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Autoxidation of rat brain homogenate: evidence for spontaneous lipid peroxidation. Comparison with the characteristics of Fe2+- and ascorbic acid-stimulated lipid peroxidation.

Aerobically-incubated brain homogenates are known to undergo autoxidation characterized by spontaneous TBARS production, presumably as a result of lipid peroxidation. However, TBARS measurement alone, because of its lack of specificity, is not sufficient to demonstrate the occurrence of lipid peroxidation in complex biological systems. This study, undertaken to determine whether or not spontaneous oxidation of rat brain homogenate is due to lipid peroxidation, measured different specific markers of this process (fatty acids, lipid aldehydes and the formation of fluorescence products) and studied changes in alpha-tocopherol. Incubation of rat brain homogenates at 37 degrees C under air led to spontaneous TBARS formation, which was accompanied by lipid aldehydes and lipid fluorescence products as well as polyunsaturated fatty acid (PUFA) degradation. Alpha-tocopherol was also consumed. On the whole, these results demonstrate that autoxidation of brain homogenate is a spontaneous lipid peroxidation process. When homogenates were exposed to Fe2+ and ascorbic acid-induced oxidative stress, lipid peroxidation was enhanced. However, spontaneous and stimulated peroxidation showed similar patterns not characteristic of classical lipid peroxidation, i.e. without the lag and accelerating phases typical of a propagating chain reaction. PUFA degradation was limited despite stimulation of peroxidation.

Animals↗

Survey of total error of precipitation and homogeneous HDL-cholesterol methods and simultaneous evaluation of lyophilized saccharose-containing candidate reference materials for HDL-cholesterol.

BACKGROUND: Standardization of HDL-cholesterol is needed for risk assessment. We assessed for the first time the accuracy of HDL-cholesterol testing in The Netherlands and evaluated 11 candidate reference materials (CRMs). METHODS: The total error (TE) of HDL-cholesterol measurements was assessed in native human sera by 25 Dutch clinical chemistry laboratories. Concomitantly, the suitability of lyophilized, saccharose-containing CRMs (n = 11) for HDL-cholesterol was evaluated. RESULTS: In the precipitation method group, which included 25 laboratories and four methods, the mean (minimum-maximum) TE was 11.5% (2.7-25.2%), signifying that 18 of 25 laboratories satisfied the TE goal of </=13% issued by the National Cholesterol Education Program (NCEP). In the homogeneous HDL-cholesterol method group, which included five laboratories, each performing two different methods, the mean (minimum-maximum) TE was 9.5% (6.0-17.3%) for the Boehringer assay and 15.7% (3.3-30.7%) for the Genzyme assay. For the Boehringer homogeneous assay, one of five laboratories did not meet the TE criterion, whereas for the Genzyme homogeneous assay, three of five laboratories exceeded the 13% criterion. The biases on the HDL-cholesterol values found by various precipitation methods were highly variable in all CRMs, irrespective of the quality, whereas the biases found by the homogeneous method from Boehringer were far less than +/-5% for the highest-quality CRMs (CRMs 4-6). CONCLUSIONS: The NCEP goal was met by 24 of 35 laboratories assessed by use of native human sera. Selectively pooled, lyophilized CRMs that are cryoprotected with 200 g/L saccharose have ample potential for use in the standardization of homogeneous HDL-cholesterol methods.

Chemical Precipitation↗

[Homogenous low-density lipoprotein assay in type III hyperlipoproteinemia].

To investigate whether homogenous analysis of serum low-density lipoprotein cholesterol(LDL-C) was applicable in type III hyperlipoproteinemic subjects, 3 reagents were used to estimate LDL-C in 2 cases with apoE 2/2 phenotype. Each measurements were compared to LDL-C levels by ultracentrifugation(density: 1.019-1.063). LDL-C levels by homogenous analysis with any of the reagents were higher than those by ultracentrifugation, and the difference was varied between the reagents: +14-24% by LDL-EX, +29-55% by Cholestest LDL, and +89-115% by Determiner LDL-C. The cross-reaction by the reagents to intermediate density lipoprotein(IDL) and very low density lipoprotein(VLDL) cholesterol was studied in a case; 22% of cholesterol in these fractions was measured by LDL-EX, 32% by Cholestest LDL, and 110% by Determiner LDL-C. A part of the sample serum was stored at -60 degrees C for several days and melted for re-analysis of homogenous LDL-C levels. After the freezing process, IDL fraction pattern on electrophoresis had been changed and homogenous LDL-C levels by all reagents were different from the measurements of native serum. These results indicated that using reagents with low cross-reaction to IDL and VLDL fractions and careful sample handling are important in homogenous LDL-C analysis in type III hyperlipoproteinemia.

