Ubiquinol-cytochrome c oxidoreductase of higher plants. Isolation and characterization of the bc1 complex from potato tuber mitochondria

A procedure is described for isolation of active ubiquinol-cytochrome c oxidoreductase (bc1 complex) from potato tuber mitochondria using dodecyl maltoside extraction and ion exchange chromatography. The same procedure works well with mitochondria from red beet and sweet potato. The potato complex has at least 10 subunits resolvable by gel electrophoresis in the presence of dodecyl sulfate. The fifth subunit carries covalently bound heme. The two largest ("core") subunits either show heterogeneity or include a third subunit. The purified complex contains about 4 mumol of cytochrome c1, 8 mumol of cytochrome b, and 20 mumol of iron/g of protein. The complex is highly delipidated, with 1-6 mol of phospholipid and about 0.2 mol of ubiquinone/mol of cytochrome c1. Nonetheless it catalyzes electron transfer from a short chain ubiquinol analog to equine cytochrome c with a turnover number of 50-170 mol of cytochrome c reduced per mol of cytochrome c1 per s, as compared with approximately 220 in whole mitochondria. The enzymatic activity is stable for weeks at 4 degrees C in phosphate buffer and for months at -20 degrees C in 50% glycerol. The activity is inhibited by antimycin, myxothiazol, and funiculosin. The complex is more resistant to funiculosin and diuron than the beef heart enzyme. The optical difference spectra of the cytochromes were resolved by analysis of full-spectrum redox titrations. The alpha-band absorption maxima are 552 nm (cytochrome c1), 560 nm (cytochrome b-560), and 557.5 + 565.5 nm (cytochrome b-566, which has a split alpha-band). Extinction coefficients appropriate for the potato cytochromes are estimated. Despite the low lipid and ubiquinone content of the purified complex, the midpoint potentials of the cytochromes (257, 51, and -77 mV for cytochromes c1, b-560, and b-566, respectively) are not very different from values reported for whole mitochondria. EPR spectroscopy shows the presence of a Rieske-type iron sulfur center, and the absence of centers associated with succinate and NADH dehydrogenases. The complex shows characteristics associated with a Q-cycle mechanism of redox-driven proton translocation, including two pathways for reduction of b cytochromes by quinols and oxidant-induced reduction of b cytochromes in the presence of antimycin.

Metabolically driven self-restoration of energy-linked functions by avocado mitochondria: general characteristics and phosphorylative aspects

To assess the restorative capacity of isolated avocado (Persea americana) fruit mitochondria, the organelles were first aged in the absence of an energy source at 25 degrees C for several hours until respiratory control and oxidative phosphorylation were greatly diminished or totally lost. Energy-linked functions were then gradually restored over a period of several hours after the addition of substrate. Restoration of respiratory control resulted from both an increase in state 3 and a decrease in state 4 respiratory rates. Either alpha-ketoglutarate or succinate served as restorants, each with distinctive rates of recovery in state 3 and state 4 respiration. ATP also served as a restorative agent but not as effectively as metabolizable substrate. ATP synthase activity was modulated by stress and restoration but neither the extent nor the rate of change was sufficient to constrain state 3 rates. Orthophosphate was released from the mitochondria during substrate-deprived stress. Restoration of phosphorylation preceded that of RC with phosphate uptake and phosphorylation being evident immediately upon the addition of substrate. During restoration [(32)P]orthophosphate was incorporated into several organic fractions: phospholipid, ATP, a trichloroacetic acid-precipitable mitochondrial fraction, and an organophosphate that accumulated in the medium in relatively large amounts. The organophosphate was tentatively identified as a hexosephosphate. Incorporation into ATP and the putative hexosephosphate continued unabated beyond the point of maximum restoration. Phosphate metabolism thus appears to be a necessary but not sufficient precondition for mitochondrial restoration and maintenance. Based on the recovery kinetics of the various phosphorylated components, the mitochondrial-bound fraction appears to be most directly linked with restoration. Results are discussed with reference to specific characteristics and components of self-restoration and to possible underlying mechanisms. We suggest that a degree of self-restoration is consistent with the quasi-autonomous nature of mitochondria and that this intrinsic capacity may be pivotal to the respiratory climacteric in senescent fruit cells and to cellular homeostasis in general.

