Two-month follow-up of the changes in vitreal constituents after argon laser coagulation of the retina in rabbits

The response of the vitreous after panretinal argon laser photocoagulation was followed over a period of 60 days. Two phases can be discerned. An an immediate reaction to the disturbance of the blood-retinal barrier at the site of the pigment epithelium the total protein content and malate dehydrogenase activity rise sharply within 3 days, 4- to 5-fold above a normal. The more protracted increase of lysosomal enzyme activities which reach their peak heigh after 14 days only, can be attributed to the action and proliferation of phagocytic cells. 2 months after treatment all parameters have returned to their normal levels.

The characterization of neuroenergetic effects of chronic L-tyrosine administration in young rats: evidence for striatal susceptibility

Tyrosinemia type II is an inborn error of metabolism caused by a deficiency in hepatic cytosolic aminotransferase. Affected patients usually present a variable degree of mental retardation, which may be related to the level of plasma tyrosine. In the present study we evaluated effect of chronic administration of L-tyrosine on the activities of citrate synthase, malate dehydrogenase, succinate dehydrogenase and complexes I, II, II-III and IV in cerebral cortex, hippocampus and striatum of rats in development. Chronic administration consisted of L-tyrosine (500 mg/kg) or saline injections 12 h apart for 24 days in Wistar rats (7 days old); rats were killed 12 h after last injection. Our results demonstrated that L-tyrosine inhibited the activity of citrate synthase in the hippocampus and striatum, malate dehydrogenase activity was increased in striatum and succinate dehydrogenase, complexes I and II-III activities were inhibited in striatum. However, complex IV activity was increased in hippocampus and inhibited in striatum. By these findings, we suggest that repeated administrations of L-tyrosine cause alterations in energy metabolism, which may be similar to the acute administration in brain of infant rats. Taking together the present findings and evidence from the literature, we hypothesize that energy metabolism impairment could be considered an important pathophysiological mechanism underlying the brain damage observed in patients with tyrosinemia type II.

Evaluation of tear malate dehydrogenase 2 in mild dry eye disease

PURPOSE

To evaluate the effect of tear malate dehydrogenase 2 on monitoring ocular surface injury in mild dry eye (DE) disease.

METHODS

A total of 15 DE patients (30 eyes) with mild subjective symptoms but no ocular surface fluorescein staining signs were enrolled in this study (DE group). The control group was 15 healthy age- and sex-matched volunteers (30 eyes). All subjects were asked to fill out a DE symptoms questionnaire and take different tests including tear MDH and MDH2 activities evaluation, tear breakup time (TBUT), Schirmer I, and slit-lamp examination of the ocular surface. We investigated different changes in tear MDH and MDH2 activities in the DE group and control group, discussed the association between tear MDH2 activity and DE symptoms, and the relationship between tear MDH2 activity and diagnostic tests (Schirmer I and TBUT). We also analyzed the changes in tear MDH2 activities after the treatment with artificial tears.

RESULTS

Tear MDH activities in the DE group and control group were 288 ± 102 U/L and 259 ± 112 U/L, respectively, and this difference was not statistically significant (P > 0.05). The tear MDH2 activities in DE group were significantly increased compared with control group. Tear MDH2 was significantly and negatively correlated with the Schirmer's value (r = -0.733, P < 0.01) and the TBUT value (r = -0.841, P < 0.01). MDH2 also had a significant positive correlation with soreness symptoms (r = 0.687, P < 0.01). Treatment with artificial tears relieved or eliminated all discomfort symptoms, together with a considerable decrease in MDH2 activities (P < 0.01), but no significant changes in the Schirmer and the TBUT tests were observed.

CONCLUSION

Tear MDH2 activity can indicate ocular surface injury in mild DE patients and may be used to monitor the response to therapy.

