Beta-oxidation of medium chain (C8-C14) fatty acids studied in isolated liver cells

The beta-oxidation and esterification of medium-chain fatty acids were studied in hepatocytes from fasted, fed and fructose-refed rats. The beta-oxidation of lauric acid (12:0) was less inhibited by fructose refeeding and by (+)-decanoyl-carnitine than the oxidation of oleic acid was, suggesting a peroxisomal beta-oxidation of lauric acid. Little lauric acid was esterified in triacylglycerol fraction, except at high substrate concentrations or in the fructose-refed state. With [1-14C]myristic acid (14:0), [1-14C]lauric acid (12:0), [1-14C]octanoic acid (8:0) and [2-14C]adrenic acid (22:4(n - 6] as substrate for hepatocytes from carbohydrate-refed rats, a large fraction of the 14C-labelled esterified fatty acids consisted of newly synthesized palmitic acid (16:0), stearic acid (18:0) and oleic acid (18:1) while intact [1-14C]oleic acid substrate was esterified directly. With [9,10-3H]myristic acid as the substrate, small amounts of shortened 3H-labelled beta-oxidation intermediates were found. With [U-14C]palmitic acid, no shortened fatty acids were detected. It was concluded that when the mitochondrial fatty acid oxidation is down-regulated such as in the carbohydrate-refed state, medium-chain fatty acids can partly be retailored to long-chain fatty acids by peroxisomal beta-oxidation followed by synthesis of C16 and C16 fatty acids which can then stored as triacylglycerol.     

A novel RNA helicase gene tightly linked to the Triplo-lethal locus of Drosophila.

The Triplo-lethal (Tpl) locus of Drosophila is the only known locus which is lethal when present in three copies rather than the normal two. After recovering a hybrid-dysgenesis-induced mutation of Tpl we used a rapid combination of transposon tagging, chromosome microdissection and PCR to clone the P element that had transposed into the Tpl region. That P element is located within the gene for a new and unique member of the RNA helicase family. This new helicase differs from all others known by having glycine-rich repeats at both the amino and carboxyl termini. Curiously, genetic analysis shows that the P element inserted into this gene is not responsible for the Tpl mutant phenotype. We present possible explanations for these findings.     

Detection of proopiomelanocortin mRNA by in situ hybridization, using a biotinylated oligodeoxynucleotide probe and avidin-alkaline phosphatase histochemistry

A synthetic 24-mer oligodeoxynucleotide complementary to the region of proopiomelanocortin (POMC) mRNA that codes for the MSH core sequence (alpha MSH/ACTH[4-11]), was synthesized and labelled in the 3'-end by use of terminal transferase. Probes tailed with either [3H]- or biotin-labelled nucleotides could be used for in situ hybridization studies. Biotinylated probes, hybridized to mouse and rat pituitary sections, were detected by avidin-alkaline phosphatase or streptavidin-alkaline phosphatase procedures and development in 5-bromo-4-chloro-3-indolyl phosphate (BCIP)-nitroblue tetrazolium (NBT). Proteinase K pretreatment of sections produced a drastic enhancement of the signal obtained, particularly in strongly fixed, paraffin-embedded material. The non-radioactive in situ hybridization technique compared favourably to radioactive in situ hybridization in terms of rapidity and precision of the localization. Controls involved deletion of the probe to prove that other components of the reaction sequence did not yield stain, digestion with RNase to prove that tissue RNA was necessary to bind the probe, prehybridization (blocking) with unlabelled probe to prove that the biotinylated probe reacted with its anti-sense region and not its tail and Northern blotting to show that the probe reacted with only one species of pituitary RNA, having the size of mouse pituitary POMC mRNA. In addition, adrenalectomy, known to increase anterior lobe POMC levels, resulted in both increased numbers and increased intensity of positive corticotroph-like cells. Synthetic oligodeoxynucleotides labelled with biotin appear to constitute attractive reagents for in situ hybridization studies when supported by appropriate control procedures.     

