Insights into the preclinical treatment of blood-stage malaria by the antibiotic borrelidin

BACKGROUND AND PURPOSE

Blood-stage Plasmodium parasites cause morbidity and mortality from malaria. Parasite resistance to drugs makes development of new chemotherapies an urgency. Aminoacyl-tRNA synthetases have been validated as antimalarial drug targets. We explored long-term effects of borrelidin and mupirocin in lethal P. yoelii murine malaria.

EXPERIMENTAL APPROACH

Long-term (up to 340 days) immunological responses to borrelidin or mupirocin were measured after an initial 4 day suppressive test. Prophylaxis and cure were evaluated and the inhibitory effect on the parasites analysed.

KEY RESULTS

Borrelidin protected against lethal malaria at 0.25 mg·kg⁻¹·day⁻¹. Antimalarial activity of borrelidin correlated with accumulation of trophozoites in peripheral blood. All infected mice treated with borrelidin survived and subsequently developed immunity protecting them from re-infection on further challenges, 75 and 340 days after the initial infection. This long-term immunity in borrelidin-treated mice resulted in negligible parasitaemia after re-infections and marked increases in total serum levels of antiparasite IgGs with augmented avidity. Long-term memory IgGs mainly reacted against high and low molecular weight parasite antigens. Immunofluorescence microscopy showed that circulating IgGs bound predominantly to late intracellular stage parasites, mainly schizonts.

CONCLUSIONS AND IMPLICATIONS

Low borrelidin doses protected mice from lethal malaria infections and induced protective immune responses after treatment. Development of combination therapies with borrelidin and selective modifications of the borrelidin molecule to specifically inhibit plasmodial threonyl tRNA synthetase should improve therapeutic strategies for malaria.

In vitro and in vivo expression of human erythrocyte pyruvate kinase in erythroid cells: a gene therapy approach

Human pyruvate kinase deficiency (PKD), an autosomal recessive disorder produced by mutations in the PKLR gene, is the most common cause of chronic nonspherocytic hemolytic anemia. Transduction of wild-type erythroid (R-type) pyruvate kinase (RPK) cDNA into deficient hematopoietic stem cells could be of potential use as rescue therapy in severe clinical cases. In this study, gammaretroviral vectors expressing human RPK were designed as possible gene therapy candidates for this disease. Through real-time quantitative reverse transcriptase-polymerase chain reaction, Western blotting, and flow cytometric analysis, we demonstrate stable RPK expression in both undifferentiated and differentiated murine erythroleukemia cells. In this in vitro assay, the proportion of transduced cells and the intensity of expression of the transgene remained unaltered after 6 months of culture. Moreover, transplanting human RPK-transduced Lin(-)Sca-1(+) mouse cells in myeloablated primary and secondary recipients rendered high proportions of erythroid precursors and mature erythrocytes expressing RPK, without inducing hematopoietic effects. These findings suggest that retroviral vectors could be useful for the delivery and expression of RPK in erythroid cells, and provide evidence of the potential use of gene therapy strategies to phenotypically correct erythroid PKD.

Assessment of dietary nutrients that influence perception of intra-oesophageal acid reflux events in patients with gastro-oesophageal reflux disease

BACKGROUND

Gastro-oesophageal reflux disease symptoms are most commonly reported postprandially, suggesting that some diet components are likely to induce symptoms more than others.

AIMS

To determine which of the various dietary nutrients is a strong predictive factor for symptom generation in association with an acid reflux event.

METHODS

Subjects with typical heartburn symptoms were evaluated by the gastro-oesophageal reflux disease Symptom Checklist, demographics questionnaire, upper endoscopy and pH testing. During the pH study, patients completed a detailed 24-h dietary intake record. This included time of meals, description of food components and the amount and type of food preparation.

RESULTS

Fifty gastro-oesophageal reflux disease patients completed all stages of the study. A total of 112 (78%) symptoms were considered as sensed reflux event. Body mass index did not correlate with having perceived reflux. Patients who consumed more cholesterol, saturated fatty acids and had more percentage calories from fat were significantly more likely to experience a perceived reflux event. Regression analysis and beta-coefficient were specifically significant for cholesterol.

CONCLUSION

Of all dietary nutrients, cholesterol enhances the most the perception of intra-oesophageal acid reflux events in patients with gastro-oesophageal reflux disease.

Effect of dietary fish oil substitution with linseed oil on the performance, tissue fatty acid profile, metabolism, and oxidative stability of Atlantic salmon

The objective of this experiment was to test the effect of total or partial substitution of dietary fish oil (FO) by linseed oil (LO) in Atlantic salmon feeding on performance, liver and muscle fatty acid composition, selected lipogenic and lipolytic enzyme activities, and flesh oxidative stability. For 12 wk, fish (220 +/- 12 g of initial BW) were fed five experimental diets in which the FO was serially replaced by 25, 50, 75, and 100% LO. Total FO replacement by LO did not (P = 0.20) affect fish final weight, biometric indices, or i.m. fat contents. Liver and muscle neutral lipid (NL) composition responded to dietary treatments in different ways. Whereas the sum of n-3 PUFA in muscle followed a linear and quadratic pattern with increasing levels of LO, a linear (P = 0.005) effect was observed in the liver NL fraction. Total n-3 and n-6 PUFA contents in the polar lipid fraction (PL) were unaffected (P = 0.356) by dietary input of LO in muscle. Activity of liver glucose-6-P-dehydrogenase (G6PD) was greater with increasing levels of LO (P = 0.004). A time effect (P < 0.001) was observed in the concentration of lipid peroxidation products, expressed as thiobarbituric acid reactive substances, in fish flesh stored under refrigeration for 9 d; however, the progressive inclusion of LO in the feed did not affect (P = 0.125) flesh oxidation stability. In summary, LO can totally replace FO in Atlantic salmon feed without affecting growth performance and muscle susceptibility to lipid oxidation. Fatty acid metabolism in the liver was affected by LO, promoting G6PD activity and eicosatetraenoic acid accumulation; however, a 100% LO replacement decreased (P < 0.001) concentrations of eicosapentaenoic and docosahexaenoic acids in salmon muscle.

