Invitro metabolism of aflatoxin B1 by rat liver nuclei

Rat liver nuclei were used to study the metabolism of aflatoxin B₁ (AFB₁). Nuclei were found to metabolize AFB₁ to aflatoxins M₁(AFM₁), Q₁(AFQ₁), and P₁(AFP₁); the formation of AFP₁ was relatively negligible. AFM₁ was preferentially formed when rats were pretreated with 3-methylcholanthrene (MC), whereas phenobarbital (PB) pretreatment enhanced the formation of both AFM₁ and AFQ₁. PB pretreatment also resulted in increased binding of AFB₁ metabolites to DNA and to other macromolecules in the nucleus. Following PB and MC pretreatment, induction specificities of the nuclear metabolism of AFB₁ were similar to those of the microsomal metabolism.     

A stimulatory subunit in the polypeptide elongation factor-1 of the chick brain

Abstract: The higher-molecular-weight elongation factor-1 (EF-1_H) of the chick brain was observed to contain three subunits (denominated α, β, and γ), contrary to a previous report that the brain EF-1_H consisted of aggregates of low-molecular-weight elongation factor- 1 (EF-1_L). Crude EF-1_H, obtained from 20-day embryonic brain, was treated with 0.4 M ammonium chloride and 0.1 mM GTP, and EF-1_βγ, was obtained using a DEAE-Sephadex column equilibrated in 0.025 mM GTP. Both EF-1_β, and EF-1_γ, were isolated by means of a DE-52 column equilibrated in 6 M urea and were found to have molecular weights of 2.8 and 4.8 × 10⁴, respectively. EF-1_β and EF-1_γ were also obtained from young rat and calf brains by the same procedures. The molecular weight of the isolated EF-1_α was 5 × 10⁴. It was found that EF-1_β stimulated the two EF-1_α-dependent reactions, i.e., phenylalanyl-tRNA binding (reaction 1) and polyphenylalanine synthesis (reaction 2), and also stimulated the nucleotide exchange reaction in the EF- 1_α-guanine nucleotide binary complex (reaction 3). The degrees of stimulation of reactions 1, 2, and 3 by the addition of EF-1_β were 2 to 3 times, about 18 times, and 2 to 3 times as much as with EF-1_α alone, respectively. The amino acid compositions of EF-1_α -1_β, and -1_γ and EF-2 were very similar to those of other eukaryotic tissues. Thus the constituents and properties of EFs of the brain were found to be basically similar to those of other tissues of eukaryotes, although EF-1_β, and EF-1, had not been reported in the brain. A possible physiological significance of EF-1_β during brain development is also discussed.     

Genetic evidence for gametophytic selection of wilt resistant alleles in chickpea

Gametophytic selection can drastically reduce the number of selection cycles during crop improvement programs. The objective of the present investigation was to test whether the nature of inheritance of two unlinked disease-resistant loci, h ₁ and h ₂, against Fusarium wilt in chickpea (Cicer arietinum L.) under gametophytic (pollen) selection was similar to that already observed at sporophytic level. A homozygous dominant (H ₁ H ₁ H ₂ H ₂) susceptible genotype JG-62 was crossed to a recessive (h ₁ h ₁ h ₂ h ₂) resistant genotype WR-315 to produce 20 F₁ hybrid seeds. In the following generation, flower buds of 10 F₁ hybrid plants were subjected to toxin stress before anthesis and the remaining ten control F₁ plants’ flowers were sprayed with water. Thirty-four selected BC₁ plants were generated by test crossing resistant WR-315 individuals with pollen from toxin-stressed F₁ individuals. Both control and treated F₁ plants were selfed to produce respective F₂ generations. Two DNA markers, CS-27_700bp and A07C_430bp, linked to susceptible alleles H ₁ and H ₂, respectively, were used to study the inheritance patterns of h ₁ and h ₂ loci in the F₂ and BC₁ generations. One hundred and forty-four selected F₂, 129 control F₂, and 34 selected backcross individuals were tested for the presence or absence of DNA markers. Except for the control F₂, observed ratios of selected F₂ and BC₁ populations exhibited significant chi-square deviations from expected monogenic and digenic ratios. Our results suggest that gametophytic selection is as effective as that realized at the sporophytic level, and that the gametophytic selection can be an effective breeding tool for plant breeding programs.     