Sequence polymorphism in the human apoB gene at position 8344

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[Follow-up study of outcome of schizophrenia]

In May to October, 1984. Jieyany County psychiatric epidemiology research group follow-up the patient 2545 cases (1979-1984) of schizophrenia. 27 cases were transfer to other localities (1.06%), 17 cases were missing (0.67%), 206 cases were dead (8.09%), 280 cases (11.00%) changed diagnosis in there years, and 2015 cases (79.17%) were followed. In this paper, the current condition of morbidity, the outcome and relation between the morbidity and prognosis were analysed. Results of present investigation show that fully recover from increased and social influence decreased as a results of conducting family therapy social prevention and support.

Purification and characterization of the proton translocating plasma membrane ATPase of red beet storage tissue

Plasma membranes were prepared from red beet (Beta vulgaris L.) storage tissue by partition in an aqueous two-phase system. A highly active proton-translocating ATPase was purified from these membranes by lysophosphatidylcholine extraction and glycerol density gradient centrifugation. The ATPase activity was inhibited by vanadate or dicyclohexyl carbodiimide, but was insensitive to azide, nitrate and molybdate at concentrations which inhibit the F1ATPase, the tonoplast ATPase, and acid phosphatase. Inhibition by vanadate was consistent with a non-competitive mechanism, with Ki = 10 microM. The Km for Mg-ATP was about 1 mM, magnesium ions were required, and the activity was stimulated by KCl and by lysophosphatidylcholine. The optimal pH was 6.5. The molecular mass by gel filtration in the presence of 2 g/liter octyl glucoside was 600 kDa, while dodecyl sulfate gel electrophoresis gave a polypeptide molecular mass of 100 kDa. After blotting onto nitrocellulose, the purified enzyme did not bind concanavalin A, although a concanavalin A-binding peptide of the plasma membrane runs to nearly the same position on the gel and showed some tendency to co-purify with the ATPase. Phospholipid vesicles into which the purified ATPase had been incorporated by the freeze-thaw technique showed vanadate-sensitive, ATP-dependent proton uptake. When the ATPase was reconstituted into lipid membranes at high protein to lipid ratios and incubated with ATP, two-dimensionally crystalline arrays of protein molecules were formed.

Exclusion of linkage between the human apolipoprotein B gene and abetalipoproteinemia

Abetalipoproteinemia (ABLP) is a rare autosomal recessive disease characterized by a lack of plasma apolipoprotein B (apo B). In this report, the hypothesis that ABLP is due to rare mutations in the apo B gene was tested. A total of eight ABLP families were studied. Apo B gene RFLPs were used to establish the haplotypes of the apo B alleles in family members. LOD score analysis was used to study the linkage between the apo B alleles and ABLP. These families were categorized arbitrarily as class I, II, III, or IV because of differences in the results derived from both haplotyping and LOD score analysis. In a class I family, affected siblings, who on the basis of the hypothesis would be expected to have the same apo B alleles, had different ones. LOD score analysis of this family gave an infinite negative number at a recombination fraction (theta) of zero. In two class II families, probands who were the result of consanguineous marriages and who, on the basis of the hypothesis, should be homozygotes for a defective apo B allele, were heterozygotes at this locus. The sum of the LOD scores from these two families was -1.7 at theta = 0. In one class III family, a parent was apparently homozygous for a particular apo B allele and yet not affected. This also contributed negatively to the LOD score. In four class IV families, disease inheritance was compatible with segregation of the apo B alleles. This, however, was not statistically significant (LOD score = 0.97 at theta = 0).(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular basis of five apolipoprotein B gene polymorphisms in noncoding regions