Functional analysis of gammaretroviral vector transduction by quantitative PCR

BACKGROUND

In a clinical setting of gene therapy, quantitative methods are required to determine recombinant viral titres and transgene mRNA expression, avoiding the use of reporter genes.

METHODS

We describe procedures based on quantitative polymerase chain reaction (qPCR) designed to assess functional titres of murine leukaemia virus (MLV) vectors, determine proviral copy numbers in transduced cells, and estimate retroviral transgene expression in both target cell lines and mice with transduced chimeric haematopoiesis.

RESULTS

Compared to EGFP titration, proviral DNA detection by qPCR was more accurate in assessing the number of infective particles in supernatants, such that average viral titres in terms of proviral copies per cell were two-fold higher. Transgene mRNA expression was directly determined from the vectors used without the need for reporter assays. A new parameter, defined here as the 'transcription index' (TI), served to establish the association between transcribed transgenic mRNA and each proviral insertion. The TI represents the potential expression of every vector or insertion in each cell type, and is thus useful as a control parameter for monitoring preclinical or clinical protocols.

CONCLUSIONS

The practical use of qPCR is demonstrated as a valuable alternative to reporter genes for the assessment and surveillance of insertion numbers and transgene expression. In combination with protein expression, this approach should be capable of establishing safer therapeutic gene doses, avoiding the potential side effects of high transduction and expression levels.

Dietary protein source affects lipid metabolism in the European seabass (Dicentrarchus labrax)

The study was undertaken to evaluate the effects of dietary protein sources on lipogenesis and fat deposition in a marine teleost, the European seabass (Dicentrarchus labrax). Four isonitrogenous (crude protein (CP, Nx6.25), 44% DM) and isoenergetic (22-23 kJ/g DM) diets were formulated to contain one of the following as the major protein source: fish meal (FM), one of two soy protein concentrates (SPC) and corn gluten meal (CGM). Apparent digestibility coefficients of the diets and raw ingredients, as well as soluble nitrogen (ammonia and urea) and phosphorus excretion were measured. Growth rates of seabass fed plant protein-based diets were significantly lower than those fed fish meal based diet. The protein utilisation was strongly correlated to the dietary essential amino acids index. Measurements of N excretion (ammonia and urea nitrogen) confirmed these data. Daily fat gain at the whole body level ranged between 1.1 to 1.7 g/kg BW, with the highest values being recorded in fish fed the fish meal based diet. Levels of plasma triglycerides and cholesterol were lower in fish fed soy protein diets than in those fed the diet solely based on fish meal. Soy protein rich diets decreased the activities of selected hepatic lipogenic enzymes (glucose 6-phosphate dehydrogenase, malic enzyme, ATP-citrate lysase, acetylcoenzyme A carboxylase and fatty acid synthetase). Highest lipogenic enzyme activities where found in fish fed the fish meal diet, except for fatty acid synthetase which was increased in seabass fed the corn-gluten meal based diets. Overall data suggest that dietary protein sources affects fat deposition and the lipogenic potential in European seabass.

Adaptation of lipid metabolism, tissue composition and flesh quality in gilthead sea bream (Sparus aurata) to the replacement of dietary fish oil by linseed and soyabean oils

Linseed (LO) and soyabean (SO) oils were evaluated as fish-oil (FO) substitutes in the diets of marketable-sized gilthead sea bream (Sparus aurata). Practical diets were designed factorially with the lipid added as follows (%): FO 100, LO 60+FO 40, LO 80+FO 20, SO 60+FO 40, SO 80+FO 20. The effects of experimental diets on growth, fatty acids patterns in liver and muscle, flesh quality variables and activities of selected enzymes involved in lipid synthesis and catabolism were determined at the end of a 7-month trial. Fatty acid composition of liver and muscle generally reflected the fatty acid composition of the diets. The n-3 PUFA levels were significantly reduced by the inclusion of vegetable oils. This tendency was more pronounced for EPA than for docosahexaenoic acid. The n-3:n-6 fatty acid ratio reached the lowest values in fish fed the SO diets; this was associated with a higher liver lipid deposition. No differences were found in fillet texture and pH. However, under conditions of forced peroxidation, muscles from fish fed the SO diets had lower peroxidation levels. Vegetable oil substitution decreased lipogenesis in liver and this effect was greatest at the highest substitution level. In contrast, muscle beta-oxidation enzymes had increased activities with vegetable oil substitution. Thus, the lower hepatic lipogenesis was correlated with an increased lipid utilisation in muscle. It is concluded that growth and lipid metabolism were affected by experimental diets.

The use of fluorescent molecular beacons in real time PCR of IgH gene rearrangements for quantitative evaluation of multiple myeloma

BACKGROUND AND OBJECTIVES Fluorescent molecular beacons have been employed as hybridization probes in real time quantitative PCR to quantify residual disease in multiple myeloma (MM).

DESIGN AND METHODS

After clinical diagnosis of MM, the CDR1, CDR2 and CDR3 regions of the IgH gene were analysed and sequenced to identify its clonal nature. Unique sequences of the clonal IgH rearrangement were used to design specific molecular beacon probes for each MM patient. A molecular beacon probe for the beta-globin gene was used as a reference control to calculate relative amounts of the clonal B-cell population.

RESULTS

Optimization of probe design resulted in the use of a competitive sequence at the IgH area target between the loop and part of the stem of the molecular beacon. Cycling conditions and fluorescence temperature acquisition were optimized for a Light Cycler. To validate this method for the follow-up of treated MM patients, we investigated accuracy, as well as interassay and intrassay reproducibility.

CONCLUSIONS

Our results indicated that real time PCR with specific molecular beacons provides a feasible, accurate and reproducible method for the determination of minimal residual disease in MM.

