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At least 19 recordsLinked to original sources

PubMed1976

Direct transfer of the phosphoryl moiety of mannitol 1-phosphate to [14C]mannitol catalyzed by the enzyme II complexes of the phosphoenolpyruvate: mannitol phosphotransferase systems in Spirochaeta aurantia and Salmonella typhimurium.

Spirochaeta aurantia possesses a phosphoenolpyruvate:mannitol phosphotransferase system which catalyzes the transmembrane transport and phosphorylation of mannitol. In vitro studies showed that both phosphoenolpyruvate and mannitol 1-phosphate could serve as phosphate donors. The phosphoenolpyruvate-dependent reaction required two soluble proteins, Enzyme SI and HPr, and an integral membrane complex, Enzyme SII. Only Enzyme SII was required for the mannitol 1-phosphate-dependent reaction. Enzyme II-dependent transphosphorylation of sugars was also demonstrated in eubacterial extracts. The results lead to the suggestion that the Enzyme II complexes of bacterial phosphotransferase systems possess nonoverlapping binding sites for sugar and sugar phosphate.

Edetic Acid↗

PubMed1977

D-Mannitol dehydrogenase from Absidia glauca. Steady-state kinetic properties and the inhibitory role of mannitol 1-phosphate.

Steady-state kinetic studies including initial velocity for mannitol oxidation and fructose reduction and product inhibition for mannitol oxidation using fructose and reduced nicotinamide adenine dinucleotide (NADH) are in accord with a reaction mechanism best described as ordered Bi-Bi with NAD+ and NADH designated as the first substrate, last product, respectively at pH 8.8. All replots of slopes and intercepts from product inhibition studies were linear. Dead-end inhibition studies using mannitol 1-phosphate gave slope-parabolic, intercept-linear noncompetitive inhibition for both NAD+ and mannitol as substrates. The dead-end inhibitor is capable of binding multiply to the E, EA, and EQ forms of the enzyme to an extent that is controlled by the concentration of substrates. The EQ complex is inferred to undergo a conformational change, E'Q equilibrium EQ, since (V1/E1) greater than (KiqV2)/(KqE1), and no evidence for dead-end complex formation with NADH can be adduced. This is interpreted to mean that the release of fructose from the central complex is faster than the isomerization of the E-NADH complex. When mannitol is saturating, the noncompetitive inhibition against NAD+, as the variable substrate, becomes parabolic uncompetitive. A replot of the slopes of the parabola against mannitol 1-phosphate remains concave upward. This situation could arise if the conformational change we infer in the EQ complex opens up additional sites on the protein which can interact with the dead-end inhibitor.

Fungi↗

PubMed1976

Mannitol production in fungi during glucose catabolism.

The levels of phosphofructokinase (EC 2.7.1.11) and mannitol-1-phosphate dehydrogenase (EC 1.1.1.17) have been determined in a number of Mucor and Penicillium species. Mannitol-1-phosphate dehydrogenase was found in only one species of mucor, Mucor rouxii, and this with a specific activity much lower than that found in Penicillium species. All of the fungi tested in the Ascomycetes class exhibited mannitol-1-phosphate dehydrogenase activity. Interference from both mannitol-1-phosphate dehydrogenase and NADH oxidase (EC 1.6.99.5) caused some difficulty initially in detecting phosphofructokinase in Penicillium species; the Penicillium phosphofructokinase is very unstable. Penicillium notatum accumulates mannitol intracellularly; detection of mannitol-1-phosphate dehydrogenase and mannitol-1-phosphatase (EC 3.1.3.22) activity in cell-free extracts indicates that the mannitol is formed from glucose via fructose-6-phosphate and mannitol-1-phosphate; no direct reduction of fructose to mannitol could be detected. The mannitol-1-phosphate dehydrogenase was specific for mannitol-1-phosphate and fructose-6-phosphate; NADP+(H) could not replace NAD+(H). The phosphatase (EC3.1.3.22) exhibited a distinct preference for mannitol-1-phosphate as substrate; all other substrates tested exhibited less than 25% of the activity observed with mannitol-1-phosphate.

Alcohol Oxidoreductases↗

PubMed1977

Mannitol oxidation in two Micromonospora isolates and in representative species of other actinomycetes.

