Effect of glucose on assimilatory sulphate reduction in Arabidopsis thaliana roots

With the aim of analysing the relative importance of sugar supply and nitrogen nutrition for the regulation of sulphate assimilation, the regulation of adenosine 5′‐phosphosulphate reductase (APR), a key enzyme of sulphate reduction in plants, was studied. Glucose feeding experiments with Arabidopsis thaliana cultivated with and without a nitrogen source were performed. After a 38 h dark period, APR mRNA, protein, and enzymatic activity levels decreased dramatically in roots. The addition of 0.5% (w/v) glucose to the culture medium resulted in an increase of APR levels in roots (mRNA, protein and activity), comparable to those of plants kept under normal light conditions. Treatment of roots with D‐sorbitol or D‐mannitol did not increase APR activity, indicating that osmotic stress was not involved in APR regulation. The addition of O‐acetyl‐L‐serine (OAS) also quickly and transiently increased APR levels (mRNA, protein, and activity). Feeding plants with a combination of glucose and OAS resulted in a more than additive induction of APR activity. Contrary to nitrate reductase, APR was also increased by glucose in N‐deficient plants, indicating that this effect was independent of nitrate assimilation. [35S]‐sulphate feeding experiments showed that the addition of glucose to dark‐treated roots resulted in an increased incorporation of [35S] into thiols and proteins, which corresponded to the increased levels of APR activity. Under N‐deficient conditions, glucose also increased thiol labelling, but did not increase the incorporation of label into proteins. These results demonstrate that (i) exogenously supplied glucose can replace the function of photoassimilates in roots; (ii) APR is subject to co‐ordinated metabolic control by carbon metabolism; (iii) positive sugar signalling overrides negative signalling from nitrate assimilation in APR regulation. Furthermore, signals originating from nitrogen and carbon metabolism regulate APR synergistically.

Life-long growth of Quercus ilex L. at natural CO2 springs acclimates sulphur, nitrogen and carbohydrate metabolism of the progeny to elevated pCO2

The aim of the present study was to analyse whether offspring of mature Quercus ilex trees grown under life-long elevated pCO2 show alterations in the physiological response to elevated pCO2 in comparison with those originating from mature trees grown at current ambient pCO2. To investigate changes in C- (for changes in photosynthesis, biomass and lignin see Polle, McKee & Blaschke Plant, Cell and Environment 24, 1075–1083, 2001), N-, and S-metabolism soluble sugar, soluble non-proteinogenic nitrogen compounds (TSNN), nitrate reductase (NR), thiols, adenosine 5′-phosphosulphate (APS) reductase, and anions were analysed. For this purpose Q. ilex seedlings were grown from acorns of mother tree stands at a natural spring site (elevated pCO2) and a control site (ambient pCO2) of the Laiatico spring, Central Italy. Short-term elevated pCO2 exposure of the offspring of control oaks lead to higher sugar contents in stem tissues, to a reduced TSNN content in leaves, and basipetal stem tissues, to diminished thiol contents in all tissues analysed, and to reduced APS reductase activity in both, leaves and roots. Most of the components of C-, N- and S-metabolism including APS reductase activity which were reduced due to short-term elevated pCO2 exposure were recovered by life-long growth under elevated pCO2 in the offspring of spring oaks. Still TSNN contents in phloem exudates increased, nitrate contents in lateral roots and glutathione in leaves and phloem exudates remained reduced in these plants. The present results demonstrated that metabolic adaptations of Q. ilex mother trees to elevated pCO2 can be passed to the next generation. Short- and long-term effects on source-to-sink relation and physiological and genetic acclimation to elevated pCO2 are discussed.

Interaction of sulfate assimilation with carbon and nitrogen metabolism in Lemna minor