Evolution of the mitochondrial control region in Palaearctic brown trout (Salmo trutta) populations: the biogeographical role of the Iberian Peninsula

In order to extend present knowledge of brown trout phylogeography in the Palaearctic, we analysed the complete mitochondrial D-loop sequence (1025-1027 bp) of all mitochondrial haplotypes of Salmo trutta found in the Iberian Peninsula and one North African haplotype. Sequence variation in the mitochondrial control region serves to identify four major haplotype groups within the Iberian Peninsula, i.e. Atlantic, Duero, Mediterranean and Andalusian. Including the Iberian haplotypes, the five main European groups previously established were increased to six: (i) an Atlantic group including two different clusters, South European and North Atlantic; (ii) a group representing an endemism restricted to the Duero basin in the Iberian Peninsula; (iii) an Adriatic-Andalusian group found in two vicariant areas including Adriatic-Ionian populations in the Mediterranean and the Andalusian basins of the southern Iberian Peninsula; (iv) a Mediterranean group with a distribution range that extends from the southwestern basins of the Iberian Peninsula to the Ionian basins of the Greek Peninsula; (v) a Danube group of wide distribution in the Black, Aral and Caspian basins; and (vi) a group comprising the S. t. marmoratus subspecies confined to the Adriatic Sea. The Iberian Peninsula appears to have acted as a physical boundary between haplotypes corresponding to Atlantic- and Mediterranean-draining rivers. Owing to its geographical position, this area has played a major role in present Palaearctic species distribution, as illustrated by its haplotype diversity.

Abdominal fat deposition and fatty acid synthesis are lower and beta-oxidation is higher in broiler chickens fed diets containing unsaturated rather than saturated fat

We evaluated the effects of dietary fat type on fat metabolism and deposition in broiler chickens. Birds were fed diets containing either 8 g dietary saturated (beef tallow) or polyunsaturated fat (sunflower oil)/100 g for 32 d. The abdominal fat deposition of chickens fed the sunflower oil-enriched diet was significantly lower than that of chickens fed the tallow-enriched diet (2.63 +/- 0.47 versus 3.03 +/- 0.44 g/100 g live wt.; P = 0.033). The specific activities of heart carnitine palmitoyltransferase I and L-3-hydroxyacyl-CoA dehydrogenase were higher (P < or = 0.03) in chickens fed the sunflower oil-enriched diets, indicating a greater rate of beta-oxidation. Liver fatty acid synthetase activity was lower (P = 0.01) in chickens fed the sunflower oil-enriched diet, suggesting reduced hepatic lipogenesis in this group. Postprandial plasma triglyceride levels were significantly lower (P < 0.05) in birds fed the sunflower oil-enriched diet, indicating a higher rate of dietary lipid clearance from the bloodstream to tissues. In conclusion, the lower fat deposition observed in broilers fed sunflower oil-enriched diets appears to be the net result of an increased rate of lipid catabolism and lower rate of fatty acid synthesis despite higher dietary fat absorption.

Short-term modulation of lipogenesis by macronutrients in rainbow trout (Oncorhynchus mykiss) hepatocytes

Rainbow trout (Oncorhynchus mykiss) hepatocytes were cultured under simulated conditions of varying nutritional status to explore the short-term modulation by dietary substrates of the main lipogenic enzymes: glucose-6-phosphate dehydrogenase (G6PD), malic enzyme (ME), ATP-citrate lyase (ACL), acetyl-CoA carboxylase (ACoAC) and fatty acid synthetase (FAS). Primary cultures were individually exposed to varying amounts of glucose, hydrolysed casein and long-chain polyunsaturated fatty acids (PUFA) for 12 h. A second set of experiments was designed to evaluate the effects of mixing different relative amounts of these macronutrients in the culture medium. Glucose concentrations of up to 20-25 mm showed a stimulatory effect on G6PD, ME, ACL and ACoAC activity while an earlier inhibitory effect on FAS was observed at 10-20 mm glucose The use of hydrolysed casein as a nutritional source of amino acids inhibited the activity of FAS and ME and stimulated G6PD, ACoAC and ACL activity Low levels of linolenic acid exerted a stimulatory effect on all the lipogenic enzymes assayed with the exception of FAS, and increased amounts showed some inhibition of lipogenic activities Eicosapentaenoic acid and docosahexaenoic acid showed a similar effect, although the former strongly inhibited FAS activity while the latter showed greater potential to inhibit ACoAC and G6PD. A complete change in the relative levels of glucose, hydrolysed casein and PUFA in turn led to changes in the enzyme activity patterns observed. The present study shows the feasibility of exploring the direct regulation of lipogenesis in isolated fish cells by varying the relative amounts of main macronutrients, mimicking in vivo dietary conditions. It is felt that such an approach may serve to investigate the macronutrient regulation of other metabolic pathways.

Mitochondrial haplotype variation and phylogeography of Iberian brown trout populations

The biogeographical distribution of brown trout mitochondrial DNA haplotypes throughout the Iberian Peninsula was established by polymerase chain reaction-restriction fragment polymorphism analysis. The study of 507 specimens from 58 localities representing eight widely separated Atlantic-slope (north and west Iberian coasts) and six Mediterranean drainage systems served to identify five main groups of mitochondrial haplotypes: (i) haplotypes corresponding to non-native, hatchery-reared brown trout that were widely distributed but also found in wild populations of northern Spain (Cantabrian slope); (ii) a widespread Atlantic haplotype group; (iii) a haplotype restricted to the Duero Basin; (iv) a haplotype shown by southern Iberian populations; and (v) a Mediterranean haplotype. The Iberian distribution of these haplotypes reflects both the current fishery management policy of introducing non-native brown trout, and Messinian palaeobiogeography. Our findings complement and extend previous allozyme studies on Iberian brown trout and improve present knowledge of glacial refugia and postglacial movement of brown trout lineages.

Supercritical carbon dioxide extraction of lipids from Eucalyptus globulus wood

Various typical lipid components of wood extractives have been isolated from Eucalyptus globulus wood by supercritical carbon dioxide modified with methanol. The influence of various extraction parameters on the yield and qualitative composition of the extracts have been studied. The extracts were analyzed by gas chromatography-mass spectrometry and compared with those obtained by Soxhlet extraction with acetone, the standard method for the determination of wood extractives. The qualitative and quantitative results obtained by both methods were in good agreement. The experimental planning to asses the influence of pressure, temperature and percentage of methanol and their interactions on the extraction efficiency was carried out with a factorial design, followed by multiple linear regression algorithm.