Mannitol kinase and mannitol-1-phosphate dehydrogenase activities were detected in two Micromonospora isolates. The presence of these enzyme activities indicates that mannitol is catabolized first to mannitol-1-phosphate and then to fructose-6-phosphate. Mannitol-oxidizing enzymes were also surveyed in representative species of four other genera of actinomycetes. Mannitol-1-phosphate dehydrogenase was detected in cell-free extracts of Streptomyces lactamdurans. In contrast, cell-free extracts of Mycobacterium smegmatis, Nocardia erythrophila, Streptomyces lavendulae, and Actinoplanes missouriensis contained mannitol dehydrogenase activity but no detectable mannitol-1-phosphate dehydrogenase activity. The mannitol dehydrogenase activities in the latter species support the operation of a pathway for catabolism of mannitol that involves the oxidation of mannitol to fructose, followed by phosphorylation to fructose-6-phosphate.

Actinomycetales↗

PubMed1979

Mannitol and maintenance hemodialysis.

The extensive use of mannitol during maintenance hemodialysis prompted a study of mannitol kinetics. In 17 patients receiving empirical mannitol therapy of mannitol kinetics. In 17 patients receiving empirical mannitol therapy, residual levels range from 19 to 100 mg% In vitro mannitol clearance exceeds 125 ml/min for the CDAK 5 and PF 1.6 dialyzers, while in vivo clearance ranges from 98 to 140 ml/min in the Triex 1, PF 1.6 and CDAK 5. Despite an apparently adequate clearance rate, mannitol administered during dialysis is incompletely removed. Repeated use of mannitol during dialysis leads to mannitol accumulation. Clinical significance of the residual mannitol levels needs further evaluation.

Humans↗

PubMed1978

Mannitol and fructose catabolic pathways of Pseudomonas aeruginosa carbohydrate-negative mutants and pleiotropic effects of certain enzyme deficiencies.

Mutant strains of Pseudomonas aeruginosa PAO were isolated on the basis of their inability to utilize mannitol as sole carbon source for growth. Four linkage groups (I through IV) among these mutant strains were resolved by two-factor crosses using the general transducing phage F116, and the strains appeared to contain point mutations as evidenced by ability to give rise to spontaneous revertants with wild phenotype on mannitol minimal agar. Group I strains were affected only in ability to grow on mannitol; all were deficient in inducible mannitol dehydrogenase activity, and all but one were deficient in inducible mannitol transport activity. Fructokinase was induced in group I strains and in wild-type bacteria during growth in the presence of mannitol but not fructose, indicating the presence of a pathway specific for endogenously generated fructose. Cells grown on fructose contained phosphoenolpyruvate:fructose-1-phosphotransferase activity, and mannitol-grown cells contained a lower level of this activity. Group II mutants were deficient in constitutive phosphoglucoisomerase, failed to grow on mannitol, grew very slowly on glycerol and fructose, but grew normally on glucose and gluconate. Group III strains were deficient in both nicotinamide adenine dinucleotide- and nicotinamide adenine dinucleotide phosphate-linked glucose-6-phosphate dehydrogenase activities that reside in a single enzyme species. 6-Phosphogluconate appeared to be the inductive effector for this enzyme, which was not required for aerobic growth on glucose or gluconate. A single mannitol-negative mutant in group IV also failed to grow on glycerol and glucose, but no biochemical lesion was identified.

Enzyme Induction↗

PubMed1979

Discrepancies in the extracellular space of sympathetic ganglia measured using different isotopes of mannitol and sucrose.

The extracellular space of rat superior cervical ganglia in vitro was measured using mannitol and sucrose labelled with tritium and carbon-14. The volumes of distribution of the 3H-labelled derivatives, especially [3H]mannitol, exceeded those of the 14C-derivatives. The divergence increased with increasing lengths of incubation. Thus, after 30 min incubation, 'spaces' (ml . g-1) were: [14Cu]mannitol, 0.407; [3H]mannitol 0.447; [14C]mannitol, 0.458; [3H]mannitol, 0.645; [14C]sucrose, 0.430; [3H]sucrose, 0.497. Using thin layer chromatography, it was shown that an average of 22% of the label in ganglia incubated for 120 min with [3H]mannitol, but only 4% with [14C]mannitol, was not associated with the parent compound. Both [3H]- and [14C]sucrose appeared to be metabolized by 11%. It is concluded that mannitol and sucrose can be metabolized in isolated ganglia and that this may lead to substantial errors in estimating the extracellular space, particularly when [3H]markers are used.