Cysteine synthesis from sulfide andO-acetyl-L-serine (OAS) is a reaction interconnecting sulfate, nitrogen, and carbon assimilation. UsingLemna minor, we analyzed the effects of omission of CO2 from the atmosphere and simultaneous application of alternative carbon sources on adenosine 5′-phosphosulfate reductase (APR) and nitrate reductase (NR), the key enzymes of sulfate and nitrate assimilation, respectively. Incubation in air without CO2 led to severe decrease in APR and NR activities and mRNA levels, but ribulose-1,5-bisphosphate carboxylase/oxygenase was not considerably affected. Simultaneous addition of sucrose (Suc) prevented the reduction in enzyme activities, but not in mRNA levels. OAS, a known regulator of sulfate assimilation, could also attenuate the effect of missing CO2 on APR, but did not affect NR. When the plants were subjected to normal air after a 24-h pretreatment in air without CO2, APR and NR activities and mRNA levels recovered within the next 24 h. The addition of Suc and glucose in air without CO2 also recovered both enzyme activities, with OAS again influenced only APR.35SO4 2− feeding showed that treatment in air without CO2 severely inhibited sulfate uptake and the flux through sulfate assimilation. After a resupply of normal air or the addition of Suc, incorporation of 35S into proteins and glutathione greatly increased. OAS treatment resulted in high labeling of cysteine; the incorporation of 35S in proteins and glutathione was much less increased compared with treatment with normal air or Suc. These results corroborate the tight interconnection of sulfate, nitrate, and carbon assimilation.

Increasing the Glutathione Content in a Chilling-Sensitive Maize Genotype Using Safeners Increased Protection against Chilling-Induced Injury

With the aim of analyzing their protective function against chilling-induced injury, the pools of glutathione and its precursors, cysteine (Cys) and gamma -glutamyl-Cys, were increased in the chilling-sensitive maize (Zea mays) inbred line Penjalinan using a combination of two herbicide safeners. Compared with the controls, the greatest increase in the pool size of the three thiols was detected in the shoots and roots when both safeners were applied at a concentration of 5 muM. This combination increased the relative protection from chilling from 50% to 75%. It is interesting that this increase in the total glutathione (TG) level was accompanied by a rise in glutathione reductase (GR; EC 1.6.4.2) activity. When the most effective safener combination was applied simultaneously with increasing concentrations of buthionine sulfoximine, a specific inhibitor of glutathione synthesis, the total gamma -glutamyl-Cys and TG contents and GR activity were decreased to very low levels and relative protection was lowered from 75% to 44%. During chilling, the ratio of reduced to oxidized thiols first decreased independently of the treatments, but increased again to the initial value in safener-treated seedlings after 7 d at 5 degreesC. Taking all results together resulted in a linear relationship between TG and GR and a biphasic relationship between relative protection and GR or TG, thus demonstrating the relevance of the glutathione levels in protecting maize against chilling-induced injury.

Response of the cholesterol metabolism to a negative energy balance in dairy cows depends on the lactational stage.

The response of cholesterol metabolism to a negative energy balance (NEB) induced by feed restriction for 3 weeks starting at 100 days in milk (DIM) compared to the physiologically occurring NEB in week 1 postpartum (p.p.) was investigated in 50 dairy cows (25 control (CON) and 25 feed-restricted (RES)). Blood samples, liver biopsies and milk samples were taken in week 1 p.p., and in weeks 0 and 3 of feed restriction. Plasma concentrations of total cholesterol (C), phospholipids (PL), triglycerides (TAG), very low density lipoprotein-cholesterol (VLDL-C) and low density lipoprotein-cholesterol (LDL-C) increased in RES cows from week 0 to 3 during feed restriction and were higher in week 3 compared to CON cows. In contrast, during the physiologically occurring NEB in week 1 p.p., C, PL, TAG and lipoprotein concentrations were at a minimum. Plasma phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) activities did not differ between week 0 and 3 for both groups, whereas during NEB in week 1 p.p. PLTP activity was increased and LCAT activity was decreased. Milk C concentration was not affected by feed restriction in both groups, whereas milk C mass was decreased in week 3 for RES cows. In comparison, C concentration and mass in milk were elevated in week 1 p.p. Hepatic mRNA abundance of sterol regulatory element-binding factor-2 (SREBF-2), 3-hydroxy-3-methylglutaryl-coenzyme A synthase 1 (HMGCS1), 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR), and ATP-binding cassette transporter (ABCA1) were similar in CON and RES cows during feed restriction, but were upregulated during NEB in week 1 p.p. compared to the non-lactating stage without a NEB. In conclusion, cholesterol metabolism in dairy cows is affected by nutrient and energy deficiency depending on the stage of lactation.