Structural defects underlying protein dysfunction in human glucose-6-phosphate dehydrogenase A(-) deficiency

The enzyme variant glucose-6-phosphate dehydrogenase (G6PD) A(-), which gives rise to human glucose-6-phosphate dehydrogenase deficiency, is a protein of markedly reduced structural stability. This variant differs from the normal enzyme, G6PD B, in two amino acid substitutions. A further nondeficient variant, G6PD A, bears only one of these two mutations and is structurally stable. In this study, the synergistic structural defect in recombinant G6PD A(-) was reflected by reduced unfolding enthalpy due to loss of beta-sheet and alpha-helix interactions where both mutations are found. This was accompanied by changes in inner spatial distances between residues in the coenzyme domain and the partial disruption of tertiary structure with no significant loss of secondary structure. However, the secondary structure of G6PD A(-) was qualitatively affected by an increase in beta-sheets substituting beta-turns related to the lower unfolding enthalpy. The structural changes observed did not affect the active site of the mutant proteins, since its spatial position was unmodified. The final result is a loss of folding determinants leading to a protein with decreased intracellular stability. This is suggested as the cause of the enzyme deficiency in the red blood cell, which is unable to perform de novo protein synthesis.

Mitochondrial DNA haplotyping of Testudo graeca on both continental sides of the Straits of Gibraltar

Testudo graeca is an endangered species of tortoise that inhabits Mediterranean areas of Africa, Asia, and Europe. Western populations are found on both sides of the Straits of Gibraltar. The effects of geographical isolation on genetic divergence were assessed by the sequence analysis of two mitochondrial DNA regions of the 12S rRNA and cytochrome b genes. Four different haplotypes were identified. A single haplotype was shared by all Spanish and some east Moroccan specimens. Two haplotypes were unique to the west Moroccan T. graeca populations and allowed the clear discrimination between individual specimens found west of the Moulouya River. Phylogenetic analysis based on the estimation of nucleotide sequence distances of the haplotypes suggests an African origin for the Spanish populations and a subspecies status for the west Moroccan pool.

The partial substitution of digestible protein with gelatinized starch as an energy source reduces susceptibility to lipid oxidation in rainbow trout (Oncorhynchus mykiss) and sea bass (Dicentrarchus labrax) muscle

We evaluated the influence of dietary gelatinized starch and protein on the fatty acid composition of muscle in rainbow trout and European sea bass and on the susceptibility of flesh to lipid peroxidation. The possibility that flesh peroxidation could be accounted for by lipogenesis and the deposition of fat was also explored. The inclusion of gelatinized starch in the diet of rainbow trout improved growth with respect to that observed in fish fed crude starch (P<.001). This was especially noticeable at the lowest concentration of dietary protein tested (P = .037); suggesting that gelatinized starch may partially replace protein in the production of energy without inducing a negative effect on growth. However, in European sea bass, the gelatinization of starch and dietary protein concentration showed no significant effect on final body weight. The intramuscular neutral lipid concentration of the sea bass was reduced by the gelatinization of dietary starch (P = .034). The highest dietary protein concentration increased the proportion of saturated fatty acids in the neutral (P = .0742) and polar (P = .0033) lipid fractions. The dietary inclusion of high levels of protein in rainbow trout led to a lower concentration of total (n-3) (P = .0457) and (n-6) (P = .0522) fatty acids and a higher concentration of total monounsaturated fatty acids (P = .0006). The inclusion of gelatinized starch led to a lower concentration of (n-3) fatty acids (P = .0034) and a higher concentration of saturated fatty acids (P = .0007). The polar fraction was hardly affected by the same treatment. A significantly lower susceptibility of the dorsal muscle to oxidation was observed in groups of European sea bass fed gelatinized starch (P<.01). A similar trend was observed in rainbow trout, although differences were not significant. The findings suggest that the digestible protein concentration of nutrient-dense diets for rainbow trout and European sea bass can be reduced with a beneficial effect on tissue lipid oxidation and no negative effects on growth and muscle composition.

Phylogeography of African fruitbats (Megachiroptera)

Joint sequences from the mitochondrial cytochrome b and 16S rRNA genes of a wide representation of Megachiroptera were employed to evaluate the traditional taxonomic arrangement of African fruitbats and to examine their origins and evolutionary relationships. The resulting phylogenetic hypotheses are inconsistent with the previously established morphology-based subdivisions of Megachiroptera at the suprageneric level. Findings indicate the existence of an African clade, which appears to be formed by two endemic clades: the epomophorines and the myonycterines. According to our topologies, the genus Rousettus is monospecific in mainland Africa. Its traditional subgenera Stenonycteris and Lissonycteris appear closer to the myonycterines than to Rousettus. Topologies also indicate that the African genus Eidolon is not phylogenetically related to any other African fruitbat. It would seem that the arrival of fruitbats in Africa was a complex process involving at least three independent colonization events. One event took place probably in the Miocene via forested corridors that connected the African and Asian rain forest blocks, as for other groups of mammals. The resulting lineage diversified into most of the extant African fruitbats. Related to this clade, the Rousettus species group is thought to have arrived in Africa in more recent times, possibly by progressive displacement from the East through India. Finally, the present topologies suggest an independent colonization of Africa by ancestors of Eidolon.

Molecular basis and enzymatic properties of glucose 6-phosphate dehydrogenase volendam, leading to chronic nonspherocytic anemia, granulocyte dysfunction, and increased susceptibility to infections

We have investigated the blood cells from a woman with a low degree of chronic nonspherocytic hemolytic anemia and frequent bacterial infections accompanied by icterus and anemia. The activity of glucose 6-phosphate dehydrogenase (G6PD) in her red blood cells (RBCs) was below detection level, and in her leukocytes less than 3% of normal. In cultured skin fibroblasts, G6PD activity was approximately 15% of normal, with 4- to 5-fold increased Michaelis constant (Km) for NADP and for glucose 6-phosphate. Activated neutrophils showed a decreased respiratory burst. Family studies showed normal G6PD activity in the RBCs from all family members, including both parents and the 2 daughters of the patient. Sequencing of polymerase chain reaction (PCR)-amplified genomic DNA showed a novel, heterozygous 514C-->T mutation, predicting a Pro172-->Ser replacement. Analysis of G6PD RNA from the patient's leukocytes and fibroblasts showed only transcripts with the 514C-->T mutation. This was explained by the pattern of X-chromosome inactivation, studied by means of the human androgen receptor (HUMARA) assay, which proved to be skewed in the patient, her mother, and one of the patient's daughters. Thus, the patient has inherited a de novo mutation in G6PD from her father and an X-chromosome inactivation determinant from her mother, causing exclusive expression of the mutated G6PD allele. Purified mutant protein from an Escherichia coli expression system showed strongly decreased specific activity, increased Km for NADP and for glucose 6-phosphate, and increased heat lability, which indicates that the defective phenotype is due to 2 synergistic molecular dysfunctions: decreased catalytic efficiency and protein instability.

