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M Hodges

Publications and source records attributed to M Hodges.

At least 37 records · Page 2Linked to original sources
PubMed1999

Simultaneous expression of NAD-dependent isocitrate dehydrogenase and other krebs cycle genes after nitrate resupply to short-term nitrogen-starved tobacco

Mitochondrial NAD-dependent (IDH) and cytosolic NADP-dependent isocitrate dehydrogenases have been considered as candidates for the production of 2-oxoglutarate required by the glutamine synthetase/glutamate synthase cycle. The increase in IDH transcripts in leaf and root tissues, induced by nitrate or NH4+ resupply to short-term N-starved tobacco (Nicotiana tabacum) plants, suggested that this enzyme could play such a role. The leaf and root steady-state mRNA levels of citrate synthase, acotinase, IDH, and glutamine synthetase were found to respond similarly to nitrate, whereas those for cytosolic NADP-dependent isocitrate dehydrogenase and fumarase responded differently. This apparent coordination occurred only at the mRNA level, since activity and protein levels of certain corresponding enzymes were not altered. Roots and leaves were not affected to the same extent either by N starvation or nitrate addition, the roots showing smaller changes in N metabolite levels. After nitrate resupply, these organs showed different response kinetics with respect to mRNA and N metabolite levels, suggesting that under such conditions nitrate assimilation was preferentially carried out in the roots. The differential effects appeared to reflect the C/N status after N starvation, the response kinetics being associated with the nitrate assimilatory capacity of each organ, signaled either by nitrate status or by metabolite(s) associated with its metabolism.

Journal Article↗
PubMed1998

Mitochondrial localization of a NADP-dependent [corrected] isocitrate dehydrogenase isoenzyme by using the green fluorescent protein as a marker.

In this work, we describe the isolation of a new cDNA encoding an NADP-dependent isocitrate dehydrogenase (ICDH). The nucleotide sequence in its 5' region gives a deduced amino acid sequence indicative of a targeting peptide. However, even if this cDNA clearly encodes a noncytosolic ICDH, it is not possible to say from the targeting peptide sequence to which subcellular compartment the protein is addressed. To respond to this question, we have transformed tobacco plants with a construct containing the entire targeting signal-encoding sequence in front of a modified green fluorescent protein (GFP) gene. This construct was placed under the control of the cauliflower mosaic virus 35S promoter, and transgenic tobacco plants were regenerated. At the same time, and as a control, we also have transformed tobacco plants with the same construct but lacking the nucleotide sequence corresponding to the ICDH-targeting peptide, in which the GFP is retained in the cytoplasm. By optical and confocal microscopy of leaf epiderm and Western blot analyses, we show that the putative-targeting sequence encoded by the cDNA addresses the GFP exclusively into the mitochondria of plant cells. Therefore, we conclude that this cDNA encodes a mitochondrial ICDH.

Amino Acid Sequence↗
PubMed1998

Effect of ploidy and homozygosity on transgene expression in primary tobacco transformants and their androgenetic progenies.

Expression of a transgene is rarely analysed in the androgenetic progenies of the transgenic plants. Here, we report differential transgene expression in androgenetic haploid and doubled haploid (DH) tobacco plants as compared to the diploid parental lines, thus demonstrating a gene dosage effect. Using Agrobacterium-mediated transformation, and bacterial reporter genes encoding neomycin phosphotransferase (nptII) and beta-glucuronidase (uidA/ GUS), driven respectively by the mas 1' and mas 2' promoters, we have generated more than 150 independent transgenic (R0) Nicotiana tabacum plants containing one or more T-DNA copies. Transgene analyses of these R0, their selfed R1 lines and their corresponding haploid progenies showed an obvious position effect (site of T-DNA insertion on chromosome) on uidA expression. However, transgene (GUS) expression levels were not proportional to transgene copy number. More than 150 haploids and doubled haploids, induced by treatment with colchicine, were produced from 20 independent transgenic R0 plants containing single and multiple copies of the uidA gene. We observed that homozygous DH plants expressed GUS at approximately 2.9-fold the level of the corresponding parental haploid plants. This increase in transgene expression may be attributed mainly to the increase (2-fold) in chromosome number. Based on this observation, we suggest a strong link between chromosome number (ploidy dosage effect) and transgene expression. In particular, we demonstrate the effect on its expression level of converting the transgene from the heterozygous (in R0 plants) to the homozygous (DH) state: e.g. an increase of 50% was observed in the homozygous DH as compared to the original heterozygous diploid plants. We propose that ploidy coupled with homozygosity can result in a new type of gene activation, creating differences in gene expression patterns.

