Hemin feedback inhibition at reticulocyte δ-aminolevulinic acid synthetase and δ-aminolevulinic acid dehydratase

Addition of hemin (5–200 μM) to a rabbit reticulocyte iron-free incubation medium, resulted in a progressive inhibition of heme synthesis as measured by incorporation of (¹⁴C)-glycine. In contrast when (¹⁴C) δ-aminolevulinic acid incorporation into heme was studied, significant inhibition below that of the (¹⁴C)-glycine control only occurred with hemin concentrations greater than 100 μM. Hemin progressively inhibited cellular and mitochondrialδ-aminolevulinic acid synthetase activity, as well as cellular δ-aminolevulinic acid dehydratase activity. The results indicated that elevated levels of hemin initially control heme synthesis by feedback inhibition at the rate-limiting enzyme of heme synthesis, δ-aminolevulinic acid synthetase. Hemin inhibition of δ-aminolevulinic acid dehydratase is only significant for the entrire heme synthetic pathway when greater than one-third of this enzyme's activity is inhibited.     

The environmental water of the middle Eocene Arctic: Evidence from δD, δ18O and δ13C within specific compounds

The extensive vertical exposure (> 150 m) of terrestrial sediments on Axel Heiberg Island, which contain thick fossiliferous lignites, presents an exceptional opportunity to follow the establishment and re-establishment of Arctic Metasequoia forests during the middle Eocene. We compared δD values in n-alkanes of chain length 23, 25, 27 and 29 with δ¹⁸O values in phenylglucosazone (P-G) derived from α-cellulose; we also analyzed %-abundance of ferns, gymnosperms and angiosperms using pollen and spores isolated from each lignite. Our results showed that forest composition was altered upon uplift, as gymnosperms became more abundant within the relatively well-drained upland sediments. This was also reflected in the small (1‰), but significant, increase in the δ¹³C value of TOM from lowland to upland environments. However, neither the δD values of n-alkanes nor the δ¹⁸O in P-G were statistically different in the upland sediments, as compared to the lowland sediments; from this we inferred that the oxygen isotope signature of environmental water available to the forests for plant growth was relatively uniform throughout the time of the fossil forests. The δD value of environmental water implied by both n-alkanes and P-G ranged from ? 168 to ? 131% and was considerably enriched compared to all environmental water samples available from the modern Arctic region (< ? 180%). In addition to indicating a warmer Eocene Arctic, subject to meteoric transport patterns different from today's, these results argue against the presence of an Eocene polar ice cap.     

Streptozotocin-induced diabetes selectively enhances antinociception mediated by δ1-but not δ2-opioid receptors

We assessed the effect of diabetes on antinociception produced by intracerebroventricular injection of δ-opioid receptor agonists [D-Pen^2,5]enkephalin (DPDPE) and [D-Ala²]deltorphin II. The antinociceptive effect of DPDPE (10 nmol), administered i.c.v., was significantly greater in diabetic mice than in non-diabetic mice. The antinociceptive effect of i.c.v. DPDPE was significantly reduced in both diabetic and non-diabetic mice following pretreatment with 7-benzylidenenaltrexone (BNTX), a selective δ₁-opioid receptor antagonist, but not with naltriben (NTB), a selective δ₂- opioid receptor antagonist. There were no significant differences in the anticiceptive effect of [D-Ala²]deltorphin II (3 nmol, i.c.v.) in diabetic and non-diabetic mice. Furthermore, the antinociceptive effect of i.c.v. [D-Ala²]deltorphin II was significantly reduced in both diabetic and non-diabetic mice following pretreatment with NTB, but not with BNTX. In conclusion, mice with diabetes are selectively hyper-responsive to supraspinal δ₁-opioid receptor-mediated antinociception, but are normally responsive to activation of δ₂-opiod receptors.     

Differential δC and δN signatures among scallop tissues: implications for ecology and physiology

There have been several studies where the isotopic composition of organisms has been determined seasonally, but fewer have examined separate organs. In this context, separate organs (e.g. gonad, digestive gland and muscle) of a suspension-feeder, the scallop Pecten maximus, were used to assess seasonal changes of both stable isotopes and biochemical components. Our study used multiple indicators [stable carbon and nitrogen isotope ratios, biochemical components and seston chlorophyll-a (chl a)] to track nutritive activity and energy allocation in P. maximus from the Bay of Brest (France). In addition to seasonal variation in the isotopic composition of P. maximus tissues, we found strong differences in the mean isotopic signatures of different organs. This has serious implications for interpretation of animal diets and potential use in animal physiology. Furthermore, we present evidence that seasonal variations of metabolism will cause changes in the isotopic composition not related to changes in the diet. Interpretation of isotopic data may require consideration of values from several separate organs. Finally, δ¹⁵N appears powerful to track metabolite fates in the scallop P. maximus.     