Increased neuronal glucose-6-phosphate dehydrogenase and sulfhydryl levels indicate reductive compensation to oxidative stress in Alzheimer disease

We analyzed glucose-6-phosphate dehydrogenase, the rate-controlling enzyme of the pentose phosphate pathway and free sulfhydryls, to study redox balance in Alzheimer disease. Glucose-6-phosphate dehydrogenase plays a pivotal role in homeostatic redox control by providing reducing equivalents to glutathione, the major nonenzymatic cellular antioxidant. There is a multitude of evidence that marks oxidative stress proximally in the natural history of Alzheimer disease. Consistent with a role for glutathione in defense against increased reactive oxygen, we found an upregulation of glucose-6-phosphate dehydrogenase together with increased sulfhydryls in Alzheimer disease. These data indicate that reductive compensation may play an important role in combating oxidative stress in Alzheimer disease.

Molecular phylogeny and morphological homoplasy in fruitbats

The present study evaluates the evolutionary framework of the Old World fruitbats based on the cytochrome b and 16S rRNA mitochondrial gene sequences from a wide range of taxa. Phylogenetic analyses indicated that morphology-based subfamilies and most suprageneric groups are nonnatural assemblages. They also support the existence of an endemic African clade of fruitbats. The discrepancy between the evolutionary relationships yielded by molecular and morphological data sets may be, at least in part, explained by the recurrent retention of primitive morphology (Rousettus-like) across different lineages. The maintenance of primitive characters in different groups of flying foxes, as well as morphological convergence in nectar-feeding bats and possibly also in short-muzzle bats, may have led to high levels of homoplasy, resulting in misleading taxonomic arrangements. This may be particularly so with respect to high taxonomic levels based on morphological characters.

Dietary fish oil and digestible protein modify susceptibility to lipid peroxidation in the muscle of rainbow trout (Oncorhynchus mykiss) and sea bass (Dicentrarchus labrax)

The effects of dietary fish oil and digestible protein (DP) levels on muscle fatty acid composition and susceptibility to lipid peroxidation were studied in two representative fish species for human nutrition, from fresh and seawater, rainbow trout (Oncorhynchus mykiss) and European sea bass (Dicentrarchus labrax). In rainbow trout, higher concentrations of dietary fat and DP led to higher weight gain (g/d) (P = 0.001 and P = 0.043 respectively). Additionally, an interaction effect was observed in this species, since the effect of DP was only evident when the dietary fat concentration was low (P = 0.043). A similar tendency was also observed in European sea bass, although with less marked differences among nutritional treatments. Trout fed on diets with a higher concentration of dietary fat had higher concentrations of intramuscular total and neutral lipids in the dorsal muscle (P = 0.005). Increased levels of dietary DP led to significantly lower concentrations of polar lipids in the dorsal muscle of both rainbow trout (P = 0.005) and European sea bass (P = 0.006). In the neutral fraction of intramuscular lipids of dorsal muscle the concentration of n-3 fatty acids was positively affected by the dietary fat concentration in both rainbow trout (P = 0.04) and sea bass (P = 0.001). Muscle homogenates from trout and sea bass fed on diets rich in fish oil showed a significantly higher susceptibility to oxidation than muscle homogenates from fish fed on low-fat diets (P = 0.001). The higher DP concentration also increased susceptibility to oxidation. Moreover, in rainbow trout an interaction effect was observed where the pro-oxidant effect was of higher magnitude when the dietary concentration of both nutrients, fat and protein, was high (P = 0.004).

Amino acid substitutions at the dimer interface of human glucose-6-phosphate dehydrogenase that increase thermostability and reduce the stabilising effect of NADP

Over 100 mutations of the G6PD gene have been documented. With the construction of the molecular model of glucose-6-phosphate dehydrogenase, based on the structure of the bacterial Leuconostoc mesenteroides glucose-6-phosphate dehydrogenase, it has been possible to superimpose these amino acid changes on to the structure of the glucose-6-phosphate dehydrogenase molecule. There are a large number of severe disease causing mutations at the dimer interface which usually cause decreased thermostability. We have used this knowledge to predict amino acid changes which would effect an increase in the stability of the dimer. The aspartic acid at residue 421 was chosen as it is a negatively charged residue at the centre of the dimer interface in an area rich in negatively charged residues. This residue was changed to a neutrally charged alanine or asparagine, or a positively charged lysine or arginine. The thermostability of the enzyme was increased when residue 421 was neutral (A or N) and increased further when positive (K or R). NADP is known to exert a concentration dependent stabilising effect on the glucose-6-phosphate dehydrogenase dimer. However the concentration-dependent stabilising effect of NADP was reduced in the residue-421 substitutions in a manner which was inversely proportional to charge change. These results suggest that changes at the dimer interface can also affect the distant (> 20 A) NADP-binding site, and vice versa; an attempt has been made to explain these interactions based on the molecular model of human glucose-6-phosphate dehydrogenase.

Glucose 6-phosphate dehydrogenase mutations causing enzyme deficiency in a model of the tertiary structure of the human enzyme

Human glucose 6-phosphate dehydrogenase (G6PD) has a particularly large number of variants resulting from point mutations; some 60 mutations have been sequenced to date. Many variants, some polymorphic, are associated with enzyme deficiency. Certain variants have severe clinical manifestations; for such variants, the mutant enzyme almost always displays a reduced thermal stability. A homology model of human G6PD has been built, based on the three-dimensional structure of the enzyme from Leuconostoc mesenteroides. The model has suggested structural reasons for the diminished enzyme stability and hence for deficiency. It has shown that a cluster of mutations in exon 10, resulting in severe clinical symptoms, occurs at or near the dimer interface of the enzyme, that the eight-residue deletion in the variant Nara is at a surface loop, and that the two mutations in the A- variant are close together in the three-dimensional structure.