A novel mutation in BCS1L associated with deafness, tubulopathy, growth retardation and microcephaly

We report a novel homozygous missense mutation in the ubiquinol-cytochrome c reductase synthesis-like (BCS1L) gene in two consanguineous Turkish families associated with deafness, Fanconi syndrome (tubulopathy), microcephaly, mental and growth retardation. All three patients presented with transitory metabolic acidosis in the neonatal period and development of persistent renal de Toni-Debré-Fanconi-type tubulopathy, with subsequent rachitis, short stature, microcephaly, sensorineural hearing impairment, mild mental retardation and liver dysfunction. The novel missense mutation c.142A>G (p.M48V) in BCS1L is located at a highly conserved region associated with sorting to the mitochondria. Biochemical analysis revealed an isolated complex III deficiency in skeletal muscle not detected in fibroblasts. Native polyacrylamide gel electrophoresis (PAGE) revealed normal super complex formation, but a shift in mobility of complex III most likely caused by the absence of the BCS1L-mediated insertion of Rieske Fe/S protein into complex III. These findings expand the phenotypic spectrum of BCS1L mutations, highlight the importance of biochemical analysis of different primary affected tissue and underline that neonatal lactic acidosis with multi-organ involvement may resolve after the newborn period with a relatively spared neurological outcome and survival into adulthood. CONCLUSION Mutation screening for BCS1L should be considered in the differential diagnosis of severe (proximal) tubulopathy in the newborn period. What is Known: • Mutations in BCS1L cause mitochondrial complex III deficiencies. • Phenotypic presentations of defective BCS1L range from Bjornstad to neonatal GRACILE syndrome. What is New: • Description of a novel homozygous mutation in BCS1L with transient neonatal acidosis and persistent de Toni-Debré-Fanconi-type tubulopathy. • The long survival of patients with phenotypic presentation of severe complex III deficiency is uncommon.

Inhibition of glutathione synthesis reduces chilling tolerance in maize

The role of glutathione (GSH) in protecting plants from chilling injury was analyzed in seedlings of a chilling-tolerant maize (Zea mays L.) genotype using buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine (gamma EC) synthetase, the first enzyme of GSH synthesis. At 25 degrees C, 1 mM BSO significantly increased cysteine and reduced GSH content and GSH reductase (GR: EC 1.6.4.2) activity, but interestingly affected neither fresh weight nor dry weight nor relative injury. Application of BSO up to 1 mM during chilling at 5 degrees C reduced the fresh and dry weights of shoots and roots and increased relative injury from 10 to almost 40%. Buthionine sulfoximine also induced a decrease in GR activity of 90 and 40% in roots and shoots, respectively. Addition of GSH or gamma EC together with BSO to the nutrient solution protected the seedlings from the BSO effect by increasing the levels of GSH and GR activity in roots and shoots. During chilling, the level of abscisic acid increased both in controls and BSO-treated seedlings and decreased after chilling in roots and shoots of the controls and in the roots of BSO-treated seedlings, but increased in their shoots. Taken together, our results show that BSO did not reduce chilling tolerance of the maize genotype analyzed by inhibiting abscisic acid accumulation but by establishing a low level of GSH. which also induced a decrease in GR activity.

Interventions for hirsutism (excluding laser and photoepilation therapy alone)