Chromosome Segregation↗
PubMed1998

Molecular characterization of higher plant NAD-dependent isocitrate dehydrogenase: evidence for a heteromeric structure by the complementation of yeast mutants.

NAD-dependent isocitrate dehydrogenase (IDH) is a key enzyme controlling the activity of the citric acid cycle. Despite more than 30 years of work, the plant enzyme remains poorly characterized. In this paper, a molecular characterization of the plant IDH is presented. Starting from probes defined according to sequence comparisons, three full-length cDNAs named Ntidha, Ntidhb and Ntidhc encoding different IDH subunits have been isolated from a Nicotiana tabacum cell suspension library. Sequence comparisons of the tobacco IDH subunits with the E. coli NADP-dependent enzyme, and the yeast IDH1 and IDH2 subunits suggested that only IDHa had the capacity to be catalytic as IDHb and IDHc were lacking certain residues implied in catalysis. The ability of antibodies raised against the recombinant IDHa protein to preferentially cross-react with IDH2 indicated that IDHa was more closely related to IDH2 than to IDH1. Complementation of yeast single IDH mutants showed that IDHb and IDHc could replace the function of the yeast regulatory IDH1 subunit. Although IDHa was unable to complement the IDH2 mutant, its catalytic function was revealed by the ability of two heteromeric enzymes, composed of either IDHa with IDHb or IDHa with IDHc, to replace IDH function in a yeast double mutant lacking both subunits. Expression studies at the protein and mRNA levels show that each subunit is present in both root and leaf tissues and that the three IDH genes respond in the same way to nitrate addition. Taken together, such observations suggest that the physiologically active enzyme is composed of the three different subunits. These results show for the first time that the plant IDH is heteromeric and that IDH subunit composition appears to be conserved between plant and animal kingdoms.

Amino Acid Sequence↗
PubMed1998

Eucalypt NADP-dependent isocitrate dehydrogenase. cDNA cloning and expression in ectomycorrhizae.

NADP-dependent isocitrate dehydrogenase (NADP-ICDH) activity is increased in roots of Eucalyptus globulus subsp. bicostata ex Maiden Kirkp. during colonization by the ectomycorrhizal fungus Pisolithus tinctorius Coker and Couch. To investigate the regulation of the enzyme expression, a cDNA (EgIcdh) encoding the NADP-ICDH was isolated from a cDNA library of E. globulus-P. tinctorius ectomycorrhizae. The putative polypeptide sequence of EgIcdh showed a high amino acid similarity with plant NADP-ICDHs. Because the deduced EgICDH protein lacks an amino-terminal targeting sequence and shows highest similarity to plant cytosolic ICDHs, it probably represents a cytoplasmic isoform. RNA analysis showed that the steady-state level of EgIcdh transcripts was enhanced nearly 2-fold in ectomycorrhizal roots compared with nonmycorrhizal roots. Increased accumulation of NADP-ICDH transcripts occurred as early as 2 d after contact and likely led to the observed increased enzyme activity. Indirect immunofluorescence microscopy indicated that NADP-ICDH was preferentially accumulated in the epidermis and stele parenchyma of nonmycorrhizal and ectomycorrhizal lateral roots. The putative role of cytosolic NADP-ICDH in ectomycorrhizae is discussed.

Amino Acid Sequence↗
PubMed1998

Reversible myocardial contraction abnormalities in patients with an acute noncardiac illness.

STUDY OBJECTIVES: Reversible myocardial contraction abnormalities are usually observed in patients with acute ischemic syndromes caused by coronary artery disease. In this study, we report the occurrence of reversible anterior-apical contraction abnormalities in patients with an acute noncardiac illness. SETTING: This was a retrospective study of 22 patients with the following characteristics: (1) hospitalization for an acute noncardiac illness; (2) appearance of deep T-wave inversion in the precordial leads of the ECG; and (3) presence of an anterior wall motion abnormality on an echocardiogram. Standard clinical information was collected together with results of serial ECGs, echocardiograms, and coronary angiograms. RESULTS: The primary diagnoses for the 22 acutely ill patients included CNS injury (n=6); sepsis (n=3); acute pulmonary disease (n=3); drug overdose or metabolic abnormality (n=7); and post noncardiac surgery (n=3). An initial echocardiogram revealed an anterior apical wall motion abnormality. At follow-up, all patients had progressive improvement in anterior wall motion with return of normal wall motion in 16 patients (73%). All patients evolved deep T-wave inversion (average, 7.8 mm) and QT interval lengthening in the precordial leads. Coronary angiography revealed a significant stenosis in the likely culprit artery (left anterior descending) in only one patient. CONCLUSION: A reversible cardiac contraction abnormality of the anterior wall and apex of the left ventricle can complicate the clinical course of critically ill patients in the absence of significant coronary artery disease. This phenomenon is associated with striking T-wave inversion and QT interval lengthening. Mechanisms other than myocardial ischemia may lead to the occurrence of reversible regional myocardial contraction abnormalities.