Improved catalytic performance of a 2-haloacid dehalogenase from Azotobacter sp. by ion-exchange immobilisation

The stability and catalytic efficacy of the L-2-haloacid dehalogenase isolated from Azotobacter sp. RC26 were studied after immobilisation on a DEAE Sephacel solid matrix. While the optimum temperature for the soluble dehalogenase falls in the range of 30-40 degrees C, the activity of the immobilised enzyme shows a four-fold increase at 60 degree C. Immobilisation on a plug-flow bioreactor extends the range of usable substrate concentration. The improved catalytic characteristics after immobilisation of the haloacid dehalogenase may be relevant for its possible utilization in biotechnological applications ranging from waste treatment to synthesis of stereoisomers.

Rapid and high sensitivity test for direct detection of bovine herpesvirus-1 genome in clinical samples

A procedure for direct detection of the BHV-1 genome in clinical samples, including semen, was developed. The method is based on the PCR amplification of a highly conserved DNA fragment within the glycoprotein gI sequence of the virus (323 bp between nt 1491 to nt 1814). The method is rapid and highly specific for all 27 subtypes assayed, which are included in the clinical and genetically different groups of BHV-1. The viral origin of the PCR product was assessed by Southern hybridization, with an internal probe. The method for DNA isolation from clinical samples included a fast extraction procedure with Chelex 100 resin allowing the loading of larger amounts of DNA in the PCR and in turn increasing the sensitivity of the method of detection. The level of sensitivity achieved by PCR was in the range of 1 TCID(50). This PCR assay may be an useful tool for BHV-1 monitoring in semen banks at low cost.

Unproductive folding of the human G6PD-deficient variant A-

Human glucose-6-phosphate dehydrogenase (G6PD) deficiency almost invariably results from the presence of missense mutations in the X-linked gene encoding G6PD. The common African deficient variant G6PD A- differs from the normal G6PD B by two amino acid substitutions. Only one of these mutations is found on its own, resulting in the nondeficient variant G6PD A. Deficiency is always associated with decreased G6PD activity in red cells, leading to a variety of clinical manifestations. A group of deficient variants, including A-, have near-normal affinity for the substrates G6P and NADP. In these cases, deficiency is caused by a decreased number of catalytically active molecules per cell due to intracellular instability of the mutated G6PD, although the mechanism for this in vivo instability is unknown. Here we report that in vitro folding of the A- variant mainly renders partially folded polypeptides that do not undergo the dimerization required for activity. Under the same conditions, the nondeficient variants B and A undergo folding to produce active dimers with normal mobilities in native gels and normal kinetic properties. The loss of intrinsic folding determinants in the A- variant may underlie the mechanism of its in vivo instability.

Semen changes in boars after experimental infection with porcine reproductive and respiratory syndrome (PRRS) virus

Eleven boars seronegative to porcine reproductive and respiratory syndrome virus (PRRSV) were trained for semen collection: five boars were inoculated intranasally with 6 x 10(6)TCID(50)/ml of PRRSV (Group A); four boars were inoculated intranasally with 6 x 10(4)TCID(50)/ml (Group B); and two boars were used as uninfected control (Group C). Semen samples were collected at 7-d intervals from 49 d prior to experimental inoculation with PRRSV to 70 d after inoculation, and were examined for sperm volume, sperm concentration, sperm morphology, sperm motility and for the presence of PRRSV. The infection in boars was demonstrated by the reisolation of PRRSV from the serum of all inoculated boars. Rectal temperatures and general health of the boars were clinically normal throughout the trial. Differences were observed in the quality of semen collected from boars after experimental infection with PRRSV. This infection induced a significant decrease in sperm motility and in spermatozoa with normal acrosomes. Of the semen samples tested for virus isolation in swine alveolar macrophages PRRSV was only isolated in 1 boar from Group B. The virus was detected in an additional semen sample in Group A by the production of an antibody titer in a biological assay. All attempts to detect PRRSV by RT-PCR in semen samples were unsuccessful. Nevertheless, from our study it is possible to suggest that the PRRSV can occasionally be transmitted in the semen during the initial phase of the disease.

A new glucose-6-phosphate dehydrogenase variant, G6PD Orissa (44 Ala-->Gly), is the major polymorphic variant in tribal populations in India

Deficiency of glucose-6-phosphate dehydrogenase (G6PD) is usually found at high frequencies in areas of the world where malaria has been endemic. The frequency and genetic basis of G6PD deficiency have been studied in Africa, around the Mediterranean, and in the Far East, but little such information is available about the situation in India. To determine the extent of heterogeneity of G6PD, we have studied several different Indian populations by screening for G6PD deficiency, followed by molecular analysis of deficient alleles. The frequency of G6PD deficiency varies between 3% and 15% in different tribal and urban groups. Remarkably, a previously unreported deficient variant, G6PD Orissa (44 Ala-->Gly), is responsible for most of the G6PD deficiency in tribal Indian populations but is not found in urban populations, where most of the G6PD deficiency is due to the G6PD Mediterranean (188 Ser-->Phe) variant. The KmNADP of G6PD Orissa is fivefold higher than that of the normal enzyme. This may be due to the fact that the alanine residue that is replaced by glycine is part of a putative coenzyme-binding site.