Restriction fragment length polymorphisms (RFLPs) are useful in linkage and clinical association studies of human diseases. In this report, we characterize the molecular basis and frequencies of two new RFLPs, AvaII and BalI, two previously reported RFLPs, HincII and PvuII, and one new sequence polymorphism in the human apolipoprotein B gene. For the AvaII RFLP, the two alleles yield either a 1 kb fragment or 0.7 and 0.3 kb fragments, and have frequencies of 20% and 80%, respectively. The polymorphic site is about 4 kb upstream of exon 1. For the BalI RFLP, the two alleles yield either a 4.9 or 6.2 kb fragment, and have about equal frequencies. The polymorphic site is within an Alu sequence in intron 20, 146 bp 5' to exon 21. The BalI recognition sequence TGGCCA is replaced by TAGCCA. For the HincII RFLP, the two alleles yield either a 1.7 or 1.3 kb fragment and have frequencies of 80% and 20%, respectively. The polymorphic site is in intron 4, 171 bp 3' to exon 4. The HincII recognition sequence GTTAAC, present in the minor allele, is replaced by GTTACC. HincII fragments of 7.4 and 7.0 kb, previously reported for this polymorphism, are the result of partial digestion at the invariant HincII site in intron 3, 334 bp 3' to exon 3. For the PvuII RFLP, the two alleles yield either a 7.5 or 5.5 kb fragment and have frequencies of 96% and 4%, respectively. The polymorphic site is within an Alu sequence in intron 4, 523 bp 5' to exon 5.(ABSTRACT TRUNCATED AT 250 WORDS)

A study of thyroidal response to thyrotropin (TSH) in decompensated liver cirrhosis

In order to improve understanding of factors that may contribute to reduced serum T4 in non-thyroidal illnesses, we have studied baseline thyroid function, serum TSH response to thyrotropin-releasing hormone (TRH), and/or increase in thyroidal radioiodine uptake and serum T4 after parenteral administration of TSH in 12 patients with decompensated liver cirrhosis. Ten age and sex matched normal volunteer subjects served as controls. Compared to control subjects, patients with hepatic cirrhosis had significantly lower mean serum total T3 (ng/dl, mean +/- SD, 56 +/- 31 vs. 147 +/- 25, P less than 0.001), total T4 (microgram/dl, 4.3 +/- 1.5 vs. 8.8 +/- 0.74, P less than 0.001), and higher TSH (microU/ml, 3.0 +/- 1.2 vs. 1.6 +/- 0.73, P less than 0.05). Serum TSH response to TRH (400 micrograms I.V.) was abnormal in seven of 12 patients so studied. The peak TSH post-TRH was subnormal in one patient and normal but delayed in six patients. The mean baseline 24 h thyroid 131I uptake was not significantly different between the two groups under study (17 +/- 12% in cirrhosis patients vs. 25 +/- 10% in normal subjects). However, six patients with hepatic cirrhosis had clearly subnormal (less than 15%) 24 h thyroid radioiodine uptake (normal range 15-47%). The mean increase in 24 h thyroid radioiodine uptake and serum T4 at about 40 h after exogenous TSH (0.1 U/kg body weight i.m.) was lower in liver cirrhosis patients than that in normal subjects, but the difference was not significant statistically.(ABSTRACT TRUNCATED AT 250 WORDS)

Hypobetalipoproteinemia due to an apolipoprotein B gene exon 21 deletion derived by Alu-Alu recombination