Effects of three different highly purified n-3 series highly unsaturated fatty acids on lipid metabolism in C57BL/KsJ-db/db mice

Triglycerides (TG) consisting of highly purified (>97%) n-3 series highly unsaturated fatty acids, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA), were administered to C57BL/KsJ-db/db mice for 4 weeks by pair-feeding to compare their effects on lipid metabolism and to evaluate the effects of DPA on lipid metabolism. The hepatic TG level and total amount was decreased by treatment with DHA and DPA compared to the control. The efficacy of DPA was greater than that of EPA, but less than that of DHA. In contrast, EPA had the greatest serum TG reducing effect. The hepatic cytosol fraction of the DHA-treated group contained the lowest fatty acid synthase (FAS) and malic enzyme (ME) activity levels. Furthermore, the DHA-treated group contained the highest serum adiponectin concentrations. These findings indicate that the strong hepatic TG-lowering effect of DHA is due to the suppression of TG synthesis. The same tendencies were observed in DPA-treated mice, and the effect was stronger than that observed in EPA-treated mice, but equivalent to that observed in DHA-treated mice. Based on these results, DPA possesses lipid metabolism-improving effects. The beneficial effects of DPA for lipid metabolism were not superior to those of EPA and DHA, and the effect was always intermediate between those of EPA and DHA.

Beneficiary effect of Tinospora cordifolia against high-fructose diet induced abnormalities in carbohydrate and lipid metabolism in Wistar rats

High intake of dietary fructose has been shown to exert a number of adverse metabolic eff ects in humans and experimental animals. The present study was designed to investigate the eff ect of the aqueous extract of Tinospora cordifolia stem (TCAE) on the adverse eff ects of fructose loading toward carbohydrate and lipid metabolism in rats. Adult male Wistar rats of body weight around 200 g were divided into four groups, two of which were fed with starch diet and the other two with high fructose (66 %) diet. Plant extract of TC (400 mg/kg/day) was administered orally to each group of the starch fed rats and the highfructose fed rats. At the end of 60 days of experimental period, biochemical parameters related to carbohydrate and lipid metabolism were assayed. Hyperglycemia, hyperinsulinemia, hypertriglyceridemia, insulin resistance, and elevated levels of hepatic total lipids, cholesterol, triglycerides, and free fatty acids (p < 0.05) observed in fructose-fed rats were completely prevented with TCAE treatment. Alterations in the activities of enzymes of glucose metabolism (hexokinase, phosphofructokinase, pyruvate kinase, glucose-6-phosphatase, fructose-1,6-bisphosphatase, and glucose-6-phosphate dehydrogenase) and lipid metabolism (fatty acid synthetase, lipoprotein lipase, and malic enzyme) as observed in the high fructose-fed rats were prevented with TCAE administration. In conclusion, our fi ndings indicate improvement of glucose and lipid metabolism in high-fructose fed rats by treatment with Tinospora cordifolia, and suggest that the plant can be used as an adjuvant for the prevention and/or management of insulin resistance and disorders related to it.

Proteomic analysis reveals metabolic changes during yeast to hypha transition in Yarrowia lipolytica

Fungal dimorphism is important for survival in different environments and has been related to virulence. The ascomycete Yarrowia lipolytica can grow as yeast, pseudomycelial or mycelial forms. We have used a Y. lipolytica parental strain and a Deltahoy1 mutant, which is unable to form hypha, to set up a model for dimorphism and to characterize in more depth the yeast to hypha transition by proteomic techniques. A two-dimensional gel electrophoresis (2-DE) based differential expression analysis of Y. lipolytica yeast and hyphal cells was performed, and 45 differentially expressed proteins were detected; nine with decreased expression in hyphal cells were identified. They corresponded to the S. cerevisiae homologues of Imd4p, Pdx3p, Cdc19, Sse1p, Sol3p, Sod2p, Xpt1p, Mdh1p and to the unknown protein YALIOB00924g. Remarkably, most of these proteins are involved in metabolic pathways, with four showing oxidoreductase activity. Furthermore, taking into account that this is the first report of 2-DE analysis of Y. lipolytica protein extracts, 35 more proteins from the 2D map of soluble yeast proteins, which were involved in metabolism, cell rescue, energy and protein synthesis, were identified.