Animals↗

PubMed1977

Influence of mannitol on contractile responses of isolated perfused arteries.

The influence of hyperosmotic mannitol on vascular smooth muscle contractile responses was examined in isolated arterial preparations. Vasoconstrictor effects of norepinephrine (NE) and potassium chloride (K+) in the perfused central artery of the rabbit's ear and in perfused mesenteric arteries of cats were significantly inhibited by infusion with Krebs bicarbonate solution made hyperosmotic with mannitol (50-200 mosM increase). Similarly, the magnitude and duration of vasoconstrictor responses to transmural stimulation of the central ear artery of the rabbit were decreased by hyperosmotic mannitol (50 mosM). Mannitol (50 mosM) produced a decrease in perfusion pressure when perfusion pressure was maintained at an increased level by K+ (60 mM). Mannitol-induced vasodilatation was not affected by ethacrynic acid (1.5 X 10(-5) M), beta adrenergic blockade or by the development of tachyphylaxis to the vasodilator effects of nitroglycerin. The concentration of cyclic adenosine-monophosphate was not changed by mannitol. Isotonic mannitol also inhibited NE-induced contractile responses. These data indicate that hyperosmotic mannitol produces vasodilatation in isolated arterial smooth muscle by a mechanism(s) that appears dissimilar from that of several other vasodilator substances and suggest that hypertonicity may not be the only factor involved in the vasodilator effect of mannitol.

Animals↗

PubMedDate not supplied

Effects of hypertonic mannitol on contractile responses and 45Ca movements in isolated canine arteries.

The effects of hyperosmotic mannitol on vascular smooth muscle contractile responses and on 45Ca movements were examined in different isolated canine arteries. Prior exposure to 50 mM mannitol decreased contractile responses elicited with dopamine (DA) in helical strips of canine terminal mesenteric arteries (Tm) and decreased the contractile response elicited with potassium (K+) in both isolated left anterior descending (LAD) and circumflex coronary arteries. Tension responses induced by norepinephrine or DA in the Tm and K+ and prostaglandin F2 alpha in LAD were relaxed by subsequent exposure to mannitol. Mannitol increased the uptake of 45Ca in Tm arteries. Exposure of the Tm and branches of the LAD to mannitol during the washout of 45Ca resulted in a decrease in the rate of loss of 45Ca; the presence of either K+, Mg2+, or ethylenediamine tetraacetic acid during the washout did not prevent the observed mannitol-induced decrease in 45Ca efflux. These effects of mannitol on 45Ca efflux without a concomitant major change in net 45Ca uptake could be attributed to an increase in bound Ca2+ at relevant membrane sites or stores. Thus, hypertonic mannitol may alter contractile responsiveness of selected canine arteries by impeding the release of bound and/or sequestered Ca2+ and, in this manner, decreasing the Ca2+ concentration at the contractile elements.

Animals↗

PubMed1979

The growth response of cells in medium made hyperosmolal with electrolytes or mannitol.

A comparison of the growth rates of established human lymphoid and tumor cell lines was performed in nutrient medium made hyperosmolal with mannitol, NaCl, or mixtures of NaCl and KCl at a constant Na/K ratio. It was found that considerably higher osmolalities were attained with mannitol than electrolytes before a reduction in the growth rate of the culture was observed. This suggests that mannitol and electrolytes affected the growth rate through different mechanisms. Mannitol uptake was studied with two of the cell lines and both cell lines were found to be permeable to mannitol. This eventually would have eliminated the osmolality gradient between the interior of the cell and the medium, and could explain why higher osmolalities were obtained with mannitol before the growth rate was effected. In addition, initial experiments showed that these cell lines may also be able to metabolize mannitol.

Carcinoma, Transitional Cell↗

PubMed1978

[Effect of mannitol on oxygen consumption of the renal cortex of rats].