Reliability of δ13C and δ15N in faeces for reconstructing savanna herbivore diet

We tested the reliability of herbivore faecal δ¹³C and δ¹⁵N values for reconstructing diet through review of an extensive database derived from a 3-year study of ungulates in South Africa's Kruger National Park. Faeces are a useful material for stable isotope studies of diet because they record dietary turnover at very short time scales, and because sampling is non-invasive. However, the validity of faecal isotope proxies may be questioned because they represent only undigested food remains. Results from Kruger Park confirm that free-ranging browsers have faecal δ¹³C consistent with C₃ feeding, grazer faeces are C₄, and mixed-feeder faeces intermediate. Although the respective ranges do not overlap, there is significant variation in faecal δ¹³C of browsers and grazers (～2.0–4.0‰) across space and through time. We demonstrate that most (～70%) of this variation can be ascribed to corresponding patterns of variation in the δ¹³C of C₃ and C₄ plants, respectively, re-enforcing the fidelity of faecal isotope proxies for diet but highlighting a need for mixing models that control for variations in plant δ¹³C in order to achieve accurate diet reconstructions. Predictions for the effects of climate (rainfall) and ecophysiology on ¹⁵N-abundance variations in mammals do not persist in faeces. Rather, faecal δ¹⁵N tracks changes in plant δ¹⁵N, with further fractionation occurring primarily due to variations in dietary protein (reflected by %N). Controlling for these effects, we show that a dual-isotope multiple source mixing model (Isosource) can extend diet reconstructions for African savanna herbivores beyond simplified C₃/C₄ distinctions, although further understanding of variations in mammal δ¹⁵N are needed for greater confidence in this approach.     

Phytochemistry and biosynthesis of δ-lactone withanolides

Withanolides are highly oxygenated natural products. These C₂₈ steroids with ergostane-based skeletons functionalized at C-22 and C-26 form six-membered δ-lactone rings. Withanolides containing a δ-lactone side chain often occur in Solanaceae and have a variety of biological activities because of their complicated structures. Characteristic spectroscopic behaviors and biosynthesis of withanolides are conducive to their structural elucidation and “biomimetic synthesis”, respectively. However, the last review to summarize their spectroscopic features and biosynthesis was in 1996. Since then, many withanolides with novel structures have been described by their spectra with biosynthesis investigated with many bioassays. This review surveys δ-lactone withanolides and emphasizes their spectral features, configurations and biosynthetic genes. The period reviewed includes through January 2014. We also include phytochemical species.     

Combined use of δ¹³C, δ18O and δ15N tracks nitrogen metabolism and genotypic adaptation of durum wheat to salinity and water deficit

? Accurate phenotyping remains a bottleneck in breeding for salinity and drought resistance. Here the combined use of stable isotope compositions of carbon (δ13C), oxygen (δ1?O) and nitrogen (δ1?N) in dry matter is aimed at assessing genotypic responses of durum wheat under different combinations of these stresses. ? Two tolerant and two susceptible genotypes to salinity were grown under five combinations of salinity and irrigation regimes. Plant biomass, δ13C, δ1?O and δ1?N, gas-exchange parameters, ion and N concentrations, and nitrate reductase (NR) and glutamine synthetase (GS) activities were measured. ? Stresses significantly affected all traits studied. However, only δ13C, δ1?O, δ1?N, GS and NR activities, and N concentration allowed for clear differentiation between tolerant and susceptible genotypes. Further, a conceptual model explaining differences in biomass based on such traits was developed for each growing condition. ? Differences in acclimation responses among durum wheat genotypes under different stress treatments were associated with δ13C. However, except for the most severe stress, δ13C did not have a direct (negative) relationship to biomass, being mediated through factors affecting δ1?O or N metabolism. Based upon these results, the key role of N metabolism in durum wheat adaptation to salinity and water stress is highlighted.     