Oxygen control prevents denitrifiers and barley plant roots from directly competing for nitrate

Abstract Two denitrifying bacteria ( Pseudomonas chlororaphis and P. aureofaciens ) and a plant (barley, Hordeum vulgare ) were used to study the effect of O₂ concentration on denitrification and NO₃⁻ uptake by roots under well-defined aeration conditions. Bacterial cells in the early stationary phase were kept in a chemostat vessel with vigorous stirring and thus a uniform O₂ concentration in the solution. Both Pseudomonads lacked N₂O reductase and so total denitrification could be directly measured as N₂O production.
Denitrification decreased to 6–13% of the anaerobic rate at 0.01% O₂ saturation (0.14 μM O₂) and was totally inhibited at 0.04% O₂ saturation (0.56 μM O₂). In this well-mixed system denitrification was 10-times more oxygen sensitive than stated in earlier reports. Uptake of nitrate by plants was measured in the same system under light. The NO₃⁻ uptake rate decreased gradually from a maximum in 21% O₂-saturated medium (air saturated) to zero at 1.6% O₂ saturation (22.4 μM O₂). Owing to the very different non-overlapping oxygen requirements of the two processes, direct competition for nitrate between plant roots and denitrifying bacteria cannot occur.     

Hematozoan parasites of Rio Grande wild turkeys from southern Texas

One hundred twenty-three of 300 blood samples (41%) taken from Rio Grande wild turkeys (Meleagris gallopavo intermedia) from three locations in southern Texas (Welder Wildlife Refuge, Chaparrosa Ranch, and Campo Alegre Ranch) and subinoculated into domestic broad-breasted white turkey poults were positive for a Plasmodium (Novyella) sp. Analysis of blood films from 350 turkeys revealed Haemoproteus meleagridis in 76% of the birds. A significantly greater mean parasite intensity was observed in birds from Welder Wildlife Refuge. Birds from the Campo Alegre Ranch exhibited a significantly higher prevalence of H. meleagridis than birds from Chaparrosa. The Plasmodium sp. was infective for canaries (Serinus canaria), bobwhites (Colinus virginianus), and ring-necked pheasants (Phasianus colchicus), but would not produce infection in white leghorn chickens (Gallus gallus) or Coturnix quail (Coturnix coturnix). Attempts to infect Culex tarsalis and C. pipiens were unsuccessful. Asexual erythrocytic synchrony was not observed when blood-induced infections were monitored in two domestic turkey poults every 4 hr for 72 hr. Exoerythrocytic stages were not found upon examination of impression smears and tissue samples taken from brain, liver, spleen, kidney, lung, and bone marrow. The Plasmodium sp. is most similar morphologically to three species in the subgenus Novyella, P. hexamerium, P. vaughani, and P. kempi. The most striking similarities are to P. hexamerium, and involve mean merozoite number, erythrocytic schizont location, and vertebrate host susceptibility. It differs from P. vaughani in being able to infect turkeys and in type of parasitized erythrocytes. Differences to P. kempi include mean merozoite number, and ability to infect pheasants, and its inability to develop in C. pipiens and C. tarsalis.     

The nucleolar RNA-binding protein B-36 is highly conserved among plants

The nucleolar protein B-36 is an RNA-associated protein which has a number of properties in common with pre-mRNA-binding proteins (hnRNP proteins). Like the hnRNP proteins, B-36 appears to be evolutionarily conserved among various eukaryotes (protists and several animal species). The conservation of B-36 throughout the plant kingdom has been investigated using a panel of nine monoclonal antibodies previously shown to recognize a minimum of four different epitopes in Physarum B-36, the protein used to generate the monoclonal antibodies. Two of the epitopes (I and III) are widely conserved in 34 kDa proteins (presumably B-36 homologues) from the various species tested (Chlamydomonas, moss, fern, oat, onion, carrot, and bean). Using immunofluorescence localization in moss and carrot protoplasts, the cross-reacting proteins were shown to be restricted to the nucleolus, further confirming their probable homology to B-36. Epitopes I and III are also unique to the B-36 homologues as demonstrated by the failure of any other bands to cross-react. Another epitope (IV) was specifically recognized in the plant B-36 homologues but exhibited greatly reduced affinity for the monoclonal antibody relative to Physarum B-36. The remaining epitope (II), unlike the others, exhibited variable conservation in the plant B-36 homologues and, in addition, was present in several other seemingly unrelated proteins. Finally, several of the plant species exhibited two cross-reacting variants at roughly the 34 kDa position and in at least one of these cases a single monoclonal antibody was able to distinguish between the two variants, a result indicating that the variants do have bona fide structural differences.(ABSTRACT TRUNCATED AT 250 WORDS)     