We have determined the oxygen consumption (QO2) in renal cortical tissue from controls and from rats which received in vivo and infusion of mannitol (600 mM) in order to study the metabolic changes which occurred in the tissue. QO2 was significantly higher (+20%, p less than 0.01) in slices from animals which received the infusion than in those from non-infused animals, when incubated in mannitol containing solutions; these slices had tubules with their lumens open. When the slices were incubated in solutions without mannitol or obtained from animals not infused with mannitol, the QO2 was lower and the tubules appeared histologically with the lumen closed. A short (2 min) exposure to 2 mM ethacrinic acid inhibited QO2 only in slices from mannitol infused animals incubated in mannitol containing solutions. Similar exposures to 1 mM ouabain inhibited QO2 both in slices from infused and from non-infused animals and independently of the composition of the incubation media. We suggest that the higher QO2 found in those slices which had their tubular lumens open, as well as the specific inhibitory effect of ethacrinic acid on the excess QO2 of such slices, might relate to transport processes, linked to tissue metabolism, and only present in tubules which have their lumens open. Such active transport process may correspond, for example, to the coupled transcellular Na+ and Cl- transport. The effects of mannitol on the tissue water content is discussed.

Animals↗

PubMed1976

D-Mannitol dehydrogenase from Absidia glauca. Purification, metabolic role, and subunit interactions.

When Absidia glauca was grown in minimal media with D-mannitol as the only source of carbon, an NAD+ specific D-mannitol dehydrogenase (EC 1.1.1.67) was induced. The crude extract also gave evidence of mannitol kinase, mannitol-1-phosphate dehydrogenase, phosphofructokinase, and L-iditol dehydrogenase activity. The heat labile purified preparation was judged enzymically homogeneous based on evidence derived from substrate specificity studies and activity staining, following disc gel electrophoresis. The enzymic monomer, with a weight of about 67000 daltons, slowly polymerizes when stored at -20 degrees C, giving a multiplicity of protein bands on electrophoresis distributed predominantly across a spectrum from dimer to pentamer, with enzymic activity resident predominantly in even multiples of the monomer. Depolymerization occurred rapidly (hours) when a frozen preparation was brought to and held between 4 and 20 degrees C. Aggregate fragmentation with sodium dodecyl sulfate showed a time-temperature dependence, terminating in a subunit component of 13000 daltons. pH optimum for polyol oxidation occurs at 9.6 (NaOH-glycine buffer) while ketose reduction proceeded most rapidly at pH 7.0-7.2 (phosphate buffer). A regulatory role is suggested for this enzyme based on dead-end inhibition by mannitol 1-phosphate, multiple enzyme forms, and its locus at the initiation site for mannitol utilization. The physiological relevance of low-temperature aggregation to regulatory control remains to be established.

Electrophoresis, Disc↗

PubMedDate not supplied

Effect of mannitol on the traumatized spinal cord. Microangiography, blood flow patterns, and electrophysiology.

The effects of mannitol on the spinal cord blood flow patterns in experimental traumatic paraplegia were correlated with microangiographic and electrophysiologic studies. At 1 hour following a therapeutic dose of mannitol (3 g/kg), an improved fluorescent intramedullary vascular pattern was detected among the mannitol-treated animals relative to those that were not treated. Within 4 hours, perfusion of many areas of the lateral white matter of the spinal cord often approximated normal in the mannitol-treated group. This pattern of perfusion was in striking contrast to that seen in the spinal cord of untreated animals, which displayed an almost total lack of fluorescing vessels at this later time. These findings correlated with an increased vascular caliber as revealed by microangiography and were postulated to be the result of a decrease in vasospasm and an expanded intramedullary blood volume following the administration of mannitol. Although mannitol therapy did not reverse the loss of the cortical evoked response observed during the 4-hour interval studied, the observation of improved blood flow patterns in the white matter is encouraging and warrants further study.

Angiography↗

PubMed1978

Free water clearance curves during saline, mannitol, glucose and urea diuresis in the rat.

