Induction of neovascularization in vivo by glycerol

Glycerol, injected into a site between the femoral vessels of the rat, induced neovascularization, both from the preexisting microcirculation and from the side of the femoral vein facing the artery-vein interstitium where the glycerol was administered. The use of glycerol together with a known angiogenic substance (PGE₂) did not modify the neocapillary density (NCD) obtained with glycerol alone. In contrast, the lower level of NCD achieved with an acylglycerol (triacetylglycerol) was increased when the latter was associated with PGE₂. Values reached were similar to, but never higher than, those for glycerol alone, or combined with PGE₂. The results suggest that glycerol and some substances containing glycerol, amongst which 1-butyrylglycerol has been previously considered¹, may stimulate angiogenesis by a direct or indirect mechanism of action.     

Effects of gastric secretagogues on tissue glycerol in the isolated amphibian gastric mucosa

Summary Histamine and theophylline, two gastric secretagogues, significantly increased tissue glycerol content by 121 and 66%, respectively, in the isolated toad gastric mucosa. This is new evidence in favor of the hypothesis that gastric segretagogues may act via lipid mobilization.This investigation was supported by Consejo de Desarrollo Científico y humanístico de la Universidad del Zulia, Maracaibo, Venezuela.     

Interaction of mitochondrial porin with cytosolic proteins

Summary Intracellular phosphorylation is an important step in active uptake and utilization of carbohydrates. For example glucose and glycerol enter the liver, cell along the extra intracellular gradient by facilitated diffusion through specific carriers and are concentrated inside the cell by phosphorylation via hexokinase or glycerol kinase. Depending on the function of the respective tissue the uptake of carbohydrates serves different metabolic purposes. In brain and kidney medulla cells which depend on carbohydrates, glucose and glycerol are taken up according to the energy demand. However, in tissues such as muscle which synthesize glycogen or like liver which additionally produce fat from glucose, the uptake of carbohydrates has to be regulated according to the availability of glucose and glycerol. How the reversible coupling of the kinases to the outer membrane pore and the mitochondrial ATP serves to fulfil these specific requirements will be explained as well as how this regulates the carbohydrate uptake in brain according to the activity of the oxidative phosphorylation and how this allows glucose uptake in liver, and muscle to persist in the presence of high glucose 6-phosphate without activating the rate of glycolysis.     

Endocannabinoids and β-amyloid-induced neurotoxicity in vivo: effect of pharmacological elevation of endocannabinoid levels

We investigated the involvement of endocannabinoids in the control of neuronal damage and memory retention loss in rodents treated with the β-amyloid peptide (1–42) (BAP). Twelve days after stereotaxic injection of BAP into the rat cortex, and concomitant with the appearance in the hippocampus of markers of neuronal damage, 2-arachidonoyl glycerol, but not anandamide, levels were enhanced in the hippocampus. VDM-11 (5 mg/kg, i.p.), an inhibitor of endocannabinoid cellular reuptake, significantly enhanced rat hippocampal and mouse brain endocannabinoid levels when administered sub-chronically starting either 3 or 7 days after BAP injection and until the 12–14th day. VDM-11 concomitantly reversed hippocampal damage in rats, and loss of memory retention in the passive avoidance test in mice, but only when administered from the 3rd day after BAP injection. We suggest that early, as opposed to late, pharmacological enhancement of brain endocannabinoid levels might protect against β-amyloid neurotoxicity and its consequences. Received 26 January 2006; received after revision 24 March 2006; accepted 12 April 2006     

Brominated diphenyl ethers from a marine bacterium associated with the spongeDysidea sp.

Summary BacteriaVibro sp. isolated from the spongeDysidea sp. were shown to biosynthesize brominated diphenyl ethers. We identified one of the bacterial brominated metabolites using gas liquid chromatography and mass spectrometry to compare this product with standard 3,5-dibromo-2-(3,5-dibromo-2-methoxyphenoxy)phenol. The latter has been isolated from ethanol extracts of the spongeDysidea sp.     

