Factor VII as a marker of hepatocellular synthetic function in liver disease.
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Factor VII levels have been measured in 100 patients with liver disease following parenteral vitamin K1 therapy. There was good agreement between specific factor VII measurements and the one-stage prothrombin time apart from six patients with compensated cirrhosis in whom the prothrombin time was prolonged despite the presence of normal factor VII levels. A mean activity of 58% was found in patients with cirrhosis. Cirrhotic patients with features of hepatic decompensation had a significantly lower mean level of activity (40%) than the "contrast" patients with surgical obstruction of the major bile ducts (93%). Patients with chronic active liver disease had moderate depression of factor VII levels and those with non-cirrhotic liver damage had mean activities similar to the contrast group. Factor VII levels could not be correlated with BSP retention but there was a correlation with serum albumin concentration. It is concluded that the prothrombin time using Quick test with a standardized thromboplastin showing good sensitivity to factor VII, eg, the Manchester reagent (BCT), provides a reliable index of coagulability in chronic liver disease, and specific factor VII assays are not indicated. (+info)
Localization of two phylloquinones, QK and QK', in an improved electron density map of photosystem I at 4-A resolution.
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An improved electron density map of photosystem I from Synechococcus elongatus calculated at 4-A resolution for the first time reveals a second phylloquinone molecule and thereby completes the set of cofactors constituting the electron transfer system of this iron-sulfur type photosynthetic reaction center: six chlorophyll a, two phylloquinones, and three Fe4S4 clusters. The location of the newly identified phylloquinone pair, the individual plane orientations of these molecules, and the resulting distances to other cofactors of the electron transfer system are discussed and compared with those determined by magnetic resonance techniques. (+info)
Effect of vitamin K1 on glucose-6-phosphate dehydrogenase deficient neonatal erythrocytes in vitro.
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AIM: To determine whether vitamin K1, which is routinely administered to neonates, could act as an exogenous oxidising agent and be partly responsible for haemolysis in glucose-6-phosphat-dehydrogenase (G-6-PD). METHODS: G-6-PD deficient (n = 7) and control (n = 10) umbilical cord blood red blood cells were incubated in vitro with a vitamin K1 preparation (Konakion). Two concentrations of Vitamin K1 were used, both higher than that of expected serum concentrations, following routine injection of 1 mg vitamin K1. Concentrations of reduced glutathione (GSH) and methaemoglobin, indicators of oxidative red blood cell damage, were determined before and after incubation, and the mean percentage change from baseline calculated. RESULTS: Values (mean (SD)) for GSH, at baseline, and after incubation with vitamin K1 at concentrations of 44 and 444 microM, respectively, and percentage change from baseline (mean (SD)) were 1.97 + 0.31 mumol/g haemoglobin, 1.89 +/- 0.44 mumol/g (-4.3 +/- 13.1%), and 1.69 +/- 0.41 mumol/g (-14.5 +/- 9.3%) for the G-6-PD deficient red blood cells, and 2.27 +/- 0.31 mumol/g haemoglobin, 2.09 +/- 0.56 mumol/g (-7.2 +/- 23.2%), and 2.12 +/- 0.38 mumol/g (-6.0 + 14.1%) for the control cells. For methaemoglobin (percentage of total haemoglobin), the corresponding values were 2.01 +/- 0.53%, 1.93 +/- 0.37% (-0.6 +/- 17.4%) and 2.06 +/- 0.43% (5.7 +/- 14.2%) for the G-6-PD deficient red blood cells, and 1.56 +/- 0.74%, 1.70 +/- 0.78% (12.7 +/- 21.9%), and 1.78 +/- 0.71% (20.6 +/- 26.8%) for the control red blood cells. None of the corresponding percentage changes from baseline was significantly different when G-6-PD deficient and control red blood cells were compared. CONCLUSIONS: These findings suggest that G-6-PD deficient red blood cells are not at increased risk of oxidative damage from vitamin K1. (+info)
The influence of vitamin K1 on the structure and phase behaviour of model membrane systems.
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Vitamin K1 is a component of the Photosystem I of plants which constitutes the major dietary form of vitamin K. The major function of this vitamin is to be cofactor of the microsomal gamma-glutamylcarboxylase. Recently, novel roles for this vitamin in the membrane have been postulated. To get insight into the influence of vitamin K1 on the phospholipid component of the membrane, we have studied the interaction between vitamin K1 and model membranes composed of dimyristoylphosphatidylcholine (DMPC) and dielaidoylphosphatidylethanolamine (DEPE). We utilized high-sensitivity differential scanning calorimetry and small-angle X-ray diffraction techniques. Vitamin K1 affected the thermotropic properties of the phospholipids, broadened and shifted the transitions to lower temperatures, and produced the appearance of several peaks in the thermograms. The presence of the vitamin gave rise to the formation of vitamin-rich domains which were immiscible with the bulk phospholipid in both the gel and the liquid-crystalline phases. Vitamin K1 was unable to alter the lamellar organization of DMPC, but we found that it produced an increase in the interlamellar repeat spacing of DMPC at 10 degrees C. Interestingly, vitamin K1 promoted the formation of inverted hexagonal HII structures in the DEPE system. We discuss the possible implications that these vitamin K1-phospholipid interactions might have with respect to the biological function of the vitamin. (+info)
Tissue phylloquinone and menaquinones in rats are affected by age and gender.