The complete nucleotide sequence of the mitochondrial DNA genome of the rainbow trout, Oncorhynchus mykiss

The complete nucleotide sequence of the mitochondrial DNA of the rainbow trout, Onchorynchus mykiss, has been determined. The total length of the molecule is 16,660 bp. The rainbow trout mitochondrial DNA has the same organization described in eutherian mammals, the clawed frog (Xenopus laevis), and the two fish species, Oriental stream loach (Crossotoma lacustre) and carp (Cyprinus carpio). Alignment and comparison of the deduced amino acid sequences of the 13 proteins encoded by rainbow trout and other vertebrate mitochondrial genomes allowed us to estimate that COI is the most conserved mitochondrial subunit (amino acid identity ranging from 85.6% to 94.8%) whereas ATPase 8 is the most variable one (amino acid identity ranging from 30.8% to 70.4%). Putative secondary structures for the 22 tRNAs found in the molecule are given along with an extensive comparison of tRNA sequences among representative species of each major group of vertebrates. In this sense, an unusual cloverleaf structure for the tRNASer(AGY) is proposed. A stem-loop structure inferred for the origin of the L-strand replication (OL) and the presence of a large polycytidine tract in the OL loop is described. The existence of this stretch instead of the usual T-rich sequence reported so far in mammal mtDNAs is explained in terms of a less-strict template dependence of the RNA primase involved in the initiation of L-strand replication.

Revised dinoflagellate phylogeny inferred from molecular analysis of large-subunit ribosomal RNA gene sequences

The nucleotide sequence analysis of the PCR products corresponding to the variable large-subunit rRNA domains D1, D2, D9, and D10 from ten representative dinoflagellate species is reported. Species were selected among the main laboratory-grown dinoflagellate groups: Prorocentrales, Gymnodiniales, and Peridiniales which comprise a variety of morphological and ecological characteristics. The sequence alignments comprising up to 1,000 nucleotides from all ten species were employed to analyze the phylogenetic relationships among these dinoflagellates. Maximum parsimony and neighbor-joining trees were inferred from the data generated and subsequently tested by bootstrapping. Both the D1/D2 and the D9/D10 regions led to coherent trees in which the main class of dinoflagellates. Dinophyceae, is divided in three groups: prorocentroid, gymnodinioid, and peridinioid. An interesting outcome from the molecular phylogeny obtained was the uncertain emergence of Prorocentrum lima. The molecular results reported agreed with morphological classifications within Peridiniales but not with those of Prorocentrales and Gymnodiniales. Additionally, the sequence comparison analysis provided strong evidence to suggest that Alexandrium minutum and Alexandrium lusitanicum were synonymous species given the identical sequence they shared. Moreover, clone Gg1V, which was determined Gymnodinium catenatum based on morphological criteria, would correspond to a new species of the genus Gymnodinium as its sequence clearly differed from that obtained in G. catenatum. The sequence of the amplified fragments was demonstrated to be a valuable tool for phylogenetic and taxonomical analysis among these highly diversified species.

Human glucose-6-phosphate dehydrogenase. Lysine 205 is dispensable for substrate binding but essential for catalysis

By site-directed mutagenesis of the cloned human glucose-6-phosphate dehydrogenase cDNA, lysine 205 (the residue that after reacting with pyridoxal-5'-phosphate renders inactive enzyme) was mutated to threonine (K205T) to remove the amino group, or to arginine (K205R) to displace the position of the amino group, in order to analyze the role of its nucleophilic group in position epsilon. Compared to the wild-type enzyme, the K205T and K205R mutants retain a specific activity of 2.6 and 11.4%, respectively; their catalytic specificity (Kcat/Km) is drastically decreased, whereas the Km values for both substrates are only slightly increased. These findings in the light of the 3D structure of G6PD suggest that the epsilon-amino group of lysine 205 can favour a hydrogen bond within the active pocket essential for catalysis.

Analysis of the transcription products of the rainbow trout (Oncorynchus mykiss) liver mitochondrial genome: detection of novel mitochondrial transcripts

We have isolated and, by electrophoresis, using agarose slab gels in the presence of methylmercury hydroxide, analyzed the mitochondrial RNA content of the liver of rainbow trout. The RNAs corresponding to most of the mitochondrial DNA-encoded genes have been identified. Furthermore, among the transcription products we have also identified the nature of the RNA 8 previously described in human mitochondria, and detected a novel transcript that may represent the mRNA for ND6.

Nucleotide sequence of the sheep mitochondrial DNA D-loop and its flanking tRNA genes

The nucleotide sequence of the sheep mitochondrial DNA displacement-loop (D-loop) region and its flanking tRNA genes has been determined. Several conserved motifs among mammals have been identified along the 1189-bp sequence of the sheep control region: ten termination-associated sequences (TASs) and one conserved sequence block (CSB-1). CSB-2 and CSB-3, which are frequently found in most species, are not present in the sheep D-loop, which shows instead a short direct repeat at their usual localization. A long polypyrimidine tract between CSB-1 and the tRNA(Phe) gene is also present. Furthermore, the sheep mtDNA D-loop region displays tandem repeats in the left domain (adjacent to the tRNA(Pro) gene) comprising three different termination-associated sequences (TAS-5, TAS-6 and TAS-7).

Lipogenic activities in rat liver are subjected to circadian rhythms

Diurnal variations were investigated in the activities of the key lipogenic enzymes in rat liver under standard experimental conditions. Fatty acid synthetase, acetyl-CoA-carboxylase, and ATP-citrate lyase showed sinusoidal circadian rhythms (statistically sustained), reaching maximum activity at night and minimum during the light period, with a fold increase value of 1.7, 2.2 and 3.2, respectively. Although a non-sinusoidal circadian rhythm was observed in the malic enzyme activity, statistically different time-dependent activity values were detected throughout a day. The observed rhythms run in parallel with that previously reported for glucose-6-phosphate dehydrogenase, suggesting a whole circadian regulation for rat liver lipogenesis.

Direct detection of the porcine reproductive and respiratory syndrome (PRRS) virus by reverse polymerase chain reaction (RT-PCR)

A method for direct detection of the porcine reproductive and respiratory syndrome (PRRS) virus was developed, based on reverse transcription of the viral RNA coupled to DNA amplification by polymerase chain reaction. A set of primers was designed from Lelystad virus sequence within ORF 7 encoding nucleocapsid protein. From seven Spanish field isolated strains the 312 bp amplified fragment was cloned and sequenced. Alignment with Lelystad virus sequence revealed a 96-97% homology. A maximum sensitivity of 6.7 TCID50 was achieved with the reported procedure in experimentally infected swine alveolar macrophages cultures. The sensitivity obtained in crude clinical samples from experimentally infected 3-weeks old pigs was approximately 10(2) TCID50. High specificity for the PRRS virus was demonstrated for the method, as none of the seven common swine virus assayed rendered DNA amplification product.

