Avian olfactory receptor gene repertoires: evidence for a well-developed sense of smell in birds?

Among vertebrates, the sense of smell is mediated by olfactory receptors (ORs) expressed in sensory neurons within the olfactory epithelium. Comparative genomic studies suggest that the olfactory acuity of mammalian species correlates positively with both the total number and the proportion of functional OR genes encoded in their genomes. In contrast to mammals, avian olfaction is poorly understood, with birds widely regarded as relying primarily on visual and auditory inputs. Here, we show that in nine bird species from seven orders (blue tit, Cyanistes caeruleus; black coucal, Centropus grillii; brown kiwi, Apteryx australis; canary, Serinus canaria; galah, Eolophus roseicapillus; red jungle fowl, Gallus gallus; kakapo, Strigops habroptilus; mallard, Anas platyrhynchos; snow petrel, Pagodroma nivea), the majority of amplified OR sequences are predicted to be from potentially functional genes. This finding is somewhat surprising as one previous report suggested that the majority of OR genes in an avian (red jungle fowl) genomic sequence are non-functional pseudogenes. We also show that it is not the estimated proportion of potentially functional OR genes, but rather the estimated total number of OR genes that correlates positively with relative olfactory bulb size, an anatomical correlate of olfactory capability. We further demonstrate that all the nine bird genomes examined encode OR genes belonging to a large gene clade, termed gamma-c, the expansion of which appears to be a shared characteristic of class Aves. In summary, our findings suggest that olfaction in birds may be a more important sense than generally believed.     

Enhanced glutathione production by evolutionary engineering of Saccharomyces cerevisiae strains

Glutathione is an important natural tripeptide mainly used because of its antioxidative properties. Commercial glutathione is microbially synthesized by yeasts and the growing demand requires the development of new production strains. An adaptive laboratory evolution strategy using acrolein as a selection agent was employed to obtain strains with an enhanced glutathione accumulation phenotype accompanied by an acrolein resistance phenotype. Two particularly interesting isolates were obtained: one with a high volumetric productivity for glutathione reaching 8.3 mg_glutathione/L h, which is twice as high as the volumetric productivity of its parental strain. This strain reached an elevated intracellular glutathione content of 3.9%. A second isolate with an even higher acrolein tolerance exhibited a lower volumetric productivity of 5.8 mg_glutathione/L h due to a growth phenotype. However, this evolved strain accumulated glutathione in 3.3‐fold higher concentration compared to its parental strain and reached a particularly high glutathione content of almost 6%. The presented results demonstrate that acrolein is a powerful selection agent to obtain high glutathione accumulation strains in an adaptive laboratory evolution experiment.     

Electroencephalography in the diagnosis of hydrocephalus in golden hamsters (Mesocricetus auratus)

The golden hamster (Mesocricetus auratus) is a popular laboratory animal and is used in a multitude of behavioural studies. However, it has been shown that it suffers from different forms of hereditary hydrocephalus, which may result in behavioural changes. This prospective study was designed to look into the usefulness of electroencephalography (EEG) measurements in the diagnosis of hydrocephalus in hamsters. The EEGs of the hydrocephalic hamsters were evaluated double-blind and showed a high-voltage slow wave activity, with a fast activity superimposed onto it. This pattern has already been well described in other hydrocephalic species and differed significantly from the EEGs that were obtained from the normal hamsters. It was concluded from our study that a background activity with an amplitude over 50 muV in combination with a frequency of < or =5 Hz was highly indicative of hydrocephalus in young hamsters. We believe that the EEG could be a very useful diagnostic tool in the screening for hydrocephalus in hamsters.     