Metabolism of prostaglndin A. II. Isolation, characterization, and synthesis of PGA1 renal.

Since the renal cortex has recently been shown to be a major site of prostaglandin A₁ (PGA₁) metabolism, studies were undertaken to isolate and characterize the major metabolites. Homogenates of rabbit cortex (500g) were incubated with ³H-PGA₁ (50mg) in the presence of NAD⁺ (50mg). Acidic lipid extracts were subjected to linear gradient silicic acid chromatography. Six radioactive peaks were recovered, of which peak 4 was unconverted PGA₁. The major metabolites (1,3) were further subjected to reversed phase partition chromatography and TLC with and without silver nitrate. Three PGA₁ analogs were then synthesized via oxidation of the secondary alcohol group at C-15 by manganese dioxide (15-keto-PGA₁). The second compound was synthesized by hydrogenation of 15-keto-PGA₁ (15-keto 13, 14-dihydro PGA₁). The third compound (13, 14-dihydro PGA₁) was obtained by direct catalytic hydrogenation of PGA₁. Purification of these substances were achieved by a combination of silicic acid and thin layer chromatography. It was found that metabolite 1 cochromatographed on TLC (AgNO3) with synthesized 15-keto 13, 14-dihydro PGA₁. Both compounds were 100 times less potent than PGA₁ in lowering rat blood pressure. Metabolite 3 cochromatographed on TLC (AgNO3) with synthesized 13, 14-dihydro PGA₁. Both were as potent as PGA₁ in lowering rat blood pressure. Metabolites 1 and 3 absorbed UV at 221 nm but not at 280 nm following alkali treatment. These studies suggest that rabbit renal cortex metabolizes PGA₁ to what appears to be biologically active 13, 14-dihydro PGA₁ and biologically inactive 15-keto 13, 14-dihydro PGA₁. It remains possible that the hypotensive effect of PGA₁ is the result of its conversion to its biologically active 13, 14-dihydro derivative.     

Release of 6-keto-prostaglandin F1α and thromboxane B2 from mouse peritoneal macrophages during their adhesion and spreading on a glass surface

The release of 6-keto-prostaglandin F_1α (6KF_1α)_and of thromboxane B₂ (TXB₂) from cells were investigated using mouse peritoneal exudate cells (PECs) and non-cultured peritoneal macrophages. They were prepared by adhesion to glass dishes and incubated for 1 hr at 37°C in 5% Co₂ in air. Both the percentage of spreading macrophages and the release of 6KF_1α and TXb₂ increased in proportion to the incubation time. 6KF_1α and TXB₂ were released from the macrophages, not from the non-adherent cells. When PECs were incubated in silicon-coated glass dishes, the spreading of macrophages was hardly detected and lower amounts of 6KF_1α and TXB₂ were released from these cells compared with cells incubated in non-treated glass dishes. These findings suggest that adhesion with the correlated spreading of macrophages on glass dishes serve as a considerable physical factor for the release of 6KF_1α and TXB₂.     

Lipid Molecular Species of Lipomyces starkeyi

The molecular species of glycerides and phospholipids of the yeast Lipomyces starkeyi IFO 0678 harvested at 60 hr, corresponding to the late exponential phase, were analyzed by gas chromatography-mass spectrometry. The major triglyceride was C_16:0–C_18:1–C_18:1. The major molecular species of phospholipid were 1–C_16:0–2–C_18:1 and 1–C_18:1–2–C_18:2. Although phosphatidylcholine and phosphatidylethanol amine were composed of several kinds of molecular species, 1–C_16:1–2–C_18:1, 1–C_18:1–2–C_18:2 and l-C_16:0–2–C_18:1, phosphatidylserine was composed of almost exclusively 1–C_16:0-2-C_18:1. The lipid and the fatty acid compositions of the yeast harvested at the different growth phases were also investigated.     