High resolution of proteins by double-inverted gradient polyacrylamide gel electrophoresis (DG-PAGE)

We have designed a new method for high resolution electrophoretic separation of proteins that have similar molecular weights. The proteins migrate first through a conventional gradient gel, in which molecular friction increases as pore size decreases. The proteins then enter an inverted sodium dodecyl sulfate (SDS) gradient gel in which friction decreases; thus, smaller molecules gradually migrate faster and achieve improved separation from larger molecules, which remain near the border between the two gels. We therefore call this technique double-inverted gradient polyacrylamide gel electrophoresis (DG-PAGE). This technique was used to resolve mixtures of aldolase, horseradish peroxidase precursors, glucose 6-phosphate dehydrogenase and pyruvate kinase. By comparison with other established methods, we show that DG-PAGE has a higher resolving power, which achieves clear separation of proteins differing as little as 0.5 kDa in molecular weight.

Unfolding and trypsin inactivation studies reveal a conformation drift of glucose-6-phosphate dehydrogenase upon binding of NADP

Binding of NADP to glucose-6-phosphate dehydrogenase (G6PD) from Dicentrarchus labrax liver has stabilized its native structure against thermal inactivation, guanidine hydrochloride unfolding and inactivation by tryptic digestion. The time-course of G6PD inactivation by guanidine hydrochloride in the presence of NADP has provided experimental evidence in favor of a conformational drift upon NADP binding to the bass enzyme. Based on the inactivation patterns obtained when the enzyme was treated with guanidine hydrochloride and trypsin, it is proposed that the enzyme conformation induced upon NADP binding is in slow equilibrium with the conformation stabilized in the absence of NADP. FPLC studies have shown that micromolar concentrations of NADP induced oligomerization of G6PD. In addition, the different K0.5 values of NADP binding to the enzyme, ranging from 1-2 microM (from trypsin inactivation) to 90 microM (from titration of the intrinsic fluorescence), suggest a step-wise binding of NADP to the oligomer, with negative cooperativity in the saturation process.

Both mutations in G6PD A- are necessary to produce the G6PD deficient phenotype

The high prevalence of glucose 6-phosphate dehydrogenase (G6PD) deficiency in African populations is due almost entirely to the enzyme variant A-, which differs from the wild-type G6PD B by two amino acid replacements, 68 Val-->Met and 126 Asn-->Asp. The non-deficient polymorphic variant G6PD A contains only the mutation 126 Asn-->Asp. The frequencies of the G6PD A and of the G6PD A- genes in parts of Africa are both about 0.2. The 68 Val-->Met mutation has not been found in a B background. This could be because the 68 Val-->Met mutation happened to arise in an A gene in the first instance, or because the 68 Val-->Met mutation alone is not sufficient to cause G6PD deficiency. We have approached this question by producing G6PD B, A, A-, and G6PD 68 Val-->Met in a bacterial expression system and analysing their biochemical properties. With each single mutation we found a slight decrease in both the specific activity and the yield of enzyme when compared to G6PD B. When both mutations were introduced together, there was a roughly additive effect on specific activity, but a much more drastic effect on enzyme yield (4% of normal). This synergistic effect was also demonstrated on thermal stability, especially at low NADP concentrations. Comparable results were produced when the replacement 119 Gln-->Glu was studied instead of 126 Asn-->Asp. We infer that the coexistence of the two mutations is responsible for enzyme deficiency in G6PD A- because they act synergistically in causing instability of the enzyme.

Purification and properties of human glucose-6-phosphate dehydrogenase made in E. coli

The cDNA for the X-chromosome encoded human glucose-6-phosphate dehydrogenase (G6PD) has been expressed in E. coli and the enzyme purified to homogeneity, using a simple one-step fractionation on 2'5'-ADP-Sepharose. By selecting one of several different expression vectors and by optimizing culture conditions a yield of more than 10 mg of pure enzyme per liter of culture is obtained reproducibly. When the recombinant enzyme and authentic G6PD purified from normal human red cells were compared, they proved to be indistinguishable by the following criteria: electrophoretic mobility in both native and denaturing conditions, the Km values for glucose 6-phosphate and NADP and the Ki value for NADPH. The recombinant enzyme, unlike the red cell enzyme, retained 100% activity when stored at 4 degrees C for over 1 year.

Glucose-6-phosphate dehydrogenase from Dicentrarchus labrax liver: kinetic mechanism and kinetics of NADPH inhibition

The kinetic mechanism of the reaction catalyzed by glucose-6-phosphate dehydrogenase (EC 1.1.1.49) from Dicentrarchus labrax liver was examined using initial velocity studies, NADPH and glucosamine 6-phosphate inhibition and alternate coenzyme experiments. The results are consistent with a steady-state ordered sequential mechanism in which NADP+ binds first to the enzyme and NADPH is released last. Replots of NADPH inhibition show an uncommon parabolic pattern for this enzyme that has not been previously described. A kinetic model is proposed in agreement with our kinetic results and with previously published structural studies (Bautista et al. (1988) Biochem. Soc. Trans. 16, 903-904). The kinetic mechanism presented provides a possible explanation for the regulation of the enzyme by the [NADPH]/[NADP+] ratio.

Circadian rhythms in enzymatic activity of rat liver arginase and glucose 6-phosphate dehydrogenase

The circadian rhythms of glucose 6-phosphate dehydrogenase (G6PD) and of arginase activities and total protein content have been studied in the livers of 24-h fasted rats. Both G6PD and arginase activities reach a maximum at night and a minimum during the light period. On the other hand, the total protein level was maximal during the light period while it decreased to its lowest level during the dark period. These results are in agreement with the existence of a lipogenesis-lipolysis circadian rhythm in the rat, since the higher G6PD activity at night provides the necessary NADPH for lipid biosynthesis. The increase in arginase activity is also in agreement with an increase in amino-acid catabolism, probably as a source of energy and metabolic intermediates.