Aged↗

Pyrimidine and purine salvage deoxyribonucleoside metabolism in hepatic and renal homogenates from rats pretreated with propylthiouracil or L-thyroxine.

OBJECTIVES: In vitro activities of thymidine kinase (TK, EC 2.7.1.21), adenosine kinase (AK, EC 2.7.1.20) and deoxycytidine kinase (dCK, EC 2.7.1.74) enzymes involved in the salvage pathway of DNA precursor synthesis, in homogenates of the rat liver and kidney, were examined. Type I iodothyronine-5'-deiodinase (5'D-I) is the main enzyme responsible for peripheral metabolism of thyroid hormones. This occurs especially in the liver, kidney and muscle. The activity of 5'D-I is inhibited bypropylthiouracil (PTU), an antithyroid drug. METHODS: The liver and kidney were collected from rats pretreated in vivo with either a 0.1% solution of PTU in drinking water for 2 weeks or injected with levothyroxine (L-T(4), 50 &mgr;g/kg BW, daily) for 2 weeks. The enzyme activities were measured by ascending chromatography and expressed asthe amounts of radioactive reaction products of the phosphorylation of dThd (for TK), ofdAdo (for AK and dCK) and of dGuo (for dCK). RESULTS: In liver homogenates, PTU-pretreatment decreased the activities of the three enzymes when compared to control values and those of L-T(4)-treated animals; also L-T(4) injections decreased the AK and dCK activities in the liver homogenates. PTU-pretreatment increased TK activity and the rate of dGuo phosphorylation in kidney homogenates, when compared to controls and to the L-T(4)-pretreated animals. Conversely, both PTU- and L-T(4)-pretreatment reduced the rate of dAdo phosphorylation in kidney homogenates. CONCLUSION: Changes in the activities of examined enzymes which participate inpyrimidine orpurine metabolism of the salvage pathway of DNA synthesis in the liver afterPTU-pretreatment (as shown herein) are similar to the changes of the 5'D-I activity after PTU-treatment (as reported by others). Thus, the observations suggest a role of the salvage pathway of DNA synthesis in the peripheral metabolism of thyroid hormones.

Journal Article↗

[Effect of ambroxol on lipid peroxidation in homogenates of the human placenta].

Free radically induced lipid peroxidation has been suggested as a possible pathogenic factor in pregnancy complications. The placenta is a potential source of lipid peroxides, due to its high lipid concentration. Cells and tissues are protected against toxic lipid peroxides by antioxidants. Ambroxol was found to be equipotent to well-known antioxidants in protecting lipids from peroxidative attack in lungs. To date there is no information on ambroxol capacity to act as a lipid antioxidant in the human placenta. Therefore, the aim of our study was to investigate the effect of ambroxol on lipid peroxidation in homogenates of the human placenta by malondialdehyde measurements. Fourteen homogenates of placentas obtained from healthy women were incubated for 24 hours (pH = 7.4, temp. 37 degrees C) without (group II) and with (group III) ambroxol hydrochloride solutions (Boehringer Ingelheim--Germany) at concentration of 2200 ng/mL. Non-incubated homogenates were treated as a control group (group I). It was found that lipid peroxidation and malondialdehyde formation is significantly higher in group II homogenates than in the control group (p < 0.05). Incubation with ambroxol (group III) caused a non-significant increase of malondialdehyde concentration in comparison with the control group and a non-significant but distinct decrease when compared with group II (incubation without ambroxol). This investigation shows that ambroxol decreases malondialdehyde formation in homogenates of the human placenta and can be regarded as lipid antioxidant.

Adult↗

Granulocyte-macrophage colony-stimulating activity in the serum of mice stimulated with homogenates of Trypanosoma gambiense.