Comparison of Nuclease P1-Malonogalactan Complex with Nuclease P1

Properties of nuclease P₁-malonogalactan complex (P₁-MG) were compared with those of the polysaccharide-free nuclease P₁. Significant difference was not observed between them in phosphomonoester splitting activity, but marked differences were observed in nucleolytic activity as follows: (1) The pH optima of P₁-MG for RNA and heat-denatured DNA were lower than those of nuclease P₁. (2) At lower than 0.001 of ionic strength, RNA and heat- denatured DNA were attacked hardly by P₁-MG, but attacked well by nuclease P₁. (3) The increase in hydrolysis rate of RNA or heat-denatured DNA with an elevation of temperature from 37°C to 70°C was not so marked in P₁-MG as compared with nuclease P₁. (4) P₁-MG hydrolyzed polynucleotides, especially native DNA, much slower than nuclease P₁.

Influence of ionic strength, pH and temperature on the nucleolytic activity of nuclease P₁-galactan (P₁-G), which was prepared by demalonylating P₁-MG enzymatically, was similar to that of nuclease P₁, except that the activity of P₁-G for native DNA was much lower than nuclease P₁.     

Specific prostaglandine E1 and A1 binding sites in rat a dipocyte plasma membranes

Rat adipocyte plasma membranes sacs have been shown to be a sensitive and specific system for studying prostaglandin binding. The binding of prostaglandin E₁ and prostaglandin A₁ increases linearly with increasing protein concentration, and is a temperature-sensitive process. Prostaglandin E₁ binding is not ion dependent, but is enhanced by GTP. Prostaglandin A₁ binding is stimulated by ions, but is not affected by GTP.Discrete binding sites for prostaglandin E₁ and A₁ were found. Scatchard plot analysis showed that the binding of both prostaglandins was biphasic, indicating two types of binding sites. Prostaglandin E₁ had association constants of 4.9 · 10⁹ 1/mole and 4 · 10⁸ 1/mole, while the prostaglandin A₁ association constants and binding capacities varied according to the ionic composition of the buffer. In Tris-HCl buffer, the prostaglandin A₁ association constants were 8.3 · 10⁸ 1/mole and 5.7 · 10⁷ 1/mole, while in the Krebs—Ringer Tris buffer, the results were 1.2 · 10⁹ 1/mole and 8.6 · 10⁶ 1/mole.Some cross-reactivity between prostaglandin E₁ and A₁ was found for their respective binding sites. Using Scatchard plot analysis, it was found that a 10-fold excess of prostaglandin E₁ inhibited prostaglandin A₁ binding by 1–20% depending upon the concentration of prostaglandin A₁ used. Prostaglandin E₁ competes primarily for the A prostaglandin high-affinity binding site. Similar Scatchard analysis using a 20-fold excess of prostaglandin A₁ inhibited prostaglandin E₁ binding by 10–40%. Prostaglandin A₁ was found to compete primarily for the E prostaglandin low-affinity receptor.All of the bound [³H]prostaglandin E₁, but only 64% of the bound [³H]-prostaglandin A₁ can be recovered unmetabolized from the fat cell membrane. There is no non-specific binding of prostaglandin E₁, but 10–15% of prostaglandin A₁ binding to adipocyte membranes is non-specific. Using a parallel line assay to measure relative affinities for the E binding site, prostaglandin E₁ > prostaglandin A₂ > prostaglandin F_2α. Prostaglandin E₂ and 16,16-dimethyl prostaglandin E₂ were equipotent with prostaglandin E₁, while other prostaglandins had lower relative affinities. 7-Oxa-13-prostynoic acid does not appear to antagonize prostaglandin activity in adipocytes at the level of the receptor.     

