The Maryland mammoth allele reduces floral stimulus activity in stem piece explants of Nicotiana tabacum (Solanaceae)

The response of axillary buds to floral stimulus activity in stem pieces was examined in two near-isogenic cultivars of tobacco that differ in the recessive maryland mammoth (mm) allele, which confers short-day behavior. All axillary buds from day-neutral plants assayed on six-internode stem pieces made few nodes (less than 20) before flowering, while axillary buds from plants homozygous for mm assayed on six-internode stem pieces either did not flower in noninductive conditions or made many nodes before flowering in inductive conditions. About 80% of day-neutral axillary buds grafted onto day-neutral stem pieces did not respond to floral stimulus in stem pieces, indicating that the floral stimulus in stem pieces is ephemeral. In other graft combinations, the proportion of axillary buds that did respond to floral stimulus in stem pieces was substantially reduced from the 20% of day-neutral buds on day-neutral stem pieces that responded. These results indicate that the mm allele probably reduces both the amount of floral stimulus activity in stem pieces and the competence of axillary buds to respond.     

Role of stem cells during diabetic liver injury

Diabetes mellitus is one of the most severe endocrine metabolic disorders in the world that has serious medical consequences with substantial impacts on the quality of life. Type 2 diabetes is one of the main causes of diabetic liver diseases with the most common being non‐alcoholic fatty liver disease. Several factors that may explain the mechanisms related to pathological and functional changes of diabetic liver injury include: insulin resistance, oxidative stress and endoplasmic reticulum stress. The realization that these factors are important in hepatocyte damage and lack of donor livers has led to studies concentrating on the role of stem cells (SCs) in the prevention and treatment of liver injury. Possible avenues that the application of SCs may improve liver injury include but are not limited to: the ability to differentiate into pancreatic β‐cells (insulin producing cells), the contribution for hepatocyte regeneration, regulation of lipogenesis, glucogenesis and anti‐inflammatory actions. Once further studies are performed to explore the underlying protective mechanisms of SCs and the advantages and disadvantages of its application, there will be a greater understand of the mechanism and therapeutic potential. In this review, we summarize the findings regarding the role of SCs in diabetic liver diseases.     

Arachidonic acid metabolism in isolated pancreatic islets. V. The enantiomeric composition of 12-hydroxy-5,8,10,14-eicosatetraenoic acid indicates synthesis by a 12-lipoxygenase rather than a monooxygenase

Recent evidence indicates that the arachidonate metabolite 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) or its precursor may act as a second messenger in stimulus-response coupling in a variety of cells including Aplysia neurons, adrenal glomerulosa cells, and pancreatic islets. The compound 12(S)-HETE is generated from the precursor 12(S)-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12(S)-HPETE), which is a product of the 12-lipoxygenase enzyme. Some cells have recently been found to produce the enantiomer 12(R)-HETE, apparently via a cytochrome P-450 monooxygenase, and the biologic actions of 12(R)-HETE and 12(S)-HETE differ. We have examined the stereochemistry of 12-HETE from isolated pancreatic islets both radiochemically and by a new mass spectrometric method capable of quantitating subnanogram amounts of 12-HETE stereoisomers. Endogenous 12-HETE from islets was found to be exclusively the S-isomer. D-Glucose stimulated both insulin secretion and islet accumulation of 12(S)-HETE but not of 12(R)-HETE. Pharmacologic inhibition of islet 12-HETE biosynthesis also suppressed glucose-induced insulin secretion. These findings suggest that islet 12-HETE is a product of a 12-lipoxygenase rather than of a cytochrome P-450 monooxygenase and further implicate 12-lipoxygenase products in stimulus-secretion coupling.     

Ethylene Oxide Resistance of Nondesiccated and Desiccated Spores of Bacillus subtilis var. niger Hermetically Sealed in Various Polymeric Films

The resistance to destruction of spores of Bacillus subtilis var. niger hermetically sealed in various polymeric films and exposed to ethylene oxide with and without relative humidity was determined. The effect of desiccation was also determined. The order of increased resistance to sterilization with regard to type of polymeric film was found to be: polyethylene equal to polyvinyl chloride, less than nylon, less than cellophane/polyethylene laminate, less than phenoxy, less than mylar/polyethylene laminate. Desiccated spores sealed in various polymeric films were much more resistant to ethylene oxide sterilization than nondesiccated spores. Relative humidity was an important factor in ethylene oxide sterilization with spores not sealed in polymeric films. However, with spores hermetically sealed in polyethylene, added relative humidity was an insignificant factor in the sterilization process.     