Infection of mice with Trypanosoma gambiense induced a rapid and transient increase in levels of serum granulocyte-macrophage colony-stimulating activity (GM-CSA) followed by an increase in the numbers of circulating neutrophils and large mononuclear cells. Similar phenomena were observed in mice injected with a trypanosomal homogenate. In such mice, levels of GM-CSA were markedly elevated as early as 1-2 days after administration of the homogenate and then rapidly decreased. Numbers of circulating neutrophils and large mononuclear cells increased within 2 and 3 days after injection of the homogenate, respectively. Induction of GM-CSA by the trypanosomal homogenate promoted colony formation by normal spleen cells, but did not support colony formation by spleen cells from mice treated with 5-fluorouracil. Serum levels of GM-CSA were elevated by injection of crude trypanosomal membrane fractions, but not by soluble components found in supernatants from centrifuged trypanosomal homogenates. GM-CSA-inducing ability of the crude membrane fraction was sensitive to heating at 60 degrees C for 30 min, treatment at pH 2.0, pronase digestion, periodate oxidation, and exposure to 0.1% sodium dodecyl sulphate. This biological activity was also reduced by trypsinization of living trypanosomes before preparation of membrane fractions. These findings suggest that the active component of parasites to induce GM-CSA is associated with a glycoprotein in the surface coat of T. gambiense. GM-CSA may be related to the haematological and immunopathological alterations that occur in African trypanosomiasis.

Animals↗

In vitro formation of organ specific proximate carcinogen of benzo(a)pyrene by rat homogenates.

In order to determine the organ specific carcinogenicity of benzo(a)pyrene (B(a)P), its metabolites, formed in vitro by incubation with the homogenates from liver, lungs, kidneys, intestine and brain of rats, were isolated by TLC and spectroscopy. B(a)P was found to be converted into a number of metabolites by different tissue homogenates. The results showed that the proximate carcinogenic metabolite, 7,8-dihydro-7,8-dihydroxy B(a)P was formed only when rat lung and kidney homogenates were incubated with B(a)P in vitro. The UV spectral analysis also confirmed the formation of this metabolite only on incubation of B(a)P with rat lung and kidney homogenates. As the proximate carcinogenic metabolite was only formed by incubating B(a)P with the homogenates from target organs, its organ specific carcinogenicity may be explained.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

Morphologic homogeneity of bacteriophages and their biological activity.

Lytic activity of morphologically homogeneous phage lysates, obtained from lysates containing morphologically inhomogeneous virions, was studied. Five series of phage lysates found to contain morphologically inhomogeneous virions were investigated. By selecting suitable hosts from each series, two or three lines were obtained which reproduced morphologically homogeneous virions. Morphologic homogeneity of these phage lines was determined by electron microscopy. In the course of this study it was found that phages with different morphologic appearance can produce similar plaques. Hence, appearance of plaques is not an adequate criterion of homogeneity of the phage. The isolated phages differed in biological activity from the original morphologically inhomogeneous bacteriophage. It was concluded that morphology is an important, and the most reliable at present, criterion of homogeneity of bacteriophages.

Bacteriolysis↗

Effect of cisplatin, carboplatin and stobadine on lipid peroxidation of kidney homogenate and phosphatidylcholine liposomes.

The effects of the nephrotoxic, anticancer agents cisplatin (CDDP) and carboplatin (CBDCA), and the free radical scavenger, stobadine, were investigated on lipid peroxidation (LPO) of rat kidney homogenates and phosphatidylcholine (PC) liposomes. Kidney homogenates were incubated in air at 37 degrees C for 6-48 h and lipid peroxidation was detected spectroscopically as absorbance (533 nm) of the thiobarbituric acid-malondialdehyde (TBA-MDA) complex. CDDP (0.3-10 mmol.l-1) increased LPO of the homogenate. CBDCA decreased the TBA-MDA absorbance, yet was found to interfere with MDA, TBA and/or with the TBA-MDA complex. Thus when CBDCA is involved, the TBA-MDA method for detection of LPO is not suitable. Stobadine (0.1 mmol.l-1 and 1 mmol.l-1) inhibited LPO either in the control homogenate and in the homogenate where peroxidation was increased by CDDP. The effect of CDDP and CBDCA on peroxidation of PC liposomes was monitored as oxygen consumption using a Clark-type oxygen electrode. CDDP increased but CBDCA decreased the rate of oxygen consumption during the peroxidation of liposomes induced by FeSO4. The results suggest that the effects of CDDP and CBDCA on LPO may be linked with their nephrotoxicity.