Stimulative effect of prostaglandins on production of hexosamine-containing substances by cultured fibroblasts (2) early effect of various prostaglandins at various doses

Early effects of various prostaglandins on the production of hexosamine-containing substances by cultured fibroblasts, which were derived from a rat carrageenin granuloma, were studied. At the stationary phase, the cells were exposed for 6 h to one of the prostaglandin A₁ (PGA₁), A₂, B₁, B₂, D₂, F_1α, F_2α, E₁, E₂ or arachidonic acid in various concentrations ranging from 0.01 to 10 μg/ml for all the stimuli and from 10 pg to 10 μg/ml for PGF_2α. The activity of the cells in incorporating ³H-glucosamine into hexosamine-containing substances (acidic) glycosaminoglycans and glycoproteins) during this period was compared with that of control cells. All the stimuli tested showed more or less stimulative effect on the synthesis of hexosamine-containing substances at their specific concentrations. PGF_2α was found to be the most potent stimulant and its stimulative effect was found significant even at the low concentration of 100 pg/ml. PGD₂, F_1α and E₂ were the next potent stimuli. Their optimum dose were around 1 μg/ml but they still had significant stimulation at the concentration of 0.01 μg/ml. Effect of PGE₂ was rather mild. Stimulation by PGA₁, A₂, B₁ and B₂ or arachidonic acid was seen at high dose, and its seemed to be non-specific. The results suggested that these prostaglandins such as PGF_2α, D₂, F_1α and E₂ play some important role on regulating the production of intercellular ground substances.     

Immunoaffinity column clean-up for the high-performance liquid chromatographic determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in urine

A method for the determination of aflatoxins B₁, B₂, G₁, G₂, M₁ and Q₁ in human urine has been developed. The 10-ml urine samples were automatically cleaned up on immunoaffinity columns and analysed by high-performance liquid chromatography (HPLC), including post-column derivatization with bromine and fluorescence detection. Average aflatoxin recoveries were: B₁ 103%, B₂ 106%, G₁ 98% and G₂ 96% in the range 6.8–73 pg/ml of urine and M₁ 103% and Q₁ 100% in the range 18–97 pg/ml of urine. The relative standard deviations were all between 1% and 21%. The determination limits of aflatoxins in urine were 6.8 pg/ml for B₁, B₂, G₁ and G₂ and 18 pg/ml for M₁ and Q₁.     

Genetic markers in Malaysians: Variants of soluble and mitochondrial glutamic oxaloacetic transaminase and salivary and pancreatic amylase,phosphoglucomutase III and saliva esterase polymorphisms

Summary Malaysians of Malay, Chinese, and Indian ancestries were electrophoretically phenotyped for Amy₁ and saliva esterase region 1(Set-1) from saliva, Amy₂ from plasma, soluble and mitochondrial GOT and PGM ₃ from leukocyte and placenta. Kadazans and Bajaus, the indigenous people of Sabah, East Malaysia were surveyed for Amy₂. Three types of variants were observed for Amy₁, one type for Amy₂. Only Indians were found to be polymorphic for Amy₁. Two GOT _s 2-1 and three GOT _m 2-1 variants were found among 281 Chinese while three GOT _m 2-1 variants were found among 311 Malays.Malaysian Malays, Chinese, and Indians were found to be polymorphic for Set-1 and PGM ₃. The gene frequencies in Malays are Set-1F=0.601±0.021, Set-1S=0.399±0.021; PGM ₃ ¹ =0.788±0.020, PGM ₃ ² =0.212±0.020; in Chinese Set-1F=0.497±0.028, Set-1S=0.503±0.028; PGM ₃ ¹ =0.745±0.024, PGM ₃ ² =0.255±0.024; in Indians, Set-1F=0.449±0.031, Set-1S=0.551±0.031; PGM ₃ ¹ =0.755±0.029, PGM ₃ ² =0.245±0.029.     