Histological, enzymohistochemical and biomechanical observation of skeletal muscle injury in rabbits

OBJECTIVE

To explore the pathophysiological and biomechanical features of skeletal muscular injury for providing a rational basis for its treatment, prevention and rehabilitation.

METHODS

In 70 adult rabbits, the left tibialis anterior (TA) muscle was stretched to injury, while the right TA muscle served as control. Histological, enzymohistochemical and biomechanical changes were observed on days 0, 1, 2, 3, and 7 after injury. Cytochrome oxidase (CCO), acid phosphatase (ACP), ATPase, succinate dehydrogenase (SDH), malate dehydrogenase (MDH), NADH-diaphorase (NADHD), glutamatedehydrogenase (GDH), alpha-glycerophosphate dehydrogenase (alpha-GPD) and lactate dehydrogenase (LDH) were measured. The examined biomechanical parameters included maximal contractile force, ultimate load, length, energy absorption, tangent stiffness, and rupture site.

RESULTS

Partial or complete rupture of TA muscle occurred near the muscle-tendon junction. There was an intense inflammatory reaction on day 1 and 2 after injury. Endomysium fibrosis and myotube formation were observed on day 3, and developed further on day 7. The activity of cell oxidases (CCO, ATPase, MDH, alpha-GPD, SDH, NADHD and GDH) showed a significant drop from day 0 to 2, and resumed with different levels on day 3. The increment of enzymatic activities continued on day 7 and the levels of NADHD and alpha-GPD reached to the levels of control muscle. Maximal contractile force was 70.17%+/-3.82% of controls immediately after injury, 54.82%+/-3.09% at 1 day, 66.41%+/-4.36% at 2 days, 78.39%+/-4.90% at 3 days and 93.64%+/-5.02% at 7 days. Ultimate load was 85.78%+/-7.54% of controls at the moment of injury, 61.44%+/-5.91% at 1 day, 49.17%+/-4.26% at 2 days, 64.43%+/-5.02% at 3 days, and 76.71%+/-6.46% at 7 days.

CONCLUSIONS

Endomysium fibrosis and scar formation at the injured site are responsible for frequent recurrence of skeletal muscle injury. Recovery of tensile load slower than that of maximal contractile force may be another cause. Whether the injured muscle returns to normal exercise is mainly determined by the tensility on which the muscle-tendon can bear rather than the maximal contractile force.

Relayed (13)C magnetization transfer: detection of malate dehydrogenase reaction in vivo

Malate dehydrogenase catalyzes rapid interconversion between dilute metabolites oxaloacetate and malate. Both oxaloacetate and malate are below the detection threshold of in vivo MRS. Oxaloacetate is also in rapid exchange with aspartate catalyzed by aspartate aminotransferase, the latter metabolite is observable in vivo using (13)C MRS. We hypothesized that the rapid turnover of oxaloacetate can effectively relay perturbation of magnetization between malate and aspartate. Here, we report indirect observation of the malate dehydrogenase reaction by saturating malate C2 resonance at 71.2 ppm and detecting a reduced aspartate C2 signal at 53.2 ppm due to relayed magnetization transfer via oxaloacetate C2 at 201.3 ppm. Using this strategy the rate of the cerebral malate dehydrogenase reaction was determined to be 9+/-2 micromol/g wet weight/min (means+/-SD, n=5) at 11.7 Tesla in anesthetized adult rats infused with [1,6-(13)C(2)]glucose.

Functional characterization and subcellular localization of the three malate dehydrogenase isozymes in Leishmania spp