Acute Disease↗
PubMed1997

Lack of coupling between secondary structure formation and collapse in a model polypeptide that mimics early folding intermediates, the F2 fragment of the Escherichia coli tryptophan-synthase beta chain.

The isolated, 101-residue long C-terminal (so called F2) fragment of the beta chain from Escherichia coli tryptophan synthase was shown previously to fold into an ensemble of conformations that are condensed, to contain large amounts of highly dynamic secondary structures, and to behave as a good model of structured intermediates that form at the very early stages of protein folding. Here, solvent perturbations were used to investigate the forces that are involved in stabilizing the secondary structure (monitored by far-UV CD) and the condensation of the polypeptide chain (monitored by dynamic light scattering) in isolated F2. It was observed that neither the ionic strength, nor the pH (between 7 and 10), nor salts of the Hofmeister series affected the global secondary structure contents of F2, whereas some of these salts affected the collapse slightly. Addition of trifluoroethanol resulted in a large increase in both the amount of secondary structure and the Stokes radius of F2. Conversely, F2 became more condensed upon raising the temperature from 4 to 60 degrees C, whereas in this temperature range, the secondary structure undergoes significant melting. These observations lead to the conclusion that, in isolated F2, there is no coupling between the hydrophobic collapse and the secondary structure. This finding will be discussed in terms of early events in protein folding.

Chemical Phenomena↗
PubMed1997

Does significant arterial hypoxemia alter vital signs?

STUDY OBJECTIVE: To determine the cardiovascular and respiratory effects of arterial hypoxemia in adult volunteers. DESIGN: Prospective, subject-controlled. SETTING: University-affiliated hospital. SUBJECTS: 16 awake, unsedated, unanesthetized adult volunteers. INTERVENTIONS: Inspired oxygen concentration (FIO2) was decreased in decrements to reduce pulse oximeter values to a range of 95% to 90%, 89% to 85%, 84% to 80%, and 79% to 70%. MEASUREMENTS AND MAIN RESULTS: Heart rate (HR), blood pressure (BP), respiratory rate (RR), arterial blood pH, gas tensions, and oxyhemoglobin saturation were determined during normoxia and each level of oxyhemoglobin desaturation. FIO2 was reduced from 21% to 10%. Arterial blood oxyhemoglobin saturation and oxygen tension ranged from 100% to 71% and 103 to 35 mmHg, respectively. There were no significant changes in RR, BP, or HR during the study. CONCLUSIONS: HR, BP, and RR are not reliable indicators of arterial hypoxemia in awake volunteers. If this finding is also true for sedated or anesthetized patients, then continuous monitoring with pulse oximetry should be used whenever patients are at risk for arterial hypoxemia. Stable HR, BP, and RR may not eliminate the possibility of significant arterial hypoxemia and impending catastrophic events.

Adult↗
PubMed1997

The human Achaete-Scute homologue 2 (ASCL2,HASH2) maps to chromosome 11p15.5, close to IGF2 and is expressed in extravillus trophoblasts.

Here we describe the cloning of the human Achaete Scute Homologue 2 (HASH2) gene, officially designated ASCL2 (Achaete Scute complex like 2), a homologue of the Drosophila Achaete and Scute genes. In mouse, this gene is imprinted and maps to chromosome 7. We mapped the human homologue close to IGF2 and H19 at 11p15.5, the human region syntenic with mouse chromosome 7, indicating that this imprinted region is highly conserved in mouse and man. HASH2 is expressed in the extravillus trophoblasts of the developing placenta only. The lack of HASH2 expression in non-malignant hydatidiform (androgenetic) moles indicates that HASH2 is also imprinted in man.

Amino Acid Sequence↗
PubMed1997

Ischemic cerebral infarction after rt-PA and heparin therapy for acute myocardial infarction. The TIMI-II pilot and randomized clinical trial combined experience.