Identification of a plasmid-borne parathion hydrolase gene from Flavobacterium sp. by southern hybridization with opd from Pseudomonas diminuta.

Parathion hydrolases have been previously described for an American isolate of Pseudomonas diminuta and a Philippine isolate of Flavobacterium sp. (ATCC 27551). The gene which encodes the broad-spectrum organophosphate phosphotriesterase in P. diminuta has been shown by other investigators to be located on a 66-kilobase (kb) plasmid. The intact gene (opd, organophosphate-degrading gene) from this degradative plasmid was cloned into M13mp10 and found to express parathion hydrolase under control of the lac promoter in Escherichia coli. In Flavobacterium sp. strain ATCC 27551, a 43-kb plasmid was associated with the production of parathion hydrolase by curing experiments. The M13mp10-cloned fragment of the opd gene from P. diminuta was used to identify a homologous genetic region from Flavobacterium sp. strain ATCC 27551. Southern hybridization experiments demonstrated that a genetic region from the 43-kb Flavobacterium sp. plasmid possessed significant homology to the opd sequence. Similar hybridization did not occur with three other native Flavobacterium sp. plasmids (approximately 23, 27, and 51 kb) present within this strain or with genomic DNA from cured strains. Restriction mapping of various recombinant DNA molecules containing subcloned fragments of both opd plasmids revealed that the restriction maps of the two opd regions were similar, if not identical, for all restriction endonucleases tested thus far. In contrast, the restriction maps of the cloned plasmid sequences outside the opd regions were not similar. Thus, it appears that the two discrete bacterial plasmids from parathion-hydrolyzing soil bacteria possess a common but limited region of sequence homology within potentially nonhomologous plasmid structures.     

Modulation of active Ca2+ uptake by the islet-cell endoplasmic reticulum.

The possible effects of calmodulin and cyclic AMP on active Ca2+ uptake by the islet-cell endoplasmic reticulum were investigated. Neither calmodulin nor cyclic AMP affected the rate of active Ca2+ uptake, or the steady-state filling capacity of the endoplasmic reticulum when measured in the absence of oxalate. Consistent with these results, calmodulin did not activate the Ca2+-stimulated ATPase activity associated with this cell fraction. During the course of these experiments., it was unexpectedly discovered that the rate of Ca2+ uptake, as well as the steady-state Ca2+ filling capacity of the endoplasmic reticulum, were markedly increased by unidentified factor(s) in the cytosol. This effect could be demonstrated by reconstitution of the membranes in cytosol, or by direct addition of fresh or dialysed cytosol to the Ca2+ uptake assays. The degree of activation by the cytosol indicates that the endoplasmic reticulum may play a prominent role in controlling beta-cell Ca2+ concentrations and that the unidentified activator(s) present in the cytosol may be involved in regulation of this function.     

Amino Acid Transport in Suspension-cultured Plant Cells: II. CHARACTERIZATION OF l-LEUCINE UPTAKE

l-Leucine (l-Leu) transport into suspension cultured Nicotiana tabacum L. cv. Wisconsin 38 cells has been investigated. Cells were batch-cultured and routinely assayed 3.5 to 4 days after subculturing. Uptake rates were measured over the concentration range of 10 micromolar to 150 millimolar. Kinetic analysis of the uptake rates indicated that uptake was multiphasic with three saturable phases and one unsaturable phase. The three saturable phases which occur in the concentration ranges of 10 to 40 micromolar, 50 to 100 micromolar, and 0.2 to 5.0 millimolar exhibited the following characteristics; (a) phases were energy-dependent as shown by 84 to 94% inhibition of uptake rates by metabolic inhibitors; (b) phases exhibited broad pH optima between 3.0 and 5.5; (c) phases showed stereospecificity for l-Leu; (d) over a 12-hour incubation period, phases concentrated l-Leu 43, 90, and 10 times when the initial l-Leu concentration was 20 micromolar, 100 micromolar, and 1.0 millimolar, respectively; (e) phases had K(m) values of 17.6 micromolar, 60.1 micromolar, and 1.38 millimolar, respectively; and (f) in the temperature range of 17 to 27 C phases had Q(10) values of 2.1, 1.4, and 1.4, respectively. l-Leu uptake in the three saturable phases was inhibited by a 20-fold higher concentration of 18 other amino acids; phenylalanine, alanine, and methionine were the most effective inhibitors, whereas aspartic acid, asparagine, histidine, and arginine were the least effective. The nonsaturable phase which was responsible for increases in the uptake rate above 5.0 mm appeared to be primarily diffusional since it was minimally influenced by metabolic inhibitors and had a Q(10) of 1.3.     