As part of a study on the malate dehydrogenase isozymes (MDHs) from Trypanosomatids, three different fractions with MDH activity were obtained from crude extracts of Leishmania mexicana promastigotes combining two different chromatographic steps. Gel filtration chromatography in native conditions showed that most of the MDH activity present in the crude extracts eluted in a single peak, which corresponded to a lower apparent molecular mass ( congruent with 57kDa) than the value expected for typical MDHs. To further characterize the leishmanial isozymes, three putative MDH genes, presumably corresponding to the mitochondrial, glycosomal and cytosolic isoforms were amplified by PCR, cloned into bacterial expression vectors, and the recombinant enzymes purified. Digitonin extraction of intact L. mexicana promastigotes and immunofluorescence microscopy of L. major promastigotes confirmed the subcellular compartmentation of each of the three isozymes. Western blot analysis showed that the three MDHs are developmentally regulated. At the protein level, these isozymes are remarkably more abundant in amastigotes than in promastigotes of L. mexicana. Altogether our results demonstrate the presence of three MDH isoforms with slightly distinct biochemical properties and different subcellular localization in Leishmania spp. Presumably the functional and biochemical features of these isozymes reflect the metabolic adaptation to the different nutrient sources these parasites have to face along their life cycle. These results also emphasize the differences among Trypanosomatids in this area of metabolism, since in the case of Trypanosoma brucei the cMDH is the only isoform expressed in bloodstream trypomastigotes, whereas in Trypanosoma cruzi cMDH is absent.

Functional characterization of phosphoenolpyruvate carboxykinase-type C4 leaf anatomy: immuno-, cytochemical and ultrastructural analyses

BACKGROUND AND AIMS

Species having C4 photosynthesis belonging to the phosphoenolpyruvate carboxykinase (PEP-CK) subtype, which are found only in family Poaceae, have the most complex biochemistry among the three C4 subtypes. In this study, biochemical (western blots and immunolocalization of some key photosynthetic enzymes) and structural analyses were made on several species to further understand the PEP-CK system. This included PEP-CK-type C4 species Urochloa texana (subfamily Panicoideae), Spartina alterniflora and S. anglica (subfamily Chloridoideae), and an NADP-ME-type C4 species, Echinochloa frumentacea, which has substantial levels of PEP-CK.

KEY RESULTS

Urochloa texana has typical Kranz anatomy with granal chloroplasts scattered around the cytoplasm in bundle sheath (BS) cells, while the Spartina spp. have BS forming long adaxial extensions above the vascular tissue and with chloroplasts in a strictly centrifugal position. Despite some structural and size differences, in all three PEP-CK species the chloroplasts in mesophyll and BS cells have a similar granal index (% appressed thylakoids). Immunolocalization studies show PEP-CK (which catalyses ATP-dependent decarboxylation) is located in the cytosol, and NAD-ME in the mitochondria, in BS cells, and in the BS extensions of Spartina. In the NADP-ME species E. frumentacea, PEP-CK is also located in the cytosol of BS cells, NAD-ME is very low, and the source of ATP to support PEP-CK is not established.

CONCLUSIONS

Representative PEP-CK species from two subfamilies of polyphyletic origin have very similar biochemistry, compartmentation and chloroplast grana structure. Based on the results with PEP-CK species, schemes are presented with mesophyll and BS chloroplasts providing equivalent reductive power which show bioenergetics of carbon assimilation involving C4 cycles (PEP-CK and NAD-ME, the latter functioning to generate ATP to support the PEP-CK reaction), and the consequences of any photorespiration.

An NADH-tetrazolium-coupled sensitive assay for malate dehydrogenase in mitochondria and crude tissue homogenates

A sensitive spectrophotometric assay for determining mitochondrial malate dehydrogenase activity is described. The assay measures NADH production by coupling it to the reduction of 2-(p-iodophenyl)-3(p-nitrophenyl)-5-phenyl tetrazolium chloride (INT). Via an intermediate electron carrier, either phenazine methosulfate or lipoamide dehydrogenase, INT accepts electrons and is reduced to a red-colored formazan, which can be quantified by spectrophotometer at 500 nm. This assay uses only commercial reagents but gives a 2-5 fold (with lipoamide dehydrogenase) or 5-20 fold (with phenazine methosulfate) activity increase over currently available assays for pure enzyme in mitochondria isolated from human neuroblastoma cells, rat brain and liver, and crude homogenates of rat brain and liver. The assay can be easily performed with 96-well plate and less than 2.5 microg protein of isolated mitochondria or crude tissue homogenate. These results suggest that this assay is a simple, sensitive, stable and inexpensive method with wide application.