Animals↗

[Maturation study of low fat Chanco cheese made with homogenized milk].

The purpose of this study was to evaluate the influence the use of homogenization of different proportions of milk--which allow to increase the yield in the process and probably to improve sensorial characteristics of the cheese--has on the ripening of low fat Chanco cheese. Five treatments (three replicates each) were studied, two corresponded to control (normal fat and low fat) and the other three treatments were low fat using partially homogenized milk in the following percentages of the total volume of milk; 12.5, 25 and 50%. Standard methodology was used to monitor the evolution of ripening in terms of moisture, fat and total protein content, ripening index (NS/NT%), lipolysis (ADV), pH, sensorial quality and micro structure of the product. The low fat treatments with homogenized milk showed less fat losses in the whey and consequently increased yields. This study allowed us to know the low fat Chanco cheese maturation profile, low fat treatments with homogenisation showed a higher degree of lipolysis than the non--homogenized low-fat control although it was lower than normal fat control. No differences in terms of the development of proteolysis were observed. The low--fat homogenized treatments did not show improvement in the flavor neither in the cheese firmness probably due to the short ripening period (21 days) of this cheese variety, nevertheless T3 presented some advantages which could be improved applying simultaneously another technological helps.

Cheese↗

[Effect of major nutrient elements on the growth and population homogeneity of the R, S and M dissociants of Pseudomonas aeruginosa and the glucose oxidation and fermentation pathways].

The population homogeneity of the stationary-phase monocultures of Pseudomonas aeruginosa dissociants was studied as a function of the initial content of major nutrient elements (C, N, and P) in the cultivation medium. The monocultures of the dissociants remained homogeneous during cultivation if the initial concentrations of the major nutrient elements were either sufficiently high or, conversely, very low, but became heterogeneous during cultivation in unbalanced (with respect to the major nutrient elements) media. At the initial concentration of nitrate in the medium equal to 0.07% or phosphate equal to 0.004-0.014%, the initially homogeneous population of R dissociant cultivated to the stationary growth phase turned out to contain 30-40% of S-type cells, whereas the initially homogeneous population of S dissociant was found to contain 50-80% of M-type cells. The population of M dissociant remained homogeneous throughout the cultivation period. R dissociant grew better at sufficiently high concentrations of glucose, nitrate, and phosphate in the medium, whereas M dissociant grew better when the initial concentrations of these nutrients were low. During the cultivation of R dissociant, the pH of the medium changed insignificantly, and the C/P ratio (the ratio of the carbon and phosphorus consumed during growth) was minimal (among the three dissociants), indicating that the R dissociant accomplishes the oxidative pathway of glucose metabolism. During the cultivation of the M dissociant, the pH of the medium dropped to 3.4-3.9, and the C/P ratio was maximal, indicating that this dissociant accomplishes the fermentative pathway of glucose metabolism. During the cultivation of the S dissociant, the pH of the medium and the C/P ratio exhibited variations, indicating that this dissociant triggers its pathways of glucose metabolism.

Carbon↗

[Pitfalls in homogeneous assays for HDL-c and LDL-c in serum].

Between 1994 and 2004, homogenous assays for HDL-C and LDL-C based on different determination principles were developed to replace complicated conventional precipitation methods. Nowadays, most laboratories employ homogenous assays. However, due to differences in principles and reactivity, measurements made by different assays do not necessarily match in some cases. HDL-C determinations may vary depending on duration and conditions of serum storage for the CDC-DCM and the homogenous assay methods, due to their different principles of determination. In patients with cholestasis, apoE-rich HDL, Lp-X and Lp-Y are occasionally observed. In these cases, the reactivity of homogenous assays for HDL-C varies markedly among the manufacturers. Furthermore, because the specific gravities of Lp-X and Lp-Y are comparable to that of LDL, these lipoproteins are grouped as LDL by ultracentrifugation, and this is a source of confusion in clinical settings. The American CDC assesses the accuracy of cholesterol assays by the BQ method, which measures the total of IDL, the narrowly-defined LDL, and Lp(a). However, of the various homogenous assays for LDL-C, reactivities to IDL and Lp (a) differ, and as a result, it is possible that type III hyperlipidemia characterized by increased IDL may be misdiagnosed.