Somatic variations on a yellow mutant in Nicotiana tabacum L. (a1+/a1a2+/a2) I. Non-reciprocal genetic events occurring in leaf cells

A greenish-yellow mutant was obtained after treatment of seeds of Nicotiana tabacum L. var. Xanthi n.c. with ethyl methanesulfonate (EMS). Two genetically independent mutations (a₁ and a₂) were isolated. The first mutation (a₁) antagonizes the function of its partially dominant a₁⁺ allele. The second mutation (a₂) is amorphous but strongly interacts with a₁.Among the nine possible genotypes at the two loci, five varied in somatic cells. The heterozygous state a₁⁺/a₁ strongly increased the frequency of both spontaneous and induced variations. However, two homozygotes also showed variations.Variants were isolated from induced and spontaneous non-reciprocal and reciprocal variations within paliside tissues by bud induction in vitro. They were genetically tested. In this first paper, only non-reciprocal variations are reported.Green variants from the greenish-yellow (J¹) dihybrid a₁⁺/a₁a₂⁺/a₂ clone had two genotypes: the first was due to true reversions of a₁ to a₁⁺, whereas the second was due to amorphous a₁⁰ mutations from a₁. These a₁⁰ mutations may well be deletions.The lightest yellow variants from J¹ were due to mutations either from a₁⁺ into a₁ or from a₂⁺ into a₂.Deletions at the a₁⁺?a₁ locus led to either yellow variations when a₁⁺ was lost, or to false reversions when the antagonistic allele a₁ was lost.Amorphous alleles at the a₁⁺?a₁ locus were also isolated from tissues other than J⁺. They gave zygotic lethality (s) that probably varied with the size of the deletions. Thus, true reversions and deletions at the a₁⁺?a₁ locus could be distinguished from one another by progeny tests.Other variants showed higher frequencies of spontaneous variations (instability). Somatic changes observed in these unstable systems were due to modifications at the marker loci. The genetic nature of this instability is not yet known.There is strong evidence that the genetic events involved in these non-reciprocal variations were deletions, conversions and point mutations. True reversions from a₁ into a₁⁺ and new mutations from a₁⁺ into a₁ were obtained only from a₁⁺/a₁. It was therefore supposed that the changes observed took place only in heterozygotes, and the conversion hypothesis was made. Attempts are being made to prove that conversions do exist in higher plants, and to find out if this process, as deletions, is induced by radiation.     

Vitellogenin in locusts (Locusta migratoria): Translation of vitellogenin mRNA in Xenopus oocytes and analysis of the polypeptide products

Cytoplasmic poly(A)⁺-RNA, prepared from fat bodies of reproductively active locust females, directed the synthesis of two large polypeptides in Xenopus oocytes. Occasionally two smaller polypeptides (X₁ and X₂) were also detectable. The two larger polypeptides were immunologically and electrophoretically indistinguishable from the unprocessed Vitellogenin polypeptides (Vg₁ and Vg₂) of locust fat bodies. Peptide patterns generated from these two translation products by Staphylococcus aureus V8 protease digestion were identical to those of Vg₁ and Vg₂. RNA isolated from allatectomized female locusts treated with the juvenile hormone analog (ZR-515) was also able to direct the synthesis of vitellogenin in Xenopus oocytes, whereas RNA isolated from mature males or allatectomized females did not. The molecular weights of fat-body Vg₁ and Vg₂ were 235,000 and 225,000, respectively and the processed vitellogenin polypeptides were found to range from 126,000 to 52,000. Electrophoretic and Chromatographic analysis of [³⁵S]methionine-containing tryptic peptides of Vg₁ and Vg₂ showed two different tryptic peptide fingerprints. Distinctly different peptide patterns were also observed when Vg₁ and Vg₂ were partially digested with V8 protease or papain. However, tryptic peptide mapping and V8 protease limited digestion mapping of fat-body X₁ and X₂ revealed that these two polypeptides were derived from Vg₁ and Vg₂. This suggests that Vg₁ and Vg₂ are products of two different vitellogenin structural genes.     

Expression of a Soluble Functional Form of the Integrin α4β1 in Mammalian Cells

The integrin α₄β₁(VLA4) has been expressed as a soluble, active, heterodimeric immunoglobulin fusion protein. cDNAs encoding the extracellular domains of the human α₄ and β₁ subunits were fused to the genomic DNA encoding the human γ1 immunoglobulin Fc domain and functional integrin fusion protein was expressed as a secreted, soluble molecule from a range of mammalian cell lines. Specific mutations were introduced into the Fc region of the molecules to promote α₄β₁ heterodimer formation. The soluble α₄β₁ Fc fusion protein exhibited divalent cation dependent binding to VCAM-1, which was blocked by the appropriate function blocking antibodies. The apparent K_d for VCAM-1 binding were similar for both the soluble and native forms of α₄β₁. In addition, the integrin–Fc fusion was shown to stain cells expressing VCAM-1 on their surface by FACs analysis. This approach for expressing soluble α₄β₁ should be generally applicable to a range of integrins.     