We report the molecular defect in an individual with homozygous hypobetalipoproteinemia. A unique TaqI restriction fragment length polymorphism was found in the midportion of the apolipoprotein B (apoB) gene using the genomic probe, pB51. The probe, which identifies TaqI fragments of 8.4 and 2.8 kilobases (kb) in normal individuals, hybridized to a single 11-kb fragment in the proband. The parents of the proband showed all three TaqI fragments, implying that they are heterozygotes for the mutant apoB allele. In this family, the mutant allele cosegregated with low total cholesterol levels and formal linkage analysis gave a decimal logarithm of the ratio score of 3.3 at a recombination frequency of 0. The polymorphic TaqI site was localized to an EcoRI fragment of 4 kb in normal individuals. The corresponding fragment in the proband was 3.4 kb, suggesting a 0.6-kb deletion in the mutant allele. Both the normal 4-kb EcoRI fragment and the mutant 3.4-kb EcoRI fragment were cloned and sequenced. In the normal allele, the 4-kb EcoRI fragment extends from intron 20 to 23. Exon 21 is flanked by Alu sequences that are in the same orientation. The mutant allele had a 694-bp deletion in this region which included a small part of the Alu sequence in intron 20, the entire exon 21, and most of the Alu sequence in intron 21. The polymorphic TaqI site, which lies within the Alu sequence in intron 21, was absent in the proband as a result of the deletion. The deletion of exon 21 results in a frame shift mutation and the introduction of a stop codon. Translation of the encoded mRNA would yield a prematurely terminated protein. This mutant apoB protein would be 1085 amino acids long with the 73 carboxyl-terminal residues out of frame. We postulate that the deletion of exon 21 is the consequence of a crossover event between the Alu sequences in introns 20 and 21 resulting in nonreciprocal exchange between two chromosomes.

Effect of cranial irradiation on hypothalamus and pituitary functions

Hypopituitarism can occur after cranial irradiation for tumors distant from the pituitary gland. Recent studies have suggested that this is hypothalamic in origin. Hypothalamic and pituitary functions were studied in 11 patients, 4 men and 7 women, 4.5 years or more after radiotherapy for nasopharyngeal carcinomas. The estimated average total dose was 5000 cGys for the hypothalamus and pituitary gland. Except for 2 women with amenorrhea and 4 men with impotency, the patients did not have evident endocrine deficiency. Baseline hormone profiles revealed normal T4, T3 and cortisol levels, 6 with elevated prolactin, 3 with reduced testosterone and 3 with slightly elevated basal TSH. The four menopausal women had impaired gonadotropin response to LHRH (100 micrograms, i.v.). Four (1 menstruating, 1 amenorrheic, 2 menopausal) women did not reach peak FSH response 4 hours after LHRH injection. The other amenorrheic woman had minimal FSH and LH response to LHRH which persisted even after 8 days of pulsatile infusion of LHRH (1 microgram/90min). TSH response to TRH (400 micrograms, i.v.) was delayed in 7 patients. GH response to human GRH (1 microgram/kg, i.v.) was impaired in 6 patients (maximal GH less than 5 mU/l). ACTH response to ovine CRH (1 microgram/kg, i.v.) was impaired in 3 patients (less than 50% elevation from baseline). Three patients who had normal GRH tests had impaired GH response to insulin hypoglycemia. Six patients had an empty sella on CT scan. From this study the following conclusions are drawn: (1) Among the four axes, GH is the most vulnerable. (2) The insulin tolerance test is still the best single test for evaluation of hypothalamic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of Light on Sterol Changes in Medicago sativa

Most vascular plants contain Delta(5)-sterols as the predominant type; however, a few species such as Medicago sativa, have mainly Delta(7)-sterols. The Delta(7)-sterols of alfalfa are isomers of the common Delta(5)-sterols and are generally assumed to be their immediate precursors. Light had a significant influence on the sterol status of M. sativa. High light intensity and a long day favored the accumulation of dihydrospinasterol; a short day and low light intensity, particularly darkness, favored spinasterol accumulation. These data for Delta(7)-sterol plants agree with those reported for Delta(5)-sterol plants; light favors the accumulation of the monounsaturated 29 carbon sterols and darkness favors the accumulation of the diunsaturated sterols. Proposed is a mechanism to explain the effect of light on the accumulation of Delta(7)- and Delta(5)-sterols.