BACKGROUND Hirsutism occurs in 5% to 10% of women of reproductive age when there is excessive terminal hair growth in androgen-sensitive areas (male pattern). It is a distressing disorder with a major impact on quality of life. The most common cause is polycystic ovary syndrome. There are many treatment options, but it is not clear which are most effective. OBJECTIVES To assess the effects of interventions (except laser and light-based therapies alone) for hirsutism. SEARCH METHODS We searched the Cochrane Skin Group Specialised Register, CENTRAL (2014, Issue 6), MEDLINE (from 1946), EMBASE (from 1974), and five trials registers, and checked reference lists of included studies for additional trials. The last search was in June 2014. SELECTION CRITERIA Randomised controlled trials (RCTs) in hirsute women with polycystic ovary syndrome, idiopathic hirsutism, or idiopathic hyperandrogenism. DATA COLLECTION AND ANALYSIS Two independent authors carried out study selection, data extraction, 'Risk of bias' assessment, and analyses. MAIN RESULTS We included 157 studies (sample size 30 to 80) comprising 10,550 women (mean age 25 years). The majority of studies (123/157) were 'high', 30 'unclear', and four 'low' risk of bias. Lack of blinding was the most frequent source of bias. Treatment duration was six to 12 months. Forty-eight studies provided no usable or retrievable data, i.e. lack of separate data for hirsute women, conference proceedings, and losses to follow-up above 40%.Primary outcomes, 'participant-reported improvement of hirsutism' and 'change in health-related quality of life', were addressed in few studies, and adverse events in only half. In most comparisons there was insufficient evidence to determine if the number of reported adverse events differed. These included known adverse events: gastrointestinal discomfort, breast tenderness, reduced libido, dry skin (flutamide and finasteride); irregular bleeding (spironolactone); nausea, diarrhoea, bloating (metformin); hot flushes, decreased libido, vaginal dryness, headaches (gonadotropin-releasing hormone (GnRH) analogues)).Clinician's evaluation of hirsutism and change in androgen levels were addressed in most comparisons, change in body mass index (BMI) and improvement of other clinical signs of hyperandrogenism in one-third of studies.The quality of evidence was moderate to very low for most outcomes.There was low quality evidence for the effect of two oral contraceptive pills (OCPs) (ethinyl estradiol + cyproterone acetate versus ethinyl estradiol + desogestrel) on change from baseline of Ferriman-Gallwey scores. The mean difference (MD) was -1.84 (95% confidence interval (CI) -3.86 to 0.18).There was very low quality evidence that flutamide 250 mg, twice daily, reduced Ferriman-Gallwey scores more effectively than placebo (MD -7.60, 95% CI -10.53 to -4.67 and MD -7.20, 95% CI -10.15 to -4.25). Participants' evaluations in one study with 20 participants confirmed these results (risk ratio (RR) 17.00, 95% CI 1.11 to 259.87).Spironolactone 100 mg daily was more effective than placebo in reducing Ferriman-Gallwey scores (MD -7.69, 95% CI -10.12 to -5.26) (low quality evidence). It showed similar effectiveness to flutamide in two studies (MD -1.90, 95% CI -5.01 to 1.21 and MD 0.49, 95% CI -1.99 to 2.97) (very low quality evidence), as well as to finasteride in two studies (MD 1.49, 95% CI -0.58 to 3.56 and MD 0.40, 95% CI -1.18 to 1.98) (low quality evidence).Although there was very low quality evidence of a difference in reduction of Ferriman-Gallwey scores for finasteride 5 mg to 7.5 mg daily versus placebo (MD -5.73, 95% CI -6.87 to -4.58), it was unlikely it was clinically meaningful. These results were reinforced by participants' assessments (RR 2.06, 95% CI 0.99 to 4.29 and RR 11.00, 95% CI 0.69 to 175.86). However, finasteride showed inconsistent results in comparisons with other treatments, and no firm conclusions could be reached.Metformin demonstrated no benefit over placebo in reduction of Ferriman-Gallwey scores (MD 0.05, 95% CI -1.02 to 1.12), but the quality of evidence was low. Results regarding the effectiveness of GnRH analogues were inconsistent, varying from minimal to important improvements.We were unable to pool data for OCPs with cyproterone acetate 20 mg to 100 mg due to clinical and methodological heterogeneity between studies. However, addition of cyproterone acetate to OCPs provided greater reductions in Ferriman-Gallwey scores.Two studies, comparing finasteride 5 mg and spironolactone 100 mg, did not show differences in participant assessments and reduction of Ferriman-Gallwey scores (low quality evidence). Ferriman-Gallwey scores from three studies comparing flutamide versus metformin could not be pooled (I² = 62%). One study comparing flutamide 250 mg twice daily with metformin 850 mg twice daily for 12 months, which reached a higher cumulative dosage than two other studies evaluating this comparison, showed flutamide to be more effective (MD -6.30, 95% CI -9.83 to -2.77) (very low quality evidence). Data showing reductions in Ferriman-Gallwey scores could not be pooled for four studies comparing finasteride with flutamide as the results were inconsistent (I² = 67%).Studies examining effects of hypocaloric diets reported reductions in BMI, but which did not result in reductions in Ferriman-Gallwey scores. Although certain cosmetic measures are commonly used, we did not identify any relevant RCTs. AUTHORS' CONCLUSIONS Treatments may need to incorporate pharmacological therapies, cosmetic procedures, and psychological support. For mild hirsutism there is evidence of limited quality that OCPs are effective. Flutamide 250 mg twice daily and spironolactone 100 mg daily appeared to be effective and safe, albeit the evidence was low to very low quality. Finasteride 5 mg daily showed inconsistent results in different comparisons, therefore no firm conclusions can be made. As the side effects of antiandrogens and finasteride are well known, these should be accounted for in any clinical decision-making. There was low quality evidence that metformin was ineffective for hirsutism and although GnRH analogues showed inconsistent results in reducing hirsutism they do have significant side effects.Further research should consist of well-designed, rigorously reported, head-to-head trials examining OCPs combined with antiandrogens or 5α-reductase inhibitor against OCP monotherapy, as well as the different antiandrogens and 5α-reductase inhibitors against each other. Outcomes should be based on standardised scales of participants' assessment of treatment efficacy, with a greater emphasis on change in quality of life as a result of treatment.