Arteriosclerosis↗

Expression of NASG gene and its role in human nasopharyngeal homogenous tissue cells.

BACKGROUND: The NASG gene has been confirmed as a tumor-suppressor gene candidate related to nasopharyngeal carcinoma (NPC) by previous studies. We further investigated the expression and the role of NASG in the homogeneous tissue cells by microdissecting the samples of tissue from human NPC, and introduced a new way to study the expression of specific genes in tumor tissue. METHODS: The RNAlater reagent was used to preserve the samples of tissue from the nasopharynx of NPC patients. The samples were microdissected to harvest the homogeneous tissue cells and then total RNA was isolated from them. The antisense RNA (aRNA) was amplified from the total RNA by "in vitro transcription (IVT)". We investigated NASG expression in the homogeneous tumor cells of NPC (22 samples) and compared it with that in the pure epithelial pillar cells of normal nasopharyngeal (10 samples) by semi-quantitative reverse transcription-polymerase chain reaction (sqRT-PCR). RESULTS: The high quality total RNA could be harvested from the microdissected homogeneous tissue cells of the nasopharynx, then sufficient aRNA was derived from it. NASG gene expression was identified using aRNA by sqRT-PCR and showed that there was significant difference between the average value of case groups and that of control group (t = -5.275, df = 30, P < 0.001). The NASG gene in the subgroups WHOII tended to express lower levels than those in the subgroup WHOIII although this difference was not statistically significant (t = -1.584, df = 20, P = 0.129 > 0.05). CONCLUSIONS: Microdissection was an effective method to obtain the homogeneous tissue cells of nasopharyngeal tissue (including the samples of NPC and non-NPC) in our study. Sufficient aRNA from amplifying total RNA could be used in sqRT-PCR to analyse the expression of NASG in the pure tissue cells. NASG should be a tumor-suppression gene candidate regarding to NPC.

Adult↗

Comparative adenylate cyclase activities in homogenate and plasma membrane fractions of Morris hepatoma 5123tc (h).

Homogenate and plasma membrane fractions of Morris hepatoma 5123tc (h) and rat liver were studied with regard to their relative basal activties of adenylate cyclase and to the comparative responsiveness of this enzyme to glucagon, sodium fluoride, epinephrine, prostaglandin E1, and insulin. The basal adenylate cyclase activities of the hepatoma fractions were found to be similar to those of liver at an adenosine 5'triphosphate concentration of 3.2 mM; if the substrate affinity (Km adenosine 5'-triphosphate) of the tumor enzyme is comparable to that of liver, these findings suggest that the reduced basal cyclic adenosine 3':5'-monophosphate levels found to occur in hepatoma 5123tc (h) probably are not due to a decreased basal rate of formation of this cyclic nucleotide. Glucagon (5.6 muM) significantly stimulated adenylate cyclase in both fractions of hepatoma and livers; however, the responsiveness of the tumor enzyme to this hormone was substantially lower than the responsiveness of liver for both homogenate and plasma membrane preparations; i.e., activities were enhanced 18-fold (relative to the basal activity)for liver homogenate compared with only a 6-fold increase for tumor. With the plasma membrane preparations, glucagon increased the activities 5- and 3.5-fold in liver and hepatoma, respectively. Sodium fluoride (10mM), in contrast to glucagon, increased the adenylate cyclase activity to approximately the same extent (about 10-fold) in the liver and hepatoma preparations. Epinephrine (100 muM) enhanced the liver and hepatoma homogenate activites 3- to 4-fold and the hepatoma plasma membrane activities 2-fold; however, the liver plasma membrane activites were not increased. Prostaglandin E1 (56.6 MUM) significantly increased adenylate cyclase activites of liver and hepatoma homogenates (i.e., 1.5- and 3-fold, respectively) but not of the plasma membrane preparations. Insulin (0.7 muM) did not significantly alter adenylate cyclase activities in any of the preparations.

