, intermittently anoxic basin. Assuming constant rates of oxidation of organic matter in equally spaced depth intervals below the pycnocline depth, the rate of denitrification was estimated to be about 62.0 µg-atom NO₃-N/liter/year. This rate is attributable to denitrification in the water column because a smaller rate was estimated for strata closer to the sediment water interface.Contribution No. 3193 from the Woods Hole Oceanographic Institution. Woods Hole, Massachusetts 02543. This study was supported in part by the National Science Foundation Grants GA 29303 and GB 6870. Reprints should be requested from the second author.     

Synthesis of the allylic gonadal steroids, 3 alpha-hydroxy-4-pregnen-20-one and 3 alpha-hydroxy-4-androsten-17-one, and of 3 alpha-hydroxy-5 alpha-pregnan-20-one

A method for the convenient synthesis of the recently isolated allylic gonadal steroids, 3 alpha-hydroxy-4-pregnen-20-one (3 alpha-dihydroprogesterone; 3 alpha-DHP) and 3 alpha-hydroxy-4-androsten-17-one (3 alpha-HA), was developed using 4-pregnene-3,20-dione (progesterone) and 4-androstene-3,17-dione as substrates and potassium trisiamylborohydride (KS-Selectride) as reducing agent. Similar reactions were also used for the reduction of 5 alpha-pregnane-3,20-dione to 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-HP). The yields were about 15%, 50%, and greater than 90% for 3 alpha-DHP, 3 alpha-HA and 3 alpha-HP, respectively. Structures of the products, including the 3 beta-isomers and the 17 alpha-epimer, formed in these reactions were determined by NMR and mass spectroscopic methods.     

Blunted pubertal growth after leukemia: a new pattern of growth hormone insufficiency

Growth, age at menarche and spontaneous GH secretion were studied in girls after treatment for acute lymphoblastic leukemia (ALL). These girls had normal prepubertal growth but subnormal pubertal growth. Mean final height was 1 SD less than expected before puberty. The average age at menarche was significantly lower than the normal mean for Swedish girls. The mean 24-hour GH secretion was severely blunted and there was no increase during puberty. We suggest that girls treated for ALL, including CNS irradiation, have a relative GH insufficiency which becomes clinically obvious only when the girls cannot respond to the increased demands for GH in puberty.     

PHOTOSYNTHESIS IN THE ANOMALOUS SECONDARY WOOD OF ATRIPLEX CONFERTIFOLIA STEMS

The anomalous secondary wood of A triplex confertifolia stems consists of vascular strands of xylem, phloem, and parenchyma embedded in fiberous conjunctive tissue. The included parenchyma contains chloroplasts and is capable of photosynthesis, as measured by¹⁴CO₂ uptake by wood in the light.     

Evolution of the Diatoms (Bacillariophyta): IV. A Reconstruction of Their Age from Small Subunit rRNA Coding Regions and the Fossil Record

Small subunit ribosomal RNA (ssu rRNA) coding regions from 30 diatoms, 3 oomycetes, and 6 pelagophytes were used to construct linearized trees, maximum-likelihood trees, and neighbor-joining trees inferred from both unweighted and weighted distances. Stochastic accumulation of sequence substitutions among the diatoms was assessed with relative rate tests. Pennate diatoms evolved relatively slowly but within the limits set by a stochastic model; centric diatoms exceeded those limits. A rate distribution test was devised to identify those taxa showing an aberrant distribution of base substitutions within the ssu rRNA coding region. First appearance dates of diatom taxa from the fossil record were regressed against their corresponding branch lengths to infer the average and earliest possible age for the origin of the diatoms, the pennate diatoms, and the centric diatom order Thalassiosirales. Our most lenient age estimate (based on the median-evolving diatom taxon in the maximum-likelihood tree or on the average branch length in a linearized tree) suggests that their average age is approximately 164–166 Ma, which is close to their earliest fossil record. Both calculations suggest that it is unlikely that diatoms existed prior to 238–266 Ma. Rate variation among the diatoms' ssu rRNA coding regions and uncertainties associated with the origin of extant taxa in the fossil record contribute significantly to the variation in age estimates obtained. Different evolutionary models and the exclusion of fast or slow evolving taxa did not significantly affect age estimates; however, the inclusion of aberrantly fast evolving taxa did. Our molecular clock calibrations indicate that the rRNA coding regions in the diatoms are evolving at approximately 1% per 18 to 26 Ma, which is the fastest substitution rate reported in any pro- or eukaryotic group of organisms to date.     

Phospholipid-metabolism of a stimulated murine T cell clone

The release of IP3 and the incorporation of arachidonic acid into phospholipids was measured in a stimulated murine alloantigen-specific, non-cytolytic T cell clone. While Concanavalin A provoked a sharp increase in IP3, Interleukin 2 had no effect on the production of IP3. An increased reacylation of phospholipids with arachidonic acid was seen within the first 4 hours after addition of Concanavalin A, while an effect upon Interleukin 2 was only observed after 8 hours of incubation with Interleukin 2. A similar retarded response to Interleukin 2 was observed in proliferation experiments. These retarded cell responses may be due to changed properties of IL 2 receptors induced by IL 2.