Insulin status differentially affects energy transduction in cardiac mitochondria from male and female rats

AIM

The incidence of coronary heart diseases (CHD), congestive heart failure (CHF) and myocardial infarction is higher in diabetic patients than in non-diabetic groups, with these incidences being more in women than in the men. Hence, we examined involvement of mitochondrial energy transduction functions.

METHODS

Mitochondrial energy metabolism in cardiomyopathy was studied using streptozotocin (STZ)-diabetic male and female rats as the model system. Effects of insulin treatment were also evaluated.

RESULTS

The body and heart weights decreased in both male and female diabetic rats. Insulin treatments resulted in significant increase in the body and heart weights in the female rats. Mitochondrial respiration rates with all the substrates tested decreased in diabetic condition in both males and females. Treatment with two dose-regimens of insulin had differential restorative effect on mitochondrial substrate oxidation in the males but caused hyper-stimulation in the females. Diabetic state brought about 19% decrease in the cytochrome aa(3) content in the female rats. Treatment with 0.6 units of insulin significantly increased the cytochrome contents in general in both the sexes whereas higher dose (1.0 unit) caused decrease in the cytochromes content in the females. Diabetic state resulted in decreased dehydrogenases activities; insulin treatments had differential effect on the dehydrogenase activity in the males and the females. The results suggest that insulin treatment-induced hyper-stimulation of respiration in female rats may lead to increased production of reactive oxygen species. Besides, increased formation of advanced glycosylated end products may further lead to increased risk of CHF and CHD.

CONCLUSIONS

The results suggest that differential effects of STZ-diabetes and insulin treatments in the female rats than in males may be the underlying cause for increased incidence of diabetic cardiomyopathies in the females.

The malate dehydrogenase isoforms from Trypanosoma brucei: subcellular localization and differential expression in bloodstream and procyclic forms

Trypanosoma brucei procyclic forms possess three different malate dehydrogenase isozymes that could be separated by hydrophobic interaction chromatography and were recognized as the mitochondrial, glycosomal and cytosolic malate dehydrogenase isozymes. The latter is the only malate dehydrogenase expressed in the bloodstream forms, thus confirming that the expression of malate dehydrogenase isozymes is regulated during the T. brucei life cycle. To achieve further biochemical characterization, the genes encoding mitochondrial and glycosomal malate dehydrogenase were cloned on the basis of previously reported nucleotide sequences and the recombinant enzymes were functionally expressed in Escherichia coli cultures. Mitochondrial malate dehydrogenase showed to be more active than glycosomal malate dehydrogenase in the reduction of oxaloacetate; nearly 80% of the total activity in procyclic crude extracts corresponds to the former isozyme which also catalyzes, although less efficiently, the reduction of p-hydroxyphenyl-pyruvate. The rabbit antisera raised against each of the recombinant isozymes showed that the three malate dehydrogenases do not cross-react immunologically. Immunofluorescence experiments using these antisera confirmed the glycosomal and mitochondrial localization of glycosomal and mitochondrial malate dehydrogenase, as well as a cytosolic localization for the third malate dehydrogenase isozyme. These results clearly distinguish Trypanosoma brucei from Trypanosoma cruzi, since in the latter parasite a cytosolic malate dehydrogenase is not present and mitochondrial malate dehydrogenase specifically reduces oxaloacetate.

Crystal structure of NAD-dependent malate dehydrogenase complexed with NADP(H)

For better understanding of the coenzyme specificity in NAD-dependent MDH (tMDH) from Thermus flavus AT-62, we determined the crystal structures of tMDH-NADP(H) complex at maximally 1.65 A resolution. The overall structure is almost the same as that of the tMDH-NADH complex. However, NADP(H) binds to tMDH in the reverse orientation, where adenine occupies the position near the catalytic center and nicotinamide is positioned at the adenine binding site of the tMDH-NADH complex. Consistent with this, kinetic analysis of the malate-oxidizing reaction revealed that NADP(+) inhibited tMDH at high concentrations. This has provided the first evidence for the alternative binding mode of the nicotinamide coenzyme, that has pseudo-symmetry in its structure, in a single enzyme.