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Phylloquinone and ten menaquinones (MK-1-MK-10) were measured in liver and eight extrahepatic tissues from male and female rats at 3, 12 and 24 mo of age. Phylloquinone and menaquinones showed characteristic tissue distribution. In liver, all 11 vitamers of vitamin K assayed were present in varying concentrations with phylloquinone and MK-6 the major forms. The only forms of vitamin K found in extrahepatic tissues were phylloquinone, MK-4 and MK-6. Brain contained only MK-4 and traces of phylloquinone. No significant gender difference was observed for phylloquinone except in heart at 3 mo of age (P +info)
Comparison of phylloquinone bioavailability from food sources or a supplement in human subjects.
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Phylloquinone (K) absorption was assessed in 22- to 30-y-old human subjects consuming a standard test meal [402 kcal (1682 kJ), 27% energy from fat]. The absorption of phylloquinone, measured over a 9-h period as the area under the curve (AUC), was higher (P < 0.01) after the consumption of a 500- microgram phylloquinone tablet [27.55 +/- 10.08 nmol/(L. h), n = 8] than after the ingestion of 495 microgram phylloquinone as 150 g of raw spinach [4.79 +/- 1.11 nmol/(L. h), n = 3]. Less phylloquinone (P < 0.05) was absorbed from 50 g of spinach (AUC = 2.49 +/- 1.11 nmol/(L. h) than from 150 g of spinach. Absorption of phylloquinone from fresh spinach (165 microgram K), fresh broccoli (184 microgram K) and fresh romaine lettuce (179 microgram K) did not differ. There was no difference in phylloquinone absorption from fresh or cooked broccoli or from fresh romaine lettuce consumed with a meal containing 30 or 45% energy as fat. (+info)
Neuroprotective effects of poly (ADP-ribose) polymerase inhibitors in transient focal cerebral ischemia of rats.
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AIM: To explore the role of poly (ADP-ribose) polymerase (PARP) in focal cerebral ischemia with reperfusion injury. METHODS: Male Wistar rats underwent 3.5-h of temporary middle cerebral artery occlusion by intraluminal suture. Infarction volume was showed with 2,3,5-triphenyltetrazolium chloride (TTC) staining and quantitated by image analysis system, neurologic scores were determined with a 0-5 grading scale. RESULTS: 3-Aminobenzamide (3-AB) 10 mg.kg-1 or nicotinamide (Nic) at 20 mg.kg-1 showed potent neuroprotective effects within 0-6 h, neurologic deficits were attenuated. With the increasing dose of PARP inhibitors, beneficial effects were compromised, particularly, administration of Nic 60 mg.kg-1 at the onset of reperfusion drastically accelerated brain damage. Phytomenadione, a selective inhibitor of mono (ADP-ribosyl) transferase, had little effect on infarction volume. CONCLUSION: Transient incomplete inhibition of PARP provides a neuroprotective effects against cerebral ischemia-reperfusion injury, with a relatively wide therapeutic window, whereas severe inhibition of this enzyme, especially in reperfusion phase, is detrimental. (+info)
Response of vitamin K status to different intakes and sources of phylloquinone-rich foods: comparison of younger and older adults.
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BACKGROUND: Phylloquinone, found in dark-green vegetables and certain plant oils, is the primary dietary source of the fat-soluble vitamin K. Limited data suggest that the relative bioavailability of phylloquinone from vegetables is lower than that from a supplement. This finding is relevant to the maintenance of optimal vitamin K status. OBJECTIVE: The objective of this study was to compare, in younger and older adults, the relative bioavailability of phylloquinone from a vegetable with that of a fortified oil. DESIGN: In a crossover design with three 15-d residency periods in a metabolic unit, younger and older men and women (n = 36) consumed a mixed diet containing 100 microg phylloquinone/d. During 2 residency periods, the mixed diet was supplemented for 5 d with either broccoli (377 microg phylloquinone/d; broccoli diet) or phylloquinone-fortified oil (417 microg/d; oil diet). The relative bioavailability of phylloquinone was defined by the difference in plasma phylloquinone, percentage serum undercarboxylated osteocalcin (%ucOC), and urinary gamma-carboxyglutamic acid in response to 5 d of supplementation. RESULTS: For both younger and older adults, plasma phylloquinone concentrations were higher (P < 0.001) and %ucOC values were lower (P = 0.001) after the broccoli and oil diets than after the mixed diet only. Overall, the response to broccoli supplementation was not significantly different from the response to the fortified oil in either age group. Urinary gamma-carboxyglutamic acid did not change in response to supplementation. CONCLUSIONS: There was no significant difference in the relative bioavailability of phylloquinone, as evidenced by the lack of a significant difference in plasma phylloquinone and %ucOC between the 2 groups after either the broccoli or oil diets for younger and older adults. (+info)