The control of δ-crystallin gene expression during lens cell development: Dissociation of cell elongation,cell division, δ-crystallin synthesis,and δ-crystallin mRNA accumulation

Previous studies have shown that freshly explanted 6-day-old embryonic chick lens epithelial cells elongate, differentially increase their synthesis of δ-crystallin, and accumulate δ-crystallin mRNA when cultured with fetal calf serum; in contrast, precultured serum-starved 6-day-old and freshly explanted 19-day-old embryonic epithelial cells divide when treated with fetal calf serum. We have explored whether the stimulation of δ-crystallin gene expression (as measured by δ-crystallin synthesis and δ-crystallin mRNA accumulation) is affected by inhibiting lens cell elongation with colchicine, and whether δ-crystallin gene expression is increased in lens epithelial cells stimulated to divide by treatment with fetal calf serum, as it is in those stimulated to elongate by treatment with serum. Three new findings were made in this study. First, the stimulation of δ-crystallin gene expression does not require elongation of the cultured lens cells. Second, a decreased proportion of δ-crystallin synthesis is observed in lens epithelial cells during normal development and during serum starvation; in neither case is this decrease associated with a reduction in the number of δ-crystallin mRNA sequences per cell. Finally, serum stimulation of lens cell division does not increase the proportion of δ-crystallin synthesis, but can promote the accumulation of δ-crystallin mRNA. Thus, the relative proportion of δ-crystallin synthesized during chick lens development is not solely a function of the number of δ-crystallin mRNA sequences in the lens cells.     

The application of δ¹⁸O and δD for understanding water pools and fluxes in a Typha marsh

The δ¹⁸O and δD composition of water pools (leaf, root, standing water and soil water) and fluxes [transpiration (T), evaporation (E)] were used to understand ecohydrological processes in a managed Typha latifolia L. freshwater marsh. We observed isotopic steady‐state T and deep rooting in Typha. The isotopic mass balance of marsh standing water showed that E accounted for 3% of the total water loss, T accounted for 17% and subsurface drainage (D) accounted for the majority (80%). There was a vertical gradient in water vapour content and isotopic composition within and above the canopy sufficient for constructing an isotopic mass balance of water vapour during some sampling periods. During these periods, the proportion of T in evapotranspiration (T/ET) was between 56 ± 17% and 96 ± 67%, and the estimated error was relatively high (>37%) because of non‐local, background sources in vapour. Independent estimates of T/ET using eddy covariance measurements yielded similar mean values during the Typha growing season. The various T/ET estimates agreed that T was the dominant source of marsh vapour loss in the growing season. The isotopic mass balance of water vapour yielded reasonable results, but the mass balance of standing water provided more definitive estimates of water losses.     

Enzymic synthesis of argininosuccinate catalyzed by δ-crystallin

Summary A fast and practical procedure has been developed for the synthesis of argininosuccinate using immobilized duck lens -crystallin as catalyst.     

Induction of δ-aminolaevulinate synthetase under environmental-stress conditions

1. Exposure of rats to environmental-stress conditions of hypobaria, hypoxia and cold did not alter the activity of hepatic delta-aminolaevulinate synthetase. 2. Induction of the enzyme by diethoxycarbonyldihydrocollidine was inhibited when the rats were exposed to hypobaria before or during the treatment with the drug but not after the initial phase when the process of induction was initiated. Neither increased concentration of the drug nor the time of induction had any effect on the inhibition under hypobaria. 3. A period of 12-24h of pre-exposure to hypobaria gave the maximum inhibition, and on longer exposure the inhibitory effect was decreased. 4. The inhibition was not a permanent effect and could be substantially reversed in 12h of withdrawal to ambient pressure. 5. Inhibition of induction was found under hypobaria and hypoxia, but not on exposure to cold. This suggests a specific effect of lack of O(2) rather than a general effect of stress. 6. It appears possible that alteration of concentration of endogenous adenine nucleotides may control the process of diethoxycarbonyldihydrocollidine-mediated induction of delta-aminolaevulinate synthetase, since treatment with ATP, cyclic AMP or theophylline produced inhibition similar to that under hypobaria and hypoxia.     

The Biosynthesis of δ-Aminolevulinic Acid in Chlorella

When autotrophically growing cultures of Chlorella are treated with levulinic acid, delta-aminolevulinic acid is excreted into the medium, providing a direct demonstration of alpha-aminolevulinic acid production in a green plant. Evidence is presented which indicates that alpha-aminolevulinic acid formation may be the the rate-controlling step of chlorophyll synthesis in Chlorella, and that control of the rate of alpha-aminolevulinic acid synthesis may be exerted at the level of production and breakdown of an enzyme which catalyzes its formation.     

Earlier Onset of δ-Retrovirus-Induced Leukemia after Splenectomy

Infection by δ-retroviruses such as human T-lymphotropic virus type 1 (HTLV-1) and bovine leukemia virus (BLV) is mostly asymptomatic. Indeed, only a minority (<5%) of δ-retrovirus infected hosts will develop either lymphoproliferative or neurodegenerative diseases after long latency periods. In fact, the host immune response is believed to tightly control viral replication but this assumption has not been definitely proven in vivo. Here, we provide direct experimental evidence demonstrating that integrity of the spleen is required to control pathogenesis. In the BLV model, we show that asplenia decreases efficiency of the immune response and induces an imbalance in cell dynamics resulting in accelerated onset of leukemia. These observations enlighten a potential threat in splenectomized HTLV-1 carriers and justify a regular preventive evaluation.     