Epigallocatechin gallate attenuates diet-induced obesity in mice by decreasing energy absorption and increasing fat oxidation

OBJECTIVE

To examine the antiobesity effect of epigallocatechin gallate (EGCG), a green tea bioactive polyphenol in a mouse model of diet-induced obesity.

METHODS

Obesity was induced in male New Zealand black mice by feeding of a high-fat diet. EGCG purified from green tea (TEAVIGO) was supplemented in the diet (0.5 and 1%). Body composition (quantitative magnetic resonance), food intake, and food digestibility were recorded over a 4-week period. Animals were killed and mRNA levels of uncoupling proteins (UCP1-3), leptin, malic enzyme (ME), stearoyl-CoA desaturase-1 (SCD1), glucokinase (GK), and pyruvate kinase (PK) were analysed in different tissues. Also investigated were acute effects of orally administered EGCG (500 mg/kg) on body temperature, activity (transponders), and energy expenditure (indirect calorimetry).

RESULTS

Dietary supplementation of EGCG resulted in a dose-dependent attenuation of body fat accumulation. Food intake was not affected but faeces energy content was slightly increased by EGCG, indicating a reduced food digestibility and thus reduced long-term energy absorption. Leptin and SCD1 gene expression in white fat was reduced but SCD1 and UCP1 expression in brown fat was not changed. In liver, gene expression of SCD1, ME, and GK was reduced and that of UCP2 increased. Acute oral administration of EGCG over 3 days had no effect on body temperature, activity, and energy expenditure, whereas respiratory quotient during night (activity phase) was decreased, supportive of a decreased lipogenesis and increased fat oxidation.

CONCLUSIONS

Dietary EGCG attenuated diet-induced body fat accretion in mice. EGCG apparently promoted fat oxidation, but its fat-reducing effect could be entirely explained by its effect in reducing diet digestibility.

Solubilization of aggregated proteins by ClpB/DnaK relies on the continuous extraction of unfolded polypeptides

The AAA+ chaperone ClpB solubilizes in cooperation with the DnaK chaperone system aggregated proteins. The mechanistic features of the protein disaggregation process are poorly understood. Here, we investigated the mechanism of ClpB/DnaK-dependent solubilization of heat-aggregated malate dehydrogenase (MDH) by following characteristics of MDH aggregates during the disaggregation reaction. We demonstrate that disaggregation is achieved by the continuous extraction of unfolded MDH molecules and not by fragmentation of large MDH aggregates. These findings support a ClpB-dependent threading mechanism as an integral part of the disaggregation reaction.

Improving estimates of trophic shift in Nile tilapia, Oreochromis niloticus (L.), using measurements of lipogenic enzyme activities in the liver

To test whether the measurement of selected enzyme activities could be used to estimate more precisely the trophic shift of C isotopes, Nile tilapia (Oreochromis niloticus) were fed semi-synthetic diets differing in their lipid contents (1.7%, 5.0%, 10.8% and 20.0%). The diets were formulated to contain the same amount of nitrogen and metabolizable energy and were made from casein, wheat starch, corn germ oil supplemented with vitamins, minerals and L-arginine. The influence of the different diets on the activity of two lipogenic enzymes, ATP-citrate lyase and malic enzyme, on delta13C values in the whole fish, the liver and their correlation was investigated. There was a strong positive correlation between delta13C values in the lipids of whole fish and those of their livers. The activities of lipogenic enzymes increased significantly with increasing trophic shift of C isotopes (Deltadelta13Cdiet-fish values) in the lipids. If the relationship between trophic shift and enzyme activity can be confirmed in situations where feed quantity and quality are not known, the determination of enzyme activities would enable better estimates of the trophic shift to be made thus significantly improving back-calculation of diets from stable isotope data.