Influence of Chilling Stress on the Intercellular Distribution of Assimilatory Sulfate Reduction and Thiols in Zea mays

Abstract: The effect of chilling on the intercellular distribution of mRNAs for enzymes of assimilatory sulfate reduction, the activity of adenosine 5′-phosphosulfate reductase (APR), and the level of glutathione was analysed in leaves and roots of maize (Zea mays L). At 25 °C the mRNAs for APR, ATP sulfurylase, and sulfite reductase accumulated in bundle-sheath only, whereas the mRNA for O-acetylserine sulfhydrylase was also detected in mesophyll cells. Glutathione was predominantly detected in mesophyll cells; however, oxidized glutathione was equally distributed between the two cell types. Chilling at 12 °C induced oxidative stress which resulted in increased concentrations of oxidized glutathione in both cell types and a prominent increase of APR mRNA and activity in bundle-sheath cells. After chilling, mRNAs for APR and sulfite reductase, as well as low APR activity, were detected in mesophyll cells. In roots, APR mRNA and activity were at higher levels in root tips than in the mature root and were greatly increased after chilling. These results demonstrate that chilling stress affected the levels and the intercellular distribution of mRNAs for enzymes of sulfate assimilation.

Assimilatory Sulfate Reduction in C3, C3-C4, and C4 Species of Flaveria

The activity of the enzymes catalyzing the first two steps of sulfate assimilation, ATP sulfurylase and adenosine 5'-phosphosulfate reductase (APR), are confined to bundle sheath cells in several C4 monocot species. With the aim to analyze the molecular basis of this distribution and to determine whether it was a prerequisite or a consequence of the C4 photosynthetic mechanism, we compared the intercellular distribution of the activity and the mRNA of APR in C3, C3-C4, C4-like, and C4 species of the dicot genusFlaveria. Measurements of APR activity, mRNA level, and protein accumulation in six Flaveria species revealed that APR activity, cysteine, and glutathione levels were significantly higher in C4-like and C4 species than in C3 and C3-C4 species. ATP sulfurylase and APR mRNA were present at comparable levels in both mesophyll and bundle sheath cells of C4 speciesFlaveria trinervia. Immunogold electron microscopy demonstrated the presence of APR protein in chloroplasts of both cell types. These findings, taken together with results from the literature, show that the localization of assimilatory sulfate reduction in the bundle sheath cells is not ubiquitous among C4 plants and therefore is neither a prerequisite nor a consequence of C4photosynthesis.

Regulation of Sulfate Assimilation by Nitrogen in Arabidopsis

Using Arabidopsis, we analyzed the effect of omission of a nitrogen source and of the addition of different nitrogen-containing compounds on the extractable activity and the enzyme and mRNA accumulation of adenosine 5′-phosphosulfate reductase (APR). During 72 h without a nitrogen source, the APR activity decreased to 70% and 50% of controls in leaves and roots, respectively, while cysteine (Cys) and glutathione contents were not affected. Northern and western analysis revealed that the decrease of APR activity was correlated with decreased mRNA and enzyme levels. The reduced APR activity in roots could be fully restored within 24 h by the addition of 4 mM each of NO3 −, NH4 +, or glutamine (Gln), or 1 mM O-acetylserine (OAS). 35SO4 2− feeding showed that after addition of NH4 +, Gln, or OAS to nitrogen-starved plants, incorporation of 35S into proteins significantly increased in roots; however, glutathione and Cys labeling was higher only with Gln and OAS or with OAS alone, respectively. OAS strongly increased mRNA levels of all three APR isoforms in roots and also those of sulfite reductase, Cys synthase, and serine acetyltransferase. Our data demonstrate that sulfate reduction is regulated by nitrogen nutrition at the transcriptional level and that OAS plays a major role in this regulation.