Spinal δ2 but not δ1 opioid receptors are involved in intracereboventricular β-endorphin-induced antinociception in the mouse

The antinociception induced by β-endorphin given intracerebroventricularly (i.c.v.) has been previously demonstrated to be mediated by the release of Met-enkephalin and subsequent stimulation of δ receptors in the spinal cord for antinociception. The present study was designed to determine what type of opioid receptor, δ1 or δ2, in the spinal cord is involved in i.c.v. β-endorphin-induced antinociception. Antinociception was assessed by the tail-flick test in male ICR mice. NTB (0.2–20 nmol) and NTI0 (0.22–2.2 nmol),selective δ2 receptor antagonists, given intrathecally (i.t.) dose-dependently attenuated i.c.v. β-endorphin-induced inhibition of the tail-flick response. On the other hand, BNTX (0.02–2.2 nmol), a selective δ1 receptor antagonist, given i.t., did not block i.c.v. β-endorphin-induced antinociception. The tail-flick inhibition induced by DAMGO, a μ receptor agonist, or U50,488H, a к receptor agonist, was not blocked by i.t. BNTX, NTB or NTI. It is concluded that δ2 but not δ1 receptors in the spinal cord are involved in i.c.v. β-endorphin-induced antinociception.     

Docking studies suggest ligand-specific δ-opioid receptor conformations

An automated docking procedure was used to study binding of a series of δ-selective ligands to three models of the δ-opioid receptor. These models are thought to represent the three ligand-specific receptor conformations. Docking results are in agreement with point mutation studies and suggest that different ligands—agonists and antagonists—may bind to the same binding site under different receptor conformations. Docking to different receptor models (conformations) also suggests that by changing to a receptor-specific conformation, the receptor may open or close different binding sites to other ligands. Figure  Ligands 5 (green) and 6 (orange) in bindingpocket BP1 of the R1 δ-opioid receptor model     

Biosynthesis of δ-aminolevulinic acid in Rhodopseudomonas sphaeroides

The biosynthesis of δ-aminolevulinic acid was investigated in three strains of Rhodopseudomonas sphaeroides. A wild-type strain (NCIB 8253) possessed both δ-aminolevulinic acid synthetase and γ,δ-dioxovaleric acid transaminase in the cytoplasmic and membrane cell fractions. δ-Aminolevulinic acid synthetase activities were not detected in extracts of mutant strains H5 and H5D. However, γ,δ-dioxovaleric acid transaminase was found in the cytoplasmic and membrane fractions of these latter two strains. Strain H5 required exogenously added δ-aminolevulinic acid for growth and bacteriochlorophyll synthesis. Strain H5D did not require this compound for growth and bacteriochlorophyll synthesis. γ,δ-Dioxovaleric acid added in the growth medium did not support the growth of H5, although it was actively transported into the cells. Addition of γ,δ-dioxovaleric acid to the growth medium did not enhance the growth of either the wild-type or H5D strains. These results indicate that ALA synthetase is not required for growth and bacteriochlorophyll synthesis in H5D and that γ,δ-dioxovaleric acid is probably not an intermediate in the formation of δ-aminolevulinic acid in the strains of Rhodopseudomonas sphaeroides studied. In strain H5D another pathway may function in the formation of δ-aminolevulinic acid other than that catalyzed by δ-aminolevulinic acid synthetase or γ,δ-dioxovaleric acid transaminase.     

Variation in hair δ13C and δ15N values in long-tailed macaques (Macaca fascicularis) from Singapore

Much of the primatology literature on stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair δ¹³C and δ¹⁵N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in δ¹³C but not δ¹⁵N. The range of variation in δ¹³C was consistent with a diet based on C₃ resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean δ¹³C value but mid-range mean δ¹⁵N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study.     

Enantioselective Dehydrochlorination of δ-Hexachlorocyclohexane and δ-Pentachlorocyclohexene by LinA1 and LinA2 from Sphingobium indicum B90A

δ-Hexachlorocyclohexane (δ-HCH), one of the prevalent isomers of technical HCH, was enantioselectively dehydrochlorinated by the dehydrochlorinases LinA1 and LinA2 from Sphingobium indicum B90A to the very same δ-pentachlorocyclohexene enantiomer. Racemic δ-pentachlorocyclohexene, however, was transformed with opposite enantioselectivities by the two enzymes. A transformation pathway based on an anti-1,2-elimination, followed by a syn-1,4-elimination and a subsequent syn-1,2-elimination is postulated.