ApoB gene MspI RFLP in exon 26 changes amino acid 3611 from Arg to Gln

An apolipoprotein B gene MspI RFLP was identified by the use of a probe to a portion of the 3' end of the gene. By Southern blotting analysis after digestion with MspI, this probe detected either a 9 kb or a 2.6 kb fragment. Family studies showed that these corresponded to alleles that segregated in a simple Mendelian fashion. The minor allele (9.0 kb) had a frequency of approximately 12% in an unrelated Caucasian population. Restriction mapping showed that the minor allele was due to the loss of an MspI site in exon 26. Sequencing of both alleles in the region containing the polymorphic MspI site revealed a single-base pair alteration which abolished the MspI site at codon 3611 of the mature apoB protein. In the major allele, this codon is CGG, which specifies Arg; whereas in the minor allele, it was CAG, which codes for Gln.

A unique AT-rich hypervariable minisatellite 3' to the ApoB gene defines a high information restriction fragment length polymorphism

A DNA restriction fragment length polymorphism has been found immediately 3' to the human apoB gene. Digestion of many different human DNAs at sites flanking the region and Southern blotting analysis reveal that this region can vary in length by approximately 300 base pairs with five alleles readily distinguishable. The length polymorphism is due to a unique AT-rich minisatellite that consists primarily of a 30-base pair tandem repeat with two structurally related subunit sequences, x (ATAATTAAATATTTT) and y (ATAATTAAAATATTT). In general, the sequences repeat in an x-y order. The AT-rich region also contains variant x and y sequences that result from C or G for A substitution. Sequence analysis of one large allele revealed the expected increased number of xy repeats. In addition, similar analysis of three different smaller alleles with the same apparent size on Southern blotting analysis showed that all were of slightly different size due to minor differences in the number of xy repeats. The heterogeneity of this AT-rich minisatellite provides the basis for a highly informative restriction fragment length polymorphism of the apoB gene and should be very useful in association and linkage analysis studies of the contribution of this locus to atherosclerosis susceptibility.

Apolipoprotein B-gene DNA polymorphisms associated with myocardial infarction

Levels of apolipoprotein B, the protein component of low-density lipoproteins, correlate with the risk of coronary heart disease. We examined whether genetic variation in apolipoprotein B is associated with myocardial infarction by studying apolipoprotein B-gene restriction-fragment-length polymorphisms in 84 patients with myocardial infarction and an equal number of matched controls. Southern blot analysis with apolipoprotein B-gene probes, performed after DNA was digested with the endonucleases XbaI and EcoRI, revealed alleles that we designated as X1, X2, and X3 and as R1 and R2, respectively. Similar studies with the endonuclease MspI revealed alleles of many different sizes (the difference was due to an insertion-deletion polymorphism), which we grouped as larger and smaller alleles and designated as ID1 and ID2, respectively. The frequencies of the X1, R1, and ID1 alleles were all significantly higher (P less than 0.01) in the cases than in the controls. None of the alleles, however, was significantly associated with variation in levels of low-density lipoprotein cholesterol or apolipoprotein B, and the functional importance of these alleles is therefore uncertain. Nonetheless, in addition to quantitative variation in apolipoprotein B levels in plasma, genetic variation at the apolipoprotein B locus may be a new and independent risk factor for myocardial infarction.

Mapping of the human APOB gene to chromosome 2p and demonstration of a two-allele restriction fragment length polymorphism