Light regulation of assimilatory sulphate reduction in Arabidopsis thaliana

Adenosine 5′-phosphosulphate reductase (APR) is considered to be a key enzyme of sulphate assimilation in higher plants. We analysed the diurnal fluctuations of total APR activity and protein accumulation together with the mRNA levels of three APR isoforms of Arabidopsis thaliana. The APR activity reached maximum values 4 h after light onset in both shoots and roots; the minimum activity was detected at the beginning of the night. During prolonged light, the activity remained stable and low in shoots, but followed the normal rhythm in roots. On the other hand, the activity decreased rapidly to undetectable levels within 24 h of prolonged darkness both in shoots and roots. Subsequent re-illumination restored the activity to 50% in shoots and to 20% in roots within 8 h. The mRNA levels of all three APR isoforms showed a diurnal rhythm, with a maximum at 2 h after light onset. The variation of APR2 mRNA was more prominent compared to APR1 and APR3. 35SO42– feeding experiments showed that the incorporation of 35S into reduced sulphur compounds in vivo was significantly higher in light than in the dark. A strong increase of mRNA and protein accumulation as well as enzyme activity during the last 4 h of the dark period was observed, implying that light was not the only factor involved in APR regulation. Indeed, addition of 0.5% sucrose to the nutrient solution after 38 h of darkness led to a sevenfold increase of root APR activity over 6 h. We therefore conclude that changes in sugar concentrations are also involved in APR regulation.

ARRANGEMENT OF GENE LOCI IN EUPLOID CHINESE HAMSTER CELLS AND GENETIC CONSEQUENCES OF REARRANGEMENT IN CHO CELLS

In both euploid Chinese hamster (Cricetulus griseus) cells and pseudodiploid Chinese hamster ovary (CHO) cells, gene assignments were accomplished by G band chromosome and isozyme analysis (32 isozymes) of interspecific somatic cell hybrids obtained after HAT selection of mouse CL 1D (TK('-)) cells which were PEG-fused with either euploid Chinese hamster cells or HPRT('-) CHO cells. Hybrids slowly segregated hamster chromosomes. Clone panels consisting of independent hybrid clones and subclones containing different combinations of Chinese hamster chromosomes and isozymes were established from each type of fusion.^ These clone panels enabled us to provisionally assign the loci for: nucleoside phosphorylase (NP), glyoxalase (GLO), glutathione reductase (GSR), adenosine kinase (ADK), esterase D (ESD), peptidases B and S (PEPB and -S) and phosphoglucomutase 2 (PGM2, human nomenclature) to chromosome 1; adenylate kinase 1 (AK1), adenosine deaminase (ADA) and inosine triosephosphatase (ITP) to chromosome 6; triosephosphate isomerase (TPI) to chromosome 8; and glucose phosphate isomerse (GPI) and peptidase D (PEPD) to chromosome 9.^ We also confirm the assignments of 6-phosphogluconate dehydrogenase (PGD), PGM1, enolase 1 (ENO1) and diptheria toxin sensitivity (DTS) to chromosome 2 as well as provisionally assign galactose-1-phosphate uridyl transferase (GALT) and AK2 to chromosome 2. Selection in either HAT or BrdU for hybrids that had retained or lost the chromosome carrying the locus for TK enabled us to assign the loci for TK, galactokinase (GALK) and acid phosphatase 1 (ACP1) to Chinese hamster chromosome 7.^ These results are discussed in relation to current theories on the basis for high frequency of drug resistant autosomal recessive mutants in CHO cells and conservation of mammalian autosomal linkage groups. ^