Adenylyl Cyclases↗

Protection against chicken leucocytozoonosis provided by immunization with spleen homogenate infected with Leucocytozoon caulleryi.

Protection against chicken leucocytozoonosis was assessed in chickens immunized with spleen homogenates from chickens that had received sporozoites of Leucocytozoon caulleryi 7 or 13 days previously. Chickens immunized with the homogenate were challenged with sporozoites of L. caulleryi and observed for changes in clinical signs, parasitemia, serum-soluble antigen, and antibody responses. In chickens immunized with either the 7-day or 13-day homogenate, clinical signs and parasitemia were moderate, mild or absent. This was the case both after immunization with the homogenate and after sporozoite challenge. Immunization with spleen homogenates demonstrated protection against chicken leucocytozoonosis.

Animals↗

Immunization of guinea-pigs against Rhipicephalus appendiculatus adult ticks using homogenates from unfed immature ticks.

Guinea-pigs immunized with homogenates of unfed larvae and nymphs of the tick Rhipicephalus appendiculatus developed significant levels of protective immunity to infestation with adults of this species. The mean engorged weight of female ticks feeding on immunized animals (181.96 +/- 05.63 mg and 170.11 +/- 11.54 mg) was reduced by an average of 46% and 51%, respectively, compared to that of female ticks feeding on control guinea-pigs, although in some individual animals the reduction was as high as 86%; the mean egg mass weight was also significantly reduced. Electrophoretic separation of the homogenates followed by immunostaining with post-infestation sera revealed several antigen bands common to all stages. Two bands of 36,500 and 23,000 molecular weight (MW) were recognized in all homogenates by post-adult infestation serum, but not by post-larval or post-nymphal infestation sera, suggesting that these may be antigens specifically involved in feeding by adult ticks, and are either not presented to the host's immune system or presented only in minimal amounts during feeding by immature stages. Sera from animals immunized with the homogenates did not recognize either of these antigens. Post-immunization sera did, however, stain two bands of 84,000 and 60,000 MW in the homogenates which were not recognized by post-infestation sera.

Animals↗

[Plasminogen activator in leukemic cell homogenate].

We examined fibrinolytic substances in homogenate of leukemic cells, normal granulocyte or mononuclear cells fraction. Plasminogen activators (PA) were significantly low in normal cells, but they were slightly increased in lymphoblastic leukemia cells and markedly increased in myeloblastic leukemia cells. In almost leukemic cells homogenate, the antigen ratio of tissue type PA (t-PA)/urokinase type PA (u-PA) was about 2.0. In especially AMMoL and AMoL, PA activity had discrepancy between euglobulin lysis time and amidolytic assay using chromogenic substrate. As PA inhibitor (PAI)-II was markedly increased in them. PAI might effect the PA assay. PA activity of leukemic cells homogenate was similar to that without t-PA stimulator and leukemic cells homogenate significantly stimulated t-PA. As both PA activity and antigen were statistically increased in leukemic cells homogenate of patient with disseminated intravascular coagulation (DIC), PA and PA stimulator in leukemic cell might play an important role in hypofibrinogenemia or DIC.

Afibrinogenemia↗

Comparison of Stomacher and Waring Blendor for homogenizing foods to be examined for Clostridium perfringens.

The Colworth Stomacher Model 400 homogenizer was compared with the Waring Blendor for preparing food homogenates to be examined for Clostridium perfringens. Forty-eight samples representing 6 different food types were inoculated with C. perfringens and examined by the AOAC official first action method for enumeration of C. perfringens in foods. Identical paired specimens of each food type were blended with the 2 devices, and plate counts were made as specified in the official first action method. The effects of frozen storage on plate counts were determined by examining 24 food samples that had been stored for 3 days at -68 degrees C and homogenized both devices. Results of a statistical analysis of the experimental data indicated no significant difference overall (P greater than 0.05) in the plate counts of homogenates prepared with the Waring Blendor or the Stomacher 400, either before or after frozen storage of the food samples. However, the overall plate count average of the 48 samples was slightly higher with the Waring Blendor than with the Stomacher 400 homogenizer.

Bacteriological Techniques↗