Physiological roles of glycerol-transporting aquaporins: the aquaglyceroporins

A subclass of aquaporin (AQP) water channels, termed aquaglyceroporins, are also able to transport glycerol and perhaps urea and other small solutes. Although extensive data exist on the physiological roles of aquaporin-facilitated water transport, until recently the biological significance of glycerol transport by the mammalian aquaglyceroporins has been unknown. There is now compelling evidence for involvement of aquaglyceroporin- facilitated glycerol transport in skin hydration and fat cell metabolism. Mice deficient in AQP3 have dry skin, reduced skin elasticity and impaired epidermal biosynthesis. Mice lacking AQP7 manifest progressive adipocyte fat accumulation and hypertrophy. These skin and fat phenotypes are attributable to impaired glycerol transport. A potential implication of these findings is the possibility of modulation of aquaglyceroporin expression or function in the therapy of skin diseases and obesity. Received 20 January 2006; received after revision 21 February 2006; accepted 20 March 2006     

The karyotype ofOxymycterus sp (Cricetidae,Rodentia) from Central Brazil

Cytogenetical data, including G-, C-bands and NORs distribution ofOxymycterus sp (2n=54; FN=64) captured in Distrito Federal, state of Goiás, Central Brazil are presented. Our results are compared to the karyotype information already available on this genus.     

Enzymes catalyzing the reduction of aldopentoses and the oxidation of pentitols in Mycobacteria]

M. phlei, grown on synthetic Sauton medium (with 6% glycerol as carbon source), had NADPH- and NADH-aldopentose reductase, as well as NAD-pentitol dehydrogenase activities; some of their properties are studied. These activities are not present in BCG grown on the same medium. All experiments of aldopentose-reductase induction in BCG on a D(+)xylose medium were negative.     

Juvenilizing effect of ecdysone mimic RH 5849 inGalleria mellonella larvae

The response of the final instar larvae ofG. mellonella to topical application of the non-steroidal ecdysone mimic, RH 5849, was age-related as well as dose-dependent. In young final instar larvae, moderate doses of RH 5849 induced perfect supernumerary larval moults, but doses equal to and higher than 8.5 μg per larva caused premature formation of larval cuticle and were lethal. Application of RH 5849 significantly increased allatotropic activity of the brain, and also activated synthesis of juvenile hormone (JH) by the corpora cardiaca/corpora allata complex. Simultaneous application of RH 5849 and FMev, a potent inhibitor of JH synthesis, to young final instar larvae lowered the incidence of perfect supernumerary larval moults. We conclude that the effect of RH 5849 on the developmental programme inG. mellonella is mediated by the corpora allata.     

Revisiting the metabolic syndrome: the emerging role of aquaglyceroporins

The metabolic syndrome (MetS) includes a group of medical conditions such as insulin resistance (IR), dyslipidemia and hypertension, all associated with an increased risk for cardiovascular disease. Increased visceral and ectopic fat deposition are also key features in the development of IR and MetS, with pathophysiological sequels on adipose tissue, liver and muscle. The recent recognition of aquaporins (AQPs) involvement in adipose tissue homeostasis has opened new perspectives for research in this field. The members of the aquaglyceroporin subfamily are specific glycerol channels implicated in energy metabolism by facilitating glycerol outflow from adipose tissue and its systemic distribution and uptake by liver and muscle, unveiling these membrane channels as key players in lipid balance and energy homeostasis. Being involved in a variety of pathophysiological mechanisms including IR and obesity, AQPs are considered promising drug targets that may prompt novel therapeutic approaches for metabolic disorders such as MetS. This review addresses the interplay between adipose tissue, liver and muscle, which is the basis of the metabolic syndrome, and highlights the involvement of aquaglyceroporins in obesity and related pathologies and how their regulation in different organs contributes to the features of the metabolic syndrome.     

Uptake and incorporation of labeled oleic acid and glycerol by the isolated and perfused liver of the Wistar rat]

After perfusion by oleic acid (9-10(-3)H) and glycerol (1(-14)C) previously starved Wistar rats, the synthesis of hepatic TG and PL follows the two following different method: -- during the first minutes of perfusions, the most important method synthesis of TG and especially of PL is a de novo synthesis utilizing glycerol and the exogenous AG. The TG synthesized are 18:1 18:1 18:1 and 16:0 18:1 18:2 the PL synthesized are LP, AP and LPC; -- during perfusions of long duration (30, 60, 120 min.), the major method of synthesis of TG and PL is an active exchange of AG of the endogenous glycerolipids. The TG synthesized are 16:0 18:1 18:1 and 16:0 18:1 18:2 the PL synthesized are PE and PC.     