Reduction of aflatoxin B1 levels by sheep saliva

This study determined the decrease of aflatoxin B₁ by sheep saliva at concentrations of 150 and 300 μg aflatoxin B-₁/L saliva. Analyses for aflatoxins B₁, M₁, and aflatoxicol (R₀) were performed after 2, 4, 6, 24, and 48 hours of incubation. Aflatoxin M₁ and R₀ were not detected and only residues of aflatoxin B₁ were found. 4 to 13% of aflatoxin B₁ were decomposed by sheep’s saliva within 2 hrs and 33 to 43% of aflatoxin B₁ after 24 hrs. Decomposition was affected by the aflatoxin concentration. Decrease of aflatoxin B₁ at 2, 4, 6 hrs was nearly three times higher at the low concentration (150 ppb) compared to the high concentration (300 ppb). After 48 hrs incubation more than 80% of the initial aflatoxin B₁ had been decomposed by the saliva.     

Structure of carbohydrate chains of fucolectin from the bark of golden rain shrub <Emphasis Type="Italic">Laburnum anagyroides</Emphasis>

A reductive LiBH₄-Bu^tOH cleavage of N-glycosylamide carbohydrate-peptide bond allowed splitting off of oligosaccharide chains of the fucolectin, the bark agglutinin from the shrub golden rain Laburnum anagyroides (LABA). Four N-glycans were isolated by HPLC, and their structures were elucidated by monosaccharide analysis and ¹H NMR (500 MHz) spectroscopy: Man₂Fuc₁Xyl₁GlcNAc₂ (M2FX), Man₃Xyl₁GlcNAc₂ (M3X), Man₃Fuc₁Xyl₁GlcNAc₂ (M3FX), and Man₃Xyl₁Fuc₁GlcNAc₃ (NM3FX). All the N-glycans contain D-xylose and three of them, L-fucose; they were found to be in a 1:8:3:1 ratio.     

Biochemical basis of hybrid vigour. The genetics of grain weight of Oryza sativa

Summary Four cathodal bands (C₁, C₂, C₃ and C₄) of esterase (E₁, C₁. 3.1) were correlated with the grain weight of rice (Oryza sativa L.). Zymogram patterns indicated intensity differences among these bands infinegrain and coarse-grain varieties. Bands C₁. and C₂ were dark in fine grain varieties whereas C₃ and C₄ were dark in coarse grain varieties. These bands were specific to endosperm. Observations on fine-grain (Kalanamak), coarse grain (SR(26)B) varieties and their reciprocal hybrids indicated the presence of 4 esterase loci G₁, G₂, G₃ and G₄, corresponding to bands C₁, C₂, C₃ and C₄, respectively. A possible model for heterosis in grain weight of rice was proposed which supports the dominance theory of heterosis. In hybrid vigour the 4 esterase loci appear to be associated with grain weight and they complemented each other in an additive manner.     

Leukotriene receptors are differently expressed in fibroblast from peripheral versus central airways in asthmatics and healthy controls