1. Free water clearances were measured during infusion of hypotonic saline, glucose, urea, and mannitol in Brattleboro rats. For each solute the free water clearances were plotted using either V or (C(H2O) + C(Na)) as the distal tubular delivery term.2. In all cases the use of (C(H2O) + C(Na)) as distal delivery term yielded a steeper relationship than when V was used. There were no significant differences in the C(H2O) to V relationship when saline, glucose and mannitol was the solute infused. Urea, however, resulted in a curve with a slope significantly less than that for the other solutes.3. When C(H2O) was plotted against (C(H2O) + C(Na)) there was still no significant difference between the slopes of the curves during saline or mannitol infusion. Use of this delivery term, however, resulted in a slope during glucose infusion which was significantly greater than that during saline or mannitol infusion. The slope for urea infusion remained lower than that for any other solute.4. Regardless of the delivery term used, there was no significant difference in the slopes of the curves for awake Wistar and awake Brattleboro rats during mannitol infusion. This indicates that the awake rat is a suitable model for free water clearance studies.5. The results indicate that NaCl and mannitol are both adequate for free water clearance and that (C(H2O) + C(Na)) is a better index of distal delivery than V.

Animals↗

PubMed1979

Enhancement of CNS penetration of methotrexate by hyperosmolar intracarotid mannitol or carcinomatous meningitis.

Intracarotid (i.c.) hyperosmolar mannitol enhances central nervous system (CNS) penetration of intravenous (i.v.) methotrexate (MTX) in normal adult rats. A fivefold augmentation in the CSF:serum and ipsilateral brain:serum MTX concentration ratios was observed 1 hour after drug administration. Intravenous mannitol had no such effect. Rats with meningeal carcinomatosis have a partial defect in blood-brain barrier function, and the CSF:serum MTX concentration ratio was 4.6 times higher in these animals than in normal rats prior to mannitol therapy. Intracarotid hyperosmolar mannitol further augmented the blood-brain barrier permeability to intravenous MTX. Intracarotid mannitol increased the therapeutic effect of MTX, since rats with meningeal carcinomatosis that received i.v. MTX and i.c. mannitol experienced a slight enhancement in survival.

Animals↗

PubMed1979

Detailed monitoring of the effects of mannitol following experimental head injury.

The experimental model of a cerebral missile injury developed by Crockard was used in three groups of Rhesus monkeys treated with mannitol. One group received mannitol 15 minutes after being injured with a BB pellet at 90 m/sec impact. Another group was wounded identically, but mannitol treatment was delayed until 1 hour after injury. The last group was wounded with the missile traveling at 180 m/sec, and mannitol was started 15 minutes after trauma. The data were contrasted with the results from the original model. After receiving mannitol, all groups showed marked improvement in mean blood pressure, cerebral perfusion pressure, cerebral blood flow, and cerebral metabolic rate of oxygen consumption out of proportion to the degree of reduction in intracranial pressure (ICP). The authors conclude that the therapeutic value of mannitol may, in some injuries, be directly related to its effects on blood flow and metabolism, as well as to its better known effects upon ICP.

Animals↗

PubMed1979

[The effect of mannitol in preventing the development of cerebral infarction--an electron microscopical investigation (author's transl)].

We have undertaken an electron microscopical investigation of the effects of mannitol on the development of cerebral infarction using an experimental model for thalamic infarction in dogs. 1) It was found that administration of 20% mannitol (2 g/kg) prior to arterial occlusion had significantly suppressive effects upon the formation of cerebral infarction following occlusion. 2) In the control group, only one animal with 30 minutes occlusion showed no pathological changes, but, in the mannitol group, dogs with normal brain tissue were seen even after 120 minutes occlusion. 3) All of the control animals with 60 minutes occlusion showed nerve cell shrinkage, but none of the mannitol treated animals showed such changes. 4) After 180 minutes of arterial occlusion, no notable differences were found between the control and mannitol groups. In one of the mannitol treated animals, cerebral infarction was more severe than in the control group.

Animals↗

PubMed1978

Effect of dose and dose schedule on the response of intracranial pressure to mannitol.

Analysis of monitoring records of 150 patients given over 1000 infusions of 20% mannitol delineared three variables affecting the response of intracranial pressure (ICP) to mannitol: the original ICP; the current dose; and the dose given over the preceding three hours. The level of ICP influenced the response to mannitol as much as the amount of mannitol; giving more mannitol than was required to bring ICP below 25 mm Hg led to the need for larger following doses. One hundred-milliliter-bolus doses were often as effective as larger doses. The results suggest that doses of mannitol given to control increased ICP should be kept as small as possible.

Humans↗