Identification and the developmental formation of carotenoid pigments in the yellow/orange Bacillus spore-formers

Spore-forming Bacillus species capable of synthesising carotenoid pigments have recently been isolated. To date the detailed characterisation of these carotenoids and their formation has not been described. In the present article biochemical analysis on the carotenoids responsible for the yellow/orange pigmentation present in Bacilli has been carried out and the identity of the carotenoids present was elucidated. Chromatographic, UV/Vis and Mass Spectral (MS) data have revealed the exclusive presence of a C(30) carotenoid biosynthetic pathway in Bacillus species. Apophytoene was detected representing the first genuine carotenoid formed by this pathway. Cultivation in the presence of diphenylamine (DPA), a known inhibitor of pathway desaturation resulted in the accumulation of apophytoene along with other intermediates of desaturation (e.g. apophytofluene and apo-ζ-carotene). The most abundant carotenoids present in the Bacillus species were oxygenated derivatives of apolycopene, which have either undergone glycosylation and/or esterification. The presence of fatty acid moieties (C(9) to C(15)) attached to the sugar residue via an ester linkage was revealed by saponification and MS/MS analysis. In source fragmentation showed the presence of a hexose sugar associated with apolycopene derivatives. The most abundant apocarotenoids determined were glycosyl-apolycopene and glycosyl-4'-methyl-apolycopenoate esters. Analysis of these carotenoids over the developmental formation of spores revealed that 5-glycosyl-4'-methyl-apolycopenoate was related to sporulation. Potential biosynthetic pathways for the formation of these apocarotenoids in vegetative cells and spores have been reconstructed from intermediates and end-products were elucidated.     

Glycerol metabolism in the hibernating black bear

Summary The contribution of glycerol to protein, carbohydrate, and lipid metabolism was studied in black bears. Special attention was directed at the role of glycerol in preventing uremia. In summer and winter, U-¹⁴C glycerol, as well asl(U¹⁴C)-alanine andd(U-¹⁴C)-glucose were injected intravenously; timed sampling of venous blood and expiratory gases was made.In winter, during hibernation,¹⁴C-label from glycerol was found in alanine and other free amino acids and plasma proteins, pyruvate, lactate, glucose and lipid esters. After 48 h, most of the¹⁴C-label in plasma was found in proteins. However, during the four days of study, no label was found in serum urea. Similar results occurred in summer except, in marked contrast to winter,¹⁴C-labeled urea was continually detected in blood. Expired¹⁴C-CO₂ was considerably lower in winter than summer and winter respiratory quotient was 0.69.In both summer and winter,¹⁴C-labeled alanine also entered plasma proteins and generated pyruvate, lactate and glucose. Once again the marked difference between active and dormant phases was demonstrated: There was no labeled plasma urea in winter while it was continually detected in summer. ¹⁴C-labeled glucose experiments revealed very slow carbohydrate metabolism in winter.These findings suggest that in winter, glycerol helps prevent uremia by serving as a carbon source for amino acid formation. The nitrogen involved in these reactions is thus diverted from urea synthesis into protein synthetic pathways. Further, glycerol also appears to serve as an active substrate for gluconeogenesis and lipogenesis in hibernation.     

Formation of Hydrogen Peroxide and Oxygen Dependence of Photosynthetic CO2 Assimilation by Intact Chloroplasts

1. Hydrogen peroxide excretion by photosynthesizing intact spinachchloroplasts was determined. The rates were dependent on theoxygen concentration and on the ATP/NADPH requirement of thefinal electron acceptor. Upon CO₂ assimilation a maximum rateof 0.9 µmol H₂O₂/mg chlorophyll/hr and half saturationat 7.5 x 10^–5 M O₂ were found. Excretion of H₂O₂ was considerablyreduced upon photosynthetic reduction of glycerate 3-phosphateor oxaloacetate.
2. Light- and HCO₃-saturated CO₂ assimilationwas inhibited bymore than 50% by anaerobic conditions, whereuponquantum efficiencywas also drastically decreased. However,no anoxic influencewas detected with glycerate 3-phosphateas the terminal electronacceptor and the quantum requirementwith this acceptor wasnot increased by anaerobiosis. Thus theenhancing effect ofoxygen on CO₂ assimilation was ascribedto an improvement ofphotosynthetic ATP supply.
3. Since thestimulation of anaerobic photosynthetic CO₂ assimilationbyoxygen was markedly greater than the concomitant increaseinH₂O₂ evolution, photosynthetic oxygen reduction alone isnotsufficient to produce the required additional ATP for theobservedenhanced CO₂ assimilation. But it provides a meansto avoidthe over-reduction of photosynthetic electron carriersand thusenables aerobic cyclic photophosphorylation. This supportsthehypothesis that cyclic photophosphorylation is not an alternativeto ATP formation by "pseudocyclic" electron transport, but ratherthat it depends on the latter.