Leukotrienes are involved in airway inflammation, and are believed to stimulate airway remodeling in asthma. The aim of the project was to investigate the expression of leukotriene receptors in peripheral and central airway fibroblasts.Peripheral and central airway fibroblasts, from asthmatics and healthy controls, were investigated for the amount of cysteinyl-leukotriene receptors (CysLT₁ and CysLT₂), leukotriene B₄ receptors (BLT₁ and BLT₂), IL-13 receptor-α₁ (IL-13Rα₁) and the IL-4 receptor (IL-4R).The mRNA expression of CysLT₁ in fibroblasts from peripheral airways was higher compared to central airways. There was no difference in CysLT₂ between peripheral and central airways. On the contrary, BLT₁ and BLT₂ were lower in fibroblasts from peripheral airways compared to central. The expression of CysLT₁ was higher than CysLT₂ in fibroblasts from peripheral airways, and the expression of BLT₁ was higher than BLT₂ in both peripheral and central airways. Both BLT₁ and BLT₂ were higher in asthmatics compared to healthy controls, while CysLT₁ and CysLT₂ did not differ. The expression of IL-13Rα₁ was higher in asthmatics compared to controls, and correlated to the BLTs. All fibroblasts stained for the different receptor proteins.Leukotriene receptors are differently expressed in fibroblasts from peripheral compared to central airways, which may explain a suggested cysteinyl-leukotriene driven remodeling mainly in the peripheral airways.     

The endogenous gibberellins of dwarf mutants of lettuce

The gibberellin (GA) content of E-1, a tall genotype of early flowering lettuce (Lactuca sativa L.), and of three selected GA-responsive dwarfs, dwf1, dwf2, and dwf2¹, has been determined using ¹³C-labeled internal standards and gas chromatographymass spectrometry (GC-MS). In the shoots of the E-1 parent, GA₁, 3-epi-GA₁, GA₃, GA₅, GA₈, GA₁₉, GA₂₀, GA₂₉, and GA₅₃ were identified by full scan GC-MS and Kovats retention indices. Purification by immunoaffinity chromatography selective for 13-hydroxy GAs, was necessary for GA identification. Relative to the parent E-1, the concentrations of GA₁, GA₈, GA₂₀, and GA₂₉ in the shoots of dwf2 plants were reduced to about 10% and in shoots of dwf2¹ plants to less than 50%. In dwf1 the levels of GA₁, GA₈, and GA₂₉ were also reduced to less than 50% of the parent E-1, but the level of GA₂₀ was fivefold higher than in E-1. Plant height was correlated with the endogenous levels of GA₁ and GA₈.     

Aerobic Biotransformation of N-Nitrosodimethylamine and N-Nitrodimethylamine by Benzene-, Butane-, Methane-, Propane-, and Toluene-Fed Cultures

N-Nitrosodimethylamine (NDMA) is an emerging contaminant of concern. N-nitrodimethylamine (DMNA) is a structural analog to NDMA. NDMA and DMNA have been found in drinking water, groundwater, and other media and are of concern due their toxicity. The authors evaluated biotransformation of NDMA and DMNA by cultures enriched from contaminated groundwater growing on benzene, butane, methane, propane, or toluene. Maximum specific growth rates of enriched cultures on butane (μ_max = 1.1 h^?1) and propane (μ_max = 0.65 h^?1) were 1 to 2 orders of magnitude higher than those presented in the literature. Growth rates of mixed cultures grown on benzene (μ_max = 1.3 h^?1), methane (μ_max = 0.09 h^?1), and toluene (μ_max = 0.99 h^?1) in these studies were similar to those presented in the literature. NDMA biotransformation rates for methane oxidizers (υ_max = 1.4 ng min^?1 mg^?1) and toluene oxidizers (υ_max = 2.3 ng min^?1 mg^?1) were comparable to those presented in the literature, whereas the biotransformation rate for propane oxidizers (υ_max = 0.37 ng min^?1 mg^?1) was lower. NDMA biotransformation rates for benzene oxidizers (υ_max = 1.02 ng min^?1 mg^?1) and butane oxidizers (υ_max = 1.2 ng min^?1 mg^?1) were comparable to those reported for other primary substrates. These studies showed that DMNA biotransformation rates for benzene (υ_max = 0.79 ng min^?1 mg^?1), butane (υ_max = 1.0 ng min^?1 mg^?1), methane (υ_max = 2.1 ng min^?1 mg^?1), propane (υ_max = 1.46 ng min^?1 mg^?1), and toluene (υ_max = 0.52 ng min^?1 mg^?1) oxidizers were all comparable. These studies highlight potential bioremediation methods for NDMA and DMNA in contaminated groundwater.