Cyanide-insensitive and Cyanide-sensitive O(2) Uptake in Wheat: II. GRADIENT-PURIFIED MITOCHONDRIA LACK CYANIDE-INSENSITIVE RESPIRATION

Wheat leaves normally produced very little ethylene, but following a water deficit stress which caused a loss of 9% initial fresh weight, ethylene production increased more than 30-fold within 4 hours and declined rapidly thereafter. The changes in ethylene production were paralleled by an increase and subsequent decrease in 1-aminocyclopropanecarboxylic acid (ACC) content. The level of S-adenosylmethionine was unaffected, suggesting that the conversion of S-adenosylmethionine to ACC is a key reaction in the production of water stress-induced ethylene. This view was further supported by the observation that application of ACC to nonstressed leaf tissue caused a 70-fold increase in ethylene production, while aminoethoxyvinylglycine, a known inhibitor of the conversion of S-adenosylmethionine to ACC, inhibited ACC accumulation as well as the surge in ethylene production if the inhibitor was applied prior to the stress treatment. Cycloheximide, an inhibitor of protein synthesis, effectively blocked both ethylene production and ACC formation, suggesting that water stress induces de novo synthesis of ACC synthase, which is the rate-controlling enzyme in the pathway of ethylene biosynthesis.     

The maryland mammoth allele and rooting both perturb the fate of florally determined apices in Nicotiana tabacum.

The stability of the florally determined state in terminal and axillary buds of two tobacco cultivars was studied. We used Hicks and Hicks Maryland Mammoth, near-isogenic cultivars of Nicotiana tabacum differing at the recessive maryland mammoth locus which confers short-day behavior. The experimental design consisted of growing plants in short-day conditions and subjecting them to three bioassays in long-day conditions: in vitro culture of apices consisting of meristems and three to four leaf primordia; rooting of buds consisting of meristems and 8 to 12 leaves, leaf primordia, and internodes; and release from apical dominance of axillary buds in situ. Cultured terminal and axillary apices expressed floral determination, indicating that meristems can be florally determined. Two lines of evidence indicate that rooting destabilizes an already acquired florally determined state: cultured apices from both axillary and terminal buds produced fewer nodes after excision than homologous buds which were rooted; and a lower percentage of rooted axillary buds from Hicks Maryland Mammoth plants expressed floral determination than did homologous axillary buds grown out in situ in noninductive conditions. Rooted buds from the two genotypes expressed floral determination at different frequencies, but produced abnormal inflorescences at similar frequencies, indicating that roots and the maryland mammoth allele influence common as well as unique processes associated with floral determination.     

Assessment of organochlorine pesticides and metals in ring‐tailed lemurs (Lemur catta) at Beza Mahafaly Special Reserve,Madagascar

Like most of Madagascar's endemic primates, ring‐tailed lemurs (Lemur catta) face a number of threats to their survival. Although habitat loss is of greatest concern, other anthropogenic factors including environmental contamination may also affect lemur health and survival. In this study, we examined ring‐tailed lemurs from the Beza Mahafaly Special Reserve (BMSR), southern Madagascar for exposure to organochlorine (OC) pesticides and metals and examined differences in contaminant concentrations between sexes and among age groups, troops, and habitats. A total of 14 pesticides and 13 metals was detected in lemur blood (24 individuals) and hair (65 individuals) samples, respectively. p,p′‐DDT, heptachlor, aldrin, heptachlor epoxide, endrin aldehyde, and endrin were among the most prevalent pesticides detected. Surprisingly, the persistent metabolite of p,p′‐DDT, p,p′‐DDE, was not detected. The most commonly detected metals were aluminum, zinc, boron, phosphorus, silicon, and copper, whereas metals considered more hazardous to wildlife (e.g. arsenic, cadmium, lead, selenium, vanadium) were not found above detection limits. Overall, concentrations of OC pesticides and metals were low and similar to those considered to be background concentrations in other studies examining the ecotoxicology of wild mammals. Few inter‐sex, ‐age, ‐troop, and ‐habitat differences in contaminant concentrations were observed, suggesting a uniform distribution of contaminants within the reserve. Several statistically significant relationships between lemur body size and contaminant concentrations were observed, but owing to the lack of supportive data regarding contaminant exposure in wild primates, the biological significance of these findings remains uncertain. Results of this study document exposure of ring‐tailed lemurs at BMSR to multiple OC pesticides and metals and provide essential baseline data for future health and toxicological evaluations of lemurs and other wild primates, especially those in regions with expanding agricultural and mining operations. Am. J. Primatol. 71:998–1010, 2009. © 2009 Wiley‐Liss, Inc.