(Received January 5, 1981; Accepted March 9, 1981)     

Studies on geranylgeranyl diphosphate synthase from rat liver: specific inhibition by 3-azageranylgeranyl diphosphate.

Geranylgeranyl diphosphate synthase from rat liver was separated from farnesyl diphosphate synthase, the most abundant and widely occurring prenyltransferase, by DEAE-Toyopearl column chromatography. The enzyme catalyzed the formation of E,E,E-geranylgeranyl diphosphate (V) from isopentenyl diphosphate (II) and dimethylallyl diphosphate (I), geranyl diphosphate (III), or farnesyl diphosphate (IV) with relative velocities of 0.09:0.15:1. 3-Azageranylgeranyl diphosphate (VII), designed as a transition-state analog for the geranylgeranyl diphosphate synthase reaction, was synthesized and found to act as a specific inhibitor for this synthase, but not for farnesyl diphosphate synthase. Diphosphate V and its Z,E,E-isomer (VI) also inhibited geranylgeranyl diphosphate synthase, but the effect was not as striking as that of the aza analog VII. Specific inhibition of geranylgeranyl diphosphate synthase by VII was also observed in experiments with 100,000g supernatants of rat brain and liver homogenates which contained isopentenyl diphosphate isomerase and prenyltransferases including farnesyl diphosphate synthase as well as geranylgeranyl diphosphate synthase. For farnesyl:protein transferase from rat brain, however, the aza compound did not show a stronger inhibitory effect than E,E,E-geranylgeranyl diphosphate.     

Cloning of two carotenoid ketolase genes from Nostoc punctiforme for the heterologous production of canthaxanthin and astaxanthin

For the heterologous synthesis of keto-carotenoids such as astaxanthin, two carotenoid ketolase genes crtW38 and crtW148, were cloned from the cyanobacterium, Nostoc punctiforme PCC 73102 and functionally characterized. Upon expression in Escherichia coli, both genes mediated the conversion of beta-carotene to canthaxanthin. However in a zeaxanthin-producing E. coli, only the gene product of crtW148 introduced 4-keto groups into the 3,3'-dihydroxy carotenoid zeaxanthin yielding astaxanthin. The gene product of crtW38 was unable to catalyze this reaction. Both ketolases differ in their interaction with a hydroxylase in the biosynthetic pathway from beta-carotene to astaxanthin.     

Loss of Ifnar1 in Pancreatic Acinar Cells Ameliorates the Disease Course of Acute Pancreatitis

Type I interferon constitutes an essential component of the combinational therapy against viral disease. Acute pancreatitis is one side effect of type I interferon-based therapy, implying that activation of type I interferon signaling affects the homeostasis and integrity of pancreatic acinar cells. Here, we investigated the role of type I interferon signaling in pancreatic acinar cells using a caerulein-induced murine model of acute pancreatitis. Pancreas-specific ablation of interferon (alpha and beta) receptor 1 (Ifnar1) partially protected animals from caerulein-induced pancreatitis, as demonstrated by reduced tissue damage. Profiling of infiltrating immune cells revealed that this dampened tissue damage response correlated with the number of macrophages in the pancreas. Pharmacologic depletion of macrophages reversed the protective effect of Ifnar1 deficiency. Furthermore, expression of chemokine (C-C motif) ligand 2 (Ccl2), a potent factor for macrophage recruitment, was significantly increased in the Ifnar1-deficient pancreas. Thus, type I interferon signaling in pancreatic acinar cells controls pancreatic homeostasis by affecting the macrophage-mediated inflammatory response in the pancreas.