ApoB is a large glycoprotein with an apparent molecular mass of 550 kDa on NaDodSO4/PAGE. It is a major constituent of most lipoproteins and plays an important role in their metabolism. Recently, apoB cDNA clones have been isolated from an expression library made with mRNA from a human hepatoma cell line. These clones, which were all 1.5-1.6 kilobases (kb) long and corresponded to the 3' end of apoB mRNA, were used to demonstrate that hepatic apoB mRNA is approximately 22 kb long. In the current report, a probe derived from one of these cDNA clones, pB8, was used for in situ hybridization experiments to map the human gene for apoB, APOB, to the distal half of the short arm of chromosome 2. This probe was also used to analyze somatic cell hybrids and, in agreement with the in situ hybridization studies, concordancy was demonstrated with chromosome 2. In addition, two hybrids with chromosome 2 translocations that contain only the short arm reacted with the pB8 probe. A third hybrid with a complex rearrangement of chromosome 2, which deleted an interstitial region and the tip of the short arm of chromosome 2, did not react. These data indicate that APOB maps to either 2p21-p23 or 2p24-pter. In further studies, DNA from normal individuals, digested with the restriction endonuclease EcoRI and subjected to Southern blot analysis with the pB8 probe, revealed a two-allele restriction fragment length polymorphism (RFLP). The major allele was 11 kb, and the minor allele was 13 kb. The minor allele was present with a frequency of 20-25%. The inheritance of the two alleles was studied in an informative family, and they segregated in a typical autosomal Mendelian fashion. The mapping studies provide the means for understanding the relationship of the APOB locus to others in the human genome, whereas the demonstration of an APOB RFLP increases our ability to assess the role of this locus in determining plasma lipoprotein levels.

Contributions of the fetoplacental unit to augmented uterine prostaglandin levels periparturition in the rat

The purpose of the present study was to determine if the acute alterations in uterine prostanoid levels at the end of pregnancy are influenced locally by the fetoplacental unit (FPU). Unilaterally pregnant rats were killed on Days 20 and 21 of pregnancy (delivery = Day 21.5) and uterine tissue was removed and analyzed for prostaglandin (PG) E, PGF, thromboxane B2 (TxB2), and 6-keto-PGF1 alpha (6KF) by radioimmunoassay. A significant (P less than 0.05) main effect of Day (20 vs. 21) and Uterine Horn (nonpregnant vs. pregnant), but no interaction for PGE, PGF, and TxB2 was detected. In contrast, a significant interaction (P less than 0.05) of Day with Uterine Horn was found for uterine 6KF levels. Examination of the simple main effects indicated an enhanced level (P less than 0.05) of 6KF in uterine tissue adjacent compared to opposite the FPU at Days 20 and 21. However, uterine 6KF levels in the nonpregnant, but not pregnant, uterine horn were greater at Day 21 compared to Day 20 of pregnancy. The lack of a significant interaction of the main effects for PGE, PGF, and TxB2 suggests that the increased levels of these PGs between Days 20 and 21 were proportional in the nonpregnant and pregnant uterine horn. Therefore, the factor(s) responsible for the augmentation in these uterine PG levels between Days 20 and 21 is(are) most likely arriving via systemic circulation. In addition, the proportionate increases in uterine PGs imply that the FPU is not conferring upon adjacent uterine tissue any unique ability to respond to systemic factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Human apolipoprotein B cDNA clone isolation and demonstration that liver apolipoprotein B mRNA is 22 kilobases in length

An expression library made in plasmids pUC8 and pUC9 with mRNA derived from the human hepatoma cell line HepG2 was screened with a rabbit antiserum to human low density lipoprotein (LDL). Approximately 12,000 clones were screened and five positives were identified. The cDNA inserts were all 1500-1600 base pairs in length. The insert from one clone, pB8, was isolated, labeled by nicktranslation, and found to cross-hybridize strongly with the other four cDNA clones. The pB8 clone produces a fusion protein of approximately equal to 37.5 kDa that reacts in electrophoretic transfer blot analysis with rabbit anti-human LDL. This reactivity can be abolished by pretreatment of the antiserum with purified human LDL, p = 1.025 - 1.050 g/ml. A pB8-derived probe was used to demonstrate that apolipoprotein B (apo B) mRNA is present in HepG2 cells and liver extracts but not in HeLa cells or extracts from small intestine, heart, aorta, spleen, brain, skeletal muscle, lung, kidney, or ovary. RNA transfer blot analysis revealed that HepG2 cell apo B mRNA was approximately equal to 22 kilobases in length. These cDNA clones should allow the isolation of the apo B gene and ultimately the elucidation of the primary structure of this protein.