BACKGROUND AND PURPOSE: Ischemic cerebral infarction (CI) is a serious complication of acute myocardial infarction (MI). Little information exists on CI after thrombolytic therapy for MI. METHODS: Of 3924 MI patients treated with recombinant tissue plasminogen activator (rt-PA) and heparin, 29 (0.7%) developed CI after treatment. All CI patients had detailed neurological evaluations, and 27 (93%) had CT scans centrally reviewed. RESULTS: Age range was 40 to 74 years (mean, 60 years); 25 patients (86%) were men, and 22 (76%) were white. The electrocardiographic location of MI was anterior in 22 (76%) and nonanterior in 7 (24%). Five CIs occurred within 6 hours, 4 between 6 to 24 hours, 8 during the remainder of the first week, 10 during the second week, and 2 others distributed over the 4 weeks after study entry. Six of 29 CIs did not involve the cerebral cortex; 9 patients (31%) had multiple CIs. Of 28 CIs thought to be embolic in origin, 17 showed strong evidence for at least one cardiac abnormality (mural clot, wall-motion abnormality, aneurysm, or atrial fibrillation) known to be associated more specifically with embolism than MI. Eight of 27 CIs (30%) with CT scans had hemorrhagic transformation of varying degrees; 5 were symptomatic. CONCLUSIONS: The time of occurrence and sites of CI after rt-PA and heparin therapy for acute MI are similar to those reported during the prethrombolytic era.

Adult↗
PubMed1997

The use of immunochromatography test cards in the diagnosis of hepatitis B surface antigen among pregnant women in West Africa.

Despite the development of successful vaccines against hepatitis B virus (HBV), Sierra Leone, like many countries lying within the geographical region where HBV infection is highly endemic, has yet to implement an immunisation or mass screening programme. However, certain sectors of the population could benefit from HBV screening if it was readily available and affordable. The use of a newly introduced immunochromatography (IC) test card for hepatitis B surface antigen (HBsAg) is examined for use among an ante-natal population in Sierra Leone, and compared with the existing reverse passive haemagglutination (R-PHA) method. The prevalence of HBsAg and hepatitis B envelope antigen (HBeAg) in the study population (n = 179) was 11.3% and 3.9%, respectively. The speed, sensitivity and simplicity of the IC method make it attractive, particularly for individual use and where laboratory facilities are minimal, but the cost of the test is comparatively high. In the African setting, pending the introduction of HBV vaccination into the Expanded Programme on Immunisation (EPI), the IC test card may be of use in the private sector where the turnover of patients is small, as a rapid means of detecting HBsAg in pregnant women who can afford both this facility and HBV vaccination of their newborn babies.

Adolescent↗
PubMed1996

Identification of a tobacco cDNA encoding a cytosolic NADP-isocitrate dehydrogenase.

A cDNA which encodes a specific member of the NADP-dependent isocitrate dehydrogenase (ICDH) multi-isoenzyme family has been isolated from a tobacco cell suspension library, and the expression pattern of ICDH transcripts examined in various plant tissues. To assign this cDNA to a specific ICDH isoenzyme, the major, cytosolic ICDH isoenzyme of tobacco leaves (ICDH1) was purified to homogeneity and its N-terminus as well as several tryptic peptides, representing 30% of the protein, were sequenced. The comparison of these amino acid sequences with the deduced protein sequence of the cDNA confirmed that this clone encodes for ICDH1. The total ICDH specific activity and protein content were higher in vascular-enriched tobacco leaf tissue than in deveined (depleted in midrib and first-order veins) leaves. Taking advantage of antibodies raised against either ICDH1 or the chloroplastic ICDH2 isoenzyme from tobacco cell suspensions, an immuno-cytochemical approach indicated that the ICDH1 isoenzyme, located in the cytosolic compartment of tobacco leaf cells, is responsible for this expression pattern. This observation was confirmed by northern blot analyses, using a specific probe obtained from the 3' non-coding region of the ICDH1 cDNA. A comparison of ICDH protein sequences shows a large degree of similarity between eukaryotes (> 60%) but a poor homology is observed when compared to Escherichia coli ICDH (< 20%). However, it was found that the amino acids implicated in substrate binding, deduced from the 3-dimensional structure of the E. coli NADP-ICDH, appear to be conserved in all the deduced eukaryotic ICDH proteins reported until now.

Amino Acid Sequence↗