Glycerol production byDunaliella

Summary Species of the unicellular algaDunaliella possess outstanding tolerance of a wide range of salinities. They can adapt to grow in salt media which range from less than 0.5 M to saturated salt solutions and withstand enormous osmotic shocks through a unique osmotic adaptation. The osmoregulating mechanism depends on photosynthetic production of glycerol, whose intracellular concentration varies in direct proportion to the extracellular salt concentration and reaches values in excess of 50% of the total dry weight of the cells.Dunaliella, and another halotolerant glycerol producing alga,Asteromonas gracilis, osmoregulate biochemically by controlling glycerol biosynthesis and degradation. 3 new enzymes, NADPH-dihydroxyacetone-reductase, dihydroxyacetone kinase and glycerol-1-phosphatase seem to be involved in the osmoregulatory response via glycerol inDunaliella andAsteromonas. A hypothetical scheme of glycerol metabolism in these algae utilizing these enzymes is presented. Growth studies ofDunaliella indoors and outdoors showed that salt concentrations favoring maximal glycerol productivity are not identical with those required for maximal algal productivity. Maximal yield of glycerol occurred around 2 M NaCl while maximal algal productivity occurred below 0.5 M NaCl. Observed yields of glycerol inDunaliella culture outdoors are compared with theoretically calculated maximal yield.     

Aquaglyceroporins: implications in adipose biology and obesity

Aquaporins (AQPs) are membrane water/glycerol channels that are involved in many physiological processes. Their primary function is to facilitate the bidirectional transfer of water and small solutes across biological membranes in response to osmotic gradients. Aquaglyceroporins, a subset of the AQP family, are the only mammalian proteins with the ability to permeate glycerol. For a long time, AQP7 has been the only aquaglyceroporin associated with the adipose tissue, which is the major source of circulating glycerol in response to the energy demand. AQP7 dysregulation was positively correlated with obesity onset and adipocyte glycerol permeation through AQP7 was appointed as a novel regulator of adipocyte metabolism and whole-body fat mass. Recently, AQP3, AQP9, AQP10 and AQP11 were additionally identified in human adipocytes and proposed as additional glycerol pathways in these cells. This review contextualizes the importance of aquaglyceroporins in adipose tissue biology and highlights aquaglyceroporins’ unique structural features which are relevant for the design of effective therapeutic compounds. We also refer to the latest advances in the identification and characterization of novel aquaporin isoforms in adipose tissue. Finally, considerations on the actual progress of aquaporin research and its implications on obesity therapy are suggested.     

A component of polyphloretin phosphate (PPP) may be an alternative substrate for ATP-glycerol transferase

Summary A low molecular weight fraction of a polyphloretin phosphate (PPP) preparation simulated glycerol in a milieu designed for enzymatic assay of glycerol. It is suggested that a component of this PPP mixture is able to act as an alternative substrate for the ATP-glycerol transfer enzyme; it becomes phosphorylated and thus initiates the series of reactions resulting in a increased conversion of NADH to NAD and the observed changes in absorbance.The authors are pleased to acknowledge the support of Dr D.C. Williams, the useful discussion with Dr M. Higgins and Dr J.J.M. Rowe and the generous supply of polyphloretin compounds from A.B. LEO Laboratories, Helsingborg, Sweden.     

Enzymatic differences in mycobacteria. Ribitol dehydrogenase]

Contrary to the tubercle Bacilli (H37Ra, BCG), Mycobacterium phlei has a ribitol-NAD dehydrogenase (that also oxidizes, although to a lesser extent, erythritol and glycerol). This difference is observed with the Bacteria grown on Sauton's medium, as well as after their adaptation to ribitol. The extracts of all these Mycobacteria reduce, NADP in the presence of glycerol, ribitol or erythritol, though very slowly.     

A reinvestigation of the chemistry of the Dufours gland of the formicine ant,Anoplolepis custodiens

The components of individual Dufours glands excised fromAnoplolepis custodiens workers were analysed by GC-MS. In addition to then-alkanes andn-alkenes previously reported² in these glands, primary alcohols (C₁₉-C₂₂), secondary alcohols (C₂₀-C₂₃), 2-ketones (C₂₀-C₂₃) and possibly carboxylate ethyl esters (C₁₉ and C₂₁) were identified as components of these glands. It seems possible that these high-boiling compounds are used by the workers in laying trails on the hot sandy surfaces of their characteristic habitat and in lining of the inner walls of nests, but no standard compounds have been available to us for any behavioral studies.     

Gonyauline: A novel endogenous substance shortening the period of the circadian clock of a unicellular alga

Summary The circadian clock in the unicellular algaGonyaulax polyedra is accelerated by a substance in extracts from the cells themselves. The extracts have been fractionated using the circadian rhythm of bioluminescence as bioassay. The active substance, termed gonyauline, has been isolated and characterized as a novel low molecular weight cyclopropanecarboxylic acid (S-methyl-cis-2-(methylthio) cyclopropanecarboxylic acid). Synthetic gonyauline has a similar shortening effect on the period of the circadian clock.