CHARACTERIZATION OF CYTOCHROME P-450 MIXED FUNCTION OXIDASE OF RAT COLON MUCOSA

Non-pregnant, female adult rats pretreated with either phenobarbital (PB) or (beta)-naphthoflavone ((beta)NF) through short-course intraperitoneal injections were shown by sodium dithionite-reduced carbon monoxide difference spectroscopy and NADPH-cytochrome c in vitro assay to contain cytochrome P-450 and NADPH-dependent reductase associated with the microsomal fraction of colon mucosa. These two protein components of the mixed function oxidase system were released from the microsomal membrane, resolved from each other, and partially purified by using a combination of techniques including solubilization in nonionic detergent followed by ultracentrifugation, anion exchange and adsorption column chromatographies, native gel electrophoresis, polyethylene glycol fractionation and ultrafiltration.^ In vitro reconstitution assays demonstrated the cytochrome P-450 fraction as the site of substrate and molecular oxygen binding. By the use of immunochemical techniques including radial immunodiffusion, Ouchterlony double diffusion and protein electroblotting, the cytochrome P-450 fraction was shown to contain at least 5 forms of the protein, having molecular weights as determined by SDS gel electrophoresis identical to the corresponding hepatic cytochrome P-450. Estimation of total cytochrome P-450 content confirmed the preferential induction of particular forms in response to the appropriate drug pretreatment.^ The colonic NADPH-dependent reductase was isolated from native gel electrophoresis and second dimensional SDS gel electrophoresis was performed in parallel to that for purified reductase from liver. Comparative electrophoretic mobilities together with immunochemical analysis, as with the cytochrome P-450s, reconstitution assays, and kinetic characterization using artificial electron acceptors, gave conclusive proof of the structural and functional homology between the colon and liver sources of the enzyme.^ Drug metabolism was performed in the reconstituted mixed function oxidase system containing a particular purified liver cytochrome P-450 form or partially pure colon cytochrome P-450 fraction plus colon or liver reductase and synthetic lipid vesicles. The two drugs, benzo{(alpha)}pyrene and benzphetamine, which are most representative of the action of system in liver, lung and kidney, were tested to determine the specificity of the reconstituted system. The kinetics of benzo{(alpha)}pyrene hydroxylation were followed fluorimetrically for 3-hydroxybenzo{(alpha)}pyrene production. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI ^

Evaluation of candidate genes for susceptibility to spina bifida

Neural tube defects (NTDs) are the most common severely disabling birth defects in the United States, with a frequency of approximately 1–2 of every 1,000 births. This text includes the identification and evaluation of candidate susceptibility genes that confer risk for the development of neural tube defects (NTDs). The project focused on isolated meningomyelocele, also termed spina bifida (SB). ^ Spina bifida is a complex disease with multifactorial inheritance, therefore the subject population (consisting of North American Caucasians and Hispanics of Mexicali-American descent) was composed of 459 simplex SB families who were tested for genetic associations utilizing the transmission disequilibrium test (TDT), a nonparametric linkage technique. Three categories of candidate genes were studied, including (1) human equivalents of genes determined in mouse models to cause NTDs, (2) HOX and PAX genes, and (3) the MTHFR gene involved in the metabolic pathway of folate. ^ The C677T variant of the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene was the first mutation in this gene to be implicated as a risk factor for NTDs. Our evaluation of the MTHFR gene provides evidence that maternal C677T homozygosity is a risk factor for upper level spina bifida defects in Hispanics [OR = 2.3, P = 0.02]. This observed risk factor is of great importance due to the high prevalence of this homozygous genotype in the Hispanic population. Additionally, maternal C677T/A1298C compound heterozygosity is a risk factor for upper level spina bifida defects in non-Hispanic whites [OR = 3.6, P = 0.03]. ^ For TDT analysis, our total population of 1128 subjects were genotyped for 54 markers from within and/or flanking the 20 candidate genes/gene regions of interest. Significant TDT findings were obtained for 3 of the 54 analyzed markers: d20s101 flanking the PAX1 gene (P = 0.019), d1s228 within the PAX7 gene (P = 0.011), and d2s110 within the PAX8 gene (P = 0.013). These results were followed-up by testing the genes directly for mutations utilizing single-strand conformational analysis (SSCA) and direct sequencing. Multiple variations were detected in each of these PAX genes; however, these variations were not passed from parent to child in phase with the positively transmitted alleles. Therefore, these variations do not contribute to the susceptibility of spina bifida, but rather are previously unreported single nucleotide polymorphisms. ^