First record of Trichinella pseudospiralis in the Slovak Republic found in domestic focus

Infection of Trichinella spp. is widespread among wildlife in Slovakia and the red fox (Vulpes vulpes) is the main reservoir of Trichinella britovi. Trichinella spiralis has been rarely documented in sylvatic and domestic animals of this country. During routine examination of domestic pigs at the slaughter, Trichinella larvae were detected by artificial digestion in a domestic pig of a large-scale breeding farm in Eastern Slovakia. The parasite has been identified by molecular (PCR) and biochemical (allozymes) analyses and by the morphology of the nurse cell as the non-encapsulated species Trichinella pseudospiralis infecting both mammals and birds. The epidemiological investigation carried out at the farm level revealed the presence of the same parasite species in other three pigs of 192 examined (2.1%), in 3 of 14 (21.4%) examined synanthropic rats (Rattus norvegicus) and in a domestic cat. The farm was characterized by inadequate sanitary conditions, insufficient nutrition, cannibalism and the presence of rat population. A different profile has been observed at the phosphoglucomutase locus in T. pseudospiralis isolates from Slovakia in comparison with the T. pseudospiralis reference isolate from the Palearctic region. This is the first documented focus of T. pseudospiralis from Central Europe. The detection in domestic pigs of a non-encapsulated parasite infecting both mammals and birds stresses the need to avoid the use of trichinelloscopy to detect this infection at the slaughterhouse.

Analysis of the activity and identification of enzymes after separation of cytosol proteins in mouse liver by microscale nondenaturing two-dimensional electrophoresis

Enzyme activities such as of fructose bisphosphatase, malate dehydrogenase and carbonic anhydrase were analyzed after cytosol proteins in the mouse liver and were separated using nondenaturing two-dimensional electrophoresis (2-DE). The activities of both fructose bisphosphatase and malate dehydrogenase were inhibited by thyroxine, and fructose bisphosphatase activity was specifically inhibited by adenosine monophosphate in nondenaturing 2-DE. Furthermore, polypeptides of the separated proteins were analyzed by peptide mass fingerprinting using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry or by peptide sequencing using electrospray ionization-tandem mass spectrometry, or both. Proteins separated by 2-DE were identified. These results indicate that the function of proteins such as enzyme activity, and their sequence structure can be analyzed, for example by peptide mapping and peptide sequencing, after the proteins have been separated by nondenaturing 2-DE. Present results also indicate analysis of enzyme activity using nondenaturing 2-DE can be applied to screen substances which affect enzyme activity.

Nondenaturing two-dimensional electrophoresis enzyme profile involving activity and sequence structure of cytosol proteins from mouse liver

After cytosol proteins in the mouse liver were separated by nondenaturing two-dimensional electrophoresis (2-DE), activities of several enzymes, such as fructose bisphosphatase, sorbitol dehydrogenase and malate dehydrogenase, transferase and sorbitol dehydrogenase, or several dehydrogenases, were analyzed on the same 2-D gel. Further, peptidase (or protease) activity can be examined by matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) when peptides such as angiotensin and adenocorticotropic hormone are incubated in the presence of the cytosol protein separated by nondenaturing 2-DE. Sequence structures of proteins on the 2-D gel were analyzed by peptide mass fingerprinting using MALDI-TOF-MS or by peptide sequencing using electrospray ionization-tandem mass spectrometry (ESI-MS/MS). The combination of activity and sequence structure accurately verified the position and activity range of the separated enzymes on the nondenaturing 2-D gel. From these results, we created a nondenaturing 2-D enzyme profile involving activities and sequence structure of cytosol proteins from mouse liver. This profile can be used for checking whether activities of enzymes were specifically or nonspecifically inhibited by inhibitors.