Phytochrome is not involved in the red-light-enhancement of the stomatal blue-light-response in wheat seedlings

The stomatal response to blue light (BL) in wheat seedlings ( Triticum aestivum L. cv. Starke II, Weibull) was enhanced by background red light (R). This enhancement was only slightly affected by the addition of background far-red light (FR). Under similar light treatments, the addition of FR induced a 43% transformation from the far-red-absorbing form towards the red-absorbing form of phytochrome from etiolated oat ( Avena sativa L. cv. Sol II), immobilized on phenyl-sepharose. Furthermore, the enhancement of the stomatal BL-response by 15 min R was not reversed by a subsequent irradiation with 5 min FR. It is concluded that the red-light-enhancement of the stomatal blue-light-response in wheat seedlings does not involve a change in the photostationary state of phytochrome.     

Dose responses of gibberellins

To determine the response type, published data for the most widely used bioassays for gibberellins have been analyzed by means of a computer program for estimating sensitivity parameters, or by interpolation. The dose response data are almost uniformly subsensitive, i. e. more than an 81-fold increase in external gibberellin concentration is required for a change from 10 to 90% of maximal response (S₉₀/S₁₀). Data for the interaction of gibberellins with artificial membranes are, in contrast, markedly ultrasensitive (S₉₀/S₁₀± 10). This difference further strengthens the view that lipid structures do not function as receptors for gibberellins. Most of the subsensitive dose responses for gibberellins can be quite precisely represented by cooperative isotherms. However, available data are insufficiently detailed for an unequivocal choice among cooperative, multiphasic or more complex kinetics.     

Detection of proopiomelanocortin mRNA by in situ hybridization,using a biotinylated oligodeoxynucleotide probe and avidin-alkaline phosphatase histochemistry

Summary A synthetic 24-mer oligodeoxynucleotide complementary to the region of proopiomelanocortin (POMC) mRNA that codes for the MSH core sequence (MSH/ACTH[4-11]), ws synthesized and labelled in the 3-end by use of terminal transferase. Probes tailed with either [³H]- or biotin-labelled nucleotides could be used for in situ hydridization studies. Biotinylated probes, hybridized to mouse and rat pituitary sections, were detected by avidinalkaline phosphatase or streptavidin-alkaline phosphatase procedures and development in 5-brome-4-chloro-3-indolyl phosphate (BCIP)-nitroblue tetrazolium (NBT). Proteinase K pretreatment of sections produced a drastic enhancement of the signal obtained, particularly in strongly fixed, paraffin-embedded material. The non-radioactive in situ hybridization technique compared favourably to radioactive in situ hybridization in terms of rapidity and precision of the localization. Controls involved deletion of the probe to prove that other components of the reaction sequence did not yield stain, digestion with RNase to prove that tissue RNA was necessary to bind the probe, prehybridazation (blocking) with unlabelled probe to prove that the biotinylated probe reacted with its anti-sense region and not its tail and Northern blotting to show that the probe reacted with only one species of pituitary RNA, having the size of mouse pituitary POMC mRNA. In addition, adrenalectomy, known to increase anterior lobe POMC, levels, resulted in both increased numbers and increased intensity of positive corticotroph-like cells. Synthetic oligodeoxynucleotides labelled with biotin appear to constitute attractive reagents for in situ hybridization studies when supported by appropriate control procedures.