Genetic diversity and population structure of Aeromonas hydrophila, Aer. bestiarum, Aer. salmonicida and Aer. popoffii by multilocus enzyme electrophoresis (MLEE)

Genetic diversity, genetic relationship, identification and population structure of 120 Aeromonas strains (including Aer. hydrophila, Aer. bestiarum, Aer. salmonicida and Aer. popoffii) isolated from various sources were studied by analysis of 15 genetic loci by multilocus enzyme electrophoresis (MLEE). All 15 loci were polymorphic, with an average of 9.4 alleles per locus and a mean genetic diversity (H) of 0.64. Cluster analysis defined at H < or = 0.7 differentiated most of the taxa analysed except the Aer. popoffii and Aer. bestiarum strains, which showed a close genetic relationship. Allelic frequencies of five loci (EST1, HEX, IDH, LDH1 and MDH) identified 94% of the strains. The index of association (IA) for the total sample was 2.38 and IA values calculated for the different populations were always significantly different from zero. These results suggest that the population structure of this Aeromonas sample is strongly clonal, confirm the taxonomic status of the analysed species in population genetics terms, and show the usefulness of MLEE for identifying Aeromonas species.

[Effect of long-term exposure to low dose gamma-irradiation on the rat thyroid status]

The effect of long-term exposure to low-dose external radiation on the rat thyroid status was studied. The experiments were carried out on Wistar female rats. The single doses absorbed were 0.1; 0.25; 0.5 Gy. The rats were irradiated 20 times (5 days x 4 weeks). The animals were decapitated after 1, 30 and 180 days following the last irradiation. Blood serum was assayed for content of thyroxin (T4) and triiodothyronine (T3) radioimmunologically. The liver was spectrophotometrically assayed for thyroid-induced NADP-malatedehydrogenase (NADP-MDH). It was shown that the long-term 0.5-Gy irradiation of the animals induced a decrease in blood T4 and T3 concentrations 1.34-1.71-fold and 1.24-1.43-fold after 1, 30 and 180 days, respectively. The T3 level was diminished most pronouncedly after 1 day, whereas that of T4--after 30 days following the exposure. With the doses of 0.1 and 0.25 Gy absorbed, the T4 and T3 concentration remained unchanged throughout all the periods studied. The activity of NADP-MDH was decreased 1.55-2.46-fold in all the experimental animals, and it was held decreased after 180 days (1.43-1.50-fold) in 0.25- and 0.5-Gy-irradiated groups, which indicates a disturbance in thyroid hormone metabolism in rats exposed chronically to low-dose radiation. After 180 days, the experimental animals experienced an elevation of thyroid gland weight on 15-20%. The thyroid status disturbance seemed to be due to both inhibited T4 and T3 biosynthesis in thyroid and disturbed hormone peripheral metabolism under radiation exposure.

Involvement of enzymes of amino acid metabolism and tricarboxylic acid cycle in bovine oocyte maturation in vitro

Few studies demonstrate at a biochemical level the metabolic profile of both cumulus cells and the oocyte during maturation. The aim of the present study was to investigate the differential participation of enzymatic activity in cumulus cells and in the oocyte during in vitro maturation (IVM) by studying the activity of enzymes involved in the control of amino acid metabolism, alanine aminotransferase (ALT) and aspartate aminotransferase (AST); and the tricarboxylic acid (TCA) cycle, isocitrate dehydrogenase (IDH) and malate dehydrogenase (MDH). No NAD-dependent isocitrate dehydrogenase (NAD-IDH) activity was recorded in cumulus-oocyte complexes (COCs). ALT, AST, NADP-dependent isocitrate dehydrogenase (NADP-IDH) and MDH enzymatic units remained constant in cumulus cells and oocytes during IVM. Specific activities increased in oocytes and decreased in cumulus cells as a result of IVM (P<0.05). Similar activity of both transaminases was detected in cumulus cells, unlike in the oocyte, in which activity of AST was 4.4 times greater than that of ALT (P<0.05). High NADP-IDH and MDH activity was detected in the oocyte. Addition of alanine, aspartate, isocitrate + NADP, oxaloacetate or malate + NAD to maturation media increased the percentage of denuded oocytes reaching maturation (P<0.05), in contrast to COCs in which differences were not observed by addition of these substrates and co-enzymes. The activity of studied enzymes and the use of oxidative substrates denotes a major participation of transaminations and the TCA cycle in the process of gamete maturation. The oocyte thus seems versatile in the use of several oxidative substrates depending on the redox state.